Transcutaneous analyte sensor systems

APPLICATIONS

0001This application claims the benefit of <patcit id="pcit0001" dnum="US62272983" dnum-type="L"><text>U.S. Provisional Application No. 62/272,983, filed December 30, 2015</text></patcit> and <patcit id="pcit0002" dnum="US62412100" dnum-type="L"><text>U.S. Provisional Application No. 62/412,100, filed October 24, 2016</text></patcit>.

FIELD

0002Various embodiments disclosed herein relate to measuring an analyte in a person. Certain embodiments relate to systems and methods for applying a transcutaneous analyte measurement system to a person.

BACKGROUND

0003Diabetes mellitus is a disorder in which the pancreas cannot create sufficient insulin (Type I or insulin dependent) and/or in which insulin is not effective (Type 2 or non-insulin dependent). In the diabetic state, the victim suffers from high blood sugar, which can cause an array of physiological derangements associated with the deterioration of small blood vessels, for example, kidney failure, skin ulcers, or bleeding into the vitreous of the eye. A hypoglycemic reaction (low blood sugar) can be induced by an inadvertent overdose of insulin, or after a normal dose of insulin or glucose-lowering agent accompanied by extraordinary exercise or insufficient food intake.

0004Conventionally, a person with diabetes carries a self-monitoring blood glucose monitor, which typically requires uncomfortable finger pricking methods. Due to the lack of comfort and convenience, a person with diabetes normally only measures his or her glucose levels two to four times per day. Unfortunately, such time intervals are so far spread apart that the person with diabetes likely finds out too late of a hyperglycemic or hypoglycemic condition, sometimes incurring dangerous side effects. Glucose levels may be alternatively monitored continuously by a sensor system including an on-skin sensor assembly. The sensor system may have a wireless transmitter which transmits measurement data to a receiver which can process and display information based on the measurements.

0005The process of applying the sensor to the person is important for such a system to be effective and user friendly. The application process can result in the sensor assembly being attached to the person in a state where it is capable of sensing glucose level information, communicating the glucose level information to the transmitter, and transmitting the glucose level information to the receiver.

0006The analyte sensor can be placed into subcutaneous tissue. A user can actuate an applicator to insert the analyte sensor into its functional location. This transcutaneous insertion can lead to incomplete sensor insertion, improper sensor insertion, exposed needles, or unnecessary pain. Thus, there is a need for a system that more reliably enables transcutaneous sensor insertion while being easy to use and relatively pain-free.

0007<patcit id="pcit0003" dnum="US20140187876A1"><text>US-A1-2014/0187876</text></patcit> discloses a sensor inserting device including a device body, a movement mechanism which inserts a detector and an insertion needle into a body of a patient by moving a sensor with the insertion needle, and a dwelling member which is arranged on a moving path of the sensor and attached to the sensor by movement of the sensor caused by the movement mechanism. The dwelling member is allowed to dwell on the skin of the patient with the sensor and the transmitter connected at a location in which the detector is inserted into the body of the patient.

SUMMARY

0008The present invention provides a sensor inserter assembly as recited in claim 1. Optional features of the sensor inserter assembly are recited in the dependent claims. Various systems and methods described herein enable reliable, simple, and pain-minimizing transcutaneous insertion of analyte sensors. Some embodiments are a system for applying an on-skin sensor assembly to skin of a host. Systems can comprise a telescoping assembly having a first portion configured to move distally relative to a second portion from a proximal starting position to a distal position along a path; a sensor module coupled to the first portion, the sensor module including a sensor, electrical contacts, and a seal; and/or a base coupled to the second portion such that the base protrudes from a distal end of the system. The base can comprise an adhesive configured to couple the sensor module to the skin. The moving of the first portion to the distal position can couple the sensor module to the base. The sensor can be an analyte sensor; a glucose sensor; any sensor described herein; and/or any other suitable sensor.

0009In some embodiments (i.e., optional and independently combinable with any of the aspects and embodiments identified herein), the sensor module can include a sensor module housing. The sensor module housing can include a first flex arm.

0010In some embodiments (i.e., optional and independently combinable with any of the aspects and embodiments identified herein), the sensor can be located within the second portion while the base protrudes from the distal end of the system such that the system is configured to couple the sensor to the base via moving the first portion distally relative to the second portion.

0011In several embodiments (i.e., optional and independently combinable with any of the aspects and embodiments identified herein), the sensor can be coupled to the sensor module while the first portion is located in the proximal starting position.

0012In some embodiments, a needle is coupled to the first portion (of the telescoping assembly) such that the sensor and the needle move distally relative to the base and relative to the second portion. The system can comprise a needle release mechanism configured to retract the needle proximally.

0013In several embodiments, the base comprises a distal protrusion having a first hole. The distal protrusion can be configured to reduce a resistance of the skin to piercing. The sensor can pass through the first hole of the distal protrusion.

0014In some embodiments, a needle having a slot passes through the first hole of the distal protrusion. A portion of the sensor can be located in the slot such that the needle is configured to move distally relative to the base without dislodging the portion of the sensor from the slot.

0015In several embodiments, the distal protrusion is convex such that the distal protrusion is configured to tension the skin while the first portion moves distally relative to the second portion to prepare the skin for piercing. The distal protrusion can be shaped like a dome.

0016In some embodiments, the adhesive comprises a second hole. The distal protrusion can be located at least partially within the second hole such that the distal protrusion can tension at least a portion of the skin beneath the second hole.

0017In several embodiments, the adhesive covers at least a majority of the distal protrusion. The adhesive can cover at zero percent, at least 30 percent, at least 70 percent, and/or less than 80 percent of the distal protrusion. The distal protrusion can protrude at least 0.5 millimeters, less than 3 millimeters, and/or less than 5 millimeters.

0018In some embodiments, a sensor module is coupled to the first portion and is located at least 3 millimeters and/or at least 5 millimeters from the base while the first portion is in the proximal starting position. The system can be configured such that moving the first portion to the distal position couples the sensor module to the base.

0019In several embodiments, the sensor is already coupled to the sensor module while the first portion is located in the proximal starting position. For example, the sensor can be coupled to the sensor module at the factory (e.g., prior to the user opening a sterile barrier). The sensor can be located within the second portion while the base protrudes from the distal end of the system.

0020In some embodiments, the sensor is coupled to a sensor module. During a first portion of the path, the sensor module can be immobile relative to the first portion, and the base can be immobile relative to the second portion. During a second portion of the path, the system can be configured to move the first portion distally relative to the second portion to move the sensor module towards the base, couple the sensor module to the base, and/or enable the coupled sensor module and the base to detach from the telescoping assembly.

0021In several embodiments, a sensor module is coupled to the sensor. The system comprises a vertical central axis oriented from a proximal end to the distal end of the system. The sensor module can comprise a first flex arm that is oriented horizontally and is coupled to the base. The first flex arm can extend from an outer perimeter of the sensor module.

0022In some embodiments, the base comprises a first proximal protrusion coupled to the first flex arm to couple the sensor module to the base. A first horizontal locking protrusion can be coupled to an end portion of the first flexible arm. A second horizontal locking protrusion can be coupled to the first proximal protrusion of the base. The first horizontal locking protrusion can be located distally under the second horizontal locking protrusion to secure the sensor module to the base. The system can be configured such that moving the first portion of the telescoping assembly to the distal position causes the first flex arm to bend to enable the first horizontal locking protrusion to move distally relative to the second horizontal locking protrusion.

0023In several embodiments, the base comprises a second proximal protrusion coupled to a second flex arm of the sensor module. The first flex arm can be located on an opposite side of the sensor module relative to the second flex arm.

0024In some embodiments, a sensor module is coupled to the sensor. The system can comprise a vertical central axis oriented from a proximal end to the distal end of the system. The base can comprise a first flex arm that is oriented horizontally and is coupled to the sensor module. The sensor module can comprise a first distal protrusion coupled to the first flex arm to couple the sensor module to the base.

0025In several embodiments, a first horizontal locking protrusion is coupled to an end portion of the first flexible arm, a second horizontal locking protrusion is coupled to the first distal protrusion of the sensor module, and the second horizontal locking protrusion is located distally under the first horizontal locking protrusion to secure the sensor module to the base. The system can be configured such that moving the first portion of the telescoping assembly to the distal position causes the first flex arm to bend to enable the second horizontal locking protrusion to move distally relative to the first horizontal locking protrusion.

0026In some embodiments, the sensor module comprises a second distal protrusion coupled to a second flex arm of the base. The first distal protrusion can be located on an opposite side of the sensor module relative to the second distal protrusion.

0027In several embodiments, a sensor module is coupled to the sensor. The first portion can comprise a first flex arm and a second flex arm that protrude distally and latch onto the sensor module to releasably secure the sensor module to the first portion while the first portion is in the proximal starting position. The sensor module can be located remotely from the base while the first portion is in the proximal starting position (e.g., such that the sensor module does not touch the base).

0028In some embodiments, the sensor module is located within the second portion while the base protrudes from the distal end of the system such that the system is configured to couple the sensor module to the base via moving the first portion distally relative to the second portion.

0029In several embodiments, the system comprises a vertical central axis oriented from a proximal end to the distal end of the system. The first and second flex arms of the first portion can secure the sensor module to the first portion such that the sensor module is releasably coupled to the first portion with a first vertical holding strength. The sensor module can comprise a third flex arm coupled with a first proximal protrusion of the base such that the sensor module is coupled to the base with a second vertical holding strength.

0030In some embodiments, the second vertical holding strength is greater than the first vertical holding strength such that continuing to push the first portion distally once the sensor module is coupled to the base overcomes the first and second flex arms of the first portion to detach the sensor module from the first portion. The third flex arm can extend from an outer perimeter of the sensor module.

0031In several embodiments, the base protrudes from the distal end of the system while the first portion of the telescoping assembly is located in the proximal starting position and the sensor is located remotely relative to the base such that the system is configured to couple the sensor to the base via moving the first portion distally relative to the second portion. The base can comprise a first radial protrusion releasably coupled with a first vertical holding strength to a second radial protrusion of the second portion of the telescoping assembly.

0032In some embodiments, the first radial protrusion protrudes inward and the second radial protrusion protrudes outward. The system can be configured such that moving the first portion to the distal position moves the second radial protrusion relative to the first radial protrusion to detach the base from the telescoping assembly.

0033In several embodiments, the first portion of the telescoping assembly comprises a first arm that protrudes distally, the second portion of the telescoping assembly comprises a second flex arm that protrudes distally, and the system is configured such that moving the first portion from the proximal starting position to the distal position along the path causes the first arm to deflect the second flex arm and thereby detach the second flex arm from the base to enable the base to decouple from the telescoping assembly. When the first portion is in the proximal starting position, the first arm of the first portion can be at least partially vertically aligned with the second flex arm of the second portion to enable the first arm to deflect the second flex arm as the first portion is moved to the distal position.

0034In some embodiments, when the first portion is in the proximal starting position, at least a section of the first arm is located directly over the second flex arm to enable the first arm to deflect the second flex arm as the first portion is moved to the distal position.

0035In several embodiments, the second flex arm comprises a first horizontal protrusion, and the base comprises a second horizontal protrusion latched with the first horizontal protrusion to couple the base to the second portion of the telescoping assembly. The first arm of the first portion can deflect the second flex arm of the second portion to unlatch the base from the second portion of the telescoping assembly.

0036In some embodiments, the system is configured to couple the sensor to the base at a first position, and the system is configured to detach the base from the telescoping assembly at a second position that is distal relative to the first position.

0037In several embodiments, a third flex arm couples the sensor to the base at a first position, the second flex arm detaches from the base at a second position, and the second position is distal relative to the first position such that the system is configured to secure the base to the telescoping assembly until after the sensor is secured to the base.

0038In some embodiments, the base protrudes from the distal end of the system while the first portion of the telescoping assembly is located in the proximal starting position and the sensor is located remotely relative to the base. The system can further comprise a spring configured to retract a needle. The needle can be configured to facilitate inserting the sensor into the skin. When the first portion is in the proximal starting position, the spring can be in a first compressed state. The system can be configured such that moving the first portion distally from the proximal starting position further increases a compression of the spring. The first compressed state places the first and second portions in tension.

0039In several embodiments, a system is configured to apply an on-skin sensor assembly to the skin of a host (i.e., a person). The system can include a telescoping assembly having a first portion configured to move distally relative to a second portion from a proximal starting position to a distal position along a path; a sensor coupled to the first portion; and/or a latch configurable to impede a needle from moving proximally relative to the first portion. The sensor can be an analyte sensor; a glucose sensor; any sensor described herein; and/or any other suitable sensor.

0040In some embodiments, the first portion is releasably secured in the proximal starting position by a securing mechanism that impedes moving the first portion distally relative to the second portion. The system can be configured such that prior to reaching the distal position, moving the first portion distally relative to the second portion releases the latch thereby causing the needle to retract proximally into the system. The system can be configured such that moving the first portion distally relative to the second portion (e.g., moving the first portion to the distal position) releases the latch thereby causing the needle to retract proximally into the system. The securing mechanism can be an interference between the first portion and the second portion of the telescoping assembly.

0041In several embodiments, a first force profile is measured along the path. The first force profile can comprise a first magnitude coinciding with overcoming the securing mechanism; a third magnitude coinciding with releasing the latch; and a second magnitude coinciding with an intermediate portion of the path that is distal relative to overcoming the securing mechanism and proximal relative to releasing the latch.

0042In some embodiments, the second magnitude is less than the first and third magnitudes such that the system is configured to promote needle acceleration during the intermediate portion of the path to enable a suitable needle speed (e.g., a sufficiently high needle speed) at a time the needle first pierces the skin.

0043In several embodiments, the first magnitude is at least 100 percent greater than the second magnitude. The first magnitude can be greater than the third magnitude such that the system is configured to impede initiating a sensor insertion cycle unless a user is applying enough force to release the latch. The first magnitude can be at least 50 percent greater than the third magnitude.

0044In some embodiments, an intermediate portion of the path is distal relative to overcoming the securing mechanism and proximal relative to releasing the latch. The system can further comprise a second force profile coinciding with the intermediate portion of the path. A proximal millimeter of the second force profile can comprise a lower average force than a distal millimeter of the second force profile in response to compressing a spring configured to enable the system to retract the needle into the telescoping assembly.

0045In several embodiments, a first force profile is measured along the path. The first force profile can comprise a first average magnitude coinciding with moving distally past a proximal half of the securing mechanism and a second average magnitude coinciding with moving distally past a distal half of the securing mechanism. The first average magnitude can be greater than the second average magnitude such that the system is configured to impede initiating a sensor insertion cycle unless a user is applying enough force to complete the sensor insertion cycle (e.g., drive the needle and/or the sensor to the intended insertion depth).

0046In some embodiments, a first force peak (coinciding with moving distally past the proximal half of the securing mechanism) is at least 25 percent higher than the second average magnitude.

0047In several embodiments, a first force profile is measured along the path. The first force profile can comprise a first magnitude coinciding with overcoming the securing mechanism and a subsequent magnitude coinciding with terminating the securing mechanism. The first magnitude can comprise a proximal vector and the subsequent magnitude can comprise a distal vector.

0048In some embodiments, the securing mechanism can comprise a radially outward protrusion extending from the first portion. The radially outward protrusion can be located proximally relative to a proximal end of the second portion while the telescoping assembly is in the proximal starting position. The radially outward protrusion can be configured to cause the second portion to deform elliptically to enable the first portion to move distally relative to the second portion.

0049In several embodiments, the securing mechanism comprises a radially outward protrusion of the first portion that interferes with a radially inward protrusion of the second portion such that the securing mechanism is configured to cause the second portion to deform elliptically to enable the first portion to move distally relative to the second portion.

0050In some embodiments, the needle is retractably coupled to the first portion by a needle holder configured to resist distal movement of the first portion relative to the second portion. The securing mechanism can comprise a flexible arm of the second portion. The flexible arm can be releasably coupled to the needle holder to releasably secure the first portion to the second portion in the proximal starting position.

0051In several embodiments, the securing mechanism comprises a frangible coupling between the first portion and the second portion while the first portion is in the proximal starting position. The system can be configured such that moving the first portion to the distal position breaks the frangible coupling.

0052In some embodiments, the securing mechanism comprises a magnet that releasably couples the first portion to the second portion while the first portion is in the proximal starting position. The magnet can be attracted to a metal element coupled to the first portion or the second portion of the telescoping assembly.

0053In several embodiments, an electric motor drives the first portion distally relative to the second portion. The electric motor can be configured to move the needle in the skin.

0054In some embodiments, an on-skin sensor system is configured for transcutaneous glucose monitoring of a host. The system can comprise a sensor module housing, in which the sensor module housing can include a first flex arm; a sensor having a first section configured for subcutaneous sensing and a second section mechanically coupled to the sensor module housing; an electrical interconnect mechanically coupled to the sensor module housing and electrically coupled to the sensor; and/or a base coupled to the first flex arm of the sensor module housing. The base can have an adhesive configured to couple the base to the skin of the host. The sensor can be an analyte sensor; a glucose sensor; any sensor described herein; and/or any other suitable sensor.

0055In several embodiments, the electrical interconnect comprises a spring. The spring can comprise a conical portion and/or a helical portion.

0056In some embodiments, the sensor module housing comprises at least two proximal protrusions located around a perimeter of the spring. The proximal protrusions can be configured to help orient the spring. A segment of the sensor can be located between the proximal protrusions.

0057In several embodiments, the sensor module housing is mechanically coupled to a base having an adhesive configured to couple the base to skin of the host.

0058In some embodiments, the proximal protrusions orient the spring such that coupling an electronics unit to the base presses the spring against a first electrical contact of the electronics unit and a second electrical contact of the sensor to electrically couple the sensor to the electronics unit.

0059In several embodiments, the sensor module housing comprises a first flex arm that is oriented horizontally and is coupled to the base. The first flex arm can extend from an outer perimeter of the sensor module housing. The base can comprise a first proximal protrusion coupled to the first flex arm to couple the sensor module housing to the base.

0060In some embodiments, the electrical interconnect comprises a leaf spring, which can include one metal layer or multiple metal layers. The leaf spring can be a cantilever spring.

0061In some embodiments, the sensor module housing comprises a proximal protrusion having a channel in which at least a portion of the second section of the sensor is located. The channel can position a first area of the sensor such that the first area is electrically coupled to the leaf spring.

0062In some embodiments, the leaf spring arcs away from the first area and protrudes proximally to electrically couple with an electronics unit. At least a portion of the leaf spring can form a "W" shape. At least a portion of the leaf spring forms a "C" shape.

0063In several embodiments, the leaf spring bends around the proximal protrusion. The leaf spring can bend at least 120 degrees and/or at least 160 degrees around the proximal protrusion. The leaf spring can protrude proximally to electrically couple with an electronics unit.

0064In some embodiments, a seal is configured to impede fluid ingress to the leaf spring. The sensor module housing can be mechanically coupled to a base. The base can have an adhesive configured to couple the base to skin of the host.

0065In several embodiments, the leaf spring is oriented such that coupling an electronics unit to the base presses the leaf spring against a first electrical contact of the electronics unit and against a second electrical contact of the sensor to electrically couple the sensor to the electronics unit. A proximal height of the seal can be greater than a proximal height of the leaf spring such that the electronics unit contacts the seal prior to contacting the leaf spring.

0066In some embodiments, the sensor module housing comprises a first flex arm that is oriented horizontally and is coupled to the base. The first flex arm can extend from an outer perimeter of the sensor module housing. The base can comprise a first proximal protrusion coupled to the first flex arm to couple the sensor module housing to the base.

0067In several embodiments, the sensor module housing comprises a channel in which at least a portion of the second section of the sensor is located. A distal portion of the leaf spring can be located in the channel such that a proximal portion of the leaf spring protrudes proximally out the channel. The sensor module housing can comprise a groove that intersects the channel. The leaf spring can comprise a tab located in the groove to impede rotation of the leaf spring.

0068In some embodiments, the sensor module housing is mechanically coupled to a base that has an adhesive configured to couple the base to skin of the host. The sensor module housing can comprise a first flex arm that is oriented horizontally and is coupled to the base. The first flex arm can extend from an outer perimeter of the sensor module housing. The base can comprise a first proximal protrusion coupled to the first flex arm to couple the sensor module housing to the base.

0069In several embodiments, electrical interconnects (such as springs or other types of interconnects) comprises a resistance of less than 100 ohms and/or less than 5 ohms. Electrical interconnects can comprise a compression force of less than 0.45359 kg (one pound) over an active compression range.

0070In some embodiments, electrical interconnects may require a compression force of less than 0.45359 kg (one pound) to compress the spring 20 percent from a relaxed position, which is a substantially uncompressed position. In some embodiments, electrical interconnects may require a compression force of less than 0.45359 kg (one pound) to compress the spring 25 percent from a relaxed position, which is a substantially uncompressed position. In some embodiments, electrical interconnects may require a compression force of less than 0.45359 kg (one pound) to compress the spring 30 percent from a relaxed position, which is a substantially uncompressed position. In some embodiments, electrical interconnects may require a compression force of less than 0.45359 kg (one pound) to compress the spring 50 percent from a relaxed position, which is a substantially uncompressed position.

0071In several embodiments, the spring is configured such that compressing the spring 25 percent from a relaxed position requires a force of at least 0.02268 kg (0.05 pounds) and less than 0.2268 kg (0.5 pounds), and requires moving an end of the spring at least 0.1 millimeter and less than 1.1 millimeter.

0072In some embodiments, a system for applying an on-skin sensor assembly to a skin of a host comprises a telescoping assembly having a first portion configured to move distally relative to a second portion from a proximal starting position to a distal position along a path; a sensor coupled to the first portion; and a base comprising adhesive configured to couple the sensor to the skin. The telescoping assembly can further comprise a third portion configured to move distally relative to the second portion.

0073In some embodiments, a first spring is positioned between the third portion and the second portion such that moving the third portion distally relative to the second portion compresses the first spring. In the proximal starting position of the telescoping assembly, the first portion can be locked to the second portion. The system can be configured such that moving the third portion distally relative to the second portion unlocks the first portion from the second portion.

0074In several embodiments, a first proximal protrusion having a first hook passes through a first hole in the second portion to lock the first portion to the second portion. The third portion can comprise a first distal protrusion. The system can be configured such that moving the third portion distally relative to the second portion engages a ramp to bend the first proximal protrusion to unlock the first portion from the second portion.

0075In some embodiments, the sensor is located within the second portion while the base protrudes from the distal end of the system such that the system is configured to couple the sensor to the base by moving the first portion distally relative to the second portion.

0076In several embodiments, a sensor module is coupled to a distal portion of the first portion such that moving the first portion to the distal position couples the sensor module to the base. The sensor can be coupled to the sensor module while the first portion is located in the proximal starting position.

0077In some embodiments, the system is configured such that moving the third portion distally relative to the second portion unlocks the first portion from the second portion and locks the third portion to the second portion.

0078In several embodiments, the system comprises a first protrusion that couples with a hole of at least one of the second portion and the third portion to lock the third portion to the second portion.

0079In some embodiments, the system comprises a second protrusion that couples with a hole of at least one of the first portion and the second portion to lock the first portion to the second portion in response to moving the first portion distally relative to the second portion.

0080In several embodiments, a first spring is positioned between the third portion and the second portion such that moving the third portion distally relative to the second portion compresses the first spring and unlocks the first portion from the second portion, which enables the compressed first spring to push the first portion distally relative to the second portion, which pushes at least a portion of the sensor out of the distal end of the system and triggers a needle retraction mechanism to enable a second spring to retract a needle.

0081In some embodiments, a system for applying an on-skin assembly to a skin of a host is provided. Advantageously, the system includes a sensor inserter assembly having a needle assembly, a sensor module, a base, an actuation member, and a retraction member, the sensor inserter assembly having an initial configuration in which at least the sensor module is disposed in a proximal starting position, the sensor inserter assembly further having a deployed configuration in which at least the sensor module and the base are disposed at a distal applied position. Preferably, the actuation member is configured to, once activated, cause the needle assembly to move a proximal starting position to a distal insertion position, and the retraction member is configured to, once activated, cause the needle assembly to move from the distal insertion position to a proximal retracted position.

0082The sensor module may comprise a sensor and a plurality of electrical contacts. In the initial configuration, the sensor can be electrically coupled to at least one of the electrical contacts. Optionally, in the initial configuration, the actuation member is in an unenergized state. In some embodiments, the actuation member can be configured to be energized by a user before being activated. In alternative embodiments, in the initial configuration, the actuation member is in an energized state.

0083In several embodiments the actuation member can include a spring. In an initial configuration, the spring can be in an unstressed state. In alternative embodiments, in the initial configuration, the spring is in a compressed state.

0084In some embodiments, the sensor inserter assembly may include a first portion and a second portion, the first portion being fixed, at least in an axial direction, with respect to the second portion at least when the sensor inserter assembly is in the initial configuration, the first portion being movable in at least a distal direction with respect to the second portion after activation of the actuation member. The first portion may be operatively coupled to the needle assembly so as to secure the needle assembly in the proximal starting position before activation of the actuation member and to urge the needle assembly toward the distal insertion position after activation of the actuation member.

0085In several embodiments, the retraction member is in an unenergized state when in the initial configuration. Advantageously, the retraction member is configured to be energized by the movement of the needle assembly from the proximal starting position to the distal insertion position. In the initial configuration, the retraction member may be in an energized state.

0086In still other embodiments, the retraction member comprises a spring. The spring may be integrally formed with the needle assembly. The spring may be operatively coupled to the needle assembly. In the initial configuration, the spring may be in an unstressed state. In other embodiments, in the initial configuration, the spring is in compression.

0087In some aspects, in the second configuration, the spring is in compression. In still other embodiments, in the second configuration, the spring is in tension.

0088In some embodiments, the sensor inserter assembly can further include a third portion, the third portion being operatively coupled to the first portion. The actuation member may be integrally formed with the third portion in certain embodiments. Optionally, the actuation member is operatively coupled to the third portion.

0089In some embodiments, the sensor inserter assembly includes interengaging structures configured to prevent movement of the first portion in the distal direction relative to the second portion until the interengaging structures are decoupled. Advantageously, the decoupling of the interengaging structures may activate the actuation member. In other embodiments, the interengaging structures may include a proximally extending tab of the first portion and a receptacle of the second portion configured to receive the proximally extending tab. Optionally, the sensor inserter assembly can include a decoupling member configured to decouple the interengaging structures. The decoupling member may have a distally extending tab of the third portion.

0090In yet other embodiments, the sensor inserter assembly can include interengaging structures configured to prevent proximal movement of the third portion with respect to the first portion. These interengaging structures may include a distally-extending latch of the third portion and a ledge of the first portion configured to engage the distally-extending latch.

0091In certain embodiments, the sensor inserter assembly can include interengaging structures configured to prevent proximal movement of the needle assembly at least when the needle assembly is in the distal insertion position. The interengaging structures can have radially-extending release features of the needle assembly and an inner surface of the first portion configured to compress the release features. Optionally, the sensor inserter assembly includes a decoupling member configured to disengage the interengaging structures of the first portion and the needle assembly. The decoupling member may include an inner surface of the second portion configured to further compress the release features. Advantageously, the system may further include a trigger member configured to activate the actuation member. The trigger member may be operatively coupled to the third portion. The trigger member may be integrally formed with the third portion. The trigger member may include a proximally-extending button. Alternatively, the trigger member may include a radially-extending button. The trigger member may be configured to decouple the interengaging structure of the first portion and the third portion.

0092In some embodiments, the system may further include a releasable locking member configured to prevent activation of the actuation member until the locking member is released. The releasable locking member may be configured to prevent proximal movement of the third portion with respect to the first portion until the locking member is released. The releasable locking member may include a proximally-extending tab of the first portion and a latch feature of the third portion configured to receive the proximally-extending tab. Advantageously, the releasable locking member is configured to prevent energizing of the sensor inserter assembly. In other aspects, the releasable locking member is configured to prevent energizing of the actuation member.

0093Embodiments may further include a system for applying an on-skin component to a skin of a host, the system may include a sensor inserter assembly having an on-skin component being movable in at least a distal direction from a proximal position to a distal position, a first securing feature configured to releasably secure the on-skin component in the proximal position, a second securing feature configured to secure the on-skin component in the distal position, and a first resistance configured to prevent movement of the on-skin component in a proximal direction at least when the on-skin component is in the distal position.

0094The first resistance feature can be configured to prevent movement of the on-skin component in a proximal direction when the on-skin component is secured in the distal position. In some embodiments, the first securing feature is configured to releasably secure the on-skin component to a needle assembly. The on-skin component may have a sensor module. The sensor module may include a sensor and a plurality of electrical contacts. Optionally, the sensor is electrically coupled to at least one of the electrical contacts, at least when the sensor inserter assembly is in the first configuration.

0095In some embodiments, the on-skin component comprises a base. The on-skin component may include a transmitter. The second securing feature can be configured to secure the on-skin component to a second on-skin component.

0096In other embodiments, the sensor inserter assembly includes at least one distally-extending leg, and wherein the first securing feature comprises an adhesive disposed on a distally-facing surface of the leg. The sensor inserter assembly may include at least one distally-extending member, and wherein the first securing feature comprises a surface of the distally-extending member configured to frictionally engage with a corresponding structure of the on-skin component. The corresponding structure of the on-skin component may include an elastomeric member. Optionally, the distally-extending member includes at least one leg of the sensor inserter assembly. The distally-extending member may include a needle.

0097In some embodiments of the system, the second securing feature includes an adhesive disposed on a distally-facing surface of the on-skin component. The second securing feature may have an elastomeric member configured to receive the on-skin component.

0098In other embodiments, the first resistance feature includes a distally-facing surface of the sensor inserter assembly. The first resistance feature may be distal to an adhesive disposed on a distally-facing surface of the on-skin component.

0099The system may further include a pusher configured to move the on-skin component from the proximal position to the distal position. Optionally, the system can further include a decoupling feature configured to decouple the pusher from the on-skin component at least after the on-skin component is in the distal position. The decoupling feature may have a frangible portion of the pusher. Optionally, the decoupling feature comprises a frangible portion of the on-skin component.

0100The system may further comprise a sensor assembly configured to couple with the on-skin component, wherein a third securing feature is configured to releasably secure the sensor assembly in a proximal position, and wherein a fourth securing feature is configured to secure the sensor assembly to the on-skin component.

0101Any of the features of each embodiment is applicable to all aspects and embodiments identified herein. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

0102These and other features, aspects, and advantages are described below with reference to the drawings, which are intended to illustrate, but not to limit, the invention. In the drawings, like reference characters denote corresponding features consistently throughout similar embodiments. <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> illustrates a schematic view of a continuous analyte sensor system, according to some embodiments.</li><li><figref idref="f0002">Figure 2</figref> illustrates a perspective view of an applicator system, according to some embodiments.</li><li><figref idref="f0002">Figure 3</figref> illustrates a cross-sectional side view of the system from <figref idref="f0002">Figure 2</figref>, according to some embodiments.</li><li><figref idref="f0003">Figure 4</figref> illustrates a perspective view of an on-skin sensor assembly, according to some embodiments.</li><li><figref idref="f0003">Figures 5 and 6</figref> illustrate perspective views of a transmitter coupled to a base via mechanical interlocks, according to some embodiments.</li><li><figref idref="f0004 f0005 f0006">Figures 7-11</figref> illustrate cross-sectional side views of the applicator system from <figref idref="f0002">Figure 3</figref>, according to some embodiments.</li><li><figref idref="f0006">Figure 12A</figref> illustrates a cross-sectional side view of a portion of the applicator system from <figref idref="f0002">Figure 3</figref>, according to some embodiments.</li><li><figref idref="f0006">Figure 12B</figref> illustrates a cross-sectional side view of a base that can be used with the applicator system shown in <figref idref="f0002">Figure 3</figref>, according to some embodiments.</li><li><figref idref="f0007">Figure 13</figref> illustrates a perspective view of a portion of the adhesive from <figref idref="f0003">Figure 4</figref>, according to some embodiments.</li><li><figref idref="f0007">Figure 14</figref> illustrates a perspective view of a portion of the applicator system from <figref idref="f0002">Figure 3</figref>, according to some embodiments.</li><li><figref idref="f0008">Figures 15 and 16</figref> illustrate perspective views of cross sections of portions of the system shown in <figref idref="f0004">Figure 7</figref>, according to some embodiments.</li><li><figref idref="f0009">Figure 17</figref> illustrates a cross-sectional view of the first portion of the telescoping assembly from <figref idref="f0004">Figure 7</figref>, according to some embodiments.</li><li><figref idref="f0009">Figures 18</figref> and <figref idref="f0010">19</figref> illustrate perspective views of portions of the applicator system from <figref idref="f0004">Figure 7</figref>, according to some embodiments.</li><li><figref idref="f0010">Figures 20</figref> and <figref idref="f0011">21</figref> illustrate perspective views of the needle after being removed from the telescoping assembly of <figref idref="f0004">Figure 7</figref>, according to some embodiments.</li><li><figref idref="f0011">Figure 22</figref> illustrates a perspective view of a cover of the telescoping assembly of <figref idref="f0004">Figure 7</figref>, according to some embodiments.</li><li><figref idref="f0012">Figure 23</figref> illustrates a schematic view of force profiles, according to some embodiments.</li><li><figref idref="f0012">Figure 24</figref> illustrates a cross-sectional side view of a portion of an applicator system, according to some embodiments.</li><li><figref idref="f0013">Figure 25</figref> illustrates a cross-sectional side view of a portion of a securing mechanism, according to some embodiments.</li><li><figref idref="f0013">Figure 26</figref> illustrates a top view of a ring, according to some embodiments.</li><li><figref idref="f0013">Figure 27</figref> illustrates a perspective view of a securing mechanism, according to some embodiments.</li><li><figref idref="f0014">Figure 28</figref> illustrates a cross-sectional perspective view of telescoping assembly with a motor, according to some embodiments.</li><li><figref idref="f0014">Figures 29</figref> and <figref idref="f0015">30</figref> illustrate cross-sectional side views of telescoping assemblies with a motor, according to some embodiments.</li><li><figref idref="f0015">Figure 31</figref> illustrates a side view of a telescoping assembly that causes rotational movement, according to some embodiments.</li><li><figref idref="f0016">Figure 32</figref> illustrates a cross-sectional perspective view of a telescoping assembly with a downward locking feature, according to some embodiments.</li><li><figref idref="f0016">Figure 33</figref> illustrates a perspective view of an on-skin senor assembly just before the electronics unit is coupled to the base, according to some embodiments.</li><li><figref idref="f0017">Figures 34 and 35</figref> illustrate perspective views of sensor modules that have springs, according to some embodiments.</li><li><figref idref="f0017">Figure 36</figref> illustrates a cross-sectional perspective view of a portion of a sensor module, according to some embodiments.</li><li><figref idref="f0018">Figure 37</figref> illustrates a perspective view of a sensor module that has springs, according to some embodiments.</li><li><figref idref="f0018">Figure 38</figref> illustrates a cross-sectional perspective view of a portion of a sensor module, according to some embodiments.</li><li><figref idref="f0019">Figure 39</figref> illustrates a perspective view of a sensor module, according to some embodiments.</li><li><figref idref="f0019">Figure 40</figref> illustrates a cross-sectional perspective view of assembly that has an offset, according to some embodiments.</li><li><figref idref="f0020">Figure 41</figref> illustrates a side view of a sensor, according to some embodiments.</li><li><figref idref="f0020">Figure 42</figref> illustrates a bottom view of a needle, according to some embodiments.</li><li><figref idref="f0020">Figure 43</figref> illustrates a front view of a needle, according to some embodiments.</li><li><figref idref="f0021">Figure 44</figref> illustrates a cross-sectional perspective view of an applicator system, according to some embodiments.</li><li><figref idref="f0021">Figure 45</figref> illustrates a cross-sectional perspective view of a portion of an applicator system, according to some embodiments.</li><li><figref idref="f0022">Figure 46</figref> illustrates a perspective view of a portion of an applicator system, according to some embodiments.</li><li><figref idref="f0022">Figure 47</figref> illustrates a perspective view of a sensor module, according to some embodiments.</li><li><figref idref="f0023">Figure 48</figref> illustrates a cross-sectional perspective view of an applicator system, according to some embodiments.</li><li><figref idref="f0023">Figure 49</figref> illustrates a cross-sectional perspective view of a proximal portion of a telescoping assembly, according to some embodiments.</li><li><figref idref="f0023">Figure 50</figref> illustrates a perspective view of a distal portion of a telescoping assembly, according to some embodiments.</li><li><figref idref="f0024">Figure 51</figref> illustrates a perspective view of a needle with adhesive, according to some embodiments.</li><li><figref idref="f0024">Figure 52</figref> illustrates a perspective view of a needle that has two separate sides, according to some embodiments.</li><li><figref idref="f0024">Figure 53</figref> illustrates a cross-sectional top view of the needle shown in <figref idref="f0024">Figure 52</figref>, according to some embodiments.</li><li><figref idref="f0024">Figure 54</figref> illustrates a perspective view of a needle that has a ramp, according to some embodiments.</li><li><figref idref="f0025">Figure 55</figref> illustrates a cross-sectional top view of four needles, according to some embodiments.</li><li><figref idref="f0025 f0026">Figures 56-58</figref> illustrate cross-sectional side views of a system that is similar to the embodiment shown in <figref idref="f0004">Figure 7</figref> except that the system does not include a needle, according to some embodiments.</li><li><figref idref="f0027">Figure 59</figref> illustrates a cross-sectional side view of a system that is similar to the embodiment shown in <figref idref="f0004">Figure 7</figref> except for the starting position and the movement of the base, according to some embodiments.</li><li><figref idref="f0027">Figure 60</figref> illustrates a perspective view of a system having a cover, according to some embodiments.</li><li><figref idref="f0028 f0029">Figures 61-63</figref> illustrate cross-sectional perspectives views of a system that is similar to the embodiment shown in <figref idref="f0004">Figure 7</figref> except that the telescoping assembly includes an extra portion, according to some embodiments.</li><li><figref idref="f0029">Figure 64</figref> illustrates a cross-sectional side view of the system shown in <figref idref="f0028 f0029">Figures 61-63</figref>, according to some embodiments.</li><li><figref idref="f0030">Figure 65</figref> illustrates a perspective view of portions of a sensor module, according to some embodiments.</li><li><figref idref="f0030">Figure 66</figref> illustrates a cross-sectional side view of the sensor module shown in <figref idref="f0030">Figure 65</figref>, according to some embodiments.</li><li><figref idref="f0031">Figure 67</figref> illustrates a perspective view of portions of a sensor module, according to some embodiments.</li><li><figref idref="f0031">Figure 68</figref> illustrates a top view of the sensor module shown in <figref idref="f0031">Figure 67</figref>, according to some embodiments.</li><li><figref idref="f0032">Figures 69 and 70</figref> illustrate perspective views of an electronics unit just before the electronics unit is coupled to a base, according to some embodiments.</li><li><figref idref="f0033">Figure 71</figref> illustrates a cross-sectional perspective view of an applicator system, according to some embodiments, in a resting state.</li><li><figref idref="f0033">Figure 72</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0033">Figure 71</figref>, with the actuation member energized.</li><li><figref idref="f0034">Figure 73</figref> illustrates a rotated cross-sectional perspective view of the applicator system of <figref idref="f0033">Figure 72</figref>.</li><li><figref idref="f0034">Figure 74</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0033">Figure 71</figref>, with the actuation member activated and with the needle assembly deployed in an insertion position.</li><li><figref idref="f0035">Figure 75</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0033">Figure 71</figref>, with the on-skin component in a deployed position and the needle assembly retracted.</li><li><figref idref="f0036">Figure 76</figref> illustrates a cross-sectional side view of another applicator system, according to some embodiments, in a resting state.</li><li><figref idref="f0036">Figure 77</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0036">Figure 76</figref>, with the actuation member energized.</li><li><figref idref="f0036">Figure 78</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0036">Figure 76</figref>, with the actuation member activated and with the needle assembly deployed in an insertion position.</li><li><figref idref="f0036">Figure 79</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0036">Figure 76</figref>, with the on-skin component in a deployed position and the needle assembly retracted.</li><li><figref idref="f0037">Figure 80</figref> illustrates a cross-sectional side view of another applicator system, according to some embodiments, in a resting state.</li><li><figref idref="f0037">Figure 81</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0037">Figure 80</figref>, with the actuation member energized.</li><li><figref idref="f0038">Figure 82</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0037">Figure 80</figref>, with the actuation member activated and with the needle assembly deployed in an insertion position.</li><li><figref idref="f0038">Figure 83</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0037">Figure 80</figref>, with the on-skin component in a deployed position and the needle assembly retracted.</li><li><figref idref="f0039">Figure 84</figref> illustrates a perspective view of the applicator system of <figref idref="f0037">Figure 80</figref>, with the first and third portions shown in cross section to better illustrate certain portions of the system, and in a resting state.</li><li><figref idref="f0039">Figure 85</figref> illustrates a perspective view of the applicator system of <figref idref="f0037">Figure 80</figref>, with the first and third portions shown in cross section to better illustrate certain portions of the system, and with the actuation member energized.</li><li><figref idref="f0040">Figure 86</figref> illustrates a cross-sectional side view of another applicator system, according to some embodiments, in a resting state in which the actuation member is already energized.</li><li><figref idref="f0040">Figure 87</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0040">Figure 86</figref>, with the actuation member activated and with the needle assembly deployed in an insertion position.</li><li><figref idref="f0040">Figure 88</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0040">Figure 86</figref>, with the on-skin component in a deployed position and the needle assembly retracted.</li><li><figref idref="f0041">Figure 89</figref> illustrates a cross-sectional side view of another applicator system, according to some embodiments, in a resting state in which the actuation member is already energized.</li><li><figref idref="f0041">Figure 90</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0040">Figure 86</figref>, with the actuation member activated and with the needle assembly deployed in an insertion position.</li><li><figref idref="f0041">Figure 91</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0040">Figure 86</figref>, with the on-skin component in a deployed position and the needle assembly retracted.</li><li><figref idref="f0042">Figure 92</figref> illustrates a side view of another applicator system, according to some embodiments, with a top trigger member, in a resting state.</li><li><figref idref="f0042">Figure 93</figref> illustrates a side view of the applicator system of <figref idref="f0042">Figure 92</figref>, after being cocked but before being triggered.</li><li><figref idref="f0043">Figure 94</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0042">Figure 92</figref>, in a resting state.</li><li><figref idref="f0043">Figure 95</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0042">Figure 92</figref> while being cocked.</li><li><figref idref="f0043">Figure 96</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0042">Figure 92</figref>, after being cocked but before being triggered.</li><li><figref idref="f0044">Figure 97</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0043">Figure 96</figref>.</li><li><figref idref="f0044">Figure 98</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0042">Figure 92</figref>, during triggering.</li><li><figref idref="f0045">Figure 99</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0042">Figure 92</figref>, after being triggered and with the needle assembly deployed in an insertion position.</li><li><figref idref="f0045">Figure 100</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0042">Figure 92</figref>, with the on-skin component in a deployed position and the needle assembly retracted.</li><li><figref idref="f0046">Figure 101</figref> illustrates a side view of another applicator system, according to some embodiments, with a side trigger member.</li><li><figref idref="f0046">Figure 102</figref> illustrates another side view of the applicator system of <figref idref="f0046">Figure 101</figref>, with the first and third portions shown in cross-section to illustrate the trigger mechanism.</li><li><figref idref="f0047">Figure 103</figref> illustrates a side view of another applicator system, according to some embodiments, with an integrated side trigger.</li><li><figref idref="f0047">Figure 104</figref> illustrates another side view of the applicator system of <figref idref="f0047">Figure 103</figref>, with the first and third portions shown in cross-section and with a portion of the second portion removed to illustrate the trigger mechanism.</li><li><figref idref="f0048">Figure 105</figref> illustrates a perspective view of another applicator system, according to some embodiments, with a safety feature.</li><li><figref idref="f0048">Figure 106</figref> illustrates a cross-sectional perspective view of a portion of the applicator system of <figref idref="f0048">Figure 105</figref>, with the safety feature in a locked configuration.</li><li><figref idref="f0049">Figure 107</figref> illustrates an enlarged view of the portion of the applicator system of <figref idref="f0048">Figure 106</figref>, with the safety feature in a locked configuration.</li><li><figref idref="f0049">Figure 108</figref> illustrates a cross-sectional perspective view of a portion of the applicator system of <figref idref="f0048">Figure 105</figref>, with the safety feature in a released configuration.</li><li><figref idref="f0049">Figure 109</figref> illustrates a cross-sectional perspective view of a portion of the applicator system of <figref idref="f0048">Figure 105</figref>, with the safety feature in a released configuration and with the third portion moved distally relative to the first portion.</li><li><figref idref="f0050">Figure 110</figref> illustrates a cross-sectional perspective view of an applicator system, according to some embodiments, in a resting and locked state, with the on-skin component secured in a proximal position.</li><li><figref idref="f0050">Figure 111</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0050">Figure 110</figref>, with the safety feature unlocked.</li><li><figref idref="f0051">Figure 112</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0050">Figure 110</figref>, with the actuation member energized.</li><li><figref idref="f0051">Figure 113</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0050">Figure 110</figref>, with the actuation member activated and with the needle assembly and on-skin component deployed in a distal position.</li><li><figref idref="f0051">Figure 114</figref> illustrates a cross-sectional perspective view of the applicator system of <figref idref="f0050">Figure 110</figref>, with the on-skin component in a deployed position and separated from the retracted needle assembly.</li><li><figref idref="f0052">Figure 115</figref> illustrates a perspective view of the needle assembly from the system of <figref idref="f0050">Figure 110</figref>, shown securing the on-skin component during deployment, with the base removed for purposes of illustration.</li><li><figref idref="f0052">Figure 116</figref> illustrates another perspective view of the needle assembly from the system of <figref idref="f0050">Figure 110</figref>, shown separated from the on-skin component, with the base removed for purposes of illustration.</li><li><figref idref="f0053">Figure 117</figref> illustrates a perspective view of a portion of the system of <figref idref="f0045">Figure 100</figref>.</li><li><figref idref="f0054">Figure 118</figref> illustrates a perspective view of the sensor module of <figref idref="f0045">Figure 100</figref>, before being coupled to the base.</li><li><figref idref="f0054">Figure 119</figref> illustrates a perspective view of the sensor module of <figref idref="f0045">Figure 100</figref>, after being coupled to the base.</li><li><figref idref="f0055">Figure 120</figref> illustrates a side view of an on-skin component and base, according to some embodiments, prior to coupling of the on-skin component to the base.</li><li><figref idref="f0055">Figure 121</figref> illustrates a perspective view of the on-skin component and base of <figref idref="f0055">Figure 120</figref>, prior to coupling of the on-skin component to the base.</li><li><figref idref="f0055">Figure 122</figref> illustrates a side view of the on-skin component and base of <figref idref="f0055">Figure 120</figref>, after coupling of the on-skin component to the base.</li><li><figref idref="f0056">Figure 123</figref> illustrates a perspective view of a portion of another applicator system, according to some embodiments, with an on-skin component coupled to a needle assembly in a proximal position.</li><li><figref idref="f0056">Figure 124</figref> illustrates a perspective view of the on-skin component and the needle assembly of <figref idref="f0056">Figure 123</figref>.</li><li><figref idref="f0057">Figure 125</figref> illustrates a perspective view of a portion of the applicator system shown in <figref idref="f0056">Figure 123</figref>, with the on-skin component separated from the needle assembly.</li><li><figref idref="f0058">Figure 126</figref> illustrates a perspective view of a portion of a securing member, shown securing an on-skin component.</li><li><figref idref="f0058">Figure 127</figref> illustrates a perspective view of a portion of the securing member of <figref idref="f0058">Figure 126</figref>, with the sensor module of the on-skin component shown in cross section, and illustrated with a decoupling feature of an applicator assembly, according to some embodiments.</li><li><figref idref="f0058">Figure 128</figref> illustrates a perspective view of the on-skin component of <figref idref="f0058">Figure 126</figref>, after decoupling of the on-skin component from the securing member.</li><li><figref idref="f0059">Figure 129</figref> illustrates a perspective view of a portion of an applicator assembly, according to some embodiments, with the second portion shown in cross section, and with a securing member shown securing an on-skin component in a proximal position.</li><li><figref idref="f0059">Figure 130</figref> illustrates a perspective view of a portion of the applicator assembly of <figref idref="f0059">Figure 129</figref>, shown with a portion of the securing member cut away to better illustrate the configuration of the securing member.</li><li><figref idref="f0060">Figure 131</figref> illustrates a perspective view of a portion of the applicator assembly of <figref idref="f0059">Figure 129</figref>, after decoupling of the on-skin component from the needle assembly, shown with portions of the on-skin component and the securing member cut away.</li><li><figref idref="f0061">Figure 132</figref> illustrates a perspective view of a portion of an applicator assembly, according to some embodiments, with the second portion shown in cross section, and with a securing member shown securing an on-skin component in a proximal position.</li><li><figref idref="f0061">Figure 133</figref> illustrates a perspective view of the needle assembly and on-skin component of <figref idref="f0061">Figure 132</figref>, after decoupling of the on-skin component from the needle assembly.</li><li><figref idref="f0062">Figure 134</figref> illustrates an exploded perspective view of a portion of an applicator assembly, according to some embodiments, with a securing member configured to releasably couple an on-skin component to a needle assembly.</li><li><figref idref="f0062">Figure 135</figref> illustrates a perspective view of a portion of the applicator assembly of <figref idref="f0062">Figure 134</figref>, with the needle assembly coupled to the on-skin component.</li><li><figref idref="f0062">Figure 136</figref> illustrates a perspective view of a portion of the applicator assembly of <figref idref="f0062">Figure 134</figref>, with the needle assembly decoupled from the on-skin component.</li><li><figref idref="f0063">Figure 137</figref> illustrates a perspective view of an applicator assembly, according to some embodiments, with an on-skin component releasably secured in a proximal position within the applicator assembly.</li><li><figref idref="f0063">Figure 138</figref> illustrates a perspective view of the applicator assembly of <figref idref="f0063">Figure 137</figref>, with the on-skin component released from securement.</li><li><figref idref="f0064">Figure 139</figref> illustrates a perspective view of the on-skin component of <figref idref="f0063">Figure 137</figref>, with the securing feature in a secured configuration.</li><li><figref idref="f0064">Figure 140</figref> illustrates a perspective view of the on-skin component of <figref idref="f0063">Figure 137</figref>, with the securing feature in a released configuration.</li><li><figref idref="f0065">Figure 141</figref> illustrates a cross-sectional perspective view of a portion of an applicator assembly, according to some embodiments, with the second and third portions shown in cross section, and showing a base coupled to an applicator.</li><li><figref idref="f0066">Figure 142</figref> illustrates a perspective view of another applicator assembly, according to some embodiments, showing a patch coupled to an applicator.</li><li><figref idref="f0066">Figure 143</figref> illustrates a perspective view of the applicator assembly of <figref idref="f0066">Figure 142</figref>, the patch decoupled from the applicator.</li></ul>

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

0103Although certain embodiments and examples are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses, and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures, systems, and/or devices described herein may be embodied as integrated components or as separate components.

0104For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein.

SYSTEM INTRODUCTION

0105U.S. Patent Publication No. <patcit id="pcit0004" dnum="US20130267811A1"><text>US-2013-0267811-A1</text></patcit> explains how <figref idref="f0001">Figure 1</figref> is a schematic of a continuous analyte sensor system 100 attached to a host (e.g., a person). The analyte sensor system 100 communicates with other devices 110-113 (which can be located remotely from the host). A transcutaneous analyte sensor system 102 comprising an on-skin sensor assembly 600 is fastened to the skin of a host via a base (not shown), which can be a disposable housing.

0106The system 102 includes a transcutaneous analyte sensor 200 and an electronics unit (referred to interchangeably as "sensor electronics" or "transmitter") 500 for wirelessly transmitting analyte information to a receiver. The receiver can be located remotely relative to the system 102. In some embodiments, the receiver includes a display screen, which can display information to a person such as the host. Example receivers include computers such as smartphones, smartwatches, tablet computers, laptop computers, and desktop computers. In some embodiments, receivers can be Apple Watches, iPhones, and iPads made by Apple Inc. In still further embodiments, the system 102 can be configured for use in applying a drug delivery device, such an infusion device, to the skin of a patient. In such embodiments, the system can include a catheter instead of, or in addition to, a sensor, the catheter being connected to an infusion pump configured to deliver liquid medicines or other fluids into the patient's body. In embodiments, the catheter can be deployed into the skin in much the same manner as a sensor would be, for example as described herein.

0107In some embodiments, the receiver is mechanically coupled to the electronics unit 500 to enable the receiver to receive data (e.g., analyte data) from the electronics unit 500. To increase the convenience to users, in several embodiments, the receiver does not need to be mechanically coupled to the electronics unit 500 and can even receive data from the electronics unit 500 over great distances (e.g., when the receiver is many feet or even many miles from the electronics unit 500).

0108During use, a sensing portion of the sensor 200 can be under the host's skin and a contact portion of the sensor 200 can be electrically connected to the electronics unit 500. The electronics unit 500 can be engaged with a housing (e.g., a base) which is attached to an adhesive patch fastened to the skin of the host.

0109The on-skin sensor assembly 600 may be attached to the host with use of an applicator adapted to provide convenient and secure application. Such an applicator may also be used for attaching the electronics unit 500 to a base, inserting the sensor 200 through the host's skin, and/or connecting the sensor 200 to the electronics unit 500. Once the electronics unit 500 is engaged with the base and the sensor 200 has been inserted into the skin (and is connected to the electronics unit 500), the sensor assembly can detach from the applicator.

0110The continuous analyte sensor system 100 can include a sensor configuration that provides an output signal indicative of a concentration of an analyte. The output signal including (e.g., sensor data, such as a raw data stream, filtered data, smoothed data, and/or otherwise transformed sensor data) is sent to the receiver.

0111In some embodiments, the analyte sensor system 100 includes a transcutaneous glucose sensor, such as is described in U.S. Patent Publication No. <patcit id="pcit0005" dnum="US20110027127A1"><text>US-2011-0027127-A1</text></patcit>. In some embodiments, the sensor system 100 includes a continuous glucose sensor and comprises a transcutaneous sensor (e.g., as described in <patcit id="pcit0006" dnum="US6565509B"><text>U.S. Pat. No. 6,565,509</text></patcit>, as described in <patcit id="pcit0007" dnum="US6579690B"><text>U.S. Pat. No. 6,579,690</text></patcit>, as described in <patcit id="pcit0008" dnum="US6484046B"><text>U.S. Pat. No. 6,484,046</text></patcit>).

0112In several embodiments, the sensor system 100 includes a continuous glucose sensor and comprises a refillable subcutaneous sensor (e.g., as described in <patcit id="pcit0009" dnum="US6512939B"><text>U.S. Pat. No. 6,512,939</text></patcit>). In some embodiments, the sensor system 100 includes a continuous glucose sensor and comprises an intravascular sensor (e.g., as described in <patcit id="pcit0010" dnum="US6477395B"><text>U.S. Pat. No. 6,477,395</text></patcit>, as described in <patcit id="pcit0011" dnum="US6424847B"><text>U.S. Pat. No. 6,424,847</text></patcit>).

0113Various signal processing techniques and glucose monitoring system embodiments suitable for use with the embodiments described herein are described in U.S. Patent Publication No. <patcit id="pcit0012" dnum="US20050203360A1"><text>US-2005-0203360-A1</text></patcit> and U.S. Patent Publication No. <patcit id="pcit0013" dnum="US20090192745A1"><text>US-2009-0192745-A1</text></patcit>. The sensor can extend through a housing, which can maintain the sensor on the skin and can provide for electrical connection of the sensor to sensor electronics, which can be provided in the electronics unit 500.

0114In several embodiments, the sensor is formed from a wire or is in a form of a wire. A distal end of the wire can be sharpened to form a conical shape (to facilitate inserting the wire into the tissue of the host). The sensor can include an elongated conductive body, such as a bare elongated conductive core (e.g., a metal wire) or an elongated conductive core coated with one, two, three, four, five, or more layers of material, each of which may or may not be conductive. The elongated sensor may be long and thin, yet flexible and strong. For example, in some embodiments, the smallest dimension of the elongated conductive body is less than 0.254 cm (0.1 inches), less than 0.1905 cm (0.075 inches), less than 0.127 cm (0.05 inches), less than 0.0635 cm (0.025 inches), less than 0.0254 cm (0.01 inches), less than 0.01016 cm (0.004 inches), and/or less than 0.00508 cm (0.002 inches).

0115The sensor may have a circular cross section. In some embodiments, the cross section of the elongated conductive body can be ovoid, rectangular, triangular, polyhedral, star-shaped, C-shaped, T-shaped, X-shaped, Y-shaped, irregular, or the like. In some embodiments, a conductive wire electrode is employed as a core. To such an electrode, one or two additional conducting layers may be added (e.g., with intervening insulating layers provided for electrical isolation). The conductive layers can be comprised of any suitable material. In certain embodiments, it may be desirable to employ a conductive layer comprising conductive particles (i.e., particles of a conductive material) in a polymer or other binder.

0116In some embodiments, the materials used to form the elongated conductive body (e.g., stainless steel, titanium, tantalum, platinum, platinum-iridium, iridium, certain polymers, and/or the like) can be strong and hard, and therefore can be resistant to breakage. For example, in several embodiments, the ultimate tensile strength of the elongated conductive body is greater than 80 kPsi and less than 500 kPsi, and/or the Young's modulus of the elongated conductive body is greater than 160 GPa and less than 220 GPa. The yield strength of the elongated conductive body can be greater than 60 kPsi and less than 2200 kPsi.

0117The electronics unit 500 can be releasably coupled to the sensor 200. The electronics unit 500 can include electronic circuitry associated with measuring and processing the continuous analyte sensor data. The electronics unit 500 can be configured to perform algorithms associated with processing and calibration of the sensor data. For example, the electronics unit 500 can provide various aspects of the functionality of a sensor electronics module as described in U.S. Patent Publication No. <patcit id="pcit0014" dnum="US20090240120A1"><text>US-2009-0240120-A1</text></patcit> and U.S. Patent Publication No. <patcit id="pcit0015" dnum="US20120078071A"><text>US-2012-0078071-A</text></patcit>. The electronics unit 500 may include hardware, firmware, and/or software that enable measurement of levels of the analyte via a glucose sensor, such as an analyte sensor 200.

0118For example, the electronics unit 500 can include a potentiostat, a power source for providing power to the sensor 200, signal processing components, data storage components, and a communication module (e.g., a telemetry module) for one-way or two-way data communication between the electronics unit 500 and one or more receivers, repeaters, and/or display devices, such as devices 110-113. Electronics can be affixed to a printed circuit board (PCB), or the like, and can take a variety of forms. The electronics can take the form of an integrated circuit (IC), such as an Application-Specific Integrated Circuit (ASIC), a microcontroller, and/or a processor. The electronics unit 500 may include sensor electronics that are configured to process sensor information, such as storing data, analyzing data streams, calibrating analyte sensor data, estimating analyte values, comparing estimated analyte values with time-corresponding measured analyte values, analyzing a variation of estimated analyte values, and the like. Examples of systems and methods for processing sensor analyte data are described in more detail in <patcit id="pcit0016" dnum="US7310544B"><text>U.S. Pat. No. 7,310,544</text></patcit>, <patcit id="pcit0017" dnum="US6931327B"><text>U.S. Pat. No. 6,931,327</text></patcit>, <patcit id="pcit0018" dnum="US20050043598A1"><text>U.S. Patent Publication No. 2005-0043598-A1</text></patcit>, <patcit id="pcit0019" dnum="US20070032706A1"><text>U.S. Patent Publication No. 2007-0032706-A1</text></patcit>, <patcit id="pcit0020" dnum="US20070016381A1"><text>U.S. Patent Publication No. 2007-0016381-A1</text></patcit>, <patcit id="pcit0021" dnum="US20080033254A1"><text>U.S. Patent Publication No. 2008-0033254-A1</text></patcit>, <patcit id="pcit0022" dnum="US20050203360A1"><text>U.S. Patent Publication No. 2005-0203360-A1</text></patcit>, <patcit id="pcit0023" dnum="US20050154271A1"><text>U.S. Patent Publication No. 2005-0154271-A1</text></patcit>, <patcit id="pcit0024" dnum="US20050192557A1"><text>U.S. Patent Publication No. 2005-0192557-A1</text></patcit>, <patcit id="pcit0025" dnum="US20060222566A1"><text>U.S. Patent Publication No. 2006-0222566-A1</text></patcit>, <patcit id="pcit0026" dnum="US20070203966A1"><text>U.S. Patent Publication No. 2007-0203966-A1</text></patcit> and <patcit id="pcit0027" dnum="US20070208245A1"><text>U.S. Patent Publication No. 2007-0208245-A1</text></patcit>.

0119One or more repeaters, receivers and/or display devices, such as a key fob repeater 110, a medical device receiver 111 (e.g., an insulin delivery device and/or a dedicated glucose sensor receiver), a smartphone 112, a portable computer 113, and the like can be communicatively coupled to the electronics unit 500 (e.g., to receive data from the electronics unit 500). The electronics unit 500 can also be referred to as a transmitter. In some embodiments, the devices 110-113 transmit data to the electronics unit 500. The sensor data can be transmitted from the sensor electronics unit 500 to one or more of the key fob repeater 110, the medical device receiver 111, the smartphone 112, the portable computer 113, and the like. In some embodiments, analyte values are displayed on a display device.

0120The electronics unit 500 may communicate with the devices 110-113, and/or any number of additional devices, via any suitable communication protocol. Example communication protocols include radio frequency; Bluetooth; universal serial bus; any of the wireless local area network (WLAN) communication standards, including the IEEE 802.11, 802.15, 802.20, 802.22 and other 802 communication protocols; ZigBee; wireless (e.g., cellular) telecommunication; paging network communication; magnetic induction; satellite data communication; and/or a proprietary communication protocol.

0121Additional sensor information is described in <patcit id="pcit0028" dnum="US7497827B"><text>U.S. Patent No. 7,497,827</text></patcit> and <patcit id="pcit0029" dnum="US8828201B"><text>U.S. Patent No. 8,828,201</text></patcit>.

0122Any sensor shown or described herein can be an analyte sensor; a glucose sensor; and/or any other suitable sensor. A sensor described in the context of any embodiment can be any sensor described herein. Thus, for example, the sensor 138 shown in <figref idref="f0004">Figure 7</figref> can be an analyte sensor; a glucose sensor; or any sensor described herein. Sensors shown or described herein can be configured to sense, measure, detect, and/or interact with any analyte.

0123As used herein, the term "analyte" is a broad term, and is to be given its ordinary and customary meaning to a person of ordinary skill in the art (and is not to be limited to a special or customized meaning), and refers without limitation to a substance or chemical constituent in a biological fluid (for example, blood, interstitial fluid, cerebral spinal fluid, lymph fluid, urine, sweat, saliva, etc.) that can be analyzed. Analytes can include naturally occurring substances, artificial substances, metabolites, or reaction products.

0124In some embodiments, the analyte for measurement by the sensing regions, devices, systems, and methods is glucose. However, other analytes are contemplated as well, including, but not limited to ketone bodies; Acetyl Co A; acarboxyprothrombin; acylcarnitine; adenine phosphoribosyl transferase; adenosine deaminase; albumin; alpha-fetoprotein; amino acid profiles (arginine (Krebs cycle), histidine/urocanic acid, homocysteine, phenylalanine/tyrosine, tryptophan); andrenostenedione; antipyrine; arabinitol enantiomers; arginase; benzoylecgonine (cocaine); biotinidase; biopterin; c-reactive protein; carnitine; camosinase; CD4; ceruloplasmin; chenodeoxycholic acid; chloroquine; cholesterol; cholinesterase; cortisol; testosterone; choline; creatine kinase; creatine kinase MM isoenzyme; cyclosporin A; d-penicillamine; de-ethylchloroquine; dehydroepiandrosterone sulfate; DNA (acetylator polymorphism, alcohol dehydrogenase, alpha 1-antitrypsin, cystic fibrosis, Duchenne/Becker muscular dystrophy, glucose-6-phosphate dehydrogenase, hemoglobin A, hemoglobin S, hemoglobin C, hemoglobin D, hemoglobin E, hemoglobin F, D-Punjab, beta-thalassemia, hepatitis B virus, HCMV, HIV-1, HTLV-1, Leber hereditary optic neuropathy, MCAD, RNA, PKU, Plasmodium vivax, sexual differentiation, 21-deoxycortisol); desbutylhalofantrine; dihydropteridine reductase; diptheria/tetanus antitoxin; erythrocyte arginase; erythrocyte protoporphyrin; esterase D; fatty acids/acylglycines; triglycerides; glycerol; free β-human chorionic gonadotropin; free erythrocyte porphyrin; free thyroxine (FT4); free triiodothyronine (FT3); fumarylacetoacetase; galactose/gal-1-phosphate; galactose-1-phosphate uridyltransferase; gentamicin; glucose-6-phosphate dehydrogenase; glutathione; glutathione perioxidase; glycocholic acid; glycosylated hemoglobin; halofantrine; hemoglobin variants; hexosaminidase A; human erythrocyte carbonic anhydrase I; 17-alpha-hydroxyprogesterone; hypoxanthine phosphoribosyl transferase; immunoreactive trypsin; lactate; lead; lipoproteins ((a), B/A-1, β); lysozyme; mefloquine; netilmicin; phenobarbitone; phenytoin; phytanic/pristanic acid; progesterone; prolactin; prolidase; purine nucleoside phosphorylase; quinine; reverse triiodothyronine (rT3); selenium; serum pancreatic lipase; sissomicin; somatomedin C; specific antibodies (adenovirus, anti-nuclear antibody, anti-zeta antibody, arbovirus, Aujeszky's disease virus, dengue virus, Dracunculus medinensis, Echinococcus granulosus, Entamoeba histolytica, enterovirus, Giardia duodenalisa, Helicobacter pylori, hepatitis B virus, herpes virus, HIV-1, IgE (atopic disease), influenza virus, Leishmania donovani, leptospira, measles/mumps/rubella, Mycobacterium leprae, Mycoplasma pneumoniae, Myoglobin, Onchocerca volvulus, parainfluenza virus, Plasmodium falciparum, poliovirus, Pseudomonas aeruginosa, respiratory syncytial virus, rickettsia (scrub typhus), Schistosoma mansoni, Toxoplasma gondii, Trepenoma pallidium, Trypanosoma cruzi/rangeli, vesicular stomatis virus, Wuchereria bancrofti, yellow fever virus); specific antigens (hepatitis B virus, HIV-1); acetone (e.g., succinylacetone); acetoacetic acid; sulfadoxine; theophylline; thyrotropin (TSH); thyroxine (T4); thyroxine-binding globulin; trace elements; transferrin; UDP-galactose-4-epimerase; urea; uroporphyrinogen I synthase; vitamin A; white blood cells; and zinc protoporphyrin.

0125Salts, sugar, protein, fat, vitamins, and hormones naturally occurring in blood or interstitial fluids can also constitute analytes in certain embodiments. The analyte can be naturally present in the biological fluid or endogenous, for example, a metabolic product, a hormone, an antigen, an antibody, and the like. Alternatively, the analyte can be introduced into the body or exogenous, for example, a contrast agent for imaging, a radioisotope, a chemical agent, a fluorocarbon-based synthetic blood, or a drug or pharmaceutical composition, including but not limited to insulin; glucagon; ethanol; cannabis (marijuana, tetrahydrocannabinol, hashish); inhalants (nitrous oxide, amyl nitrite, butyl nitrite, chlorohydrocarbons, hydrocarbons); cocaine (crack cocaine); stimulants (amphetamines, methamphetamines, Ritalin, Cylert, Preludin, Didrex, PreState, Voranil, Sandrex, Plegine); depressants (barbiturates, methaqualone, tranquilizers such as Valium, Librium, Miltown, Serax, Equanil, Tranxene); hallucinogens (phencyclidine, lysergic acid, mescaline, peyote, psilocybin); narcotics (heroin, codeine, morphine, opium, meperidine, Percocet, Percodan, Tussionex, Fentanyl, Darvon, Talwin, Lomotil); designer drugs (analogs of fentanyl, meperidine, amphetamines, methamphetamines, and phencyclidine, for example, Ecstasy); anabolic steroids; and nicotine. The metabolic products of drugs and pharmaceutical compositions are also contemplated analytes. Analytes such as neurochemicals and other chemicals generated within the body can also be analyzed, such as, for example, ascorbic acid, uric acid, dopamine, noradrenaline, 3-methoxytyramine (3MT), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxytryptamine (5HT), 5-hydroxyindoleacetic acid (FHIAA), and intermediaries in the Citric Acid Cycle.

0126Many embodiments described herein use an adhesive (e.g., the adhesive 126 in <figref idref="f0004">Figure 7</figref>). One purpose of the adhesive can be to couple a base, a sensor module, and/or a sensor to a host (e.g., to skin of the host). The adhesive can be configured for adhering to skin. The adhesive can include a pad (e.g., that is located between the adhesive and the base). Additional adhesive information, including adhesive pad information, is described in <patcit id="pcit0030" dnum="US83560315" dnum-type="L"><text>U.S. Patent Application No. 14/835,603, which was filed on August 25, 2015</text></patcit>.

DISTAL BASE LOCATION

0127As noted above, systems can apply an on-skin sensor assembly to the skin of a host. The system can include a base that comprises an adhesive to couple a glucose sensor to the skin.

0128In some applicators, the base is hidden deep inside the applicator until the user moves the needle distally with the base. One challenge with this approach is that the insertion site (on the skin of the host) is not ideally prepared for sensor and/or needle insertion. For example, the distal end of the applicator may be a hoop that presses against the skin. The pressure of the applicator on the skin can cause the area of the skin within the hoop to form a convex shape. In addition, the skin within the hoop can be too easily compressed such that the skin lacks sufficient resilience and firmness. In this state, the sensor and/or needle may press the skin downward without immediately piercing the skin, which may result in improper sensor and/or needle insertion.

0129In several embodiments, the base is coupled to a telescoping assembly such that the base protrudes from the distal end of the system while the glucose sensor is located remotely from the base and is located within the telescoping assembly. This configuration enables the base to prepare the insertion site of the skin for sensor and/or needle insertion (e.g., by compressing the skin). Thus, these embodiments can dramatically improve the reliability of sensor and/or needle insertion while reducing pain associated with sensor and/or needle insertion.

0130The system can hold the base in a position that is distal relative to a glucose sensor module such that a glucose sensor is not attached to the base and such that the glucose sensor can move relative to the base. Moving the glucose sensor module distally towards the base can attach the glucose sensor to the base. This movement can occur as a result of compressing an applicator.

0131<figref idref="f0002">Figure 2</figref> illustrates a perspective view of an applicator system 104 for applying at least portions of an on-skin sensor assembly 600 (shown in <figref idref="f0003">Figure 4</figref>) to skin of a host (e.g., a person). The system can include a sterile barrier having a shell 120 and a cap 122. The cap 122 can screw onto the shell 120 to shield portions of the system 104 from external contaminants.

0132The electronics unit 500 (e.g., a transmitter having a battery) can be detachably coupled to the sterile barrier shell 120. The rest of the applicator system 104 can be sterilized, and then the electronics unit 500 can be coupled to the sterile barrier shell 120 (such that the electronics unit 500 is not sterilized with the rest of the applicator system 104).

0133The user can detach the electronics unit 500 from the sterile barrier shell 120. The user can also couple the electronics unit 500 to the base 128 (as shown in <figref idref="f0003">Figure 6</figref>) after the applicator system 104 places at least a portion of a sensor in a subcutaneous position (for analyte sensing).

0134Many different sterilization processes can be used with the embodiments described herein. The sterile barrier 120 and/or the cap 122 can block gas from passing through (e.g., can be hermetically sealed). The hermetic seal can be formed by threads 140 (shown in <figref idref="f0002">Figure 3</figref>). The threads 140 can be compliant such that they deform to create a seal. The threads 140 can be located between the sterile barrier shell 120 and the cap 122.

0135The cap 122 can be made polypropylene and the shell 120 can be made from polycarbonate (or vice versa) such that one of the cap 122 and the shell 120 is harder than the other of the cap 122 and the 120. This hardness (or flexibility) difference enables one of the components to deform to create the thread 140 seal.

0136In some embodiments, at least one of the shell 120 and the cap 122 includes a gas-permeable material to enable sterilization gases to enter the applicator system 104. For example, as explained in the context of <figref idref="f0027">Figure 60</figref>, the system can include a cover 272h.

0137Referring now to <figref idref="f0002">Figure 3</figref>, the threads 140 can be configured such that a quarter rotation, at least 15 percent of a full rotation, and/or less than 50 percent of a full rotation uncouples the cap 122 from the shell 120. Some embodiments do not include threads 140. The cap 122 can be pushed onto the shell 120 (e.g., during assembly) even in some threaded embodiments.

0138A cap 122 can be secured to the shell 120 by a frangible member 142 configured such that removing the cap 122 from the shell 120 brakes the frangible member 142. The frangible member 142 can be configured like the safety ring (with a frangible portion) of a plastic soda bottle. Unscrewing the cap from the plastic soda bottle breaks the safety ring from the soda bottle's cap. This approach provides evidence of tampering. In the same way, the applicator system 104 can provide tamper evidence (due to the frangible member 142 being broken by removing the cap 122 from the shell 122).

0139U.S. Patent Publication No. <patcit id="pcit0031" dnum="US20130267811A1"><text>US-2013-0267811-A1</text></patcit>; <patcit id="pcit0032" dnum="US62165837" dnum-type="L"><text>U.S. Patent Application No. 62/165,837, which was filed on May 15, 2015</text></patcit>; and <patcit id="pcit0033" dnum="US62244520" dnum-type="L"><text>U.S. Patent Application No. 62/244,520, which was filed on October 21, 2015</text></patcit>, include additional details regarding applicator system embodiments.

0140<figref idref="f0002">Figure 3</figref> illustrates a cross-sectional view of the system 104. A glucose sensor module 134 is configured to couple a glucose sensor 138 to the base 128 (e.g., a "housing"). The telescoping assembly 132 is located in a proximal starting position such that the glucose sensor module 134 is located proximally relative to the base 128 and remotely from the base 128. The telescoping assembly 132 is configured such that collapsing the telescoping assembly 132 connects the glucose sensor module 134 to the base 128 via one or more mechanical interlocks (e.g., snap fits, interference features).

0141The sterile barrier shell 120 is coupled to a telescoping assembly 132. After removing the cap 122, the system 104 is configured such that compressing the sterile barrier shell 120 distally (while a distal portion of the system 104 is pressed against the skin) can insert a sensor 138 (shown in <figref idref="f0003">Figure 4</figref>) into the skin of a host to place the transcutaneous, glucose analyte sensor 138. In many figures shown herein, the sterile barrier shell 120 and cap 122 are hidden to increase the clarity of other features.

0142Collapsing the telescoping assembly 132 also pushes at least 2.5 millimeters of the glucose sensor 138 out through a hole in the base 128 such that at least 2.5 millimeters of the glucose sensor 138 that was previously located proximally relative to a distal end of the base protrudes distally out of the base 128. Thus, in some embodiments, the base 128 can remain stationary relative to a distal portion of the telescoping assembly 132 while the collapsing motion of the telescoping assembly 132 brings the glucose sensor module 134 towards the base 128 and then couples the sensor module 134 to the base 128.

0143This relative motion between the sensor module 134 and the base 128 has many benefits, such as enabling the base to prepare the insertion site of the skin for sensor and/or needle insertion (e.g., by compressing the skin). The starting position of the base 128 also enables the base 128 to shield people from a needle, which can be located inside the applicator system 104. For example, if the base 128 were directly coupled to the sensor module 134 in the proximal starting position of the telescoping assembly, the needle may protrude distally from the base 128. The exposed needle could be a potential hazard. In contrast, the distal starting position of the base 128 enables the base 128 to protect people from inadvertent needle insertion. Needle protection is especially important for caregivers (who are not the intended recipients of the on-skin sensor assembly 600 shown in <figref idref="f0003">Figure 4</figref>).

0144<figref idref="f0003">Figure 4</figref> illustrates a perspective view of the on-skin sensor assembly 600, which includes the base 128. An adhesive 126 can couple the base 128 to the skin 130 of the host. The adhesive 126 can be a foam adhesive suitable for skin adhesion. A glucose sensor module 134 is configured to couple a glucose sensor 138 to the base 128.

0145The applicator system 104 (shown in <figref idref="f0002">Figure 2</figref>) can couple the adhesive 126 to the skin 130. The system 104 can also secure (e.g., couple via mechanical interlocks such as snap fits and/or interference features) the glucose sensor module 134 to the base 128 to ensure the glucose sensor 138 is coupled to the base 128. Thus, the adhesive 126 can couple the glucose sensor 138 to the skin 130 of the host.

0146After the glucose sensor module 134 is coupled to the base 128, a user (or an applicator) can couple the electronics unit 500 (e.g., a transmitter) to the base 128 via mechanical interlocks such as snap fits and/or interference features. The electronics unit 500 can measure and/or analyze glucose indicators sensed by the glucose sensor 138. The electronics unit 500 can transmit information (e.g., measurements, analyte data, glucose data) to a remotely located device (e.g., 110-113 shown in <figref idref="f0001">Figure 1</figref>).

0147<figref idref="f0003">Figure 5</figref> illustrates a perspective view of the electronics unit 500 coupled to the base 128 via mechanical interlocks such as snap fits and/or interference features. Adhesive 126 on a distal face of the base 128 is configured to couple the sensor assembly 600 to the skin. <figref idref="f0003">Figure 6</figref> illustrates another perspective view of the electronics unit 500 coupled to the base 128.

0148Any of the features described in the context of <figref idref="f0001 f0002 f0003">Figures 1-6</figref> can be applicable to all aspects and embodiments identified herein. For example, many embodiments can use the on-skin sensor assembly 600 shown in <figref idref="f0003">Figure 4</figref> and can use the sterile barrier shell 120 shown in <figref idref="f0002">Figure 2</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

0149<figref idref="f0004 f0005 f0006">Figures 7-11</figref> illustrate cross-sectional views of the applicator system 104 from <figref idref="f0002">Figure 3</figref>. The sterile barrier shell 120 and the cap 134 are hidden in <figref idref="f0004 f0005 f0006">Figures 7-11</figref> to facilitate viewing the telescoping assembly 132.

0150The telescoping assembly 132 is part of a system for applying an on-skin sensor assembly 600 to skin of a host (shown in <figref idref="f0003">Figure 4</figref>). The telescoping assembly 132 can apply portions of the system to the host. Additional portions of the system can be added to the on-skin sensor assembly 600 after the applicator system 104 couples initial portions of the sensor assembly 600 to the host. For example, as shown in <figref idref="f0003">Figure 4</figref>, the electronics unit 500 (e.g., a transmitter) can be coupled to the on-skin sensor assembly 600 after the applicator system 104 (shown in <figref idref="f0002">figure 3</figref>) couples the base 128, the glucose sensor module 134, and/or the glucose sensor 138 to the skin 130 of the host.

0151In some embodiments, the applicator system 104 (shown in <figref idref="f0002">Figure 3</figref>) couples at least one, at least two, at least three, at least four, and/or all of the following items to the skin of the host: the electronics unit 500, the glucose sensor module 134, the glucose sensor 138, the base 128, and the adhesive 126. The electronics unit 500 can be located inside the applicator system 104 such that the applicator system 104 is configured to couple the electronics unit 500 to the skin of the host.

0152<figref idref="f0004">Figure 7</figref> illustrates a telescoping assembly 132 having a first portion 150 (e.g., a "pusher") configured to move distally relative to a second portion 152 (e.g., a "needle guard") from a proximal starting position to a distal position along a path 154. <figref idref="f0004">Figure 7</figref> illustrates the telescoping assembly 132 in the proximal starting position. <figref idref="f0004">Figure 8</figref> illustrates the telescoping assembly 132 moving between the proximal starting position and the distal position. <figref idref="f0006">Figure 11</figref> illustrates the telescoping assembly 132 in the distal position. The path 154 (shown in <figref idref="f0004">Figure 7</figref>) represents the travel between the proximal starting position and the distal position.

0153A first set of items can be immobile relative to the first portion 150, and a second set of items can be immobile relative to the second portion 152 while the first set of items move relative to the second set of items.

0154Referring now to <figref idref="f0004">Figure 7</figref>, the glucose sensor 138 and the sensor module 134 are coupled to the first portion 150 (e.g., such that they are immobile relative to the first portion 150 during a proximal portion of the path 154). The base 128 is coupled to the second portion 152 such that the base 128 protrudes from a distal end of the system (e.g., the base protrudes from a distal end of the telescoping assembly 132). The base 128 comprises adhesive 126 configured to eventually couple the glucose sensor 138 to the skin (e.g., after at least a portion of the glucose sensor 138 is rigidly coupled to the base 128).

0155In <figref idref="f0004">Figure 7</figref>, the glucose sensor 138 and the sensor module 134 are located within the second portion 152 while the base 128 protrudes from the distal end of the system (e.g., from the distal end of the telescoping assembly 132) such that the system is configured to couple the glucose sensor 138 to the base 128 via moving the first portion 150 distally relative to the second portion 152. The progression shown in <figref idref="f0004 f0005 f0006">Figures 7-11</figref> illustrates moving the first portion 150 distally relative to the second portion 152.

0156The sensor module 138 is coupled to a distal portion of the first portion 150 such that moving the first portion 150 to the distal position (as described above) couples the sensor module 134 to the base 128. The glucose sensor 138 is coupled to the sensor module 134 (e.g., immobile relative to the sensor module 134) while the first portion 150 is located in the proximal starting position. The glucose sensor 138 can include a distally protruding portion and a proximal portion. The proximal portion can be rigidly coupled to the sensor module 134 such that the proximal portion cannot move relative to the sensor module 134 even though the distally protruding portion may bend relative to the sensor module 134.

0157A needle 156 (e.g., a "C-shaped" needle) is coupled to the first portion 150 such that the glucose sensor 138 and the needle 156 move distally relative to the base 128 and relative to the second portion 152. The system can further comprise a needle release mechanism 158 configured to retract the needle 156 proximally.

0158The needle 156 can have many different forms. Many different types of needles 156 can be used with the embodiments described herein. <figref idref="f0024 f0025">Figures 51-55</figref> illustrate various needle embodiments that can be used with any of the embodiments described herein.

0159The needle 156 can guide the sensor 138 into the skin of the host. A distal portion of the sensor 138 can be located in a channel of the needle 156 (as shown in <figref idref="f0020">Figure 42</figref>). Sometimes, a distal end of the sensor 138 sticks out of the needle 156 and gets caught on tissue of the host as the sensor 138 and needle 156 are inserted into the host. As a result, the sensor 138 may buckle and fail to be inserted deeply enough into the subcutaneous tissue. In other words, in some embodiments, the sensor wire must be placed within the channel of the C-shaped needle 156 to be guided into the tissue and must be retained in the channel 330 during deployment.

0160The risk of the sensor 138 sticking out of the channel 330 (and thereby failing to be property inserted into the host) can be greatly diminished by the embodiment illustrated in <figref idref="f0024">Figure 51</figref>. In this embodiment, adhesive 376 bonds a distal portion of the glucose sensor 138 into the channel 330 of the needle 156. Retracting the needle 156 can break the bond of the adhesive 376 to enable a distal portion of the sensor 138 to stay in a subcutaneous location while the needle 156 is retracted (and even after the needle 156 is retracted).

0161The risk of the sensor 138 sticking out of the channel 330 (and thereby failing to be property inserted into the host) can be greatly diminished by the embodiment illustrated in <figref idref="f0024">Figures 52 and 53</figref>. In this embodiment, the needle 156a comprises two sides, which can be separated by slots 378. The sensor 138 can have a width that is larger than the width of the slots 378 such that the sensor 138 cannot come out of the channel 330a until the two sides of the needle 156a are moved apart (to widen the slots 378).

0162The embodiment illustrated in <figref idref="f0024">Figure 54</figref> can be used with any of the other embodiments described herein. The needle 156b includes a ramp 380 at the distal end of the channel 330b. The distal end of the needle 156b can include a conical tip 382. The ramp 380 can be configured to push the sensor 138 out of the channel 330b of the needle 156b as the needle 156b is retracted into the telescoping assembly 132 (shown in <figref idref="f0004">Figure 7</figref>).

0163<figref idref="f0025">Figure 55</figref> illustrates cross sectional views of different needles 156c, 156d, 156e, 156f, which can be used as needle 156 in <figref idref="f0004">Figure 7</figref> or in any other embodiment described herein. Needle 156c includes an enclosed channel 330c. Needles 156d, 156e, 156f are C-needles, although many other C-needle shapes can be used in several embodiments. The ends of the needle 156d can be angled relative to each other. In some embodiments, the ends of the needle can be angled away from each other, in an opposite fashion as shown by 156d. In some embodiments, the ends of the needle can have flared edges, in which the flared edges are rounded to prevent the sensor from contacting sharp edges. The ends of the needle 156e can be parallel and/or flat relative to each other. The outside portion of the channel 330f can be formed by walls that are straight and/or parallel to each other (rather than by curved walls as is the case for other needles 156d, 156e). Some needles 156d can be manufactured via laser cutting, some needles 156e can be manufactured via wire electrical discharge machining ("EDM"), and some needles 156f can be manufactured via stamping.

0164As shown in <figref idref="f0004">Figure 7</figref>, a needle hub 162 is coupled to the needle 156. The needle hub includes release features 160 that protrude outward. In some embodiments, the release features can comprise one, two, or more flexible arms. Outward ends 164 of the release features 160 catch on inwardly facing overhangs 166 (e.g., undercuts, detents) of the first portion 150 such that moving the first portion 150 distally relative to the second portion 152 causes the needle retraction mechanism 158 to move distally until a release point.

0165At the release point, proximal protrusions 170 of the second portion 152 engage the release features 160 (shown in <figref idref="f0005">Figure 9</figref>), which forces the release features 160 to bend inward until the release features 160 no longer catch on the overhangs 166 of the first portion 150 (shown in <figref idref="f0005">Figure 10</figref>). Once the release features 160 no longer catch on the overhangs 166 of the first portion 150, the spring 234 of the needle retraction mechanism 158 pushes the needle 156 and the needle hub 162 proximally relative to the first portion 150 and relative to the second portion 152 until the needle no longer protrudes distally from the base 128 and is completely hidden inside the telescoping assembly 132 (shown in <figref idref="f0006">Figure 11</figref>).

0166The needle 156 can be removed from the embodiment illustrated in <figref idref="f0004">Figure 7</figref> to make a needle-free embodiment. Thus, a needle 156 is not used in some embodiments. For example, a distal end of the glucose sensor 138 can be formed in a conical shape to enable inserting the glucose sensor 138 into the skin without using a needle 156. Unless otherwise noted, the embodiments described herein can be formed with or without a needle 156.

0167In several embodiments, a needle can help guide the glucose sensor 138 (e.g., at least a distal portion of the glucose sensor) into the skin. In some embodiments, a needle is not part of the system and is not used to help guide the glucose sensor 138 into the skin. In needle embodiments and needle-free embodiments, skin piercing is an important consideration. Failing to properly pierce the skin can lead to improper placement of the glucose sensor 138.

0168Tensioning the skin prior to piercing the skin with the glucose sensor 138 and/or the needle 156 can dramatically improve the consistency of achieving proper placement of the glucose sensor 138. Tensioning the skin can be accomplished by compressing the skin with a distally protruding shape (e.g., a convex shape) prior to piercing the skin and at the moment of piercing the skin with the glucose sensor 138 and/or the needle 156.

0169<figref idref="f0006">Figure 12A</figref> illustrates a portion of the cross section shown in <figref idref="f0004">Figure 7</figref>. The base 128 includes an optional distally facing protrusion 174 located distally relative to the second portion 152 (and relative to the rest of the telescoping assembly 132). The distal protrusion 174 is convex and is shaped as a dome. In some embodiments, the distal protrusion 174 has block shapes, star shapes, and cylindrical shapes. Several base 128 embodiments do not include the protrusion 174.

0170The distal protrusion 174 can be located farther distally than any other portion of the base 128. The distal protrusion 174 can extend through a hole 176 in the adhesive 126 (as also shown in <figref idref="f0003">Figure 5</figref>). A distal portion of the convex protrusion 174 can be located distally relative to the adhesive 126 while a proximal portion of the convex protrusion 174 is located proximally relative to the adhesive 126.

0171The distal protrusion 174 has a hole 180 through which the needle 156 and/or the glucose sensor 138 can pass. The distal protrusion 174 can compress the skin such that the distal protrusion 174 is configured to reduce a resistance of the skin to piercing.

0172<figref idref="f0006">Figure 12B</figref> illustrates a cross sectional view of a base 128b that is identical to the base 128 illustrated in <figref idref="f0004">Figures 7</figref> and <figref idref="f0006">12B</figref> except for the following features: The base 128b does not include a protrusion 174. The base 128b includes a funnel 186 (e.g., a radius) on the distal side of the hole 180b.

0173Like the embodiment shown in <figref idref="f0006">Figure 12A</figref>, the sensor 138 (e.g., an analyte sensor) and/or the needle 156 (shown in <figref idref="f0006">Figure 12A</figref>) can pass through the hole 180b (shown in <figref idref="f0006">Figure 12B</figref>). The funnels 182, 186 can be mirror images of each other or can be different shapes. The base 128b can be used with any of the embodiments described herein.

0174<figref idref="f0007">Figure 13</figref> illustrates a perspective view of a portion of the adhesive 126. The needle 156 can have many different shapes and cross sections. In some embodiments, the needle 156 includes a slot 184 (e.g., the channel 330 shown in <figref idref="f0020">Figures 42 and 43</figref>) into which at least a portion of the glucose sensor 138 can be placed.

0175The needle 156 having a slot 184 passes through the hole 180 of the distal protrusion and through the hole 176 of the adhesive 126. A portion of the glucose sensor 138 is located in the slot 184 such that the needle 156 is configured to move distally relative to the base 128 (shown in <figref idref="f0006">Figure 12A</figref>) without dislodging the portion of the glucose sensor 138 from the slot 184. The distal protrusion 174 is convex such that the distal protrusion 174 is configured to tension the skin while the first portion 150 moves distally relative to the second portion 152 of the telescoping assembly 132 (shown in <figref idref="f0004">Figure 7</figref>) to prepare the skin for piercing.

0176As mentioned above, the adhesive 126 comprises a hole 176 through which at least a portion of the distal protrusion 174 of the base 128 can pass. The distal protrusion 174 is located within the hole 176 of the adhesive 126 such that the distal protrusion 174 can tension at least a portion of the skin within the second hole (e.g., located under the hole 176). The hole 176 can be circular or any other suitable shape. The hole 176 can be sized such that at least a majority of the distal protrusion 174 extends through the hole 176. A perimeter of the hole 176 can be located outside of the distal protrusion 174 such that the perimeter of the hole 176 is located radially outward relative to a perimeter of the protrusion 174 where the protrusion 174 connects with the rest of the base 128.

0177In some embodiments, the hole 176 of the adhesive 126 is large enough that the adhesive 126 does not cover any of the distal protrusion 174. In some embodiments, the adhesive 126 covers at least a portion of or even a majority of the distal protrusion 174. Thus, the adhesive 126 does not have to be planar and can bulge distally in an area over the distal protrusion 174.

0178In several embodiments, the adhesive 126 has a non-uniform thickness such that the thickness of the adhesive 126 is greater in an area surrounding a needle exit area than in other regions that are farther radially outward from the needle exit area. Thus, the distal protrusion 174 can be part of the adhesive 126 rather than part of the base 128. However, in several embodiments, the base 128 comprises the adhesive 126, and the distal protrusion 174 can be formed by the plastic of the base 128 or by the foam adhesive 126 of the base 128.

0179The needle 156 includes a distal end 198 and a heel 194. The heel 194 is the proximal end of the angled portion of the needle's tip. The purpose of the angled portion is to form a sharp end to facilitate penetrating tissue. The sensor 138 has a distal end 208.

0180During insertion of the needle 156 and the sensor 138 into the tissue; as the needle 156 and the sensor 138 first protrude distally from the system; and/or while the needle 156 and the sensor 138 are located within the telescoping assembly, the end 208 of the sensor 138 can be located at least 0.1 millimeter proximally from the heel 194, less than 1 millimeter proximally from the heel 194, less than 3 millimeters proximally from the heel 194, and/or within plus or minus 0.5 millimeters of the heel 194; and/or the end 208 of the sensor 138 can be located at least 0.3 millimeters proximally from the distal end 198 of the needle 156 and/or less than 2 millimeters proximally from the distal end 198.

0181Referring now to <figref idref="f0006">Figure 12A</figref>, the distal protrusion 174 can protrude at least 0.5 millimeters and less than 5 millimeters from the distal surface of the adhesive 126. In embodiments where the adhesive 126 has a non-planar distal surface, the distal protrusion 174 can protrude at least 0.5 millimeters and less than 5 millimeters from the average distal location of the adhesive 126.

0182As described above, in some embodiments the base is coupled to a telescoping assembly such that the base protrudes from the distal end of the system while the glucose sensor is located remotely from the base and is located within the telescoping assembly. In other embodiments, however, the base is coupled to a telescoping assembly such that the base is located completely inside the telescoping assembly and the base moves distally with the sensor as the first portion is moved distally relative to the second portion of the telescoping assembly.

0183For example, <figref idref="f0027">Figure 59</figref> illustrates a base 128 coupled to the sensor module 134 and to the sensor 138 while the first portion 150 of the telescoping assembly 132f is located in the proximal starting position. The base 128 moves distally as the first portion 150 is moved distally relative to the second portion 152. The base 128 can be coupled to a distal end portion of the first portion 150 while the first portion 150 is located in the proximal starting position. All of the features and embodiments described herein can be configured and used with the base 128 positioning described in the context of <figref idref="f0027">Figure 59</figref>.

0184All of the embodiments described herein can be used with the base coupled to a telescoping assembly such that the base is located completely inside the telescoping assembly and the base moves distally with the sensor as the first portion is moved distally relative to the second portion of the telescoping assembly. All of the embodiments described herein can be used with the base coupled to a telescoping assembly such that the base protrudes from the distal end of the system while the glucose sensor is located remotely from the base and is located within the telescoping assembly.

SENSOR MODULE DOCKING AND BASE DETACHMENT

0185As explained above, maintaining the base against the skin during insertion of the sensor and/or needle enables substantial medical benefits. Maintaining the base against the skin, however, can necessitate moving the sensor relative to the base during the insertion process. Once inserted, the sensor needs to be coupled to the base to prevent the sensor from inadvertently dislodging from the base. Thus, there is a need for a system that enables the sensor to move relative to the base and also enables locking the sensor to the base (without being overly burdensome on users).

0186Maintaining the base against the skin during the distal movement of the sensor and/or needle is enabled in many embodiments by unique coupling systems that secure the sensor (and the sensor module) to a first portion of a telescoping assembly and secure the base to a second portion of the telescoping assembly. Moving the first portion towards the second portion of the telescoping assembly can align the sensor with the base while temporarily holding the sensor. Then, the system can couple the sensor to the base. Finally, the system can detach the base and sensor from the telescoping assembly (which can be disposable or reusable with a different sensor).

0187As illustrated in <figref idref="f0003">Figure 4</figref>, the sensor module 134 and the glucose sensor 138 are not initially coupled to the base 128. Coupling the sensor module 134 and the glucose sensor 138 to the base 128 via compressing the telescoping assembly 132 and prior to detaching the base 128 from the telescoping assembly 132 can be a substantial challenge, yet is enabled by many of the embodiments described herein.

0188As illustrated in <figref idref="f0004">Figures 7</figref> and <figref idref="f0007">14</figref>, the sensor module 134 (and the glucose sensor 138) can be located remotely from the base 128 even though they are indirectly coupled via the telescoping assembly 132. In other words, the sensor module 134 (and the glucose sensor 138) can be coupled to the first portion 150 of the telescoping assembly 132 while the base 128 is coupled to the second portion 152 of the telescoping assembly 132. In this state, the sensor module 134 and the glucose sensor 138 can move relative to the base 128 (e.g., as the sensor module 134 and the glucose sensor 138 move from the proximal starting position to the distal position along the path to "dock" the sensor module 134 and the glucose sensor 138 to the base 128).

0189After the sensor module 134 and the glucose sensor 138 are "docked" with the base 128, the system can detach the base 128 from the telescoping assembly 132 to enable the sensor module 134, the glucose sensor 138, and the base 128 to be coupled to the skin by the adhesive 126 while the telescoping assembly 132 and other portions of the system are discarded.

0190As shown in <figref idref="f0004">Figure 7</figref>, the sensor module 134 is coupled to the first portion 150 and is located at least 5 millimeters from the base 128 while the first portion 150 is in the proximal starting position. The system is configured such that moving the first portion 150 to the distal position couples the sensor module 134 to the base 128 (as shown in <figref idref="f0006">Figure 11</figref>). The glucose sensor 138 is coupled to the sensor module 134 while the first portion 150 is located in the proximal starting position. The glucose sensor 138 is located within the second portion 152 while the base 128 protrudes from the distal end of the system.

0191Arrow 188 illustrates the proximal direction in <figref idref="f0004">Figure 7</figref>. Arrow 190 illustrates the distal direction in <figref idref="f0004">Figure 7</figref>. Line 172 illustrates a horizontal orientation. As used herein, horizontal means within plus or minus 20 degrees of perpendicular to the central axis 196.

0192<figref idref="f0008">Figure 15</figref> illustrates a perspective view of a cross section of portions of the system shown in <figref idref="f0004">Figure 7</figref>. The cross section cuts through the hole 180 of the base 128. Visible portions include the sensor module 134, the sensor 138, a seal 192, the needle 156, the base 128, and the adhesive 126. The sensor module 134 is in the proximal starting position. The seal 192 is configured to block fluid (e.g., bodily fluid) from entering the glucose sensor module 134.

0193The glucose sensor 138 is mechanically coupled to the sensor module 134. The glucose sensor 138 runs into an interior portion of the sensor module 134 and is electrically coupled to interconnects in the interior portion of the sensor module 134. The interconnects are hidden in <figref idref="f0008">Figure 15</figref> to facilitate seeing the proximal portion of the glucose sensor 138 inside the interior portion of the sensor module 134. Many other portions of the system are also hidden in <figref idref="f0008">Figure 15</figref> to enable clear viewing of the visible portions.

0194In many embodiments, the sensor module 134 moves from the position shown in <figref idref="f0008">Figure 15</figref> until the sensor module 134 snaps onto the base 128 via snap fits that are described in more detail below. <figref idref="f0006">Figure 11</figref> illustrates the sensor module 134 snapped to the base 128. This movement from the proximal starting position to the "docked" position can be accomplished by moving along the path 154 (shown in <figref idref="f0004">Figure 7</figref> and illustrated by the progression in <figref idref="f0004 f0005 f0006">Figures 7-11</figref>). (The arrow representing the path 154 is not necessarily drawn to scale.)

0195Referring now to <figref idref="f0004">Figures 7</figref> and <figref idref="f0008">15</figref>, during a first portion of the path 154, the sensor module 134 is immobile relative to the first portion 150, and the base 128 is immobile relative to the second portion 152 of the telescoping assembly 132. During a second portion of the path 154, the system is configured to move the first portion 150 distally relative to the second portion 152; to move the sensor module 134 towards the base 128; to move at least a portion of the sensor 138 through a hole 180 in the base 128; to couple the sensor module 134 to the base 128; and to enable the coupled sensor module 134 and the base 128 to detach from the telescoping assembly 132.

0196<figref idref="f0004">Figure 7</figref> illustrates a vertical central axis 196 oriented from a proximal end to the distal end of the system. (Part of the central axis 196 is hidden in <figref idref="f0004">Figure 7</figref> to avoid obscuring the arrow that represents the path 154 and to avoid obscuring the needle 156.)

0197<figref idref="f0008">Figure 15</figref> illustrates a flex arm 202 of the sensor module 134. The flex arm 202 is oriented horizontally and is configured to secure the sensor module 134 to a protrusion of the base 128. In some embodiments, the flex arm 202 is an alignment arm to prevent and/or impede rotation of the sensor module 134 relative to the base 128.

0198<figref idref="f0008">Figure 16</figref> illustrates a perspective view of a cross section in which the sensor module 134 is coupled to the base 128 via flex arms 202. Interconnects 204 protrude proximally to connect the sensor module 134 to the electronics unit 500 (e.g., a transmitter).

0199Referring now to <figref idref="f0008">Figures 15 and 16</figref>, the flex arms 202 extend from an outer perimeter of the sensor module 134. The base 128 comprises protrusions 206 that extend proximally from a planar, horizontal portion of the base 128.

0200Referring now to <figref idref="f0008">Figure 16</figref>, each of the proximal protrusions 206 of the base 128 are coupled to a flex arm 202 of the sensor module 134. Thus, the coupling of the proximal protrusions 206 to the flex arms 202 couples the sensor module 134 to the base 128.

0201Each proximal protrusion 206 can include a locking protrusion 212 that extends at an angle of at least 45 degrees from a central axis of each proximal protrusion 206. In some embodiments, the locking protrusions 212 extend horizontally (e.g., as shown in <figref idref="f0008">Figure 15</figref>). Each horizontal locking protrusion 212 is coupled to an end portion 210 of a flexible arm 202.

0202The end portion 210 of each flexible arm 202 can extend at an angle greater than 45 degrees and less than 135 degrees relative to a central axis of the majority of the flexible arm 202. The end portion 210 of each flexible arm 202 can include a horizontal locking protrusion (e.g., as shown in <figref idref="f0008">Figure 15</figref>).

0203In <figref idref="f0008">Figures 15 and 16</figref>, a first horizontal locking protrusion is coupled to an end portion 210 of the first flexible arm 202. A second horizontal locking protrusion 212 is coupled to the first proximal protrusion 206 of the base 128. In <figref idref="f0008">Figure 16</figref>, the first horizontal locking protrusion is located distally under the second horizontal locking protrusion 212 to secure the sensor module 134 to the base 128. The system is configured such that moving the first portion 150 of the telescoping assembly 132 to the distal position (shown in <figref idref="f0006">Figure 11</figref>) causes the first flex arm 202 to bend to enable the first horizontal locking protrusion of the flex arm 202 to move distally relative to the second horizontal locking protrusion 212. Thus, the flex arm 202 is secured between the locking protrusion 212 and the distal face of the base 128.

0204At least a portion of the flex arm 202 (e.g., the end portion 210) is located distally under the horizontal locking protrusion 212 of the base 128 to secure the sensor module 134 to the base 128. The system is configured such that moving the first portion 150 of the telescoping assembly 132 to the distal position causes the flex arm 202 (e.g., the end portion 210) to bend away (e.g., outward) from the rest of the sensor module 134 to enable the horizontal locking protrusion of the flex arm 202 to go around the locking protrusion 212 of the proximal protrusion 206. Thus, at least a portion of the flex arm 202 can move distally relative to the horizontal locking protrusion 212 of the proximal protrusion 206 of the base 128.

0205The sensor module 134 can have multiple flex arms 202 and the base can have multiple proximal protrusions 206 configured to couple the sensor module 134 to the base 128. In some embodiments, a first flex arm 202 is located on an opposite side of the sensor module 134 relative to a second flex arm 202 (e.g., as shown in <figref idref="f0008">Figures 15 and 16</figref>).

0206In some embodiments, the base 128 comprises flex arms (e.g., like the flex arms 202 shown in <figref idref="f0008">Figures 15 and 16</figref>) and the sensor module 134 comprises protrusions that couple to the flex arms of the base 128. The protrusions of the sensor module 134 can be like the protrusions 206 shown in <figref idref="f0008">Figures 15 and 16</figref> except that, in several embodiments, the protrusions extend distally towards the flex arms of the base 128. Thus, the base 128 can be coupled to the sensor module 134 with flex arms and mating protrusions regardless of whether the base 128 or the sensor module 134 includes the flex arms.

0207In several embodiments, a sensor module is coupled to the glucose sensor. The system comprises a vertical central axis oriented from a proximal end to the distal end of the system. The base comprises a first flex arm that is oriented horizontally and is coupled to the sensor module. The sensor module comprises a first distal protrusion coupled to the first flex arm to couple the sensor module to the base. A first horizontal locking protrusion is coupled to an end portion of the first flexible arm. A second horizontal locking protrusion is coupled to the first distal protrusion of the sensor module. The second horizontal locking protrusion is located distally under the first horizontal locking protrusion to secure the sensor module to the base. The system is configured such that moving the first portion of the telescoping assembly to the distal position causes the first flex arm to bend to enable the second horizontal locking protrusion to move distally relative to the first horizontal locking protrusion. The sensor module comprises a second distal protrusion coupled to a second flex arm of the base. The first distal protrusion is located on an opposite side of the sensor module relative to the second distal protrusion.

0208Docking the sensor module 134 to the base 128 can include securing the sensor module 134 to the first portion 150 of the telescoping assembly 132 while the first portion 150 moves the sensor module 134 towards the base 128. This securing of the sensor module 134 to the first portion 150 of the telescoping assembly 132 needs to be reliable, but temporary so the sensor module 134 can detach from the first portion 150 at an appropriate stage. The structure that secures the sensor module 134 to the first portion 150 of the telescoping assembly 132 generally needs to avoid getting in the way of the docking process.

0209<figref idref="f0009">Figure 17</figref> illustrates a cross-sectional view of the first portion 150 of the telescoping assembly 132. <figref idref="f0009">Figure 17</figref> shows the glucose sensor module 134 and the needle 156. Some embodiments do not include the needle 156. Many items are hidden in <figref idref="f0009">Figure 17</figref> to provide a clear view of the flex arms 214, 216 of the first portion 150.

0210The first portion 150 comprises a first flex arm 214 and a second flex arm 216 that protrude distally and latch onto the sensor module 134 to releasably secure the sensor module 134 to the first portion 150 while the first portion 150 is in the proximal starting position (shown in <figref idref="f0004">Figure 7</figref>). The flex arms 214, 216 can couple to an outer perimeter of the sensor module 134 such that distal ends of the flex arms 214, 216 wrap around a distal face of the sensor module 134. In some embodiments, the distal ends of the flex arms 214, 216 are located distally of the sensor module 134 while the first portion 150 is in the proximal starting position.

0211The base 128 is hidden in <figref idref="f0009">Figure 17</figref>, but in the state illustrated in <figref idref="f0009">Figure 17</figref>, the sensor module 134 is located remotely from the base 128 to provide a distance of at least 3 millimeters from the sensor module 134 to the base 128 while the first portion 150 is in the proximal starting position. This distance can be important to enable the base to rest on the skin as the needle 156 and/or the glucose sensor 138 pierce the skin and advance into the skin during the transcutaneous insertion.

0212Referring now to <figref idref="f0004">Figures 7</figref> and <figref idref="f0009">17</figref>, the sensor module 134 is located within the second portion 152 while the base 128 protrudes from the distal end of the system such that the system is configured to couple the sensor module 134 to the base 128 via moving the first portion 150 distally relative to the second portion 152. The sensor module 134 is located within the second portion 152 while the base 128 protrudes from the distal end of the system even though the sensor module 134 is moveable relative to the second portion 152 of the telescoping assembly 132. Thus, the first portion 150 moves the sensor module 134 through an interior region of the second portion 152 of the telescoping assembly 132 without moving the base 128 through the interior region of the second portion 152.

0213The system comprises a vertical central axis 196 oriented from a proximal end to the distal end of the system. The first flex arm 214 and the second flex arm 216 of the first portion 150 secure the sensor module 134 to the first portion 150 such that the sensor module 134 is releasably coupled to the first portion 150 with a first vertical holding strength (measured along the vertical central axis 196).

0214As shown in <figref idref="f0008">Figures 15 and 16</figref>, the sensor module 134 is coupled to the base 128 via at least one flex arm 202 such that the sensor module 134 is coupled to the base 128 with a second vertical holding strength. The flex arms 202 can extend from an outer perimeter of the sensor module 134. The flex arms 202 can be part of the base 128.

0215Referring now to <figref idref="f0009">Figure 17</figref>, in some embodiments, the second vertical holding strength is greater than the first vertical holding strength such that continuing to push the first portion 150 distally once the sensor module 134 is coupled to the base 128 overcomes the first and second flex arms 214, 216 of the first portion 150 to detach the sensor module 134 from the first portion 150.

0216In some embodiments, the second vertical holding strength is at least 50 percent greater than the first vertical holding strength. In several embodiments, the second vertical holding strength is at least 100 percent greater than the first vertical holding strength. In some embodiments, the second vertical holding strength is less than 400 percent greater than the first vertical holding strength.

0217<figref idref="f0003">Figure 6</figref> illustrates the on-skin sensor assembly 600 in a state where it is attached to a host. The on-skin sensor assembly 600 can include the glucose sensor 138 and/or the sensor module 134 (shown in <figref idref="f0004">Figure 7</figref>). In some embodiments, the on-skin sensor assembly 600 includes the needle 156. In several embodiments, however, the on-skin sensor assembly 600 does not include the needle 156.

0218As explained above, maintaining the base against the skin during insertion of the sensor and/or needle enables substantial medical benefits. Maintaining the base against the skin, however, can complicate detaching the base from the applicator. For example, in some prior-art systems, the base detaches after the base moves downward distally with a needle. This relatively long travel can enable several base detachment mechanisms. In contrast, when the base is maintained in a stationary position as the needle moves towards the base, releasing the base can be problematic.

0219Many embodiments described herein enable maintaining the base 128 against the skin during insertion of the sensor 138 and/or the needle 156. As mentioned above in the context of <figref idref="f0004 f0005 f0006">Figures 7-11</figref>, after the sensor module 134 is coupled to the base 128, the sensor module 134 and the base 128 need to detach from the telescoping assembly 132 to secure the glucose sensor 138 to the host and to enable the telescoping assembly to be thrown away, recycled, or reused.

0220As shown in <figref idref="f0004 f0005 f0006">Figures 7-11</figref>, several embodiments hold the base 128 in a stationary position relative to the second portion 152 of the telescoping assembly 132 as the sensor module 134 moves towards the base 128. Referring now to <figref idref="f0009">Figure 18</figref>, once the sensor module 134 is attached to the base 128, the system can release the base 128 by bending flex arms 220 that couple the base 128 to the second portion 152. <figref idref="f0009">Figure 18</figref> shows the system in a state prior to the sensor module 134 docking with the base 128 to illustrate distal protrusions 222 of the first portion 150 aligned with the flex arms 220 such that the distal protrusions 222 are configured to bend the flex arms 220 (via the distal protrusions 222 contacting the flex arms 220).

0221The distal protrusions 222 bend the flex arms 220 to detach the base 128 from the telescoping assembly 132 (shown in <figref idref="f0004">Figure 7</figref>) after the sensor module 134 is coupled to the base 128 (as shown in <figref idref="f0006">Figures 11</figref> and <figref idref="f0008">16</figref>). The flex arms 220 can include a ramp 224. A distal end of the distal protrusions 222 can contact the ramp 224 and then can continue moving distally to bend the flex arm 220 as shown by arrow 228 in <figref idref="f0009">Figure 18</figref>. This bending can uncouple the flex arm 220 from a locking feature 230 of the base 128. This unlocking is accomplished by the first portion 150 moving distally relative to the second portion 152, which causes the distal protrusions 222 to move as shown by arrow 226.

0222An advantage of the system shown in <figref idref="f0009">Figure 18</figref> is that the unlocking movement (of the arm 220 bending as shown by arrow 228) is perpendicular (within plus or minus 20 degrees) to the input force (e.g., as represented by arrow 226). Thus, the system is designed such that the maximum holding capability (e.g., of the locking feature 230) can be many times greater than the force necessary to unlock the arm 220 from the base 128. As a result, the system can be extremely reliable and insensitive to manufacturing variability and normal use variations.

0223In contrast, if the holding force and the unlocking force were oriented along the same axis (e.g., within plus or minus 20 degrees), the holding force would typically be equal to or less than the unlocking force. However, the unique structure shown in <figref idref="f0009">Figure 18</figref> allows the holding force to be at least two times larger (and in some cases at least four times larger) than the unlocking force. As a result, the system can prevent inadvertent unlocking of the base 128 while having an unlocking force that is low enough to be easily provided by a user or by another part of the system (e.g., a motor).

0224Another advantage of this system is that it controls the locking and unlocking order of operation. In other words, the structure precludes premature locking and unlocking. In a medical context, this control is extremely valuable because reliability is so critical. For example, in several embodiments, the process follows this order: The sensor module 134 couples to the base 128. Then, the first portion 150 releases the sensor module 134. Then, the second portion 152 releases the base 128. In several embodiments, the vertical locations of various locking and unlocking structures are optimized to ensure this order is the only order that is possible as the first portion 150 moves from the proximal starting position to the distal position along the path described previously. (Some embodiments use different locking and unlocking orders of operation.)

0225<figref idref="f0004">Figure 7</figref> illustrates the base 128 protruding from the distal end of the system while the first portion 150 of the telescoping assembly 132 is located in the proximal starting position. The sensor module 134 and at least a majority of the glucose sensor 138 are located remotely relative to the base 128. The system is configured to couple the sensor module 134 and the glucose sensor 138 to the base 128 via moving the first portion 150 distally relative to the second portion 152.

0226Referring now to <figref idref="f0009">Figures 18</figref> and <figref idref="f0010">19</figref>, the base 128 comprises a first radial protrusion 230 (e.g., a locking feature) releasably coupled with a first vertical holding strength to a second radial protrusion 232 (e.g., a locking feature) of the second portion 152 of the telescoping assembly 132 (shown in <figref idref="f0004">Figure 7</figref>). The first radial protrusion 230 protrudes inward and the second radial protrusion protrudes outward 232. The system is configured such that moving the first portion 150 to the distal position moves the second radial protrusion 232 relative to the first radial protrusion 230 to detach the base 128 from the telescoping assembly 132.

0227The first portion 150 of the telescoping assembly 132 comprises a first arm 222 that protrudes distally. The second portion 152 of the telescoping assembly 132 comprises a second flex arm 220 that protrudes distally. The first arm 222 and the second flex arm 220 can be oriented within 25 degrees of each other (as measured between their central axes). The system is configured such that moving the first portion 150 from the proximal starting position to the distal position along the path 154 (shown in <figref idref="f0004">Figure 7</figref>) causes the first arm 222 to deflect the second flex arm 220, and thereby detach the second flex arm 220 from the base 128 to enable the base 128 to decouple from the telescoping assembly 132 (shown in <figref idref="f0004">Figure 7</figref>). Thus, the flex arm 220 is configured to releasably couple the second portion 152 to the base 128.

0228When the first portion 150 is in the proximal starting position, the first arm 222 of the first portion 150 is at least partially vertically aligned with the second flex arm 220 of the second portion 152 to enable the first arm 222 to deflect the second flex arm 220 as the first portion is moved to the distal position.

0229The first arm 222 and the second arm 220 can be oriented distally such that at least a portion of the first arm 222 is located proximally over a protrusion (e.g., the ramp 224) of the second arm 220. This protrusion can be configured to enable a collision between the first arm 222 and the protrusion to cause the second arm 220 to deflect (to detach the base 128 from the second portion 152).

0230In the embodiment illustrated in <figref idref="f0009">Figure 18</figref>, when the first portion 150 is in the proximal starting position, at least a section of the first arm 222 is located directly over at least a portion of the second flex arm 220 to enable the first arm 222 to deflect the second flex arm 220 as the first portion 150 is moved to the distal position described above. The second flex arm 220 comprises a first horizontal protrusion (e.g., the locking feature 232). The base 128 comprises a second horizontal protrusion (e.g., the locking feature 230) latched with the first horizontal protrusion to couple the base 128 to the second portion 152 of the telescoping assembly 132. The first arm 222 of the first portion 150 deflects the second flex arm 220 of the second portion 152 to unlatch the base 128 from the second portion 152, which unlatches the base 128 from the telescoping assembly 132.

0231Referring now to <figref idref="f0004">Figure 7</figref>, the system is configured to couple the glucose sensor 138 to the base 128 at a first position. The system is configured to detach the base 128 from the telescoping assembly 132 at a second position that is distal relative to the first position.

0232A third flex arm (e.g., flex arm 202 in <figref idref="f0008">Figure 15</figref>) couples the glucose sensor 138 to the base 128 at a first position. The second flex arm (e.g., flex arm 220 in <figref idref="f0009">Figure 18</figref>) detaches from the base at a second position. The second position is distal relative to the first position such that the system is configured to secure the base 128 to the telescoping assembly 132 until after the glucose sensor 138 is secured to the base 128.

SPRING COMPRESSION

0233Needles used in glucose sensor insertion applicators can be hazardous. For example, inadvertent needle-sticks can transfer diseases. Using a spring to retract the needle can reduce the risk of needle injuries.

0234Referring now to <figref idref="f0004">Figure 7</figref>, a spring 234 (e.g., a coil spring) can be used to retract the needle hub 162 that supports the c-shaped needle 156. The needle hub 162 can be released at the bottom of insertion depth (to enable the needle 156 to retract). For example, when the needle 156 reaches a maximum distal position, a latch 236 can release to enable the spring 234 to push the needle 156 proximally into a protective housing (e.g., into the first portion 150, which can be the protective housing).

0235Many applicators use pre-compressed springs. Many applicators use substantially uncompressed springs that are compressed by a user as the user compresses the applicator. One disadvantage of a pre-compressed spring is that the spring force can cause the components to creep (e.g., change shape over time), which can compromise the reliability of the design. One disadvantage of an uncompressed spring is that the first and second portions of the telescoping assembly can be free to move slightly relative to each other (when the assembly is in the proximal starting position). This "chatter" of the first and second portions can make the assembly seem weak and flimsy.

0236Many of the components described herein can be molded from plastic (although springs are often metal). Preventing creep in plastic components can help ensure that an applicator functions the same when it is manufactured and after a long period of time. One way to reduce the creep risk is to not place the parts under a load (e.g., in storage) that is large enough to cause plastic deformation during a storage time.

0237Generating the retraction energy by storing energy in a spring during deployment limits the duration of load on the system. For example, the retraction force of the spring can be at least partially generated by collapsing the telescoping assembly (rather storing the system with a large retraction force of a fully pre-compressed spring).

0238Transcutaneous and implantable sensors are affected by the in vivo properties and physiological responses in surrounding tissues. For example, a reduction in sensor accuracy following implantation of the sensor is one common phenomenon commonly observed. This phenomenon is sometimes referred to as a "dip and recover" process. Dip and recover is believed to be triggered by trauma from insertion of the implantable sensor, and possibly from irritation of the nerve bundle near the implantation area, resulting in the nerve bundle reducing blood flow to the implantation area.

0239Alternatively, dip and recover may be related to damage to nearby blood vessels, resulting in a vasospastic event. Any local cessation of blood flow in the implantation area for a period of time leads to a reduced amount of glucose in the area of the sensor. During this time, the sensor has a reduced sensitivity and is unable to accurately track glucose. Thus, dip and recover manifests as a suppressed glucose signal. The suppressed signal from dip and recover often appears within the first day after implantation of the signal, most commonly within the first 12 hours after implantation. Dip and recover normally resolves within 6-8 hours.

0240Identification of dip and recover can provide information to a patient, physician, or other user that the sensor is only temporarily affected by a short-term physiological response, and that there is no need to remove the implant as normal function will likely return within hours.

0241Minimizing the time the needle is in the body limits the opportunity for tissue trauma that can lead to phenomena such as dip and recover. Quick needle retraction helps to limit the time the needle is in the body. A large spring retraction force can quickly retract the needle.

0242The embodiment illustrated in <figref idref="f0004">Figure 7</figref> solves the "chatter" problem, avoids substantial creep, and enables quick needle retraction. The embodiment places the spring 234 in a slight preload between the first portion 150 and the second portion 152 of the telescoping assembly 132. In other words, when the first portion 150 is in the proximal starting position, the spring 234 is in a slightly compressed state due to the relaxed length of the spring 234 being longer than the length of the chamber in which the spring 234 resides inside the telescoping assembly 132.

0243In some embodiments, the relaxed length of the spring 234 is at least 4 percent longer than the length of the chamber. In several embodiments, the relaxed length of the spring 234 is at least 9 percent longer than the length of the chamber. In some embodiments, the relaxed length of the spring 234 is less than 18 percent longer than the length of the chamber. In several embodiments, the relaxed length of the spring 234 is less than 30 percent longer than the length of the chamber.

0244The spring 234 is compressed farther when the first portion 150 is moved distally relative to the second portion 152. In some embodiments, this slight preload has a much shorter compression length than the compression length of typical fully pre-compressed springs. In several embodiments, the preload causes a compression length of the spring 234 that is less than 25 percent of the compression length of the fully compressed spring 234. In some embodiments, the preload causes a compression length of the spring 234 that is greater than 3 percent of the compression length of the fully compressed spring 234. The slight preload eliminates the "chatter" while having a force that is too small to cause substantial creep of non-spring components in the system.

0245The spring 234 can be inserted into the first portion 150 via a hole 238 in the proximal end of the first portion 150. Then, the needle hub 162 (and the attached C-shaped needle 156) can be loaded through the proximal side of the first portion 150 of the telescoping assembly (e.g., via the hole 238 in the proximal end of the first portion 150).

0246The needle hub 162 is slid through the first portion 150 until radial snaps (e.g., the release feature 160 of the needle hub 162) engage a section of the first portion 150 (see the latch 236). Thus, the spring 234 is placed with a slight preload between the needle hub 162 and a distal portion of the first portion 150 of the telescoping assembly 132.

0247During applicator activation and the telescoping (e.g., collapsing of the first portion 150 into the second portion 152), the spring 234 is compressed farther. At the bottom of travel (e.g., at the distal ending position), the radial snaps of the needle hub 162 are forced radially inward by features (e.g., the protrusions 170) in the telescoping assembly 132 (as shown by the progression of <figref idref="f0004 f0005 f0006">Figures 7-11</figref>). This releases the needle hub 162 and allows the spring 234 to expand to drive the needle 156 proximally out of the host (and into the first portion 150 and/or the second portion 152).

0248As shown in <figref idref="f0004">figure 7</figref>, the base 128 protrudes from the distal end of the system while the first portion 150 of the telescoping assembly 132 is located in the proximal starting position and the glucose sensor 138 is located remotely relative to the base 128. The glucose sensor 138 is moveably coupled to the base 128 via the telescoping assembly 132 because the glucose sensor 138 is coupled to the first portion 150 and the base 128 is coupled to the second portion 152 of the telescoping assembly 132.

0249The system includes a spring 234 configured to retract a needle 156. The needle 156 is configured to facilitate inserting the glucose sensor 138 into the skin. In some embodiments, the system does not include the needle 156.

0250When the first portion 150 is in the proximal starting position, the spring 234 is in a first compressed state. The system is configured such that moving the first portion 150 distally from the proximal starting position increases a compression of the spring 234. The first compressed state places the first portion 150 and second portion 152 in tension. Latching features hold the first portion 150 and second portion 152 in tension. In other words, in the proximal starting position, the latching features are configured to prevent the spring 234 from pushing the first portion 150 proximally relative to the second portion 152. The latching features resist the first compressed state.

0251In several embodiments, the potential energy of the first compressed state is less than the amount of potential energy necessary to retract the needle 156. This low potential energy of the partially pre-compressed spring 234 is typically insufficient to cause creep, yet is typically sufficient to eliminate the "chatter" described above.

0252Redundant systems can help ensure that the needle 156 (and in some cases the sensor 138) can always be removed from the host after they are inserted into the host. If in extreme cases the necessary needle removal force is greater than the spring retraction force, the user can pull the entire telescoping assembly 132 proximally to remove the needle 156 and/or the sensor 138 from the host.

0253Some embodiments include a secondary retraction spring. In other words, in some embodiments, the spring 234 in <figref idref="f0004">Figure 7</figref> is actually two concentric springs. (In several embodiments, the spring 234 is actually just one spring.) The secondary spring can be shorter than the primary retraction spring. The secondary retraction spring can provide additional needle retraction force and can enable additional tailoring of the force profile.

0254Many users desire to minimize the amount of material they throw away (as trash). Moving the needle 156 to the back of the applicator post deployment enables easy access to remove the needle 156 post deployment.

0255<figref idref="f0010">Figure 20</figref> illustrates a perspective view of the needle 156, the needle hub 162, and the spring 234 just after they were removed proximally from the hole 238 in a proximal end of the first portion 150 of the telescoping assembly 132.

0256The hole 238 is an opening at a proximal end of the applicator. The hole 238 is configured to enable removing the needle 156, the needle hub 162, and/or the spring 234. This opening can be covered by a removable cover (e.g., a sticker, a hinged lid).

0257<figref idref="f0011">Figures 21 and 22</figref> illustrate perspective views where a removable cover 272 is coupled to the first portion 150 to cover the hole 238 through which the needle 156 can be removed from the telescoping assembly 132. A hinge 274 can couple the cover 272 to the first portion 150 such that the cover 272 can rotate to close the hole 238 (as shown in <figref idref="f0011">Figure 22</figref>) and rotate to open the hole 238 (as shown in <figref idref="f0011">Figure 21</figref>).

0258Removing the cover 272 can enable a user to remove the needle 156 from the applicator (e.g., the telescoping assembly 132) such that the user can throw the needle 156 in a sharps container and reuse the applicator with a new needle. Removing the needle 156 from the applicator can also enable throwing the rest of the applicator into a normal trash collector to reduce the amount of trash that needs to be held by the sharps container.

0259The features described in the context of <figref idref="f0010 f0011 f0027">Figures 20-22 and 60</figref> can be combined with any of the embodiments described herein.

0260<figref idref="f0027">Figure 60</figref> illustrates a perspective view of another telescoping assembly embodiment 132h. The cover 272h is adhered to a proximal end of the telescoping assembly 132h to cover a hole configured to retrieve a needle after the needle retracts (e.g., as described in the context of <figref idref="f0011">Figures 21 and 22</figref>). Peeling the cover 272h from the telescoping assembly 132h can enable a user to dump the needle 156 (shown in <figref idref="f0004">Figure 7</figref>) into a sharps container.

0261In this embodiment, the cover 272h is a flexible membrane such as a Tyvek label made by E. I. du Pont de Nemours and Company ("DuPont"). The cover 272h can include an adhesive to bond the cover 272h to the proximal end of the telescoping assembly 132h.

0262In some embodiments, a second cover 272 is adhered to a distal end of the telescoping assembly 132h to cover the end of the telescoping assembly 132h through which the sensor 138 (shown in <figref idref="f0004">Figure 7</figref>) passes. The distal end of the telescoping assembly 132h can also be covered by a plastic cap 122h.

0263The cover 272h can be configured to enable sterilization processes to pass through the material of the cover 272h to facilitate sterilization of the interior of the telescoping assembly 132h. For example, sterilization gases can pass through the cover 272h.

0264Any of the features described in the context of <figref idref="f0027">Figure 60</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0027">Figure 60</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-59 and 61-70</figref>.

0265The telescoping assembly 132h can use the same interior features and components as described in the context of <figref idref="f0004">Figure 7</figref>. One important difference is that the first portion 150h slides on an outer surface of the second portion 152 (rather than sliding inside part of the second portion 152 as shown in <figref idref="f0004">Figure 7</figref>). Also, the telescoping assembly 132h does not use a sterile barrier shell 120 (as shown in <figref idref="f0002">Figure 2</figref>).

0266Any of the features described in the context of <figref idref="f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011">Figures 7-22</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011">Figures 7-22</figref> can be combined with the embodiments described in the context of <figref idref="f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 23-70</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

FORCE PROFILES

0267Referring now to <figref idref="f0004">Figure 7</figref>, in some embodiments, moving the first portion 150 of the telescoping assembly 132 distally relative to the second portion 152 typically involves placing the distal end of the system against the skin of the host and then applying a distal force on the proximal end of the system. This distal force can cause the first portion 150 to move distally relative to the second portion 152 to deploy the needle 156 and/or the glucose sensor 138 into the skin.

0268The optimal user force generated axially in the direction of deployment is a balance between preventing accidental premature deployment and ease of insertion. A force that is ideal at a certain portion of distal actuation may be far less than ideal at another portion of distal actuation.

0269The user places the applicator (e.g., the telescoping assembly 132) against the skin surface and applies a force distally on the applicator (e.g., by pushing down on the proximal end of the applicator). When the user-generated force exceeds a threshold, the applicator collapses (e.g., telescopes distally) and the user drives the sensor into the body.

0270Several embodiments include unique force profiles that reduce accidental premature deployment; dramatically increase the likelihood of complete and proper deployment; and reduce patient discomfort. Specific structures enable these unique force profiles. For example, the following structures can enable the unique force profiles described herein: structures that hold the telescoping assembly 132 in the proximal starting position; structures that attach the sensor module 134 to the base 128; structures that release the sensor module 134 from the first portion 150; structures that prevent the needle 156 from retracting prematurely; structures that retract the needle 156; structures that release the base 128 from the second portion 152; structures that pad the collision at the distal position; and structures that hold the telescoping assembly 132 in a distal ending position. These structures are described in various sections herein.

0271Several embodiments include a system for applying an on-skin sensor assembly 600 to a skin 130 of a host (shown in <figref idref="f0003">Figure 4</figref>). Referring now to <figref idref="f0004">Figure 7</figref>, the system can comprise a telescoping assembly 132 having a first portion 150 configured to move distally relative to a second portion 152 from a proximal starting position to a distal position along a path 154; a glucose sensor 138 coupled to the first portion 150; and a latch 236 configurable to impede a needle 156 from moving proximally relative to the first portion.

0272The first portion 150 is releasably secured in the proximal starting position by a securing mechanism (e.g., the combination of 240 and 242 in <figref idref="f0004">Figure 7</figref>) that impedes moving the first portion 150 distally relative to the second portion 152. The system is configured such that prior to reaching the distal position and/or by reaching the distal position, moving the first portion 150 distally relative to the second portion 152 releases the latch 236 thereby causing the needle 156 to retract proximally into the system.

0273In several embodiments, the securing mechanism is formed by an interference between the first portion 150 and the second portion 152. The interference can be configured to impede the first portion 150 from moving distally relative to the second portion 152. For example, a radially outward protrusion 240 of the first portion 150 can collide with a proximal end 242 of the second portion 152 such that moving the first portion 150 distally requires overcoming a force threshold to cause the first portion 150 and/or the second portion 152 to deform to enable the radially outward protrusion 240 to move distally relative to the proximal end 242 of the second portion 152.

0274The system can include a first force profile measured along the path 154. As shown in <figref idref="f0012">Figure 23</figref>, the force profile 244 can include force on the Y axis and travel distance on the X axis. Referring now to <figref idref="f0004">Figures 7</figref> and <figref idref="f0012">23</figref>, the force profile 244 can be measured along the central axis 196.

0275One way in which the force profile 244 can be measured is to place the telescoping assembly 132 against the skin; place a force gauge such as a load cell on the proximal end of the telescoping assembly 132; calibrate the measurement system to account for the weight of the force gauge; and then press on the proximal side of the force gauge to drive the telescoping assembly 132 from the proximal starting position to the distal position along the path 154. <figref idref="f0012">Figure 23</figref> illustrates force versus distance from the proximal starting position based on this type of testing procedure.

0276The first force profile 244 can comprise a first magnitude 246 coinciding with overcoming the securing mechanism (e.g., 240 and 242), a third magnitude 250 coinciding with releasing the latch 236 (e.g., releasing the needle retraction mechanism), and a second magnitude 248 coinciding with an intermediate portion of the path 154 that is distal relative to overcoming the securing mechanism and proximal relative to releasing the latch 236.

0277In several embodiments, the second magnitude 248 is a peak force associated with compressing a needle retraction spring (e.g., the spring 234 in <figref idref="f0004">Figure 7</figref>) prior to beginning to release the latch 236. This peak force can be at least 0.2268 kg (0.5 pounds), at least 0.68039 kg (1.5 pounds), less than 1.81437 kg (4 pounds), and/or less than 2.72155 kg (6 pounds).

0278In several embodiments, the third magnitude 250 is a peak force associated with releasing the needle retraction mechanism. This peak force can be at least 0.45359 kg (1 pound), at least 0.90718 kg (2 pounds), less than 1.81437 kg (4 pounds), and/or less than 2.72155 kg (6 pounds).

0279In some embodiments, the second magnitude 248 is less than the first magnitude 246 and the third magnitude 250 such that the system is configured to promote needle acceleration during the intermediate portion of the path 154 to enable a suitable needle speed at a time the needle 156 (or the glucose sensor 138) first pierces the skin.

0280The first magnitude 246 can be the peak force required to overcome the securing mechanism (e.g., 240 and 242). This peak force can be at least 2.26796 kg (5 pounds), at least 2.72155 kg (6 pounds), less than 4.53592 kg (10 pounds), and/or less than 5.44311 kg (12 pounds). The first magnitude 246 can be at least 100 percent greater than the second magnitude 248. The first magnitude 246 can be at least 200 percent greater than the second magnitude 248. The second magnitude 248 can be during a portion of the force profile 244 where the compression of the spring 234 is at least 50 percent of the maximum spring compression reached just before the needle 156 begins to retract proximally. The slope of the force profile 244 can be positive for at least 1 millimeter during the time at which the second magnitude 248 is measured (due to the increasing spring force as the spring compression increases).

0281The first magnitude 246 can be greater than the third magnitude 250 (and/or greater than the second magnitude 248) such that the system is configured to impede initiating a glucose sensor insertion cycle unless a user is applying enough force to release the latch 236. For example, the force necessary for the protrusion 240 to move distally relative to the proximal end 242 can deliberately be designed to be greater than the force necessary to retract the needle 156.

0282To provide a sufficient safety margin, the first magnitude 246 can be at least 50 percent greater than the third magnitude 250. In some embodiments, the first magnitude 246 is at least 75 percent greater than the third magnitude 250. To avoid a system where the first magnitude 246 is unnecessarily high in light of the forces required along the path 154 distally relative to the first magnitude 246, the first magnitude 246 can be less than 250 percent greater than the third magnitude 250.

0283A second force profile 252 can coincide with the intermediate portion of the path 154. For example, the second magnitude 248 can be part of the second force profile 252. This second force profile 252 can include a time period in which the slope is positive for at least 1 millimeter, at least 2.5 millimeters, less than 8 millimeters, and/or less than 15 millimeters (due to the increasing spring force as the spring compression increases).

0284A proximal millimeter of the second force profile 252 comprises a lower average force than a distal millimeter of the second force profile 252 in response to compressing a spring 234 configured to enable the system to retract the needle 156 into the telescoping assembly 132.

0285The system also includes a first force profile 254 (measured along the path 154). The first force profile 254 comprises a first average magnitude coinciding with moving distally past a proximal half of the securing mechanism and a second average magnitude coinciding with moving distally past a distal half of the securing mechanism. The first average magnitude is greater than the second average magnitude such that the system is configured to impede initiating a glucose sensor insertion cycle unless a user is applying enough force to complete the glucose sensor insertion cycle.

0286A first force peak 256 coincides with moving distally past the proximal half of the securing mechanism. The first force peak 256 is at least 25 percent higher than the second average magnitude.

0287The first force profile 254 comprises a first magnitude 246 coinciding with overcoming the securing mechanism and a subsequent magnitude coinciding with terminating the securing mechanism (e.g., moving past the distal portion of the securing mechanism). The first magnitude 246 comprises a proximal vector and the subsequent magnitude comprises a distal vector. <figref idref="f0012">Figure 23</figref> is truncated at zero force, so the distal vector appears to be have a magnitude of zero in <figref idref="f0012">Figure 23</figref>, although the actual value is negative (e.g., negative 0.90718 kg (2 pounds)).

0288The proximal vector means the system is resisting the distal movement of the first portion 150 relative to the second portion 152. The distal vector means that the second half of the securing mechanism can help propel the needle 156 and the sensor 138 towards the skin and/or into the skin. In other words, the distal vector assists the distal movement of the first portion 150 relative to the second portion 152.

0289The third force profile 260 can include many peaks and values due to the following events: the sensor module 134 docking to the base 128; the base detaching from the second portion 152 (and thus detaching from the telescoping assembly 132); the release feature 160 of the needle hub 162 defecting inward due to the proximal protrusions 170 of the second portion 152; the latch 236 releasing; the needle 156 retracting into an inner chamber of the first portion 150; and/or the first portion 150 hits the distal position (e.g., the end of travel).

0290As shown in <figref idref="f0004">Figure 7</figref>, the securing mechanism can be a radially outward protrusion 240 (of the first portion 150) configured to collide with a proximal end 242 of the second portion 152 such that moving the first portion 150 distally requires overcoming a force threshold to cause the first portion 150 and/or the second portion 152 to deform to enable the radially outward protrusion 240 to move distally relative to the proximal end 242 of the second portion 152. The radially outward protrusion 240 is configured to cause the second portion 152 to deform elliptically to enable the first portion 150 to move distally relative to the second portion 152.

0291<figref idref="f0012">Figure 24</figref> illustrates another securing mechanism. At least a section of the first portion 150 interferes with a proximal end 242 of the second portion 152 such that pushing the first portion 150 distally relative to the second portion 152 requires a force greater than a force threshold. The force threshold is the minimum force necessary to deform at least one of the first portion 150 and the second portion 152 to overcome the interference 266, which is shown inside a dashed circle in <figref idref="f0012">Figure 24</figref>.

0292Many different interference geometries and types are used in various embodiments. The interference can be between the first portion 150 and the second portion 152. The interference can be between the needle hub 162 and the second portion 152. For example, the interference can resist the distal movement of the needle hub 162.

0293In some embodiments, the first portion 150 includes a taper 262. Once an interfering section of the first portion 150 moves distally past the interference area 266, the taper 262 makes the system such that the interference 266 no longer impedes distal movement of the first portion 150.

0294The second portion 152 can also have a taper 263. The taper 263 can be on an interior surface of the second portion 152 such that the interior size gets larger as measured proximally to distally along the taper 263.

0295The interfering portion 242 of the second portion 152 can include a ramp (as shown in <figref idref="f0012">Figure 24</figref>) to aid the deformation described above. The interfering section of the first portion 150 is located proximally relative to the interfering section of the second portion 152.

0296The securing mechanism can comprise a radially outward protrusion (e.g., 240 in <figref idref="f0004">Figure 7</figref>) of the first portion 150 that interferes with a radially inward protrusion of the second portion 152 (e.g., as shown by the interference 266 in <figref idref="f0012">Figure 24</figref>) such that the securing mechanism is configured to cause the second portion 152 to deform elliptically to enable the first portion 150 to move distally relative to the second portion 152.

0297Any of the features described in the context of <figref idref="f0012 f0013 f0014 f0015 f0016">Figures 24-32</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0012 f0013 f0014 f0015 f0016">Figures 24-32</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-23 and 33-70</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

0298<figref idref="f0013">Figure 25</figref> illustrates a cross sectional view of a portion of an embodiment in which the needle holder (e.g., the needle hub 162) is configured to resist distal movement of the first portion 150 relative to the second portion 152b. The second portion 152b is like other second portions 150 described herein (e.g., as shown in <figref idref="f0004">Figure 7</figref>) except that the second portion 152b includes flex arms 276 that are at least part of the securing mechanism. The flex arms 276 are releasably coupled to the needle holder to releasably secure the first portion 150 to the second portion 152b in the proximal starting position (as shown in <figref idref="f0004">Figure 7</figref>).

0299The needle 156 (shown in <figref idref="f0004">Figure 7</figref>) is retractably coupled to the first portion 150 by the needle holder 162. The needle holder 162 is configured to resist distal movement of the first portion 150 relative to the second portion 152b due to a chamfer and/or a ramp 278 interfering with flex arms 276. Pushing the first portion 150 distally requires overcoming the force necessary to deflect the flex arms 276 outward such that the flex arms 276 move out of the way of the ramp 278.

0300<figref idref="f0013">Figure 27</figref> illustrates a perspective view of another securing mechanism, a frangible release 280. <figref idref="f0013">Figure 26</figref> illustrates a top view of a frangible ring 282. The ring 282 includes two frangible tabs 284 that protrude radially inward. In some embodiments, the tabs 284 are radially inward protrusions on opposite sides of the ring 282 relative to each other. The frangible member (e.g., the ring 282) can be part of the first portion 150, the second portion 152, or any other portion of the system. For example, the frangible member can be a feature of a molded second portion 152.

0301The ring 282 can be made of a brittle material configured to enable the tabs 284 to break when the first portion 150 is pushed distally relative to the second portion 152. For example, a section of the first portion 150 can be located proximally over the tab 284 when the first portion 150 is in the proximal starting position (as shown in <figref idref="f0013">Figure 27</figref> by the frangible release 280). Moving the first portion 150 distally can cause the section of the first portion 150 to bend and/or break the tab 284.

0302In some embodiments, a radially outward protrusion 286 of the first portion 150 is configured to bend and/or break the tab 284. The ring 282, the tab 284, and the other components described herein can be molded from a plastic such as acrylonitrile butadiene styrene, polyethylene, and polyether ether ketone. (Springs, interconnects, and needles can be made of steel.) In some embodiments, the ring 282 is at least 0.2 millimeters thick, at least 0.3 millimeters thick, less than 0.9 millimeters thick, and/or less than 1.5 millimeters thick.

0303The ring 282 can be secured between the first portion 150 and the second portion 152 of the telescoping assembly 132. The ring 282 can wrap around a perimeter of the first portion 150 and can be located proximally relative to the second portion 152 such that the ring 282 rests against a proximal end of the second portion 152.

0304The ring 282 enables a frangible coupling between the first portion 150 and the second portion 152 while the first portion 150 is in the proximal starting position. In <figref idref="f0013">Figure 27</figref>, the system is configured such that moving the first portion 150 to the distal position breaks the frangible coupling (e.g., the frangible release 280).

0305In some embodiments, the tabs 284 are not part of a ring 282. The tabs 284 can be part of the second portion 152 or part of the first portion 150.

0306<figref idref="f0013">Figure 27</figref> also includes a magnet system 290. The magnet system 290 includes a magnet and a metal element in close enough proximity that the magnet is attracted to the metal element (e.g., a metal disk). For example, the second portion 152 can include a magnet, and the first portion 150 can include the metal element. In several embodiments, the second portion 152 can include a metal element, and the first portion 150 can include the magnet.

0307The magnet and metal element can be located such that they are located along a straight line oriented radially outward from the central axis 196 (shown in <figref idref="f0004">Figure 7</figref>). This configuration can position the magnet for sufficient attraction to the metal element to resist movement of the first portion 150. For example, when the first portion 150 is in the proximal starting position, the magnetic force of the magnet system 290 can resist distal movement of the first portion. Thus, the magnet releasably couples the first portion 150 to the second portion 152 while the first portion 150 is in the proximal starting position.

0308In several embodiments, a user can compress an internal spring or the spring can be pre-compressed (e.g., compressed fully at the factory). The telescoping assembly can include a button 291 configured to release the spring force to cause the needle and/or the sensor to move into the skin.

0309The cover 272h described in the context of <figref idref="f0027">Figure 60</figref> can be adhered to the proximal end of the first portion 150 shown in <figref idref="f0013">Figure 27</figref>. The cover 272h can be used with any of the embodiments described herein.

0310<figref idref="f0015">Figure 31</figref> illustrates a side view of a telescoping assembly 132e having a first portion 150e and a second portion 152e. The first portion 150e includes a radially outward protrusion 286e configured to engage a radially inward ramp 296 located on an interior wall of the second portion 152e. When a user applies a distal, axial force on the first portion 150e, the protrusion 286e collides with the ramp 296. The angle of the ramp causes the first portion 150e to rotate relative to the second portion 152e. This rotation resists the distal force and acts as a securing mechanism. Once the protrusion 286e moves beyond the distal end of the ramp 296, the ramp 296 no longer causes rotation, and thus, no longer acts as a securing mechanism.

0311Many of the embodiments described herein rely on a compressive force of a person. Many unique structures enable the force profiles described herein. The structures help ensure the compressive force caused by a person pushing distally on a portion of the system results in reliable performance. One challenge of relying on people to push downward on the system to generation appropriate forces is that the input force can vary substantially by user. Even a single user can apply different input forces on different occasions.

0312One solution to this variability is to replace the need for a user-generated input force with a motor-generated force. The motor can provide reliable input forces. Motors also enable varying the force at different sections of the path from the proximal starting position to the distal position.

0313<figref idref="f0014 f0015">Figures 28-30</figref> illustrates embodiments of telescoping assemblies 132c, 132d that include motors 290c, 290d to drive a needle 156 and/or a glucose sensor 138 into the skin. The motors 290c, 290d can be linear actuators that use an internal magnetic system to push a rod distally and proximally. The linear actuators can also convert a rotary input into linear motion to push a rod distally and proximally. The movement of the rod can move various portions of the system including the needle 156, the needle hub 162c, the first portion 150c, 150d of the telescoping assembly 132c, 132d, the sensor module 134, and/or the sensor 138. The motors 290c, 290d can include internal batteries to supply electricity for the motors 290c, 290d.

0314<figref idref="f0014">Figure 28</figref> illustrates a perspective, cross-sectional view of an embodiment in which the motor 290c pushes the needle hub 162c distally relative to the motor 290c and relative to the second portion 152c. The needle hub 162c can include a rod that slides in and out of the housing of the motor 292c. The distal movement of the needle hub 162c can push at least a portion of the needle 156 and/or the sensor 138 (shown in <figref idref="f0004">Figure 7</figref>) into the skin. The distal movement of the needle hub 162c can move the sensor module 134 distally such that the sensor module 134 docks with the base 128. This coupling can precede the detachment of the base 128 from the telescoping assembly 132c.

0315<figref idref="f0014">Figures 29</figref> and <figref idref="f0015">30</figref> illustrate side, cross-sectional views of another motor embodiment. In this embodiment, the rod 294 of the motor 292d is coupled to and immobile relative to the second portion 152d of the telescoping assembly 132d. The motor 292d is coupled to and immobile relative to the first portion 150d of the telescoping assembly 132d. As a result, pulling the rod 294 into the housing of the motor 292d causes the first portion 150d to move distally relative to the second portion 152d. The glucose module 134 is coupled to a distal portion of the first portion 150d (as described herein). Thus, the glucose sensor 138 is moved distally into the skin of the host and the glucose module 134 is coupled to the base 128. As illustrated in <figref idref="f0014">Figures 29</figref> and <figref idref="f0015">30</figref>, the embodiment does not include a needle. Similar embodiments can include a needle.

0316<figref idref="f0016">Figure 32</figref> illustrates a perspective, cross-section view of the telescoping assembly 132. In some embodiments, a protrusion 302 of the first portion 150 couples with a hole 304 of the second portion 152. The protrusion 302 can be oriented distally to latch with the hole 304 in response to the first portion 150 reaching the distal position.

0317In several embodiments, a protrusion 302 of the second portion 152 couples with a hole 304 of the first portion 150. The protrusion 302 can be oriented proximally to latch with the hole 304 in response to the first portion 150 reaching the distal position.

0318The protrusion 302 can be a flex arm that is at least 10 millimeters long, at least 15 millimeters long, and/or less than 50 millimeters long. The protrusion 302 can include an end portion that protrudes at an angle relative to the central axis of the majority of the protrusion 302. This angle can be at least 45 degrees, at least 75 degrees, less than 110 degrees, and/or less than 135 degrees.

0319Coupling the protrusion 302 to the hole 304 can permanently lock the first portion 150 in a downward position (that is distal to the proximal starting position and is within 3 millimeter of the distal position) while the needle 156 is in a retracted state. This locking can prevent the system from being reused and can prevent needle-stick injuries.

0320Any of the features described in the context of <figref idref="f0012">Figure 23</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0012">Figure 23</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-22 and 24-70</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

INTERCONNECTS

0321Referring now to <figref idref="f0003">Figure 4</figref>, in many embodiments, the electronic unit 500 drives a voltage bias through the sensor 138 so that current can be measured. Thus, the system is able to analyze glucose levels in the host. The reliability of the electrical connection between the sensor 138 and the electronics unit 500 is critical for accurate sensor data measurement.

0322In many embodiments, the host or a caregiver create the electrical connection between the sensor 138 and the electronics unit 500. A seal 192 can prevent fluid ingress as the electronics unit 500 is pressed onto the glucose sensor module 134. Oxidation and corrosion can change electrical resistance of the system and are sources of error and noise in the signal.

0323The electrical connections should be mechanically stable. Relative movement between the parts of the electrical system can cause signal noise, which can hinder obtaining accurate glucose data.

0324A low-resistance electrical connection is more power efficient. Power efficiency can help maximize the battery life of the electronics unit 500.

0325In embodiments where the host or caregiver must compress the electrical interconnect and/or seal 192, minimizing the necessary force increase user satisfaction. Lowering the user-applied force makes the transmitter easier to install. If the necessary force is too great, users and caregivers may inadvertently fail to apply adequate force, which can jeopardize the reliability and performance of the system. The force that the user needs to apply to couple the electronics unit 500 to the base 128 and sensor module 134 is strongly influenced by the force necessary to compress the interconnect. Thus, there is a need for an electrical interconnect with a lower compression force.

0326Manufacturing variability, host movement, and temperature variations while the host is using the on-skin sensor assembly 600 necessitate providing a robust electrical connection throughout an active compression range (which encompasses the minimum and maximum compression states reasonably possible). Thus, there is a need for electrical connections that are tolerant of compression variation within the active compression range.

0327Metallic springs (e.g., coil or leaf springs) can be compressed between the sensor 138 and the electronics unit 500 to provide a robust, reliable electrical connection that requires a low compression force to couple the electronics unit 500 to the base 128.

0328<figref idref="f0016">Figure 33</figref> illustrates a perspective view of an on-skin senor assembly just before the electronics unit 500 (e.g., a transmitter) is snapped onto the base 128. Coupling the electronics unit 500 to the base 128 can compress the seal 192 to prevent fluid ingress and can compress an interconnect (e.g., springs 306) to create an electrical connection 310 between the glucose sensor 138 and the electronics unit 500.

0329Creating the electrical connection 310 and/or coupling the electronics unit 500 to the base 128 can cause the electronics unit 500 (e.g., a transmitter) to exit a sleep mode. For example, conductive members (e.g., of the sensor module 134 and/or of the base 128) can touch electrical contacts of the electronics unit 500 (e.g., electrical contacts of a battery of the electronics unit 500), which can cause the electronics unit 500 to exit a sleep mode. The conductive member of the sensor module 134 and/or of the base 128 can be a battery jumper that closes a circuit to enable electricity from the battery to flow into other portions of the electronics unit 500.

0330Thus, creating the electrical connection 310 and/or coupling the electronics unit 500 to the base 128 can "activate" the electronics unit 500 to enable and/or to prepare the electronics unit 500 to wirelessly transmit information to other devices 110-113 (shown in <figref idref="f0001">Figure 1</figref>). U.S. Patent Publication No. <patcit id="pcit0034" dnum="US20120078071A1"><text>US-2012-0078071-A1</text></patcit> includes additional information regarding transmitter activation.

0331The distal face of the electronics unit 500 can include planar electrical contacts that touch the proximal end portions of the springs 306. The distal end portions of the springs 306 can contact various conductive elements of the glucose sensor 138. Thus, the springs 306 can electrically couple the electronics unit 500 to the various conductive elements of the glucose sensor 138. In the illustrated embodiment, two metallic springs 306 electrically connect the glucose sensor 138 and the electronics unit 500. Some embodiments use one spring 306. Other embodiments use three, four, five, ten, or more springs 306.

0332Metallic springs 306 (e.g., gold-plated springs) are placed above the sensor wire 138 in the sensor module 134. The sensor 138 is located between a rigid polymer base 128 and the bottom surface of the spring 306. The top surface of the spring 306 contacts a palladium electrode located in the bottom of the electronics module 500. The rigid electronics module 500 and the rigid polymer base 128 are brought together creating a compressed sandwich with the sensor 138 and the spring 306.

0333The springs 306 can be oriented such that their central axes are within 25 degrees of the central axis 196 of the telescoping assembly 132 (shown in <figref idref="f0004">Figure 7</figref>). The springs 306 can have a helical shape. The springs 306 can be coil springs or leaf springs.

0334Springs 306 can have ends that are plain, ground, squared, squared and ground, or any other suitable configuration. Gold, copper, titanium, and bronze can be used to make the springs 306. Springs 306 can be made from spring steel. In several embodiments, the steels used to make the springs 306 can be low-alloy, medium-carbon steel or high-carbon steel with a very high yield strength. The springs 306 can be compression springs, torsion springs, constant springs, variable springs, helical springs, flat springs, machined springs, cantilever springs, volute springs, balance springs, leaf springs, V-springs, and/or washer springs.

0335Some embodiments use a spring-loaded pin system. The spring system can include a receptacle. A pin can be located partially inside the receptacle such that the pin can slide partially in and out of the receptacle. A spring can be located inside the receptacle such that the spring biases the pin outward towards the electronics unit 500. The receptacle can be electrically coupled to the sensor 138 such that pressing the electronics unit 500 onto the spring-loaded pin system electrically couples the electronics unit 500 and the sensor 138.

0336Mill-Max Mfg. Corp. of Oyster Bay, New York, U.S.A. ("Mill-Max") makes a spring-loaded pin system with a brass-alloy shell that is plated with gold over nickel. One Mill-Max spring-loaded pin system has a stainless steel spring and an ordering code of 0926-1-15-20-75-14-11-0.

0337In several embodiments, the electronics unit 500 includes a battery to provide electrical power to various electrical components (e.g., a transmitter) of the electronics unit 500.

0338In some embodiments, the base 128 can include a battery 314 that is located outside of the electronics unit 500. The battery 314 can be electrically coupled to the electrical connection 310 such that coupling the electronics unit 500 to the base 128 couples the battery 314 to the electronics unit 500. <figref idref="f0011">Figures 22B and 22C</figref> of U.S. Patent Publication No. <patcit id="pcit0035" dnum="US20090076360A1"><text>US-2009-0076360-A1</text></patcit> illustrate a battery 444, which in some embodiments, can be part of the base (which can have many forms including the form of base 128 shown in <figref idref="f0016">Figure 33</figref> herein).

0339<figref idref="f0017">Figure 34</figref> illustrates a perspective view of the sensor module 134. Protrusions 308 can secure the springs 306 to the sensor module 134. (Not all the protrusions 308 are labeled in order to increase the clarity of <figref idref="f0017">Figure 34</figref>.) The protrusions 308 can protrude distally.

0340At least three, at least four, and/or less than ten protrusions 308 can be configured to contact a perimeter of a spring 306. The protrusions 308 can be separated by gaps. The gaps enable the protrusions 308 to flex outward as the spring 306 is inserted between the protrusions 308. The downward force of coupling the electronics unit 500 to the base 128 can push the spring 306 against the sensor 138 to electrically couple the spring 306 to the sensor 138. The sensor 138 can run between at least two of the protrusions 308.

0341<figref idref="f0016">Figure 33</figref> illustrates an on-skin sensor system 600 configured for transcutaneous glucose monitoring of a host. The on-skin sensor system 600 can be used with the other components shown in <figref idref="f0004">Figure 7</figref>. The sensor module 134 can be replaced with the sensor modules 134d, 134e shown in <figref idref="f0017">Figures 35</figref> and <figref idref="f0018">37</figref>. Thus, the sensor modules 134d, 134e shown in <figref idref="f0017">Figures 35</figref> and <figref idref="f0018">37</figref> can be used with the other components shown in <figref idref="f0004">Figure 7</figref>.

0342Referring now to <figref idref="f0016">Figures 33</figref> and <figref idref="f0017">34</figref>, the system 600 can include a sensor module housing 312; a glucose sensor 138a, 138b having a first section 138a configured for subcutaneous sensing and a second section 138b mechanically coupled to the sensor module housing 312; and an electrical interconnect (e.g., the springs 306) mechanically coupled to the sensor module housing 312 and electrically coupled to the glucose sensor 138a, 138b. The springs can be conical springs, helical springs, or any other type of spring mentioned herein or suitable for electrical connections.

0343The sensor module housing 312 comprises at least two proximal protrusions 308 located around a perimeter of the spring 306. The proximal protrusions 308 are configured to help orient the spring 306. A segment of the glucose sensor 138b is located between the proximal protrusions 308 (distally to the spring 306).

0344The sensor module housing 312 is mechanically coupled to the base 128. The base 128 includes an adhesive 126 configured to couple the base 128 to skin of the host.

0345The proximal protrusions 308 orient the spring 306 such that coupling an electronics unit 500 to the base 128 presses the spring 306 against a first electrical contact of the electronics 500 unit and a second electrical contact of the glucose sensor 138b to electrically couple the glucose sensor 138a, 138b to the electronics unit 500.

0346Referring now to <figref idref="f0016 f0017 f0018">Figures 33 and 35-38</figref>, the system 600 can include a sensor module housing 312d, 312e; a glucose sensor 138a, 138b having a first section 138a configured for subcutaneous sensing and a second section 138b mechanically coupled to the sensor module housing 312d, 312e; and an electrical interconnect (e.g., the leaf springs 306d, 306e) mechanically coupled to the sensor module housing 312d, 312e and electrically coupled to the glucose sensor 138a, 138b. The sensor modules 134d, 134e can be used in place of the sensor module 134 shown in <figref idref="f0004">Figure 7</figref>. The leaf springs 306d, 306e can be configured to bend in response to the electronics unit 500 coupling with the base 128.

0347As used herein, cantilever springs are a type of leaf spring. As used herein, a leaf spring can be made of a number of strips of curved metal that are held together one above the other. As used herein in many embodiments, leaf springs only include one strip (e.g., one layer) of curved metal (rather than multiple layers of curved metal). For example, the leaf spring 306d in <figref idref="f0017">Figure 35</figref> can be made of one layer of metal or multiple layers of metal. In some embodiments, leaf springs include one layer of flat metal secured at one end (such that the leaf spring is a cantilever spring).

0348As shown in <figref idref="f0017">Figures 35 and 36</figref>, the sensor module housing 312d comprises a proximal protrusion 320d having a channel 322d in which at least a portion of the second section of the glucose sensor 138b is located. The channel 322d positions a first area of the glucose sensor 138b such that the area is electrically coupled to the leaf spring 306d.

0349As shown in the cross-sectional, perspective view of <figref idref="f0017">Figure 36</figref>, the leaf spring 306d arcs away from the first area and protrudes proximally to electrically couple with an electronics unit 500 (shown in <figref idref="f0016">Figure 33</figref>). At least a portion of the leaf spring 306d forms a "W" shape. At least a portion of the leaf spring 306d forms a "C" shape. The leaf spring 306d bends around the proximal protrusion 320d. The leaf spring 306d protrudes proximally to electrically couple with an electronics unit 500 (shown in <figref idref="f0016">Figure 33</figref>). The seal 192 is configured to impede fluid ingress to the leaf spring 306d.

0350The leaf spring 306d is oriented such that coupling an electronics unit 500 to the base 128 (shown in <figref idref="f0016">Figure 33</figref>) presses the leaf spring 306d against a first electrical contact of the electronics unit 500 and a second electrical contact of the glucose sensor 138b to electrically couple the glucose sensor 138a, 138b to the electronics unit 500. The proximal height of the seal 192 is greater than a proximal height of the leaf spring 306d such that the electronics unit 500 contacts the seal 192 prior to contacting the leaf spring 306d.

0351Referring now to <figref idref="f0016 f0018">Figures 33 and 37-38</figref>, the sensor module housing 312e comprises a channel 322e in which at least a portion of the second section of the glucose sensor 138b is located. A distal portion of the leaf spring 306e is located in the channel 322e such that a proximal portion of the leaf spring 306e protrudes proximally out the channel 322e.

0352The sensor module housing 312e comprises a groove 326e that cuts across the channel 322e (e.g., intersects with the channel 322e). The leaf spring 306e comprises a tab 328 located in the groove to impede rotation of the leaf spring. At least a portion of the leaf spring 306e forms a "C" shape.

0353<figref idref="f0017">Figures 36</figref> and <figref idref="f0018">38</figref> illustrate two leaf spring shapes. Other embodiments use other types of leaf springs. Elements shown in <figref idref="f0016 f0017 f0018">Figures 33-38</figref> can be combined.

0354Referring now to <figref idref="f0016 f0017 f0018">Figures 33-38</figref>, interconnects 306, 306d, 306e can comprise a palladium contact, an alloy, a clad material, an electrically conductive plated material, gold plated portions, silver material, and/or any suitable conductor. Interconnects 306, 306d, 306e described herein can have a resistance of less than 5 ohms, less than 20 ohms, and/or less than 100 ohms. Many interconnect embodiments enable a resistance of approximately 2.7 ohms or less, which can significantly increase battery life compared to higher resistance alternatives.

0355Reducing the force necessary to compress an interconnect 306, 306d, 306e (e.g., as an electronics unit 500 is coupled to the base 128) can reduce coupling errors and difficulties. For example, if the necessary force is high, odds are substantial that users will inadvertently fail to securely couple the electronics unit 500 to the base 128. In some cases, if the necessary force is too high, some users will be unable to couple the electronics unit 500 to the base 128. Thus, there is a need for systems that require less force to couple the electronics unit 500 to the base 128.

0356Many embodiments described herein (e.g., spring embodiments) dramatically reduce the force necessary to couple the electronics unit 500 to the base 128. The interconnects 306, 306d, 306e can have a compression force of at least 0.02268 kg (0.05 pounds); less than 0.2268 kg (0.5 pounds), less than 0.45359 kg (1 pound), less than 1.36078 kg (3 pounds); and/or less than 2.04117 kg (4.5 pounds) over an active compression range.

0357In some embodiments, the interconnects 306, 306d, 306e may require a compression force of less than 0.45359 kg (one pound) to compress the spring 20 percent from a relaxed position, which is a substantially uncompressed position. In some embodiments, the interconnects 306, 306d, 306e may require a compression force of less than 0.45359 kg (one pound) to compress the spring 25 percent from a relaxed position, which is a substantially uncompressed position. In some embodiments, the interconnects 306, 306d, 306e may require a compression force of less than 0.45359 kg (one pound) to compress the spring 30 percent from a relaxed position, which is a substantially uncompressed position. In some embodiments, the interconnects 306, 306d, 306e change dependency to independent claim) may require a compression force of less than 0.45359 kg (one pound) to compress the spring 50 percent from a relaxed position, which is a substantially uncompressed position.

0358Springs 306, 306d, 306e can have a height of 2.6 millimeters, at least 0.5 millimeters, and/or less than 4 millimeters. The seal 192 can have a height of 2.0 millimeters, at least 1 millimeter, and/or less than 3 millimeters. In some embodiments, in their relaxed state (i.e., a substantially uncompressed state), springs 306, 306d, 306e protrude (e.g., distally) at least 0.2 millimeters and/or less than 1.2 millimeters from the top of the seal 192.

0359When the electronics unit 500 is coupled to the base 128, the compression of the springs 306, 306d, 306e can be 0.62 millimeters, at least 0.2 millimeters, less than 1 millimeter, and/or less than 2 millimeters with a percent compression of 24 percent, at least 10 percent, and/or less than 50 percent. Active compression range of the springs 306, 306d, 306e can be 16 to 40 percent, 8 to 32 percent, 40 to 57 percent, 29 to 47 percent, at least 5 percent, at least 10 percent, and/or less than 66 percent.

0360In some embodiments, the electrical connection between the sensor 138 and the electronics unit 500 is created at the factory. This electrical connection can be sealed at the factory to prevent fluid ingress, which can jeopardize the integrity of the electrical connection.

0361The electrical connection can be made via any of the following approaches: An electrode can pierce a conductive elastomer (such that vertical deformation is not necessary); the sensor can be "sandwiched" (e.g., compressed) between adjacent coils of a coil spring; conductive epoxy; brazing; laser welding; and resistance welding.

0362Referring now to <figref idref="f0003">Figures 4, 6</figref>, <figref idref="f0004">7</figref>, and <figref idref="f0016">33</figref>, one key electrical connection is between the electronics unit 500 (e.g., a transmitter) and the sensor module 134. Another key electrical connection is between the sensor module 134 and the glucose sensor 138. Both connections should be robust to enable connecting the sensor module 134 to the base 128, and then connecting the base 128 and sensor module 134 to the electronics unit 500 (e.g., a transmitter). A stable sensor module 134 allows the sensor module 134 to couple to the base 128 without causing signal noise in the future.

0363These two key electrical connections can be made at the factory (e.g., prior to the host or caregiver receiving the system). These electrical connections can also be made by the host or caregiver when the user attaches the electronics unit 500 to the base 128 and/or the sensor module 134.

0364In some embodiments, the connection between the glucose sensor 138 and the sensor module 134 can be made at the factory (e.g., prior to the user receiving the system), and then the user can couple the electronics unit 500 to the sensor module 134 and/or the base 128. In several embodiments, the electronics unit 500 can be coupled to the sensor module 134 and/or to the base 128 at the factory (e.g., prior to the user receiving the system), and then the user can couple this assembly to the glucose sensor 138.

0365Any of the features described in the context of <figref idref="f0016 f0017 f0018">Figures 33-38</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0016 f0017 f0018">Figures 33-38</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-32 and 39-70</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

0366Referring now to <figref idref="f0016">Figure 33</figref>, the battery 314 can be located inside the electronics unit 500 or can be part of the base 128. Maximizing the life of the battery 314 is important to many reasons. For example, the electronics unit 500 may be in storage for months or even years before it is used. If the battery 413 is substantially depleted during this storage, the number of days that a host can use the electronics unit (e.g., to measure an analyte) can be dramatically diminished.

0367In some embodiments, the electronics unit 500 is in a low-power-consumption state (e.g., a "sleep" mode) during storage (e.g., prior to being received by the host). This low-power-consumption state can drain the battery 314. Thus, there is a need for a system that reduces or even eliminates battery power consumption during storage and/or prior to the electronics unit 500 being coupled to the base 128.

0368As described in the context of <figref idref="f0016">Figure 33</figref>, creating the electrical connection 310 and/or coupling the electronics unit 500 to the base 128 can cause the electronics unit 500 (e.g., a transmitter) to exit a sleep mode. For example, conductive members (e.g., of the sensor module 134 and/or of the base 128) can touch electrical contacts of the electronics unit 500 (e.g., electrical contacts of a battery of the electronics unit 500), which can cause the electronics unit 500 to exit a sleep mode and/or can begin the flow of electrical power from the battery. The conductive member of the sensor module 134 and/or of the base 128 can be a battery jumper that closes a circuit to enable electricity from the battery to flow into other portions of the electronics unit 500.

0369Thus, creating the electrical connection 310 and/or coupling the electronics unit 500 to the base 128 can "activate" the electronics unit 500 to enable and/or to prepare the electronics unit 500 to wirelessly transmit information to other devices 110-113 (shown in <figref idref="f0001">Figure 1</figref>). U.S. Patent Publication No. <patcit id="pcit0036" dnum="US20120078071A1"><text>US-2012-0078071-A1</text></patcit> includes additional information regarding electronics unit 500 activation (e.g., transmitter activation).

0370<figref idref="f0030">Figure 65</figref> illustrates a perspective view of portions of a sensor module 134j. Some items, such as springs and sensors, are hidden in <figref idref="f0030">Figure 65</figref> to clarify that the sensor module 134j can use any spring or sensor described herein. The sensor module 134j can use any of the springs 306, 306d, 306e; sensors 138, 138a, 138b; protrusions 308; channels 322d, 322e; and grooves 326e described herein (e.g., as shown in <figref idref="f0017 f0018 f0019">Figures 34-40</figref>). The sensor module 134j can be used in the place of any other sensor module described herein. The sensor module 134j can be used in the embodiment described in the context of <figref idref="f0004">Figure 7</figref> and can be used with any of the telescoping assemblies described herein.

0371<figref idref="f0030">Figure 66</figref> illustrates a cross-sectional side view of the sensor module shown in <figref idref="f0030">Figure 65</figref>. Referring now to <figref idref="f0030 f0031 f0032">Figures 65-70</figref>, the sensor module 134j includes a conductive jumper 420f (e.g., a conductive connection that can comprise metal). The conductive jumper 420f is configured to electrically couple two electrical contacts 428a, 428b of the electronics unit 500 (e.g., a transmitter) in response to coupling the electronics unit 500 to the sensor module 134j and/or to the base 128.

0372The conductive jumper 420f can be located at least partially between two electrical connections 426 (e.g., springs 306, 306d, 306e shown in <figref idref="f0017 f0018">Figures 34-38</figref>). The conductive jumper 306f can include two springs 306f coupled by a conductive link 422f. A first spring 306f of the jumper 420f can be coupled to a first contact 428a, and a second spring 306f of the jumper 420f can be coupled to a second contact 428b, which can complete an electrical circuit to enable the battery to provide electricity to the electronics unit 500. The springs 306f can be leaf springs, coil springs, conical springs, and/or any other suitable type of spring. In some embodiments, the springs 306f are proximal protrusions that are coupled with the contacts 428a, 428b.

0373As shown in <figref idref="f0030">Figure 66</figref>, the conductive link 422f can be arched such that a sensor 138b (shown in <figref idref="f0017">Figure 34</figref>) passes under and/or through the arched portion of the conductive link 422f. In several embodiments, the conductive link 422f is oriented within plus or minus 35 degrees of perpendicular to the sensor 138b such that the conductive link 422f crosses over the portion of the sensor 138b that is located inside the seal area (e.g., within the interior of the seal 192).

0374<figref idref="f0031">Figure 67</figref> illustrates a perspective view of portions of a sensor module 134k that is similar to the sensor module 134j shown in <figref idref="f0030">Figures 65 and 66</figref>. <figref idref="f0031">Figure 68</figref> illustrates a top view of the sensor module 134k shown in <figref idref="f0031">Figure 67</figref>.

0375Referring now to <figref idref="f0031">Figures 67 and 68</figref>, the sensor module 134k includes a different type of conductive jumper 420g, which includes two helical springs 306g conductively coupled by a conductive link 422g. The conductive link 422g is configured to cross over or under the sensor 138b (shown in <figref idref="f0017">Figure 34</figref>). As shown in <figref idref="f0031">Figures 67 and 68</figref>, the springs 306g are conical springs, however, some embodiments do not use conical springs. The springs 306g are configured to electrically couple two electrical contacts 428a, 428b of the electronics unit 500 to start the flow the electricity within the electronics unit 500. Thus, the conductive jumper 420g can "activate" the electronics unit 500. The conductive jumper 420g can be used with any of the sensor modules described herein.

0376<figref idref="f0032">Figures 69 and 70</figref> illustrate perspective views of an electronics unit 500 just before the electronics unit 500 is coupled to a base 128. As shown in <figref idref="f0032">Figure 70</figref>, the electronics unit 500 can have two electrical contacts 428a, 428b configured to be electrically coupled to a conductive jumper 420f (shown in <figref idref="f0030">Figures 65 and 66</figref>), 420g (shown in <figref idref="f0031">Figures 67 and 68</figref>). The electronics unit 500 can also have two electrical contacts 428c, 428d configured to be electrically coupled to the springs 306, 306d, 306e (shown in <figref idref="f0017 f0018">Figures 34-38</figref>) and/or to any other type of electrical connection 426 between the sensor 138 (shown in <figref idref="f0019">Figure 39</figref>) and the electronics unit 500.

0377Coupling the electronics unit 500 to the sensor module 134k and/or to the base 128 can electrically and/or mechanically couple the electrical contacts 428a, 428b to the conductive jumper 420f (shown in <figref idref="f0030">Figure 65</figref>), 420g (shown in <figref idref="f0031">Figure 67</figref>).

0378Coupling the electronics unit 500 to the sensor module 134k and/or to the base 128 can electrically and/or mechanically couple the electrical contacts 428c, 428d to the springs 306, 306d, 306e (shown in <figref idref="f0017 f0018">Figures 34-38</figref>) and/or to any other type of electrical connection 426 (e.g., as shown in <figref idref="f0031">Figure 67</figref>) between the sensor 138 (shown in <figref idref="f0019">Figure 39</figref>) and the electronics unit 500.

0379Any of the features described in the context of <figref idref="f0030 f0031 f0032">Figures 65-70</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0030 f0031 f0032">Figures 65-70</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029">Figures 1-64</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

NEEDLE ANGLE AND OFFSET

0380<figref idref="f0020">Figure 43</figref> shows a front view of a "C-shaped" needle 156. <figref idref="f0020">Figure 42</figref> illustrates a bottom view of the C-shaped needle 156. The needle 156 includes a channel 330. A section 138a (shown in <figref idref="f0017">Figure 34</figref>) of the glucose sensor 138 (labeled in <figref idref="f0004">Figure 7</figref>) that is configured for subcutaneous sensing can be placed in the channel 330 (as shown in <figref idref="f0019">Figure 40</figref>).

0381The needle 156 can guide the sensor 138 into the skin of the host. A distal portion of the sensor 138 can be located in the channel 330 of the needle 156. Sometimes, a distal end of the sensor 138 sticks out of the needle 156 and gets caught on tissue of the host as the sensor 138 and needle 156 are inserted into the host. As a result, the sensor 138 may buckle and fail to be inserted deeply enough into the subcutaneous tissue. In other words, in some embodiments, the sensor wire must be placed within the channel 330 of the C-shaped needle 156 to be guided into the tissue and must be retained in the channel 330 during deployment.

0382The risk of the sensor 138 sticking out of the channel 330 (and thereby failing to be property inserted into the host) can be greatly diminished by placing the sensor 138 in the channel 330 of the needle 156 with a particular angle 338 (shown in <figref idref="f0020">Figure 41</figref>) and offset 336 (shown in <figref idref="f0019">Figure 40</figref>. Position B 334 in <figref idref="f0020">Figure 42</figref> illustrates a sensor sticking out of the channel 330.

0383The angle 338 and offset 336 cause elastic deformation of the sensor 138 to create a force that pushes the sensor 138 to the bottom of the channel 300 (as shown by position A 332 in <figref idref="f0020">Figure 42</figref>) while avoiding potentially detrimental effects of improper angles 338 and offset 336. The angle 338 and offset 336 can also cause plastic deformation of the sensor 138 to help shape the sensor 138 in a way that minimizes the risk of the sensor 138 being dislodged from the channel 330 during insertion into the skin.

0384In several embodiments, the angle 338 and offset 336 shape portions of the sensor 138 for optimal insertion performance. For example, the angle 338 can bend the sensor 138 prior to placing portions of the sensor 138 in the channel 330 of the needle 156.

0385As illustrated in <figref idref="f0019">Figure 39</figref>, a portion of the glucose sensor 138b (also labeled in <figref idref="f0017">Figure 34</figref>) can be placed in a distally facing channel 342 (which, in some embodiments, is a tunnel). This channel 342 can help orient the glucose sensor 138b towards the channel 330 of the needle 156 (shown in <figref idref="f0020">Figure 43</figref>).

0386As illustrated in <figref idref="f0020">Figure 41</figref>, the glucose sensor 138 can include an angle 338 between a portion of the glucose sensor 138 that is coupled to the sensor module housing 312 (shown in <figref idref="f0017">Figure 34</figref>) and a portion of the glucose sensor that is configured to be inserted into the host. In some embodiments, this angle 338 can be formed prior to coupling the sensor 138 to the sensor module house 312 (shown in <figref idref="f0017">Figure 34</figref>) and/or prior to placing a portion of the sensor 138 in the channel 330 of the needle 156 (shown in <figref idref="f0020">Figure 43</figref>).

0387Referring now to <figref idref="f0020">Figure 41</figref>, an angle 338 that is less than 110 degrees can result in deployment failures (e.g., with an offset of 0.1524 cm (0.06 inches) plus 0.1524 cm (0.06 inches) and/or minus 0.0762 cm (0.03 inches)). In some embodiments, an angle 338 that is less than 125 degrees can result in deployment failures (e.g., with an offset of 0.1524 cm (0.06 inches) plus 0.1524 cm (0.06 inches) and/or minus 0.0762 cm (0.03 inches)). An angle 338 of 145 degrees (plus 5 degrees and/or minus 10 degrees) can reduce the probability of deployment failures. In some embodiments, the angle 338 is at least 120 degrees and/or less than 155 degrees.

0388In some embodiments, a manufacturing method includes bending the sensor 138 prior to placing portions of the sensor 138 in the channel 330 of the needle 156. In this manufacturing method, an angle is measured from a central axis of a portion of the glucose sensor 138 that is coupled to the sensor module housing 312 (shown in <figref idref="f0017">Figure 34</figref>) and a portion of the glucose sensor that is configured to be inserted into the needle. According to this angle measurement, an angle that is greater than 70 degrees can result in deployment failures (e.g., with an offset of 0.1524 cm (0.06 inches) plus 0.1524 cm (0.06 inches) and/or minus 0.0762 cm (0.03 inches)). In some embodiments, an angle that is greater than 55 degrees can result in deployment failures (e.g., with an offset of 0.1524 cm (0.06 inches) plus 0.1524 cm (0.06 inches) and/or minus 0.0762 cm (0.03 inches)). An angle of 35 degrees (plus 10 degrees and/or minus 5 degrees) can reduce the probability of deployment failures. In some embodiments, the angle is at least 25 degrees and/or less than 60 degrees.

0389An offset 336 (shown in <figref idref="f0019">Figure 40</figref>) that is too large can result in the sensor 138 not being reliably held in the channel 330 (shown in <figref idref="f0020">Figure 42</figref>). In other words, a large offset 336 can result in the sensor 138 being located in position B 334 rather than securely in position A 332. An offset 336 that is too small can place too much stress on the sensor 138, which can break the sensor 138. In light of these factors, in several embodiments, the offset 336 is at least 0.0508 cm (0.02 inches), at least 0.1016 cm (0.04 inches), less than 0.2032 cm (0.08 inches), and/or less than 0.3302 cm (0.13 inches). In some embodiments, the offset 336 is equal to or greater than 0.1524 cm (0.06 inches) and/or less than or equal to 0.254 cm (0.10 inches). The offset 336 is measured as shown in <figref idref="f0019">Figure 40</figref> from the root of the needle 156.

0390In some embodiments, at least a portion of the bend of the sensor 138 can include a strain relief. For example, the bend of the sensor 138 can be encapsulated in a polymeric tube or an elastomeric tube to provide strain relief for the sensor 138. In some instances, the entire bend of the sensor 138 can be encapsulated in a polymeric tube or an elastomeric tube. In some embodiments, the tube is composed of a soft polymer. The polymeric tube or elastomeric tube can encapsulate the sensor 138 by a heat shrink process. In some embodiments, a silicone gel may be applied to the sensor at or near channel 342 (shown in <figref idref="f0019">FIG. 39</figref>), or along at least a portion of the underside of proximal protrusion 320d (shown in <figref idref="f0017">FIG. 35</figref>).

0391The needle channel width 344 (shown in <figref idref="f0020">Figure 42</figref>) can be 0.03048 cm (0.012 inches). In some embodiments, the width 344 is equal to or greater than 0.0254 cm (0.010 inches) and/or less than or equal to 0.0381 cm (0.015 inches). The width 344 of the channel 330 is measured at the narrowest span in which the glucose sensor 138 could be located.

0392Referring now to <figref idref="f0019">Figure 40</figref>, a funnel 182 in the base 128 can help guide the needle 156 and/or the glucose sensor 138 into the hole 180. The funnel 182 and the hole 180 can help secure the sensor 138 in the C-shaped needle 156 during storage and deployment. For example, the hole 180 can be so small that there is not extra room (within the hole 180) for the sensor 138 to exit the channel 330 (shown in <figref idref="f0020">Figure 42</figref>) of the needle 156.

0393Another role of the funnel 182 and hole 180 is to support the needle 156 and/or the sensor 138 against buckling forces during insertion of the needle 156 and/or the sensor 138 into the host.

0394The funnel 182 and the hole 180 also protect against inadvertent needle-stick injuries (because they are too small to enable, for example, a finger to reach the needle 156 prior to needle deployment).

0395The sensor module 134 is unable to pass through the funnel 182 and hole 180 (e.g., due to the geometries of the sensor module 134 and the funnel 182). Preventing the sensor module 134 from passing through the base 128 ensures the sensor module 134 is removed from the host's body when the base 128 is detached from the host. The angle 338 can prevent all of the sensor 138 from passing through the hole 180 to ensure the sensor 138 is removed from the host's body when the base 128 is detached from the host.

0396Any of the features described in the context of <figref idref="f0019 f0020">Figures 39-43</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0019 f0020">Figures 39-43</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-38 and 44-70</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

NEEDLE-FREE

0397Some embodiments use a needle to help insert a glucose sensor into subcutaneous tissue. Some people, however, are fearful of needles. In addition, needle disposal can require using a sharps container, which may not be readily available.

0398Many embodiments do not use a needle to insert the sensor, which can help people feel more comfortable inserting the sensor and can eliminate the need to use a sharps container to dispose of the applicator or portions thereof.

0399U.S. Patent Publication No. <patcit id="pcit0037" dnum="US20110077490A1"><text>US-2011-0077490-A1</text></patcit>, U.S. Patent Publication No. <patcit id="pcit0038" dnum="US20140107450A1"><text>US-2014-0107450-A1</text></patcit>, and U.S. Patent Publication No. <patcit id="pcit0039" dnum="US20140213866A1"><text>US-2014-0213866-A1</text></patcit> describe several needle-free embodiments.

0400Any of the embodiments described herein can be used with or without a needle. For example, the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023">Figures 1-50</figref> can be used with or without a needle. For example, the embodiment shown in <figref idref="f0004">Figure 7</figref> can be used in a very similar way without the needle 156. In this needle-free embodiment, moving the first portion 150 distally drives a distal portion of the glucose sensor 138 into the skin (without the use of a needle 156). In needle-free embodiments, the sensor 138 can have sufficient buckling resistance such that (when supported by the hole 180) the sensor 138 does not buckle. Sharpening a distal tip of the sensor 138 can also facilitate needle-free insertion into the host.

0401<figref idref="f0025">Figure 56</figref> illustrates an embodiment very similar to the embodiment shown in <figref idref="f0004">Figure 7</figref> except that the embodiment of <figref idref="f0025">Figure 56</figref> does not include a needle. The telescoping assembly 132b pushes the sensor 138 (which can be any type of analyte sensor) into the body of the host. The embodiment shown in <figref idref="f0025">Figure 56</figref> does not include a needle hub 162, a spring 234, or a needle retraction mechanism 158 (as shown in <figref idref="f0004">Figure 7</figref>) but can include any of the items and features described in the context of other embodiments herein.

0402<figref idref="f0026">Figure 57</figref> illustrates the first portion 150 moving distally relative to the second portion 152 of the telescoping assembly 132b to move the sensor module 134 and the sensor 138 towards the base 128 in preparation to couple the sensor module 134 and the sensor 138 to the base 128.

0403<figref idref="f0026">Figure 58</figref> illustrates the first portion 150 in a distal ending position relative to the second portion 152. The sensor module 134 and the sensor 138 are coupled to the base 128. The base 128 is no longer coupled to the telescoping assembly 132b such that the telescoping assembly 132b can be discarded while leaving the adhesive 126 coupled to the skin of the host (as described in the context of <figref idref="f0003">Figures 4-6</figref>).

0404The embodiment illustrated in <figref idref="f0025 f0026">Figures 56-58</figref> can be integrated into the applicator system 104 shown in <figref idref="f0002">Figures 2 and 3</figref>.

0405The items and features described in the context of <figref idref="f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023">Figures 12A-50</figref> can also be used with the embodiment illustrated in <figref idref="f0025 f0026">Figures 56-58</figref>. Items and features are described in the context of certain embodiments to reduce redundancy. The items and features shown in all the drawings, however, can be combined. The embodiments described herein have been designed to illustrate the interchangeability of the items and features described herein.

0406<figref idref="f0021">Figures 44 and 45</figref> illustrate another embodiment of a telescoping assembly 132g. This embodiment includes a first portion 150g that moves distally relative to a second portion 152g to push a glucose sensor 138g through a hole in a base 128g and into a host.

0407The first portion 150g (e.g., a pusher) of the telescoping assembly 132g can include a distal protrusion 352 that supports a substantially horizontal section of the glucose sensor 138g (e.g., as the glucose sensor 138g protrudes out from the sensor module 134g). The end of the distal protrusion 352 can include a groove 354 in which at least a portion of the glucose sensor 138g is located. The groove 354 can help retain the glucose sensor 138g. The distal protrusion 352 can provide axial support to the glucose sensor 138g (e.g., to push the glucose sensor 138g distally into the tissue of the host).

0408The base 128g can include a funnel 182g that faces proximally to help guide a distal end of the glucose sensor 138g into a hole 180g in the base 128g. The hole 180g can radially support the sensor 138g as the sensor 138g is inserted into the tissue of the host.

0409When the first portion 150g of the telescoping assembly 132g is in the proximal starting position, the distal end of the glucose sensor 138g can be located in the hole 180g to help guide the glucose sensor 138g in the proper distal direction.

0410The hole 180g can exit a convex distal protrusion 174g in the base 128g. The convex distal protrusion 174g can help tension the skin prior to sensor insertion. As described more fully in other embodiments, the base 128g can rest against the skin of the host as the sensor module 134g moves distally towards the base 128g and then is coupled to the base 128g.

0411The telescoping assembly 132g (e.g., an applicator) does not include a needle. As a result, there is no sharp in the applicator, which eliminates any need for post-use sharp protection. This design trait precludes a need for a retraction spring or needle hub. The distal end of the sensor wire 138g can be sharpened to a point to mitigate a need for an insertion needle.

0412The telescoping assembly 132g (e.g., an applicator) can include the first portion 150g and the second portion 152g. The base 128g can be coupled to a distal end of the first portion 150g. The glucose sensor 138g and the sensor module 134g can be coupled to a distal end of the first portion 150g such that he applicator does not require a spring, needle, or needle hub; the first portion 150g is secured in a proximal starting position by an interference between the first portion 150g and the second portion 152g of the telescoping assembly 132g; and/or applying a distal force that is greater than a breakaway threshold of the interference causes the first portion 150g to move distally relative to the second portion 152g (e.g., until the sensor 138g is inserted into the tissue and the sensor module 134g is coupled to the base 128g).

0413<figref idref="f0022">Figures 46 and 47</figref> illustrate a similar needle-free embodiment. This embodiment does not use the distal protrusion 352 shown in <figref idref="f0021">Figure 45</figref>. Instead, the sensor module 134h includes a distally oriented channel 358 that directs the sensor 138h distally such that the glucose sensor 138h includes a bend that is at least 45 degrees and/or less than 135 degrees. A channel cover 362 secures the glucose sensor 138h in the distally oriented channel 358.

0414The embodiments illustrated in <figref idref="f0021 f0022">Figures 44-47</figref> can be integrated into the applicator system 104 shown in <figref idref="f0002">Figures 2 and 3</figref>. Referring now to <figref idref="f0002">Figure 2</figref>, the electronics unit 500 (e.g., a transmitter having a battery) can be detachably coupled to the sterile barrier shell 120. The rest of the applicator system 104 can be sterilized, and then the electronics unit 500 can be coupled to the sterile barrier shell 120 (such that the electronics unit 500 is not sterilized with the rest of the applicator system 104).

0415The items and features described in the context of <figref idref="f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 12A-43 and 48-70</figref> can also be used with the embodiments illustrated in <figref idref="f0021 f0022">Figures 44-47</figref>. Items and features are described in the context of certain embodiments to reduce redundancy. The items and features shown in all the drawings, however, can be combined. The embodiments described herein have been designed to illustrate the interchangeability of the items and features described herein.

0416Any of the features described in the context of <figref idref="f0021 f0022">Figures 44-47</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0021 f0022">Figures 44-47</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-43 and 48-70</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

0417In some embodiments, the sensor 138 can be deployed (e.g., into the skin of the host) in response to coupling the electronics unit 500 (e.g., a transmitter) to the base 128. The sensor 138 can be any type of analyte sensor (e.g., a glucose sensor).

0418Premature deployment of the sensor 138 can cause insertion of the sensor 138 into the wrong person and/or insufficient sensor insertion depth. Premature deployment can also damage the sensor 138, which in some embodiments, can be fragile. Thus, there is a need to reduce the likelihood of premature sensor deployment.

0419One way to reduce the likelihood of premature sensor deployment is for the system to include an initial resistance (e.g., to coupling the electronics unit 500 to the base 128). The initial resistance can necessitate a force buildup prior to overcoming the initial resistance. When the initial resistance is overcome, the sensor 138 is typically deployed faster than would be the case without an initial resistance (e.g., due to the force buildup, which can be at least 0.2268 kg (0.5 pounds), 0.45359 kg (1 pound), and/or less than 2.26796 kg (5 pounds)). This fast deployment can reduce pain associated with the sensor insertion process.

0420In some embodiments, the resistance to coupling the electronics unit 500 to the base 128 after overcoming the initial resistance is less than 10 percent of the initial resistance, less than 40 percent of the initial resistance, and/or at least 5 percent of the initial resistance. Having a low resistance to coupling the electronics unit 500 to the base 128 after overcoming the initial resistance can enable fast sensor insertion, which can reduce the pain associated with the sensor insertion process.

0421<figref idref="f0025 f0026">Figures 56-58</figref> illustrate the first portion 150 deploying the sensor 138 into the skin of the host. In some embodiments, the first portion 150 is replaced with the electronics unit 500 shown in <figref idref="f0003">Figure 4</figref> such that coupling the electronics unit 500 to the base 128 pushes the sensor 138 into the skin of the host. Referring now to <figref idref="f0003 f0025 f0026">Figures 4 and 56-58</figref>, the protrusion 240 (as explained in other embodiments) can be a portion of the electronics unit 500 such that moving the electronics unit distally relative to the second portion 152 and/or coupling the electronics unit 500 to the base 128 requires overcoming the initial resistance of the protrusion 240.

0422In some embodiments configured such that the sensor 138 is deployed (e.g., into the skin of the host) in response to coupling the electronics unit 500 to the base 128, a telescoping assembly 132b is not used. Instead, features of the base 128 provide the initial resistance to coupling the electronics unit 500 to the base 128. Although the locking feature 230 in <figref idref="f0016">Figure 33</figref> is used for different purposes in some other embodiments, the locking feature 230 of the base 128 can couple with a corresponding feature of the electronics unit 500. This coupling can require overcoming an initial resistance.

0423Any of the features and embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-70</figref> can be applicable to all aspects and embodiments in which the sensor 138 is deployed (e.g., into the skin of the host) in response to coupling the electronics unit 500 (e.g., a transmitter) to the base 128.

VERTICAL LOCKING

0424After a telescoping assembly (e.g., an applicator) has been used to insert a glucose sensor, the needle used to insert the glucose sensor could inadvertently penetrate another person. To guard against this risk, the telescoping assembly can protect people from subsequent needle-stick injuries by preventing the first portion of the telescoping assembly from moving distally relative to the second portion after the sensor has been inserted into the host.

0425<figref idref="f0023">Figure 48</figref> illustrates a perspective, cross-sectional view of a telescoping assembly 132i that includes a first portion 150i and a second portion 152i. Referring now to <figref idref="f0023">Figures 48-50</figref>, the first portion 150i is configured to telescope distally relative to the second portion 152i. The second portion 152i of the telescoping assembly 132i can include a proximal protrusion 364 that can slide past a lock-out feature 366 of the first portion 150i of the telescoping assembly 132i as the first portion 150i is moved distally.

0426The proximal protrusion 364 can be biased such that elastic deformation of the proximal protrusion 364 creates a force configured to press the proximal protrusion 364 into the bottom of the lock-out feature 366 once the proximal protrusion 364 engages the lock-out feature 366.

0427The proximal protrusion 364 does not catch on the lock-out feature 366 as the first portion 150i moves distally a first time. Once the first portion 150i is in a distal ending position, a spring can push the first portion 150i to a second proximal position. Rather than returning to the starting proximal position, the proximal protrusion 364 catches on the lock-out feature 366 (due to the bias of the proximal protrusion 364 and the distally facing notch 368 of the lock-out feature 366).

0428Once a proximal end of the proximal protrusion 364 is captured in the lock-out feature 366, the rigidity of the proximal protrusion 364 prevents the first portion 150i of the telescoping assembly 132i from moving distally a second time.

0429As the first portion 150i moves distally relative to the second portion 152i, a ramp 370 of the first portion 150i pushes the proximal protrusion 364 outward (towards the lock-out feature 366). The proximal protrusion 364 can be located between two distal protrusions 372 of the first portion 150i. The distal protrusions 372 can guide the proximal protrusion 364 along the ramp 370.

0430As a portion of the proximal protrusion 364 slides along the ramp 370 (as the first portion 150i moves distally), the ramp bends the proximal protrusion 364 until a portion of the proximal protrusion 364 that was previously between the two distal protrusions 372 is no longer between the distal protrusions 372. Once the portion of the proximal protrusion 364 is no longer between the two distal protrusions 372, the proximal protrusion 364 is in a state to catch on the notch 368. The notch 368 can be part of the distal protrusions 372.

0431The second portion 152i of the telescoping assembly 132i can include a proximal protrusion 364, which can be oriented at an angle between zero and 45 degrees relative to a central axis). The first portion 150i of the telescoping assembly 132i can include features that cause the proximal protrusion 364 to follow a first path as the first portion 150i moves distally and then to follow a second path as the first portion 150i moves proximally. The second path includes a locking feature 366 that prevents the first portion 150i from moving distally a second time.

0432The first portion 150i can include a ramp 370 that guides the proximal protrusion 364 along the first path. A distal protrusion (e.g., the ramp 370) of the first portion 150i can bias the proximal protrusion 364 to cause the proximal protrusion 364 to enter the second path as the first portion 150i moves proximally. The proximal protrusion 364 can be a flex arm. The lock 366 can comprise a distally facing notch 368 that catches on a proximal end of the proximal protrusion 364.

0433As shown in <figref idref="f0023">Figures 48 and 50</figref>, the telescoping assembly 132i can include a sensor module 134i. The sensor module 134i can be any of the sensor modules described herein.

0434Any of the features described in the context of <figref idref="f0023">Figures 48-50</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0023">Figures 48-50</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032">Figures 1-47 and 51-70</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

DUAL-SPRING ASSEMBLY

0435Partial sensor insertion can lead to suboptimal sensing. In some cases, partial sensor insertion can create a needle-stick hazard (due to the needle not retracting into a protective housing). Thus, there is a need for systems that ensure full sensor insertion.

0436The embodiment illustrated in <figref idref="f0028 f0029">Figures 61-64</figref> dramatically reduces the odds of partial sensor insertion by precluding sensor insertion until sufficient potential energy is stored in the system. The potential energy is stored in a first spring 402.

0437The system includes many items from the embodiment illustrated in <figref idref="f0004">Figure 7</figref> (e.g., the base 128 and the sensor module 134). The system includes an optional needle 156 and needle hub 162. The embodiment illustrated in <figref idref="f0028 f0029">Figures 61-64</figref> can also be configured to be needle-free by removing the needle 156, the second spring 234, the needle hub 162, and the needle retraction mechanism 158.

0438The telescoping assembly 132k has three portions 150k, 152k, 392. Moving the third portion 392 distally relative to the second portion 152k stores energy in the first spring 402 (by compressing the first spring 402). Once the first portion 150k is unlocked from the second portion 152k, the energy stored in the compressed first spring 402 is used to push the first portion 150k distally relative to the second portion 152k to drive the sensor 138 (shown in <figref idref="f0004">Figure 7</figref>) into the skin of the host.

0439To ensure the first portion 150k does not move distally relative to the second portion 152k until the first spring 402 is sufficiently compressed (and thus has enough stored energy), the first portion 150k is locked to the second portion 152k. Once the first spring 402 is sufficiently compressed (and thus has enough stored energy), the system unlocks the first portion 150k from the second portion 152k to enable the stored energy to move the sensor 138 (and in some embodiments the needle 156) into the skin of the host.

0440The telescoping assembly 132k can lock the third portion 392 to the second portion 152k in response to the third portion 392 reaching a sufficiently distal position relative to the second portion 152k. A protrusion 408 can couple with a hole 410 to lock the third portion 392 to the second portion 152k.

0441Some embodiments do not include locking protrusion 408 and do not lock the third portion 392 to the second portion 152k in response to the third portion 392 reaching a sufficiently distal position relative to the second portion 152k.

0442In several embodiments, sufficiently distal positions are at least 3 millimeters, at least 5 millimeters, and/or less than 30 millimeters distal relative to the proximal starting position.

0443The telescoping assembly 132k can lock the first portion 150k to the second portion 152k in response to the first portion 150k reaching a sufficiently distal position relative to the second portion 152k. A protrusion 412 (e.g., a distal protrusion) can couple with a hole 414 (e.g., in a surface that is within plus or minus 30 degrees of perpendicular to the central axis of the telescoping assembly 132k) to lock the first portion 150k to the second portion 152k.

0444Some embodiments include a needle 156 to help insert a sensor into skin of a host. In embodiments that include a needle 156, the telescoping assembly 132k can include the needle retraction mechanism 158 described in the context of <figref idref="f0004">Figure 7</figref>. Moving the first portion 150k to a sufficiently distal position relative to the second portion 152k can trigger the needle retraction mechanism 158 (e.g., can release a latch) to enable a second spring 234 to retract the needle 156.

0445<figref idref="f0028">Figure 61</figref> illustrates a system for applying an on-skin sensor assembly 600 (shown in <figref idref="f0003">Figures 4-6</figref>) to a skin of a host. The system comprises a telescoping assembly 132k having a first portion 150k configured to move distally relative to a second portion 152k from a proximal starting position (e.g., the position shown in <figref idref="f0028">Figure 61</figref>) to a distal position (e.g., the position shown in <figref idref="f0029">Figure 64</figref>) along a path; a sensor 138 (shown in <figref idref="f0029">Figure 64</figref>) coupled to the first portion 150k; and a base 128 comprising adhesive 126 configured to couple the sensor 138 to the skin. The telescoping assembly 132k can further comprise a third portion 392 configured to move distally relative to the second portion 152k.

0446In some embodiments, the first portion 150k is located inside of the second portion 152k such that the second portion 152k wraps around the first portion 150k in a cross section taken perpendicularly to the central axis of the telescoping assembly 132k.

0447In some embodiments, a first spring 402 is positioned between the third portion 392 and the second portion 152k such that moving the third portion 392 distally relative to the second portion 152k compresses the first spring 402. The first spring 402 can be a metal helical spring and/or a metal conical spring. In several embodiments, the first spring 402 is a feature molded as part of the third portion 392, as part of the second portion 152k, or as part of the first portion 150k. The first spring 402 can be molded plastic.

0448The telescoping assembly 132k can be configured such that the first spring 402 is not compressed in the proximal starting position and/or not compressed during storage. In several embodiments, the telescoping assembly 132k can be configured such that the first spring 402 is not compressed more than 15 percent in the proximal starting position and/or during storage (e.g., to avoid detrimental spring relaxation and/or creep of other components such as at least one of the third portion 392, the second portion 152k, and the first portion 150k).

0449Some embodiments that include a needle 156 do not include a needle hub 162. In these embodiments, the second spring 234 can be located between the second portion 152k and the first portion 150k such that moving the first portion 150k distally relative to the second portion 152k compresses the second spring 234 to enable the second spring 234 to push the first portion 150k proximally relative to the second portion 152k to retract the needle 156 (e.g., after sensor insertion).

0450In several embodiments, the second spring 234 is compressed while the telescoping assembly 132k is in the proximal starting position. For example, the second spring 234 can be compressed at the factory while the telescoping assembly 132k is being assembled such that when the user receives the telescoping assembly 132k, the second spring 234 is already compressed (e.g., compressed enough to retract the needle 156).

0451The second spring 234 can have any of the attributes and features associated with the spring 234 described in the context of other embodiments herein (e.g., in the context of the embodiment of <figref idref="f0004">Figure 7</figref>).

0452In some embodiments, the movement of the sensor module 134 (e.g., an analyte sensor module) and the sensor 138 (e.g., an analyte sensor) relative to the base 128 can be as described in the context of other embodiments (e.g., as shown by the progression illustrated by <figref idref="f0004 f0005 f0006">Figures 7-11</figref>).

0453In the proximal starting position of the telescoping assembly 132k, the first portion 150k can be locked to the second portion 152k. The system can be configured such that moving the third portion 392 distally relative to the second portion 152k unlocks the first portion 150k from the second portion 152k.

0454In several embodiments, a first proximal protrusion 394 having a first hook 396 passes through a first hole 398 in the second portion 152k to lock the first portion 150k to the second portion 152k. The third portion 392 can comprise a first distal protrusion 404. The system can be configured such that moving the third portion 392 distally relative to the second portion 152k engages a ramp 406 to bend the first proximal protrusion 394 to unlock the first portion 150k from the second portion 152k.

0455In some embodiments, the sensor 138 is located within the second portion 152k while the base 128 protrudes from the distal end of the system such that the system is configured to couple the sensor 138 to the base 128 by moving the first portion 150k distally relative to the second portion 152k.

0456In several embodiments, a sensor module 134 is coupled to a distal portion of the first portion 150k such that moving the first portion 150k to the distal position couples the sensor module 134 to the base 128. This coupling can be as described in the context of other embodiments herein. The sensor 138 can be coupled to the sensor module 134 while the first portion 150k is located in the proximal starting position.

0457The system can be configured such that the third portion 392 moves distally relative to the second portion 152k before the first spring 402 moves the first portion 150k distally relative to the second portion 152k. The system can be configured such that moving the third portion 392 distally relative to the second portion 152k unlocks the first portion 150k from the second portion 150k and locks the third portion 392 to the second portion 152k.

0458A first protrusion 408 couples with a hole 410 of at least one of the second portion 152k and the third portion 392 to lock the third portion 392 to the second portion 152k.

0459In some embodiments, the system comprises a second protrusion 412 that couples with a hole 414 of at least one of the first portion 150k and the second portion 152k to lock the first portion 150k to the second portion 152k in response to moving the first portion 150k distally relative to the second portion 152k.

0460In several embodiments, a first spring 402 is positioned between the third portion 392 and the second portion 152k such that moving the third portion 392 distally relative to the second portion 152k compresses the first spring 402 and unlocks the first portion 150k from the second portion 152k, which enables the compressed first spring 402 to push the first portion 150k distally relative to the second portion 152k, which pushes at least a portion of the sensor 138 out of the distal end of the system and triggers a needle retraction mechanism 158 to enable a second spring 234 to retract a needle 156.

0461In yet another aspect, disclosed herein is a dual spring-based sensor insertion device having a pre-connected sensor assembly (i.e. an analyte sensor electrically coupled to at least one electrical contact before sensor deployment). Such a sensor insertion device provides convenient and reliable insertion of a sensor into a user's skin by a needle as well as reliable retraction of a needle after the sensor is inserted, which are features that provide convenience to users as well as predictability and reliability of the insertion mechanism. The reliability and convenience of a dual spring based sensor insertion device having an automatic insertion and automatic retraction provide is a significant advancement in the field of sensor insertion devices. Furthermore, such a device can provide both safety and shelf stability.

0462In several embodiments, the insertion device can include a first spring and a second spring. In such embodiments, either or both of the first spring and the second spring can be integrally formed with portions of a telescoping assembly, such as the first portion and the second portion of a telescoping assembly. In several embodiments, either or both of the first spring and the second spring can be formed separately from and operatively coupled to portions of the telescoping assembly. For example, in some embodiments, the insertion spring can be integrally formed with a portion of the telescoping assembly while the retraction spring is a separate part which is operatively coupled to a portion of the telescoping assembly.

0463In some embodiments, rather than being configured to undergo compression during energization, either or both of the first spring and the second spring can be configured to undergo tensioning during energization. In these embodiments, the couplings between the springs and the portions of the telescoping assembly, as well as the couplings between the moving portions of the assembly (for example in the resting state, and during activation, deployment, and retraction) can be adjusted to drive and/or facilitate the desired actions and reactions within the system. For example, in an embodiment employing a tensioned retraction spring to drive the insertion process, the retraction spring can be coupled to or integrally formed with the second portion of the telescoping assembly. In such an embodiment, the retraction spring can be pre-tensioned in the resting state. In other such embodiments, the retraction spring can be untensioned in the resting state, and tensioned during the sensor insertion process.

0464In several embodiments, either or both of the first spring and the second spring can be substantially unenergized and/or unstressed when the system is in a resting state. In several embodiments, either or both of the first spring and the second spring can be energized and/or stressed when the system is in a resting state. As used herein, the term "energized" means that enough potential energy is stored in the spring to perform the desired actions and reactions within the system. In some embodiments, the first spring can be partly energized in the resting state, such that the user can supply a lesser amount of force to fully energize the first spring. In some embodiments, the second spring can be partly energized in the resting state, such that the energy stored in the first spring (either in the resting state or after energization by a user) can provide force to energize the second spring. In some embodiments, the energy stored in the first spring can provide sufficient force to energize the second spring to at least retract the needle from the skin. In some embodiments, either or both of the first spring and the second spring can be compressed or tensioned by 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% in the resting state. In other embodiments, either or both of the first spring and the second spring can be compressed or tensioned by 50% or less, 40% or less, 30% or less, 20% or less, 15% or less, 10% or less, 5% or less, or 0% in the resting state.

0465In embodiments in which both the first spring and the second spring are substantially unenergized in the resting state, they can be stressed by the same amounts, similar amounts, or entirely different amounts. In embodiments in which both the first spring and the second spring are effectively energized in the resting state, they can be stressed by the same amounts, similar amounts, or entirely different amounts. In embodiments in which the second spring is substantially unenergized in the resting state, the first spring can be configured to store enough energy to drive both the desired movement in the system (e.g., the movement of the first portion in a distal direction), as well as the energization of the second spring.

0466With reference now to <figref idref="f0033 f0034 f0035">Figures 71-75</figref>, another embodiment of a system 104m for applying an on-skin sensor assembly to skin of a host is illustrated. The embodiment illustrated in <figref idref="f0033 f0034 f0035">Figures 71-75</figref> may reduce the potential of incomplete sensor insertion by precluding sensor insertion until sufficient potential energy is stored in the system. The potential energy for inserting the sensor can be stored in an actuator, such as a first spring 402m. The embodiment may provide other advantages such as controlled speed, controlled force, and improved user experience.

0467The system 104m may include many features from the embodiment illustrated in <figref idref="f0004">Figure 7</figref> (e.g., the needle 156, the base 128 and the sensor module 134). The system 104m may include alternative elements, such as, but not limited to, a needle hub 162m, a second spring 234m, and a needle retraction mechanism 158m. The embodiment illustrated in <figref idref="f0033 f0034 f0035">Figures 71-75</figref> can also be configured to be needle-free by removing the needle 156, the second spring 234m, the needle hub 162m, and the needle retraction mechanism 158m. In such embodiments, the sensor may be a self-insertable sensor.

0468The system 104m may include many features that are similar to those of the embodiment illustrated in <figref idref="f0028 f0029">Figures 61-64</figref> (e.g., a telescoping assembly 132m) including a first portion 150m, a second portion 152m, and a third portion 392m; with locking features 396m and 398m configured to releasably lock the first portion 150m to the second portion 152m until the third portion 392m has reached a sufficiently distal position relative to the second portion 152m to compress the first spring 402m and store enough energy in the spring 402m to drive insertion of the sensor 138 (and in some embodiments the needle 156) into the skin of a host; locking features 408m and 410m configured to lock the third portion 392m to the second portion 152m (e.g., to prevent proximal movement of the third portion 392m relative to the second portion 152m) in response to the third portion 392m reaching a sufficiently distal position relative to the second portion 152m; unlocking features 404m and 406m configured to unlock the locking features 396m and 398m at least after the third portion 392m is locked to the second portion 152m and/or the first spring 402m is sufficiently compressed; locking features 412m and 414m configured to lock the first portion 150m to the second portion 152m in response to the first portion 150m reaching a sufficiently distal position relative to the second portion 152m to drive the sensor 138 (and in some embodiments the needle 156) into the skin of the host; and a needle retraction mechanism 158m configured to unlock the needle hub 162m from the first portion 150m (e.g., to allow proximal movement of the needle hub 162m with respect to the first portion 150m) at least once the needle hub 162m has reached a sufficiently distal position and thereby enable a second spring 234m to retract the needle 156).

0469<figref idref="f0033">Figure 71</figref> illustrates a cross-sectional perspective view of the applicator system 104m in a resting state (e.g., as provided to the consumer, before activation by the user and deployment of the applicator system). As illustrated in the figure, the first spring 402m can be neither in tension nor compression, such that the first spring is substantially unenergized. In some embodiments, the first spring 402m can be slightly in tension or slightly in compression (e.g., neither tensioned nor compressed by more than 15 percent) in a resting state, such that the first spring is substantially or mostly unenergized in the resting state. In some embodiments, the first spring can be effectively unenergized, e.g. can be minimally energized but not to an extent that would create any type of chain reaction in the system, in a resting state.

0470In the embodiment illustrated in <figref idref="f0033 f0034 f0035">Figures 71-75</figref>, the first spring 402m is integrally formed as part of the third portion 392m. In some embodiments, the first spring 402m can be integrally formed as part of other components of the system 104m, such as, but not limited to, the first portion 150m, second portion 152m, etc. An integrally formed spring such as the one illustrated in <figref idref="f0033 f0034 f0035">Figures 71-75</figref> offers advantages including the reduction in the number of parts in a system as well as the reduction in the amount of assembly processes. The first spring 402m can be molded plastic. As illustrated in <figref idref="f0033">Figure 71</figref>, in the resting state, the second spring 234m is also substantially unenergized (e.g., neither tensioned nor compressed by more than 15 percent). The second spring 234m is integrally formed as part of the needle hub 162m. In some embodiments, the second spring 234m can be integrally formed as part of other components of the system 104m, such as, but not limited to, the first portion 150m, second portion 152m, base 128, etc. The second spring 234m can be molded plastic. Such a configuration can simplify manufacture and assembly of the system 104m, while avoiding detrimental relaxation and/or creep of the first spring 402m, the second spring 234m, or other components of the system 104m during storage and/or before deployment. It is also contemplated that in other embodiments, the first spring 402m and/or the second spring 234m can comprise metal.

0471In some embodiments, first spring 402m and/or second spring 234m can comprise a molded plastic, such as, but not limited to: polycarbonate (PC), acrylonitrile butadiene styrene (ABS), PC/ABS blend, Nylon, polyethylene (PE), polypropylene (PP), and Acetal. In some embodiments, first spring 402m and/or second spring 234m have a spring constant less than 1.75127 N/mm (10 lb/inch).

0472Applicator system 104 may be energized by moving one component relative to another. For example, moving the third portion 392m distally relative to the second portion 152m, when the second portion 152m is placed against the skin of a host or another surface can store energy in the first spring 402m as it compresses against first portion 150m. The third portion 392m may be moved distally until the locking features 408m and 410m (see <figref idref="f0034">Figure 73</figref>) engage together. In some embodiments, the third portion 392m may be moved further distally until unlocking features 404m engages locking feature 396m. Unlocking feature 404m may engage and release locking feature 396m and allow first portion 150m to move distally. In some embodiments, locking features 408m and 410m couple together before locking feature 396m is disengaged from locking feature 398m. In other embodiments, unlocking feature 404m engages locking feature 396m and causes locking feature 396m to disengage from locking feature 398m, locking features 408m and 410m may couple together. In some embodiments, locking feature 408m is a protrusion featuring a hook portion, locking feature 410m is a hole featuring an angled surface, unlocking feature 404m is a distal protrusion featuring an angled surface, locking feature 396m is a hook featuring a ramp 406m, and locking feature 398m is an aperture. The sensor module 134 remains in a proximal starting position while the first spring 402m is being energized.

0473<figref idref="f0033">Figure 72</figref> illustrates a cross-sectional perspective view of the applicator system 104m, with the first spring 402m compressed and with the unlocking features 404m and 406m engaged so as to unlock the first portion 150m from the second portion 152m. Until the first portion 150m is unlocked from the second portion 152m, the sensor module 134 remains at its proximal starting position, and the second spring 234m remains substantially unenergized. <figref idref="f0034">Figure 73</figref> illustrates a rotated cross-sectional perspective view of the applicator system 104m, and shows the locking features 408m and 410m engaged to prevent proximal movement of the third portion 392m with respect to the second portion 152m. In some embodiments, as illustrated in <figref idref="f0034">Figure 73</figref>, the system can include a secondary locking feature 409m which is configured to cooperate with the opening 410m to prevent the third portion 392 from falling off or otherwise separating from the remainder of the system 104m prior to deployment.

0474<figref idref="f0034">Figure 74</figref> illustrates a cross-sectional perspective view of the applicator system 104m, with the system 104m having been activated by the disengagement of the first portion 150m with respect to the second portion 152m. As can be seen in <figref idref="f0034">Figure 74</figref>, once the first portion 150m and the second portion 152m are disengaged or released, the potential energy stored in the first spring 402m drives the first portion 150m in a distal direction along with the needle hub 162m and the sensor module 134. This movement compresses the second spring 234m and deploys the needle 156 and the sensor module 134 distally to a distal insertion position in which the sensor module 134 is coupled to the base 128 and the needle 156 extends distally of the base 128. Once the needle 156 and the sensor module 134 reach the distal insertion position, the locking features 412m, 414m (see <figref idref="f0034">Figure 73</figref>) engage to prevent proximal movement of the first portion 150m with respect to the second portion 152m, and the unlocking features of the needle retraction mechanism 158m (e.g., the proximal protrusions 170m, the release feature 160m, and the latch 236m comprising ends 164m of the release feature 160m and overhangs 166m of the first portion 150m) cooperate to release the latch 236m. Optionally, the user may hear a click after the second spring 243m is activated, which may indicate to the user that the cap is locked in place.

0475Once the latch 236m is released, the potential energy stored in the compressed second spring 234m drives the needle hub 162m back in a proximal direction, while the first portion 150m remains in a distal deployed position along with the sensor module 134. The potential energy stored can be between 0.1134 kg (0.25 pounds) to 1,81437 kg (4 pounds). In preferred embodiments, the potential energy stored is between about 0.45359 to 0.90718 kg (1 to 2 pounds). <figref idref="f0035">Figure 75</figref> illustrates a cross-sectional perspective view of the applicator system 104m with the sensor module 134 in a distal deployed position, coupled to the base 128, and with the needle hub 162m retracted to a proximal retracted position.

0476Systems configured in accordance with embodiments may provide an inherently safe and shelf stable system for insertion of a sensor. An unloaded (i.e. substantially uncompressed and substantially unactivated) spring may not fire prematurely. Indeed, such a system is largely incapable of unintentional firing without direct interaction from a user since the first spring and/or second spring are substantially un-energized on the shelf. Moreover, it is contemplated that a system having a substantially uncompressed spring prior to activation possesses shelf stability since elements of the system are not exposed to a force or phase change over time (such as creep, environment, defects from time dependent load conditions, etc.) as compared to pre-energized insertion devices. Substantially uncompressed first and second springs can provide a system where the substantially unenergized first spring 404m is configured to load energy sufficient to drive a sensor from a proximal position to a distal position and also to transfer energy to the second spring 234m to drive a needle to a fully retracted position.

0477Other embodiments can also be configured to achieve these benefits. For example, <figref idref="f0036">Figures 76-79</figref> illustrate another embodiment of a system 104n for applying an on-skin sensor assembly to skin of a host. The system 104n includes many features that are similar to those of the embodiment illustrated in <figref idref="f0033 f0034 f0035">Figures 71-75</figref> (e.g., a telescoping assembly 132n including a first portion 150n, a second portion 152n, and a third portion 392n; a needle hub 162n; a first spring 402n; and a second spring 234n). In the embodiment illustrated in <figref idref="f0036">Figures 76-79</figref>, the first spring 402n is formed separately from and operatively coupled to the third portion 392n. The second spring 234n is formed separately from and operatively coupled to the needle hub 162n. The first spring and/or the second spring can each comprise a helical spring having a circular cross section. In some embodiments, the first spring and/or the second spring can each comprise a helical spring having a square or non-circular cross section. The first spring and/or the second spring can comprise metal, such as, but not limited to, stainless steel, steel, or other types of metals. Alternatively, in some embodiments, one or both of the first spring and the second spring can be integrally formed with a portion of the applicator assembly. For example and without limitation, in some embodiments the first spring can be integrally formed with the first portion. In some embodiments, the second spring can be integrally formed with the needle hub. In several embodiments, the first spring and/or the second spring can be molded plastic, such as, but not limited to, PC or ABS.

0478<figref idref="f0036">Figure 76</figref> illustrates a cross-sectional side view of the system 104n in a resting state, in which both the first spring 402n and the second spring 234n are unstressed and unenergized. In the resting state, the first portion 150n can be fixed with respect to the second portion 152n, at least in an axial direction, whereas the third portion 392n is movable in at least a distal direction with respect to the first portion 150n. The first portion 150n and the second portion 152n can be fixed with respect to one another in any suitable fashion, for example by cooperating releasable locking features (e.g., the locking features as described in <figref idref="f0033 f0034 f0035">Figures 71-75</figref>, or similar features) coupled to or forming part of the first portion 150n and the second portion 152n. The system 104n includes an on-skin component 134n which is releasably coupled to the needle hub 162n. The on-skin component can comprise a sensor module, such as the sensor module 134 described in connection with <figref idref="f0002">Figure 3</figref>, or a combined sensor module and base assembly, or an integrated sensor module/base/transmitter assembly, or any other component which is desirably applied to the skin of a host, whether directly or indirectly, for example via an adhesive patch.

0479In the resting state illustrated in <figref idref="f0036">Figure 76</figref>, the on-skin component 134n is disposed at a proximal starting position, between the proximal and distal ends of the system 104n. The distal end of the needle 156 may also be disposed between the proximal and distal ends of the system 104n. In the resting state, the distal end of the first spring 402n abuts a proximally-facing surface of the first portion 150n. The application of force against the proximally-facing surface of the third portion 392n causes the third portion 392n to move distally with respect to the first portion 150n, compressing and thus energizing the first spring 402n. In some embodiments, this process may be similar to the spring energization process described in connection with <figref idref="f0033">Figure 71</figref>.

0480<figref idref="f0036">Figure 77</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0036">Figure 76</figref>, with the first spring 402n energized. When the third portion 392n has been moved sufficiently distally to energize the first spring 402n, the third portion 392n becomes fixed, at least in an axial direction, with respect to the second portion 152n. At or about the same time (e.g. simultaneously or subsequently), the first portion 150n becomes movable in at least a distal direction with respect to the second portion 152n. The third portion 392n and the second portion 150n can be fixed with respect to one another in any suitable fashion, for example by cooperating locking features (e.g., the locking features described in <figref idref="f0033 f0034 f0035">Figures 71-75</figref>, or similar features) coupled to or forming part of the third portion 392n and the second portion 152n, which are configured to engage with one another once the third portion 392n has reached a sufficiently distal position. The first portion 150n and the second portion 152n can be rendered movable with respect to one another by structure(s) (not shown in <figref idref="f0036">Figures 76-79</figref>) configured to release the locking features which coupled them together in the resting configuration illustrated in <figref idref="f0036">Figure 76</figref>. The first portion 150n includes overhangs (sometimes referred to as detents, undercuts, and/or needle hub engagement features) 166n which cooperate with release feature 160n of the needle hub 162n to fix the needle hub 162n with respect to the first portion 150n, both while the system is in a resting state and during energization of the spring 392n.

0481<figref idref="f0036">Figure 78</figref> illustrates a cross-sectional side view of the system 104n, with the first portion 150n and the second portion 152n unlocked, activating the first spring 402n and allowing the energy stored therein to drive the first portion 150n in a distal direction. The movement of the first portion 150n also urges the needle hub 162n (as well as the on-skin component 134n which is coupled to the needle hub 162n) in a distal direction, compressing the second spring 234n against a proximally-facing surface of the second portion 152n, coupling the on-skin component 134n to the base 128n, and driving the needle 156 into the distal insertion position illustrated in <figref idref="f0036">Figure 78</figref>. When the needle hub 162n has reached a sufficiently distal position to achieve these functions, the ends of the release feature 160n contact ramps 170n of the second portion 152n which cause the release feature 160n to compress inward (towards the central axis of the system 104n), disengaging the ends of the release feature 160n from the overhangs 166n. In some embodiments, this process may be similar to the spring compression process described in connection with <figref idref="f0034">Figure 74</figref>. In some embodiments, ramps 170n are proximally facing ramps. In other embodiments, ramps 170n are distally facing ramps (not shown). In some embodiments, the release feature or features can be configured to be compressed inward (or otherwise released) by relative rotational movement of certain components of the system, such as, for example, by twisting or other rotational movement of the first portion with respect to the second portion. In some embodiments, the release feature or features can extend in a direction normal to the axis of the system, and/or can extend circumferentially about the axis of the system, instead of (or in addition to) extending generally parallel to the axis of the system as illustrated in <figref idref="f0036">Figure 78</figref>.

0482<figref idref="f0036">Figure 79</figref> illustrates a cross-sectional side view of the system 104n, with the needle hub 162n released from engagement with the overhangs 166, activating the second spring 234n and allowing the energy stored therein to drive the needle hub 162n in a proximal direction. As the needle hub 162n retracts to a proximal position, the on-skin component 134n decouples from the needle hub 162n to remain in a deployed position, coupled to the base 128n.

0483<figref idref="f0037 f0038 f0039">Figures 80-85</figref> illustrate another embodiment of a system 104p for applying an on-skin sensor assembly to skin of a host. A sensor insertion system such as the one illustrated in <figref idref="f0037 f0038 f0039">Figures 80-85</figref> may provide enhanced predictability in spring displacement of the second energized spring 234p because the second spring 234p is already compressed. Such a configuration can aid in properly ensuring the needle is retracted at a sufficient distance from the skin. In some embodiments, a system incorporating a pre-energized retraction spring can provide effective and reliable insertion and retraction while requiring a lesser amount of user-supplied force than, for example, a system in which both the insertion and retraction springs are substantially unenergized prior to deployment, making such a configuration more convenient for at least some users. Further, in some embodiments, a system incorporating one or more metal springs can provide effective and reliable insertion and retraction while requiring a lesser amount of force than a system in which both the insertion and retraction springs comprise plastic. The system 104p includes many features that are similar to those of the embodiment illustrated in <figref idref="f0036">Figures 76-79</figref> (e.g., a telescoping assembly 132p including a first portion 150p, a second portion 152p, and a third portion 392p; a needle hub 162p; a first spring 402p; a second spring 234p; an on-skin component 134n, and a base 128p). In the embodiment illustrated in <figref idref="f0037 f0038 f0039">Figures 80-85</figref>, the first spring 402p is formed separately from and operatively coupled to the third portion 392p. The second spring 234p is formed separately from and operatively coupled to the needle hub 162p. The first spring and/or the second spring can comprise metal. Alternatively, in some embodiments, one or both of the first spring and the second spring can be integrally formed with a portion of the applicator assembly. For example and without limitation, in some embodiments the first spring can be integrally formed with the first portion. In some embodiments, the second spring can be integrally formed with the needle hub. In several embodiments, the first spring and/or the second spring can be molded plastic.

0484<figref idref="f0037">Figure 80</figref> illustrates a cross-sectional side view of the system 104p in a resting state, in which the first spring 402p is substantially unstressed and unenergized, but in which the second spring 234n is pre-energized (e.g., compressed). In the resting state illustrated in <figref idref="f0037">Figure 80</figref>, the first portion 150p is locked to the second portion 152p so as to prevent proximal or distal movement of the first portion 150p with respect to the second portion 152p. The first portion 150p and the second portion 152n can be locked together in any suitable fashion, for example by cooperating releasable locking features 396p and 398p (see <figref idref="f0039">Figures 84 and 85</figref>) coupled to or forming part of the first portion 150p and the second portion 152p. The needle hub 162n is also releasably fixed to the first portion 150p. The needle hub 162n can be fixed to the first portion 150p in any suitable fashion, for example by features of the first portion 150p configured to engage or compress release feature (sometimes referred to as needle hub resistance features) 160p of the needle hub 162p.

0485In the resting state illustrated in <figref idref="f0037">Figure 80</figref>, the on-skin component 134p is disposed at a proximal starting position, such that the distal end of the needle 156 is disposed between the proximal and distal ends of the system 104p. In the resting state, the distal end of the first spring 402p abuts a proximally-facing surface of the first portion 150p. The application of force against the proximally-facing surface of the third portion 392p causes the third portion 392p to move distally with respect to the first portion 150p, compressing and thus energizing the first spring 402p. In some embodiments, this process may be similar to the spring energization process described in connection with <figref idref="f0036">Figure 76</figref>.

0486<figref idref="f0037">Figure 81</figref> illustrates a cross-sectional side view of the system 104p of <figref idref="f0037">Figure 80</figref>, after the third portion 392n has been moved to a sufficiently distally position to energize the first spring 402p and optionally lock the third portion 392p to the second portion 152p. The third portion 392n and the second portion 150n can lock together in any suitable fashion, for example by cooperating locking features (e.g., the locking features described in <figref idref="f0036">Figures 76-79</figref>, or similar features) coupled to or forming part of the third portion 392p and the second portion 152p. At or about the same time as the third portion 392p locks to the second portion 152p (e.g. simultaneously or subsequently), the unlocking features 404p and 406p (see <figref idref="f0039">Figures 84 and 85</figref>) cooperate to release the lock between the first portion 150p and the second portion 152p.

0487<figref idref="f0038">Figure 82</figref> illustrates a cross-sectional side view of the system 104p, with the first spring 402p activated to drive the first portion 150p in a distal direction. The movement of the first portion 150p also urges the needle hub 162p (as well as the on-skin component 134p which is coupled to the needle hub 162p) in a distal direction, coupling the on-skin component 134p to the base 128p, and also driving the needle 156 in a distal direction, past a distal end of the system 104p. At or about the time the needle hub 162p reaches the distal insertion position illustrated in <figref idref="f0038">Figure 82</figref> (e.g., immediately before, simultaneously, or subsequently), the ends of the release feature 160p contact ramps 170p of the second portion 152p, causing the release feature 160p to compress inward (towards the central axis of the system 104p), unlocking the needle hub 162p from the first portion 150p and releasing or activating the second spring 234p. In some embodiments, ramps 170p are proximally facing ramps. In other embodiments, ramps 170p are distally facing ramps (not shown). Activation of the second spring 234p urges the needle hub 162p in a proximal direction.

0488<figref idref="f0038">Figure 83</figref> illustrates a cross-sectional side view of the system 104p, with the needle hub 162p unlocked from the first portion 150p and retracted to a proximal position. As the needle hub 162p retracts to a proximal position, the on-skin component 134p decouples from the needle hub 162p to remain in a deployed position, coupled to the base 128p.

0489<figref idref="f0039">Figure 84</figref> illustrates a perspective view of the system 104p in a resting state, with the first portion 150p and the third portion 392p shown in cross section to better illustrate certain portions of the system 104p, such as the locking features 396p, 398p and the unlocking features 404p, 406p. <figref idref="f0039">Figure 85</figref> illustrates another perspective view of the system 104p, also with the first portion 150p and the third portion 392p shown in cross section, with the first spring 402p energized but not yet activated.

0490<figref idref="f0040">Figures 86-88</figref> illustrate another embodiment of a system 104q for applying an on-skin sensor assembly to skin of a host, wherein the insertion spring is pre-compressed and the retraction spring is substantially uncompressed. Such a system may allow a user to activate the insertion and retraction of a needle with fewer steps. It is contemplated that advantages may include a relatively smaller applicator size and more predictable spring displacement of the first spring because the first spring is already compressed, thereby aiding in ensuring proper needle insertion into the skin of a user. In some embodiments, a system incorporating a pre-energized insertion spring can provide effective and reliable insertion and retraction while requiring a lesser amount of user-supplied force than, for example, a system in which both the insertion and retraction springs are substantially unenergized prior to deployment, making such a configuration more convenient for at least some users. The system 104q includes many items that are similar to those of the embodiment illustrated in <figref idref="f0036">Figures 76-79</figref> (e.g., a telescoping assembly 132q including a first portion 150q, a second portion 152q, and a third portion 392q; a needle hub 162q; a first spring 402q; a second spring 234q; an on-skin component 134q, and a base 128q). In the system 104q, the first spring 402q is formed separately from and operatively coupled to the third portion 392q. The second spring 234q is formed separately from and operatively coupled to the needle hub 162q. The first spring and/or the second spring can comprise metal. Alternatively, in some embodiments, one or both of the first spring and the second spring can be integrally formed with a portion of the applicator assembly.

0491<figref idref="f0040">Figure 86</figref> illustrates a cross-sectional side view of the system 104q in a resting state, in which the first spring 402q is already energized but in which the second spring 234q is substantially unenergized (e.g. mostly uncompressed or unstressed; can be partially energized). In the resting state illustrated in <figref idref="f0040">Figure 86</figref>, the first portion 150q is locked to the second portion 152q so as to prevent proximal or distal movement of the first portion 150q with respect to the second portion 152q. The first portion 150q and the second portion 152q can be locked together in any suitable fashion, for example by cooperating releasable locking features (e.g., the locking features described in <figref idref="f0036">Figures 76-79</figref> or other suitable locking features) coupled to or forming part of the first portion 150q and the second portion 152q. The needle hub 162q is also releasably locked to the first portion 150q. The needle hub 162q can be locked to the first portion 150q in any suitable fashion, for example by features of the first portion 150q configured to engage or compress release feature 160q of the needle hub 162q. The third portion 392q and the second portion 152q are also locked together, so as to prevent relative movement of the third portion 392p and the second portion 152q in the axial direction. The third portion 392q and the second portion 152q can be locked together in any suitable fashion, for example by cooperating locking features (not shown in <figref idref="f0040 f0041">Figures 86-89</figref>), which may be coupled to or form part of the third portion 392q and the second portion 152q. In the resting state illustrated in <figref idref="f0037">Figure 80</figref>, the on-skin component 134q is disposed at a proximal starting position, such that the distal end of the needle 156 is disposed between the proximal and distal ends of the system 104q.

0492To trigger deployment of the system 104q, the locking features coupling the first portion 150q to the second portion 152q can be unlocked, decoupling these two portions and thereby releasing or activating the first spring 402q. The locking features can be unlocked by a user-activated trigger mechanism, such as, for example, a button disposed on or in a top or side surface of the system 104q, or a twist-release feature configured to disengage the locking features when the third portion 392q is rotated about the axis of the system, relative to the first portion 150q and/or the second portion 152q. Some examples of triggering mechanisms are described in connection with <figref idref="f0042 f0043 f0044 f0045 f0046 f0047">Figures 92-104</figref>.

0493<figref idref="f0040">Figure 87</figref> illustrates a cross-sectional side view of the system 104q, after the first portion 150q and the second portion 152q have been unlocked. As can be seen in <figref idref="f0040">Figure 87</figref>, the first spring 402q drives the first portion 150q in a distal direction as the first spring 402q expands. The movement of the first portion 150q also urges the needle hub 162q (as well as the on-skin component 134q which is coupled to the needle hub 162q) in a distal direction, coupling the on-skin component 134q to the base 128q, compressing the second spring 234q, and driving the needle 156 in a distal direction past a distal end of the system 104q. At or about the time the needle hub 162q reaches the distal insertion position illustrated in <figref idref="f0040">Figure 87</figref> (e.g., immediately before, simultaneously, or subsequently), the ends of the release feature 160q contact interference features 170q of the second portion 152q, causing the release feature 160q to compress inward (towards the central axis of the system 104q), unlocking the needle hub 162q from the first portion 150q and activating the now-energized second spring 234q. In some embodiments, interference features 170q are proximally facing interference features. In other embodiments, interference features 170q are distally facing interference features (not shown).

0494Activation of the second spring 234q by the user or mechanisms urges the needle hub 162q in a proximal direction, while the on-skin component 134q, having been coupled to the base 128q, remains in a deployed distal position. <figref idref="f0040">Figure 88</figref> illustrates a cross-sectional side view of the system 104q, with the on-skin component 134q in a deployed position and the needle hub 162q retracted to a proximal position.

0495<figref idref="f0041">Figures 89-91</figref> illustrate another embodiment of a system 104r for applying an on-skin sensor assembly to skin of a host. It is contemplated that the system 104r as illustrated with reference to <figref idref="f0041">Figures 89-91</figref> provides for predictable spring displacement of the first spring 402r because it is compressed, thereby aiding in proper needle insertion into the skin of the user. Moreover, it is contemplated that the compressed second spring 234r provides predictable spring displacement and aids in properly ensuring that the needle is properly retracted from the skin of the user. In some embodiments, a system incorporating pre-energized insertion and retraction springs can provide effective and reliable insertion and retraction while requiring a lesser amount of user-supplied force than, for example, a system in which one or both of the insertion and retraction springs are substantially unenergized prior to deployment, making such a configuration more convenient for at least some users. The system 104r includes many items that are similar to those of the embodiment illustrated in <figref idref="f0036">Figures 76-79</figref> (e.g., a telescoping assembly 132r including a first portion 150r, a second portion 152r, and a third portion 392r; a needle hub 162r; a first spring 402r; a second spring 234r; an on-skin component 134r, and a base 128r). As illustrated in <figref idref="f0041">Figures 89-91</figref>, both the first spring 402r and the second spring 234r are pre-compressed. In the system 104r, the first spring 402r is formed separately from and operatively coupled to the third portion 392r. The second spring 234r is formed separately from and operatively coupled to the needle hub 162r. The first spring and/or the second spring can comprise metal. Alternatively, in some embodiments, one or both of the first spring and the second spring can be integrally formed with a portion of the applicator assembly.

0496<figref idref="f0041">Figure 89</figref> illustrates a cross-sectional side view of the system 104r in a resting state, in which both the first spring 402r and the second spring 234r are pre-energized (e.g., compressed sufficiently to drive the needle insertion and retraction processes). In the resting state illustrated in <figref idref="f0041">Figure 89</figref>, the first portion 150r is locked to the second portion 152r so as to prevent proximal or distal movement of the first portion 150r with respect to the second portion 152r. The first portion 150r and the second portion 152r can be locked together in any suitable fashion, for example by cooperating releasable locking features (e.g., the locking features described in connection with <figref idref="f0037 f0038">Figures 80-83</figref>, or other suitable locking features) coupled to or forming part of the first portion 150r and the second portion 152r. The needle hub 162r is also releasably locked to the first portion 150r. The needle hub 162r can be locked to the first portion 150r in any suitable fashion, for example by features of the first portion 150r configured to engage or compress release feature 160r of the needle hub 162r. The third portion 392r and the second portion 152r are also locked together, so as to prevent relative movement of the third portion 392p and the second portion 152r in at least the axial direction. The third portion 392r and the second portion 152r can be locked together in any suitable fashion, for example by cooperating locking features (not shown in <figref idref="f0041">Figures 89-91</figref>), which may be coupled to or form part of the third portion 392r and the second portion 152r. In the resting state illustrated in <figref idref="f0041">Figure 89</figref>, the on-skin component 134r is disposed at a proximal starting position, such that the distal end of the needle 156 is disposed between the proximal and distal ends of the system 104r.

0497To trigger deployment of the system 104r, the locking features coupling the first portion 150r to the second portion 152r can be unlocked, decoupling these two portions and thereby releasing or activating the first spring 402r. <figref idref="f0041">Figure 90</figref> illustrates a cross-sectional side view of the system 104r, after the first portion 150r and the second portion 152r have been unlocked. As can be seen in <figref idref="f0041">Figure 90</figref>, the first spring 402r drives the first portion 150r in a distal direction as the first spring 402r expands or decompresses. The movement of the first portion 150r also urges the needle hub 162r (as well as the on-skin component 134r which is coupled to the needle hub 162r) in a distal direction until the on-skin component 134r is coupled to the base 128r, and until the needle 156 reaches a distal insertion position beyond a distal end of the system 104r. At or about the time the needle hub 162r reaches the distal insertion position illustrated in <figref idref="f0040">Figure 87</figref> (e.g., immediately before, simultaneously, or subsequently), the ends of the release feature 160r contact corresponding interference features 170r of the second portion 152r, causing the release feature 160r to compress inward (towards the central axis of the system 104r), unlocking the needle hub 162r from the first portion 150r and releasing or activating the second spring 234r.

0498Activation of the second spring 234r drives the needle hub 162r in a proximal direction, while the on-skin component 134r, having been coupled to the base 128r, remains in a deployed distal position. <figref idref="f0041">Figure 91</figref> illustrates a cross-sectional side view of the system 104r, with the on-skin component 134r in a deployed position and the needle hub 162r retracted to a proximal position. From this configuration, the system 104r can be removed and separated from the deployed on-skin component 134r and the base 128r.

0499<figref idref="f0042 f0043 f0044 f0045">Figures 92-100</figref> illustrate yet another embodiment of a system 104s for applying an on-skin sensor assembly to skin of a host comprising a safety feature to prevent accidental firing of the sensor insertion device. The system 104s includes many items that are similar to those of the embodiment illustrated in <figref idref="f0036">Figures 76-79</figref> (e.g., a telescoping assembly 132s including a first portion 150s, a second portion 152s, and a third portion 392s; a needle hub 162s; a first spring 402s; a second spring 234s; an on-skin component 134s, and a base 128s). In the system 104s, the first spring 402s may be formed separately from and operatively coupled to the third portion 392s. The second spring 234s may be formed separately from and operatively coupled to the needle hub 162s. The first spring and/or the second spring can comprise metal. Alternatively, in some embodiments, either or both of the first spring and the second spring can be integrally formed with a portion of the applicator assembly.

0500<figref idref="f0042">Figure 92</figref> illustrates a side view of the system 104s in a resting state, in which the first spring 402s is unstressed and unenergized, but in which the second spring 234s is already energized (e.g., compressed). The system 104s includes a cocking mechanism 702 by which the first spring 402s can be energized (e.g. compressed) without automatically triggering deployment of the first portion 150s or activation of the first spring 402s. The system 104s also includes a trigger button 720 configured to activate the first spring 402s after the system is cocked. <figref idref="f0042">Figure 93</figref> illustrates a side view of the applicator system 104s, after being cocked but before being triggered.

0501<figref idref="f0043">Figure 94</figref> illustrates a cross-sectional perspective view of the system 104s in a resting state, showing the first spring 402s substantially uncompressed. The cocking mechanism 702 includes a pair of proximally-extending lever arms 704, each with a radially-extending angled tab 706. In some embodiments, the lever arms 704 can be integrally formed with the second portion 152s, as shown in <figref idref="f0043">Figure 94</figref>, while in other embodiments, the lever arms 704 can be separate from and operatively coupled to the second portion 152s. In the resting state illustrated in <figref idref="f0043">Figure 94</figref>, the angled tabs 706 extend through distal apertures 708 in the third portion 392s so as to prevent proximal movement of the third portion 392s with respect to the second portion 152s. The angled tabs 706 are also configured to inhibit distal movement of the third portion 392s with respect to the second portion 152s, unless and until a sufficient amount of force is applied to the third portion 392s to deflect the angled tabs 706 and the lever arms 704 inward, as illustrated in <figref idref="f0043">Figure 95</figref>.

0502As sufficient force is applied to the third portion 392s in a distal direction (e.g. by the hand or thumb of a user), the angled tabs 706 deflect inward and release from engagement with the distal apertures 708, allowing the third portion 392s to move distally with respect to the second portion 152s. This may allow the user to compress and energize the first spring 402s. When the third portion 392s has reached a sufficiently distal position to compress the first spring 402s enough to drive the sensor into the skin of a host, the angled tabs 706 engage with proximal apertures 710 of the third portion 392s to lock the position of the third portion 392s with respect to the second portion 152s, as illustrated in <figref idref="f0043">Figure 96</figref>. The angled tabs 706 may be configured to generate a "click" sound when engaged to proximal apertures 710 so as to prevent proximal movement of the third portion 392s with respect to the second portion 152s, so that a user can feel and/or hear when these parts are engaged. In the configuration illustrated in <figref idref="f0043">Figure 96</figref>, the system 104s is energized in which the third portion 392 is in a cocked position. The system 104s is ready to deploy the sensor, but does not deploy until further action is taken by the user.

0503<figref idref="f0044">Figure 97</figref> illustrates a cross-sectional side view of the system 104s, in a cocked but untriggered state. In this state, the first portion 150s is locked to the second portion 152s so as to prevent proximal or distal movement of the first portion 150s with respect to the second portion 152s. The first portion 150s and the second portion 152s can be locked together in any suitable fashion, for example by cooperating releasable locking features 396s and 398s operatively coupled to or forming part of the first portion 150s and the second portion 152s. The trigger button 720 includes a distally-extending protrusion 722 which, once depressed to a sufficiently distal position by a user, is configured to cooperate with an unlocking feature 406s of the locking feature 396s to decouple the first portion 150s from the second portion 152s. The trigger button 720 can be operatively coupled to the third portion 392s, as illustrated in <figref idref="f0042 f0043 f0044 f0045">Figures 92-100</figref>, or can be integrally formed with the third portion, for example as a lever arm formed within a proximal or side surface of the third portion. In some embodiments, the trigger button can be disposed at the top of the system (such that the application of force in the distal direction triggers the system to activate), or at a side of the system (such that the application of force in a radially inward direction, normal to the direction of needle deployment, triggers system to activate).

0504<figref idref="f0044">Figure 98</figref> illustrates a cross-sectional side view of the energized system 104s as the trigger button 720 has been depressed sufficiently to cause the protrusion 722 to flex the locking feature 396s radially inward, disengaging it from the opening 398s and unlocking the first portion 150s from the second portion 152s. Depressing the trigger button 720 thus activates the first spring 402, pushing the first portion 150s and the needle hub 162s, along with the on-skin component 134s which is coupled thereto, in a distal direction until the on-skin component is coupled to the base 128s, as illustrated in <figref idref="f0045">Figure 99</figref>. At or about the time the needle hub 162s reaches the distal insertion position illustrated in <figref idref="f0045">Figure 99</figref> (e.g., immediately before, simultaneously, or subsequently), corresponding release features of the needle hub 162s and the first portion 150s can engage (via, for example, the release features described in any of <figref idref="f0036 f0037 f0038 f0039 f0040 f0041">Figures 76-91</figref>, or any other suitable release features), releasing the needle hub 162s from the first portion 150s and releasing or activating the second spring 234s. Activation of the second spring 234s urges the needle hub 162s in a proximal direction.

0505<figref idref="f0045">Figure 100</figref> illustrates a cross-sectional side view of the applicator system of <figref idref="f0042">Figure 92</figref>, with the on-skin component 134s in a deployed position and the needle hub 162s retracted to a proximal position. As the needle hub 162s retracts to a proximal position, the on-skin component 134s decouples from the needle hub 162s to remain in a deployed position, coupled to the base 128s. From this configuration, the remainder of the system 104s can be removed and separated from the deployed on-skin component 134s and the base 128s.

0506Any of the features described in the context of any of <figref idref="f0028 f0029 f0030 f0031 f0032 f0033 f0034 f0035 f0036 f0037 f0038 f0039 f0040 f0041 f0042 f0043 f0044 f0045">Figures 61-99</figref> can be applicable to all aspects and embodiments identified herein. For example, the embodiments described in the context of <figref idref="f0028 f0029">Figures 61-64</figref> can be combined with the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0030 f0031 f0032">Figures 1-60 and 65-70</figref>. As another example, any of the embodiments described in the context of <figref idref="f0042 f0043 f0044 f0045 f0046 f0047 f0048 f0049">Figures 92-109</figref> can be combined with any of the embodiments described in the context of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0030 f0031 f0032 f0033 f0034 f0035 f0036 f0037 f0038 f0039 f0040 f0041 f0050 f0051 f0052 f0053 f0054 f0055 f0056 f0057 f0058 f0059 f0060 f0061 f0062 f0063 f0064 f0065 f0066">Figures 1-60 and 65-91 and 110-143</figref>. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

TRIGGER MECHANISMS AND SAFETY LOCKS

0507In some embodiments, the application of enough force to sufficiently energize the first spring to drive insertion of the sensor can also serve to activate the first spring. In other embodiments, the energizing of the first spring can be decoupled from the activation of the first spring, requiring separate actions on the part of the user to energize (e.g. compress) the first spring and to trigger deployment of the system.

0508For example, the embodiment illustrated in <figref idref="f0042 f0043 f0044 f0045">Figures 92-100</figref> includes a trigger mechanism in the context of a user-energized actuator. In such an embodiment, the user first cocks the system 104s to energize the first spring 402s, and then, in a separate action, triggers the activation of the first spring 402s using the trigger button 720. The locking feature is easy to release by the user and when combined with a trigger mechanism, allows for single handed use.

0509In some embodiments, the actuator or insertion spring is already energized when the system is in a resting state. In these embodiments, a trigger mechanism, such as the trigger mechanism described in the context of <figref idref="f0042 f0043 f0044 f0045">Figures 92-100</figref>, can be used to activate the already-energized insertion spring without any action by the user to energize the spring.

0510<figref idref="f0046">Figure 101</figref> illustrates a side view of one such applicator system 104t, with a side trigger button 730. The system 104t can be configured substantially similar to the system 104q or the system 104r illustrated within the context of <figref idref="f0040 f0041">Figures 86-88 and 89-91</figref>, respectively, with like reference numerals indicating like parts. As can be seen in <figref idref="f0046">Figure 101</figref>, the trigger button 730 is operatively coupled to the third member 392t.

0511<figref idref="f0046">Figure 102</figref> illustrates another side view of the system 104t, with the first portion 150t and the third portion 392t shown in cross-section to illustrate the trigger mechanism. As can be seen in <figref idref="f0046">Figure 102</figref>, the trigger button 730 includes a protrusion 732 that extends radially inward, toward a central axis of the system 104t. The protrusion 732 is radially aligned with the locking feature 396t of the first portion 150t. When a user exerts a sideways (e.g., radially inward) force on the trigger button 730, the protrusion 732 urges the locking feature 396t radially inward, releasing it from engagement with the ledge feature 398t (which may be configured similarly to, for example, the ledge locking feature 398p illustrated in <figref idref="f0039">Figures 84 and 85</figref>) in the second portion 152t and activating the first spring 402t. In other embodiments, the locking features 396, 398 can comprise cooperating structure of a key/keyway mechanism which is configured to release when the features 396, 398 are brought into a certain orientation with respect to one another (e.g., using a radially applied force, an axially applied force, a twisting movement or rotational force, or other type of activation).

0512<figref idref="f0047">Figure 103</figref> illustrates a side view of another applicator system 104u, with an integrated side trigger button 730. The system 104u can be configured substantially similar to the system 104q or the system 104r illustrated within the context of <figref idref="f0040 f0041">Figures 86-88 and 89-91</figref>, respectively, with like reference numerals indicating like parts. As can be seen in <figref idref="f0047">Figure 103</figref>, the trigger button 740 is a distally-extending lever arm integrally formed in the third member 392u. <figref idref="f0047">Figure 104</figref> illustrates another side view of the system 104u, with the first portion 150u and the third portion 392u shown in cross-section to better illustrate the trigger mechanism. As can be seen in <figref idref="f0047">Figure 104</figref>, the trigger button 740 is radially aligned with a radially-extending tab 742 of the first portion 150u. The tab 742 is connected to the locking feature 396u via an elongated member 394u, which acts as a lever arm. In some embodiments, tab 742 locking feature 396u, and elongated member 394u are integrally formed together. When a user exerts a sideways (e.g., radially inward) force on the trigger button 740, the button 740 pushes the tab 742 radially inward, releasing the locking feature 396u from engagement with the locking feature 398u in the second portion 152u and activating the first spring 402u.

0513Trigger mechanisms such as those described in the context of any of <figref idref="f0042 f0043 f0044 f0045 f0046 f0047">Figures 92-104</figref> can be used in embodiments comprising pre-energized actuators or insertion springs, as well as in embodiments comprising user-energized actuators or insertion springs.

0514In several embodiments, a sensor inserter system can include a safety mechanism configured to prevent premature energizing and/or actuation of the insertion spring. <figref idref="f0048 f0049">Figures 105-109</figref> illustrate one such system 104v, which incorporates a safety lock mechanism 750. <figref idref="f0048">Figure 105</figref> illustrates a perspective view of the system 104v. The system 104v can be configured substantially similar to any of the systems 104m, 104n, 104p illustrated within the context of <figref idref="f0033 f0034 f0035 f0036 f0037 f0038 f0039 f0040">Figures 71-87</figref>, with like reference numerals indicating like parts. The safety lock mechanism 750 includes a release button 760, which can be integrally formed with the third portion 392v as shown in <figref idref="f0048">Figure 105</figref> (similar to the trigger button 740 described in connection with <figref idref="f0047">Figures 103-104</figref>), or which can be operatively coupled to the third portion 392v. In the system 104v, the release button 760 comprises a lever arm which is integrally formed in a side of the third portion 392v, although other configurations (e.g. a top button) are also contemplated. The release button can be configured to protrude radially from a side or a top of the third portion, or can be configured with an outer surface which is flush with the surrounding surface of the third portion 392v.

0515<figref idref="f0048">Figure 106</figref> illustrates a cross-sectional perspective view of a portion of the system 104v, with the safety mechanism 750 in a locked configuration and the first spring 402v unenergized. The safety mechanism 750 includes a proximally-extending locking tab 752 of the second portion and an inwardly-extending overhang (or undercut) 754 of the third portion 392v. In the locked configuration illustrated in <figref idref="f0048">Figure 106</figref>, the tab 752 is flexed radially outward and its proximal end is constrained by the overhang 754, preventing distal movement of the third portion 392v with respect to the second portion 152v and thus preventing energization of the spring 392v. The release button 760 includes a protrusion 758 which extends inwardly, in radial alignment with a portion of the tab 752. A lateral (e.g. radially inward) force applied to the release button 760 pushes the tab 752 radially inward, sliding the proximal end of the tab 752 against an angled surface 756 of the overhang 754 and out of engagement with the overhang 754, so that the tab 752 can release to an unstressed configuration as shown in <figref idref="f0049">Figure 108</figref>. Once the tab 752 is released, the third portion 392v can be moved distally with respect to the second portion 152v, for example to energize the first spring 402v. In some embodiments, as illustrated in <figref idref="f0049">Figure 109</figref>, the tab 752 can be configured to prevent further distal movement of the third portion 392v beyond a desired threshold, for example by abutting a distally-facing surface 762 of the third portion 392v.

0516Although the safety lock mechanism 750 is illustrated in the context of a system configured to be energized by a user, in some embodiments, a pre-energized system can also employ a safety lock mechanism, for example to prevent premature triggering or activation of an already energized spring.

0517In some embodiments, the locking and unlocking (and/or coupling and decoupling) of the components of a sensor inserter assembly can follow this order: The sensor inserter assembly begins in a resting state in which the third portion 392 is locked with respect to the first portion 150, the first portion 150 is locked with respect to the second portion 152, and the sensor module 134 is coupled to the first portion 150 (optionally via the needle hub 162). Before energizing or triggering of the insertion spring 402, the third portion 392 is unlocked with respect to the first portion 150 and/or the second portion 150. The insertion spring 402, if not already energized, is then energized by distal movement of the third portion 392. Then, the third portion 392 is locked with respect to the second portion 152. The first portion 150 is then released from the second portion 152 to activate the insertion spring 402. As the insertion spring 402 deploys, the sensor module 134 couples to the base 128. Then the first portion 150 (and/or the needle hub 162) releases the sensor module 134, and the second portion 152 releases the base 128. In several embodiments, the locations of the various locking and unlocking (and/or coupling and decoupling) structures along the axis of the assembly are optimized to ensure this order is the only order that is possible. (Some embodiments use different locking and unlocking orders of operation.)

0518Systems such as those illustrated in <figref idref="f0042 f0043 f0044 f0045 f0046 f0047 f0048 f0049">Figures 92-109</figref> provide reliable trigger mechanisms to release an insertion spring when the insertion spring is in a loaded condition. It is contemplated such systems provide several advantages to the user including ease in firing, single handed firing (by allowing the user to hold onto the sides of the insertion device and fire the insertion device using the same hand). It is contemplated that a system comprising a top trigger can provide a smaller width profile than a system having a side button while requiring less user dexterity.

RELEASE AFTER DEPLOYMENT

0519In several embodiments, a sensor inserter system is configured to move an on-skin component (such as, for example, a sensor module 134, a sensor assembly (for example comprising a sensor, electrical contacts, and optionally a sealing structure), a combination sensor module and base, an integrated sensor module and transmitter, an integrated sensor module and transmitter and base, or any other component or combination of components which is desirably attached to the skin of a host) from a proximal starting position within the sensor inserter system to a distal deployed position in which it can attach to the skin of a host, while at the same time inserting a sensor (which may form part of the on-skin component) into the skin of the host. In some embodiments, the sensor is coupled to electrical contacts of the on-skin component during the deployment and/or insertion process. In other embodiments, the on-skin component is pre-connected, that is to say, the sensor is coupled to electrical contacts of the on-skin component before the deployment and/or insertion processes begin. The sensor assembly can be pre-connected, for example, during manufacture or assembly of the system.

0520Thus, in several embodiments, a sensor inserter system can be configured to releasably secure the on-skin component in its proximal starting position, at least before or until deployment of the inserter system, and can also be configured to release the on-skin component in a distal position after the inserter system is deployed. In some embodiments, the system can be configured to couple the on-skin component to a base and/or to an adhesive patch during the deployment process, either as the on-skin component is moved from the proximal starting position to the distal deployed position or once it reaches the distal deployed position. In some embodiments, the system can be configured to separate from (or become separable from) the on-skin component, base, and/or adhesive patch after the on-skin component is deployed in the distal position and the needle hub (if any) is retracted.

0521In embodiments, various mechanical interlocks (e.g., snap fits, friction fits, interference features, elastomeric grips) and/or adhesives can be used to couple the on-skin component to the sensor inserter system and releasably secure it in a proximal starting position, and/or to couple the on-skin component (and base, if any) to the adhesive patch once the on-skin component is deployed. In addition, various mechanical features (e.g. snap fits, friction fits, interference features, elastomeric grips, pushers, stripper plates, frangible members) and/or adhesives can be used to decouple the on-skin component from the sensor inserter system once it reaches the distal deployed position. Further, various mechanical features, (e.g. snap fits, friction fits, interference features, elastomeric grips, pushers, stripper plates, frangible members) and/or adhesives can be used to separate, unlock, or otherwise render separable the on-skin component, base, and/or adhesive patch from the remainder of the system after the on-skin component is deployed in the distal position and the needle hub (if any) is retracted.

0522With reference now to <figref idref="f0050 f0051 f0052 f0053 f0054">Figures 110-119</figref>, a sensor inserter system 104w according to some embodiments is illustrated. The system 104w can be configured substantially similar to the system 104v illustrated within the context of <figref idref="f0048 f0049">Figures 105-109</figref> and system 104m illustrated within the context of <figref idref="f0033 f0034 f0035">Figures 71-75</figref>, with like reference numerals indicating like parts. The system 104w includes, for example, a telescoping assembly 132w including a first portion 150w, a second portion 152w, and a third portion 392w; a safety mechanism 750, a needle hub 162w; a first spring 402w; a second spring 234w; an on-skin component 134w, and a base 128w.

0523<figref idref="f0050">Figure 110</figref> illustrates a cross-sectional perspective view of the system 104w in a resting and locked state, with the on-skin component 134w secured in a proximal starting position. In this state, as well as in the unlocked state illustrated in <figref idref="f0050">Figure 111</figref> and the energized state illustrated in <figref idref="f0051">Figure 112</figref>, the on-skin component 134w is secured in the proximal starting position by a securement member 800. As can be seen in <figref idref="f0050">Figure 110</figref>, the system 104w includes a secondary locking feature 409w, configured as a ledge extending from the distal end of the locking protrusion 408w, which is configured to cooperate with an opening 410w to prevent the third portion 392 from moving in a proximal direction with respect to the second portion 152w prior to deployment. In the embodiment illustrated in <figref idref="f0050 f0051 f0052 f0053 f0054">Figures 110-119</figref>, the securement member 800 is integrally formed with the needle hub 162w. In other embodiments, the securement member can be integrally formed with the first portion 150w. In still other embodiments, the securement member can be separately formed from and operatively coupled to the needle hub 162w and/or to the first portion 150w. The securement member 800 extends substantially parallel to the needle 158. In the embodiment illustrated in <figref idref="f0050 f0051 f0052 f0053 f0054">Figures 110-119</figref>, the securement member 800 comprises a pair of distally-extending legs 802 (see <figref idref="f0052">Figures 115 and 116</figref>). Some embodiments can, however, include only one distally-extending leg 802, while others can include three, four, or more legs 802. In embodiments comprising only one leg 802, the leg can be configured to adhere or otherwise couple to a center region or a perimeter of the on-skin component. In embodiments comprising more than one leg 802, the legs can be configured to adhere or otherwise couple to the on-skin component symmetrically or asymmetrically about a center of the on-skin component. The legs 802 can have an ovoid cross section, or can have any other suitable cross section, including circular, square, triangular, curvilinear, L-shaped, O-shaped, U-shaped, V-shaped, X-shaped, or any other regular or irregular shape or combination of shapes. In embodiments, the securement member 800 can comprise legs, columns, protrusions, and/or elongate members, or can have any other suitable configuration for holding the on-skin component in the proximal starting position.

0524<figref idref="f0051">Figure 113</figref> illustrates a cross-sectional perspective view of the system 104w, in an activated state, with the insertion spring 402w activated, the retraction spring 234w energized, and the needle hub 162w and the securement member 800 moved to a distal deployed position. The on-skin component 134w, being coupled to the securement member 800 until this stage, has also been moved to a distal deployed position. When the on-skin component 134w reaches the distal deployed position, it is coupled to the base 128w.

0525<figref idref="f0051">Figure 114</figref> illustrates a cross-sectional perspective view of the system 104w after the on-skin component has been coupled to the base 128w and the needle hub 162w (along with the securement member 800) has been retracted to a proximal position. After the on-skin component 134w is coupled to the base 128w, a resistance member 804 facilitates decoupling of the on-skin component 134w from the securement member 800 by resisting unwanted proximal movement of the on-skin component 134w away from the base 128w. Generally, the resistance member 804 can be a backstop or backing structure configured to inhibit or prevent, or otherwise resist any tendency of the on-skin component 134w to move in a proximal direction as the securement member 800, which is releasably coupled to the on-skin component 134w, moves in a proximal direction. Because the first portion 150w is fixed to the second portion 152w at this stage, and the needle hub 162w is released from the first portion 150w, the needle hub 162w can retract in a proximal direction while the first portion 150w (and the resistance member 804) remains planted in a distal position, inhibiting proximal movement of the on-skin component 134w. The energy stored in the retraction spring 234w is sufficient to overcome a retention force and decouple the on-skin component 134w from the securement member 800 and urge the needle hub 162 in a proximal direction. The potential energy stored can be between 0.1134 kg (0.25 pounds) to 1,81437 kg (4 pounds). In preferred embodiments, the potential energy stored is between about 0.45359 to 0.90718 kg (1 to 2 pounds).

0526In some embodiments, a sensor inserter system can be configured such that the on-skin component couples with the base at approximately the same time the retraction mechanism is activated. In some embodiments, a sensor inserter system can be configured such that the on-skin component couples with the base before the retraction mechanism is activated, before the second spring is activated, or otherwise before the second spring begins retracting the needle hub in a proximal direction away from the deployed position. In some embodiments, a sensor inserter system can be configured such that the second spring is activated at least 0.05 seconds, at least 0.1 seconds, at least 0.2 seconds, at least 0.3 seconds, at least 0.4 seconds, at least 0.5 seconds, at least 0.6 seconds, at least 0.7 seconds, at least 0.8 seconds, at least 0.8 seconds, at least 1 second, or longer than 1 second after the on-skin component couples with the base. In other embodiments, a sensor inserter system can be configured such that the second spring is activated at most 0.05 seconds, at most 0.1 seconds, at most 0.2 seconds, at most 0.3 seconds, at most 0.4 seconds, at most 0.5 seconds, at most 0.6 seconds, at most 0.7 seconds, at most 0.8 seconds, at most 0.8 seconds, or at most 1 second after the on-skin component couples with the base.

0527The on-skin component 134w is now coupled with the base 128w. The base 128w (and adhesive patch) is initially coupled to the second portion 152w by a latch or flex arm 220w coupled to an undercut or locking feature 230w (similarly shown in <figref idref="f0009 f0010">FIGS. 18-19</figref>). When the first portion 150w reaches its most distal position during insertion of the sensor 138, a delatching feature of the first portion 150w pushes the latch of the second portion 152w out of the undercut. This decouples the base 128w from the second portion 152w, and thus allows the user to take the remainder of the system 104w off the skin, leaving only the adhesive patch, the base 128w, and the on-skin component 134w on the skin.

0528In the embodiment illustrated in <figref idref="f0050 f0051 f0052 f0053 f0054">Figures 110-119</figref>, the resistance member 804 is integrally formed with the first portion 150w. In other embodiments, the resistance member can be integrally formed with the second portion 152w. In still other embodiments, the resistance member can be separately formed from and operatively coupled to the first portion 150w and/or to the second portion 152w. In the embodiment illustrated in <figref idref="f0050 f0051 f0052 f0053 f0054">Figures 110-119</figref>, the resistance member 804 comprises a distally-facing surface of the first portion 150w.

0529The system 104w can be configured to couple the on-skin component 134w to the base 128w via an adhesive 806. <figref idref="f0052">Figure 115</figref> illustrates a perspective view of the needle hub 162w, shown securing the on-skin component 134w during deployment, with the base 128w removed to illustrate the adhesive 806 disposed on a distally-facing surface of the on-skin component 134w. The adhesive 806 can be configured to couple the on-skin component 134w to the base 128w on contact. Alternatively or in addition to the adhesive 806, some embodiments can include an adhesive disposed on a proximally-facing surface of the base, so as to couple the on-skin component to the base upon contact. In some embodiments, the adhesive can be a pressure-sensitive adhesive. In some embodiments, the securement member can be configured to couple the on-skin component to the needle hub only along a plane extending normal to the axial direction of the system. In addition or in the alternative, the securement can be configured to couple the on-skin component in a lateral or radial direction.

0530<figref idref="f0052">Figure 116</figref> illustrates another perspective view of the needle hub 162w, shown decoupled from the on-skin component 134w, with the base 128w removed to illustrate the adhesive 808 disposed on the distally-facing surfaces of the securement member 800. The adhesive 808 can be configured to couple the on-skin component 134w to the securement member 800 while in the proximal starting position and during movement of the on-skin component 134w in the proximal direction, and to allow the release of the on-skin component 134w from the securement member 800 after the on-skin component 134w is coupled to the base 128w. Alternatively or in addition to the adhesive 808, some embodiments can include an adhesive disposed on a proximally-facing surface of the on-skin component 134w. In some embodiments, the adhesive can be a pressure-sensitive adhesive. In some embodiments, the adhesive 808 can have a smaller surface area and/or a lower adhesion strength than the adhesive 806, such that the adhesion strength of the adhesive 806 which couples the on-skin component to the base outweighs the adhesion strength of the adhesive 808 which couples the on-skin component to the securement member. In other embodiments, the adhesion strength of the adhesive 808 can be the same or greater than the adhesion strength of the adhesive 806. In these embodiments, a resistance member can be employed to facilitate the decoupling of the on-skin component 134w from the securement member 800 after deployment.

0531<figref idref="f0053">Figure 117</figref> illustrates a perspective view of a portion of the system 104w, illustrating the resistance member 804. The resistance member 804 is configured to rest above and/or contact a proximally-facing surface of the on-skin component 134w, at least when the on-skin component 134w is in a distal deployed position. The resistance member 804 can serve to inhibit proximal movement of the on-skin component 134w as the needle hub 162w and securement member 800 retract in a proximal direction. The resistance member 804 can function in a manner similar to a stripper plate in punch and die manufacturing or injection molding processes.

0532In embodiments, the resistance member can have any configuration suitable for resisting decoupling of the on-skin component from the base. In the embodiment illustrated in <figref idref="f0050 f0051 f0052 f0053 f0054">Figures 110-119</figref>, the resistance member 804 has a curvilinear cross section, and extends through an arc of roughly 300 degrees about the perimeter of the on-skin component 134w. In some embodiments, the resistance member 804 can extend through an arc of roughly 30 degrees, 60 degrees, 90 degrees, 120 degrees, 150 degrees, 180 degrees, 210 degrees, 240 degrees, 270 degrees, 300 degrees, or 330 degrees about the perimeter of the on-skin component 134w, or through an arc greater than, less than, or within a range defined by any of these numbers. In some embodiments, the resistance member 804 can extend continuously or discontinuously about the perimeter of the on-skin component. In some embodiments, the resistance member 804 can extend about the entire perimeter of the on-skin component. In some embodiments, the resistance member 804 can comprise one or more contact points or surfaces that hold the on-skin component 134w in the distal position as the securement feature 800 moves in an opposite (e.g., proximal) direction.

0533In other embodiments, the resistance member 804 can comprise multiple discrete members (e.g., legs) configured to contact multiple locations about the perimeter of the on-skin component 134w. For example, in some embodiments, the resistance member 804 can include at least two legs disposed apart from one another about a center point of the on-skin component. In some embodiments, the resistance member 804 can include two legs disposed roughly 180 degrees about a center point of the on-skin component. In some embodiments, the resistance member 804 can include three legs disposed roughly 120 degrees about a center point of the on-skin component. In such an embodiment, the legs can be arranged symmetrically about the on-skin component (e.g. with radial symmetry, or reflectional/bilateral symmetry).

0534<figref idref="f0053">Figure 117</figref> also illustrates locator features 810 which can be formed in, or integrally coupled to, the first portion 150w and/or the resistance member 804. The locator features 810 can comprise distally-extending tabs of the first portion 150w and/or of the resistance member 804. The locator features 810 can be configured to align with corresponding indentations 812 in the on-skin component (see <figref idref="f0054">Figure 119</figref>) so as to ensure proper positioning of the sensor module 134w with respect to the first portion 150w and/or the resistance member 804 during assembly.

0535<figref idref="f0054">Figure 118</figref> illustrates a perspective view of the sensor module 134w, before being coupled to the base 128w by contacting the adhesive 806. The base 128w itself is coupled (for example by an adhesive) to a proximal surface of an adhesive patch 900. <figref idref="f0054">Figure 119</figref> illustrates a perspective view of the sensor module 134w after being coupled to the base 128w on the adhesive patch 900.

0536In embodiments, providing a resistance member can facilitate a reliable transfer of the on-skin component to the base, by creating a counterforce against the securement member as the needle hub retracts in the proximal direction. The counterforce allows the securement member to separate from the on-skin component while inhibiting or preventing the disengagement of the on-skin component from the base (if any) and/or from the adhesive patch. In embodiments, the retraction spring can be configured to store and provide sufficient energy to both retract the needle and decouple the on-skin component from the needle hub. The combination of the resistance member and securement member can also be configured to provide positional control of the on-skin component from a secured configuration (e.g., in the proximal starting position and during movement of the on-skin component toward the distal deployed position) to a released configuration (when the on-skin component reaches the distal deployed position and/or couples to the base and/or adhesive patch).

0537It is contemplated that providing a base which begins in the distal deployed position when the system is in a resting or stored state can serve to protect the needle (and the user) before the system is deployed. For example, a base which is coupled to a distal end of the system in a resting or pre-deployment state can prevent a user from reaching into the distal end of the system and pricking him or herself. This configuration can thus potentially reduce needle stick hazards. In addition, a base which is coupled to a distal end of the system in a resting or pre-deployment state facilitate the setting of the adhesive patch on the skin before deployment. For example, with such a configuration, the user can use the body of the sensor inserter system to assist in applying a force in a distal direction to adhere the adhesive patch to the skin. In addition, the base can provide structural support to guide the needle into the skin during deployment.

0538<figref idref="f0055">Figures 120-122</figref> illustrate another configuration for coupling an on-skin component to a base, in accordance with several embodiments. <figref idref="f0055">Figure 120</figref> shows a side view of an on-skin component 134x and a base 128x, prior to coupling of the on-skin component 134x to the base 128x. The on-skin component 134x includes a distally-extending sensor 138, and the base 128x is coupled to an adhesive patch 900. <figref idref="f0055">Figure 121</figref> illustrates a perspective view of these same components. The base 128x comprises a flexible elastomeric member with a proximally-extending ridge 814 extending about a proximally-facing surface 816. The base 128x can have a shape configured to correspond to a shape of the on-skin component 134x. In a relaxed state, as illustrated in <figref idref="f0055">Figures 120 and 121</figref>, and before making contact with the on-skin component 134x, the base 128x has a deformed, somewhat convex curvature. The base 128x and the adhesive patch 900 can be coupled to the other components of a sensor inserter assembly in this configuration. During deployment, as the on-skin component 134x begins to contact the base 128x, the proximally-facing surface 816 flexes up to meet the distal surface of the on-skin component 134x, causing the ridge 814 to grip securely about the perimeter of the on-skin component 134x, as illustrated in <figref idref="f0055">Figure 122</figref>.

0539<figref idref="f0056">Figure 123</figref> illustrates a perspective view of a portion of another inserter system 104y, according to some embodiments. The system 104y can be configured substantially similar to any of the systems 104 illustrated herein, with like reference numerals indicating like parts. The inserter system 104y includes an on-skin component 134y which includes a combination sensor module and base. In embodiments, the combination sensor module and base can be integrally formed with one another, as illustrated in <figref idref="f0056">Figure 123</figref>, or operatively coupled to one another. The system 104y also includes a securement member 800y which is configured to releasably secure the on-skin component 134y in a proximal starting position, at least until the system 104y is activated. The securement member 800y is integrally formed with the needle hub 162y, and includes three proximally-extending legs 802y configured to releasably couple to (e.g. via adhesive 808) various locations on the proximal surface of the on-skin component 134y. It is contemplated that the addition of a third (or further) leg 802y can help to balance the sensor module and prevent it from canting to one side or another during deployment and/or retraction. The system 104y also includes a resistance member 804. The resistance member 804 may be integrally molded with first portion 150y.

0540<figref idref="f0056">Figure 124</figref> illustrates another perspective view of the on-skin component 134y and the needle hub 162y, with the remainder of the system 104y removed to illustrate the configuration of the securement member 800y. <figref idref="f0057">Figure 125</figref> illustrates a perspective view of a portion of the applicator system shown in <figref idref="f0056">Figure 123</figref>, with the on-skin component 134y in a released configuration and separated from the needle hub 162y and with two of the legs 802y removed for purposes of illustration. The resistance member 804y can be configured to encompass or at least partially encompass the sensor module portion of the on-skin component 134y. The resistance member 804y can comprise one or more elongate members, columns, legs, and/or protrusions, or can have any other suitable configuration for facilitating the release of the on-skin component from the needle hub 162y. The resistance member 804y (or any portion thereof) can have a curvilinear cross section, as illustrated in <figref idref="f0057">Figure 125</figref>, or can have any other suitable cross section, including circular, square, triangular, ovoid, L-shaped, O-shaped, U-shaped, V-shaped, X-shaped, or any other regular or irregular shape or combination of shapes.

0541As shown in <figref idref="f0057">Figure 125</figref>, the system 104y can include an adhesive patch 818 disposed on the distally-facing surface of the on-skin component 134y. The adhesive patch 818 can be configured to couple the on-skin component 134y to the skin on contact. In some embodiments, the adhesive patch can be a pressure-sensitive adhesive. In some embodiments, the adhesive patch 818 is a double sided adhesive, in which an adhesive is disposed on both the proximally facing surface of the adhesive patch 818 and the distally facing surface of the adhesive patch 818. The proximally facing adhesive can be configured to couple with the distal end of the on-skin component 134y, and the distally facing adhesive can be configured to couple with the skin. In other embodiments, the proximally facing surface of the adhesive patch 818 is configured to couple with the distally facing surface of the on-skin component by a coupling process such as, but not limited to, heat staking, fastening, welding, or bonding. In some embodiments, the adhesive patch 818 can be covered by a removable liner prior to deployment. In other embodiments, the adhesive patch 818 can be exposed (e.g., uncovered) within the system prior to deployment.

0542Alternatively, in some embodiments the adhesive patch 818 can be releasably secured to the distal end of the system before deployment, with an adhesive disposed on a proximally-facing surface of the adhesive patch 818, so as to couple the on-skin component to the adhesive patch 818 upon contact as part of the sensor insertion process. In addition, in such an embodiment, the adhesive patch 818 can include an adhesive disposed on a distally-facing surface of the adhesive patch 818 to couple the on-skin component to the skin.

0543Such a configuration can include fewer components to be coupled and decoupled during the deployment and insertion process, which can increase reliability of systems configured in accordance with embodiments. For example, systems configured in accordance with embodiments can reduce the chance of improper transfer of system components to the skin. In addition, it is contemplated that embodiments comprising an adhesive patch disposed within the system in a resting state (as opposed to an adhesive patch disposed at a distal end of the system in the resting state) can allow for the system to be more easily re-positioned on the skin as many times as desired before being adhered to the skin.

0544<figref idref="f0058">Figures 126-128</figref> illustrate another configuration for releasably securing an on-skin component in a proximal position, in accordance with several embodiments. <figref idref="f0058">Figure 126</figref> illustrates a perspective view of a portion of a securement member 800z shown secured to an on-skin component 134z comprising a sensor module. The securement member 800z can include at least one leg 802z. As shown in the figure, the securement member 800z includes two proximally-extending legs 802z. The on-skin component 134z includes two elastomeric grips 824 extending laterally from the sensor module. The grips 824 are sized and shaped to cooperate with laterally-facing surfaces of the legs 802z to releasably secure the on-skin component 134z in a proximal position. In the embodiment illustrated in <figref idref="f0058">Figures 126-128</figref>, the grips 824 are integrally formed with the sensor module, and have a bracket-shaped cross section, as viewed in a plane extending normal to the axial direction. In embodiments, the securement member 800z and the grips 824 can have any suitable cooperating configuration to allow the on-skin component 134z to releasably couple the securement member 800z to the grips 824, for example via a friction fit, interference fit, or corresponding undercut engagement features. Some embodiments can additionally employ an adhesive disposed between the securement member 800z and the on-skin component 134z, to provide additional securement of the on-skin component 134z.

0545<figref idref="f0058">Figure 127</figref> illustrates a perspective view of a portion of the securement member 800z, with the sensor module of the on-skin component 134z shown in cross section to illustrate the configuration of the grips 824. <figref idref="f0058">Figure 127</figref> also shows a decoupling feature 804z configured to resist proximal movement of the on-skin component 134z after deployment of the on-skin component 134z to the distal deployed position, for example during retraction of the needle hub 162z. The decoupling feature 804z can be fixed with respect to the remainder of the sensor inserter system as the needle hub 162z retracts in a proximal direction, providing enough resistance to overcome the friction fit (and adhesive, if any) between the securement member 800z and the grips 824 to release the securement member 800z from the grips 824. <figref idref="f0058">Figure 128</figref> illustrates a perspective view of the on-skin component 134z, after decoupling of the on-skin component 134z from the securing member 800z.

0546<figref idref="f0059 f0060">Figures 129-131</figref> illustrate still another configuration for releasably securing an on-skin component, in accordance with several embodiments. <figref idref="f0059">Figure 129</figref> illustrates a perspective view of a portion of a sensor inserter assembly 104aa with the second portion 150aa shown in cross section, and with a securing member 800aa shown securing an on-skin component 134aa in a proximal position. The on-skin component 134aa may comprise an integrally formed sensor module/base assembly. As shown in the figure, the securement member 800aa comprises an elastomeric cap which is coupled to a portion of the on-skin component 134aa. As shown, the securement member 800aa can be coupled to a protrusion (or neck) 826 formed in the on-skin component 134aa. <figref idref="f0059">Figure 130</figref> illustrates a perspective view of a portion of the assembly 104aa of <figref idref="f0059">Figure 129</figref>, shown with a portion of the securing member 800aa cut away to better illustrate the configuration of the securing member 800aa and the protrusion 826. The protrusion 826 can be configured to encircle, or at least partially encircle, the needle 158 when it extends in a proximal direction through the on-skin component 134aa. The protrusion 826 can also be configured to secure the securement member 800aa to the on-skin component 134aa. The securement member 800aa has an opening 828 which is sized and shaped to create a friction fit between the opening 828 and the needle 158. In the configuration illustrated in <figref idref="f0059">Figures 129 and 130</figref>, with the needle 158 extending distally through the securement member 800aa and the protrusion 826, the friction fit between the securement member 800aa and the needle 158 serves to resist at least distal movement of the on-skin component 134aa with respect to the needle 158.

0547The embodiment illustrated in <figref idref="f0059 f0060">Figures 129-131</figref> may also include a resistance member 804aa. The resistance member may be substantially similar to any resistance member described in <figref idref="f0050 f0051 f0052 f0053 f0054 f0055 f0056 f0057 f0058">Figures 110-128</figref>. The resistance member 804aa can include a distally-facing surface of the first portion 150aa, and can have a similar configuration to the resistance member 804 described in the context of <figref idref="f0053">Figure 117</figref>. The resistance member 804aa can provide enough resistance in a distal direction to allow the second spring and needle hub (not shown) to overcome the friction fit between the securement member 800aa and the needle 158. It is contemplated that this would allow the needle 158 to retract away from the skin and at the same time allow the needle to decouple from the securement member 800aa. <figref idref="f0060">Figure 131</figref> illustrates a perspective view of a portion of the assembly 104aa, after decoupling of the on-skin component 134aa from the needle 158, shown with the protrusion 826 of the on-skin component 134aa and the securing member 800aa cut away for purposes of illustration.

0548<figref idref="f0061">Figures 132-133</figref> illustrate another configuration for releasably securing an on-skin component in a proximal position, in accordance with several embodiments. <figref idref="f0061">Figure 132</figref> illustrates a perspective view of a portion of a securement member 800ab shown secured to an on-skin component 134ab comprising a sensor module, with the second portion 150ab shown in cross section. The securement member 800ab may include at least one engagement feature. As shown in the figure, the at least one engagement feature can be two proximally-extending legs 802ab. The on-skin component 134ab may include at least one receiving feature. As shown, the at least one receiving feature can be two elastomeric grips 824ab extending laterally from the on-skin component 134ab. The grips 824ab are deformable and sized and shaped to receive the legs 802ab via friction or interference fit and thereby releasably secure the on-skin component 134ab in a proximal position. In the embodiment illustrated in <figref idref="f0061">Figures 132-133</figref>, the legs 802ab of the securement member 800ab have a circular cross-section. The grips 824ab are integrally formed with the sensor module, and have an annular-shaped cross section, as viewed in a plane extending normal to the axial direction. The grips 824ab may each include an opening which can be configured to receive the legs 802ab via frictional engagement. In embodiments, the securement member 800ab and the grips 824ab can have any suitable cooperating configuration to releasably couple the securement member 800ab to the grips 824ab. Some embodiments can additionally employ an adhesive disposed axially between the securement member 800ab and the on-skin component 134ab, to provide additional securement of the on-skin component 134ab in the proximal starting position. <figref idref="f0061">Figure 133</figref> illustrates a perspective view of the needle hub 162ab and the on-skin component 134ab, after decoupling of the on-skin component 134ab from the needle hub 162ab.

0549<figref idref="f0062">Figures 134-136</figref> illustrate yet another configuration for releasably securing an on-skin component in a proximal position. <figref idref="f0062">Figure 134</figref> illustrates an exploded perspective view of a portion of an assembly 134ac, with a securement member 800ac configured to releasably couple an on-skin component 134ac to a needle hub 162ac. The securement member 800ac may include at least one engagement feature. As shown in the figure, the securement member 800ac can include two proximally-extending legs 802ac. The on-skin component 134ac includes two elastomeric grips 824ac extending laterally from the sensor module. The grips 824ac are sized and shaped to receive the legs 802ac in a snap fit to securely hold the on-skin component 134ac in a proximal position. In the embodiment illustrated in <figref idref="f0062">Figures 134-136</figref>, the legs 802ac of the securement member 800ac have a circular cross-section, with a recessed section 832 configured to receive the grips 824ac. The grips 824ac can be integrally formed with the sensor module, each grip having a frangible link 830 coupling the grips 824ac to the sensor module. The grips 824ac have an annular-shaped cross section, as viewed in a plane extending normal to the axial direction, the grips being configured to receive the recessed sections 832 of the legs in a secure interlocking engagement. In embodiments, the securement member 800ab and the grips 824ab can have any suitable cooperating configuration to securely couple the securement member 800ac to the grips 824ac and prevent slippage of the grips along the legs 802ac as the needle hub 162ac deploys and as it retracts after deployment. Some embodiments can additionally employ an adhesive disposed axially between the securement member 800ac and the on-skin component 134ab, to provide additional securement of the on-skin component 134ac in the proximal starting position and during deployment.

0550<figref idref="f0062">Figure 135</figref> illustrates a perspective view of a portion of the system 104ac, with the securement member 800ac securely coupled to the on-skin component 134ac. Some embodiments can additionally employ an adhesive disposed axially between the securement member 800ac and the on-skin component 134ac, to provide additional securement of the on-skin component 134ac in the proximal starting position. The frangible links 830 are configured to shear or otherwise detach upon application of a minimum threshold of force, as the needle hub 162 retracts in a proximal direction after deployment, separating the grips 824ac from the remainder of the on-skin component 134ac and leaving the on-skin component 824ac in the deployed distal position. <figref idref="f0062">Figure 136</figref> illustrates a perspective view of a portion of the system 104ac, with the frangible links 830 broken and the securement member 800ac decoupled from the on-skin component 134ac. In some embodiments, a resistance member can also be employed to prevent proximal movement of the on-skin component 134ac as the needle hub 162ac retracts, facilitating the breakage of the frangible links 830.

0551Frangible couplings can also be employed between an on-skin component and the second portion of a sensor inserter system to releasably secure the on-skin component in a proximal starting position prior to deployment. For example, <figref idref="f0063 f0064">Figures 137-140</figref> illustrate various perspective views of a sensor inserter system 104ad with an on-skin component 134ad releasably secured in a proximal position within the system 104ad. The on-skin component 134ad can include a combination sensor module and base disposed on an adhesive patch 900ad. To facilitate in releasably securing the on-skin component 134ad to the second portion 152ad, the second portion 152ad can include at least one distally-extending protrusion 834. As shown in the figure, the second portion 152ad includes four distally-extending protrusions 834 configured to securely couple with corresponding sockets 836 formed in or otherwise extending from the adhesive patch 900ad. The sockets 836 are connected to the adhesive patch 900ad via frangible links 838, which can also be integrally formed in the adhesive patch 900ad. In the resting state illustrated in <figref idref="f0063">Figure 137</figref>, the adhesive patch 900ad is secured in a proximal position by the coupling of the sockets 836 to the posts 838. As the system 104ad is deployed and a force is applied to the on-skin component 134ad in a distal direction, the frangible links 838 detach, allowing the adhesive patch 900ad (and the on-skin component 134ad which is already coupled thereto) to move to the distal deployed position. <figref idref="f0063">Figure 138</figref> illustrates a perspective view of the sensor inserter system 104ad, with the frangible links 838 detached and the adhesive patch 900ad released from securement. <figref idref="f0064">Figures 139 and 140</figref> illustrate perspective views of the adhesive patch 900ad and the on-skin component 134ad, with the frangible links 838 in intact and detached configurations, respectively. Once the frangible links 838 are detached and the on-skin component 134ad (along with the patch 900ad) is deployed in the distal position, the remainder of the system 104ad can easily be lifted off the skin of the host and removed.

0552<figref idref="f0065">Figure 141</figref> illustrates another configuration for releasably securing a base and adhesive patch to a sensor inserter assembly. <figref idref="f0065">Figure 141</figref> illustrates a cross-sectional perspective view of a portion of a system 104ae, with the first portion 150ae, the second portion 152ae, and the third portion 392ae shown in cross section. The system 104ae includes an on-skin component 134ae which is releasably secured in a proximal starting position. The system 104ae also includes a base 128ae coupled to an adhesive patch 900ae. The base 128ae and the adhesive patch 900ae are disposed in a distal position, at a distal end of the system 104ae. The base 128ae is coupled to the system 104ae via a plurality of ribs 840 extending radially inward from the second portion 152ae. The ribs 840 can be sized and shaped to grip the edges of the base 128ae with a friction/interference fit. The friction/interference fit between the ribs 840 and the base 128ae can be configured to be strong enough to securely couple the base 128ae to the system 104ae during storage and prior to deployment, but weak enough that the adhesive coupling between the adhesive patch 900ae and the skin of the host overcomes the strength of the friction fit. Thus, once the adhesive patch 900ae is adhered to the skin of the host, the second portion 152ae can be lifted off the base 128ae and the sensor system 104ae can be removed without pulling the base 128 in a proximal direction. In some embodiments, the base 128ae may comprise an elastomeric material. Further, in some embodiments, the base 128ae may have a hardness value less than a hardness value of the on-skin component 134ae. In other embodiments, the base 128ae may have a hardness value more than a hardness value of the on-skin component 134ae.

0553<figref idref="f0066">Figures 142 and 143</figref> illustrate yet another configuration for releasably securing an adhesive patch, optionally including a base, to a sensor inserter system. <figref idref="f0066">Figure 142</figref> shows a sensor inserter system 104af with an adhesive patch 900af coupled to the second portion 152af of the system 104af. <figref idref="f0066">Figure 143</figref> shows the system 104af with the patch 900af separated from the second portion 152af. As shown in <figref idref="f0066">Figure 143</figref>, the second portion 152af includes a plurality of adhesive dots 842 disposed on a distally-facing surface or edge of the second portion 152af. The adhesive dots 842 can be configured to be strong enough to securely couple the adhesive patch 900af (and base, if any) to the system 104af during storage and prior to deployment, but weak enough that the adhesive coupling between the adhesive patch 900af and the skin of the host overcomes the strength of the adhesive dots 842. Thus, once the adhesive patch 900af is adhered to the skin of the host, the second portion 152af can be lifted off the applicator patch 900af (and base, if any) and the sensor system 104af can be removed without pulling the adhesive patch 900af (or base, if any) in a proximal direction. Alternatively or in addition to the adhesive dots 842, some embodiments can include an adhesive disposed on a proximally-facing surface of the adhesive patch 900af. In some embodiments, the adhesive can be a pressure-sensitive adhesive.

INTERPRETATION

0554For ease of explanation and illustration, in some instances the detailed description describes exemplary systems and methods in terms of a continuous glucose monitoring environment; however it should be understood that the scope of the invention is not limited to that particular environment, and that one skilled in the art will appreciate that the systems and methods described herein can be embodied in various forms. Accordingly any structural and/or functional details disclosed herein are not to be interpreted as limiting the systems and methods, but rather are provided as attributes of a representative embodiment and/or arrangement for teaching one skilled in the art one or more ways to implement the systems and methods, which may be advantageous in other contexts.

0555For example, and without limitation, described monitoring systems and methods may include sensors that measure the concentration of one or more analytes (for instance glucose, lactate, potassium, pH, cholesterol, isoprene, and/or hemoglobin) and/or other blood or bodily fluid constituents of or relevant to a host and/or another party.

0556By way of example, and without limitation, monitoring system and method embodiments described herein may include finger-stick blood sampling, blood analyte test strips, non-invasive sensors, wearable monitors (e.g. smart bracelets, smart watches, smart rings, smart necklaces or pendants, workout monitors, fitness monitors, health and/or medical monitors, clipon monitors, and the like), adhesive sensors, smart textiles and/or clothing incorporating sensors, shoe inserts and/or insoles that include sensors, transdermal (i.e. transcutaneous) sensors, and/or swallowed, inhaled or implantable sensors.

0557In some embodiments, and without limitation, monitoring systems and methods may comprise other sensors instead of or in additional to the sensors described herein, such as inertial measurement units including accelerometers, gyroscopes, magnetometers and/or barometers; motion, altitude, position, and/or location sensors; biometric sensors; optical sensors including for instance optical heart rate monitors, photoplethysmogram (PPG)/pulse oximeters, fluorescence monitors, and cameras; wearable electrodes; electrocardiogram (EKG or ECG), electroencephalography (EEG), and/or electromyography (EMG) sensors; chemical sensors; flexible sensors for instance for measuring stretch, displacement, pressure, weight, or impact; galvanometric sensors, capacitive sensors, electric field sensors, temperature/thermal sensors, microphones, vibration sensors, ultrasound sensors, piezoelectric/piezoresistive sensors, and/or transducers for measuring information of or relevant to a host and/or another party.

0558None of the steps described herein is essential or indispensable. Any of the steps can be adjusted or modified. Other or additional steps can be used. Any portion of any of the steps, processes, structures, and/or devices disclosed or illustrated in one embodiment, flowchart, or example in this specification can be combined or used with or instead of any other portion of any of the steps, processes, structures, and/or devices disclosed or illustrated in a different embodiment, flowchart, or example. The embodiments and examples provided herein are not intended to be discrete and separate from each other.

0559The section headings and subheadings provided herein are nonlimiting. The section headings and subheadings do not represent or limit the full scope of the embodiments described in the sections to which the headings and subheadings pertain. For example, a section titled "Topic 1" may include embodiments that do not pertain to Topic 1 and embodiments described in other sections may apply to and be combined with embodiments described within the "Topic 1" section.

0560Some of the devices, systems, embodiments, and processes use computers. Each of the routines, processes, methods, and algorithms described in the preceding sections may be embodied in, and fully or partially automated by, code modules executed by one or more computers, computer processors, or machines configured to execute computer instructions. The code modules may be stored on any type of non-transitory computer-readable storage medium or tangible computer storage device, such as hard drives, solid state memory, flash memory, optical disc, and/or the like. The processes and algorithms may be implemented partially or wholly in application-specific circuitry. The results of the disclosed processes and process steps may be stored, persistently or otherwise, in any type of non-transitory computer storage such as, for example, volatile or non-volatile storage.

0561Any of the features of each embodiment is applicable to all aspects and embodiments identified herein. Moreover, any of the features of an embodiment is independently combinable, partly or wholly with other embodiments described herein in any way, e.g., one, two, or three or more embodiments may be combinable in whole or in part. Further, any of the features of an embodiment may be made optional to other aspects or embodiments. Any aspect or embodiment of a method can be performed by a system or apparatus of another aspect or embodiment, and any aspect or embodiment of a system can be configured to perform a method of another aspect or embodiment.

0562The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. In addition, certain method, event, state, or process blocks may be omitted in some implementations. The methods, steps, and processes described herein are also not limited to any particular sequence, and the blocks, steps, or states relating thereto can be performed in other sequences that are appropriate. For example, described tasks or events may be performed in an order other than the order specifically disclosed. Multiple steps may be combined in a single block or state. The example tasks or events may be performed in serial, in parallel, or in some other manner. Tasks or events may be added to or removed from the disclosed example embodiments. The example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from, or rearranged compared to the disclosed example embodiments.

0563Conditional language used herein, such as, among others, "can," "could," "might," "may," "e.g.," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. The terms "comprising," "including," "having," and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations and so forth. Also, the term "or" is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Conjunctive language such as the phrase "at least one of X, Y, and Z," unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to be present.

0564The term "and/or" means that "and" applies to some embodiments and "or" applies to some embodiments. Thus, A, B, and/or C can be replaced with A, B, and C written in one sentence and A, B, or C written in another sentence. A, B, and/or C means that some embodiments can include A and B, some embodiments can include A and C, some embodiments can include B and C, some embodiments can only include A, some embodiments can include only B, some embodiments can include only C, and some embodiments can include A, B, and C. The term "and/or" is used to avoid unnecessary redundancy.

0565To the extent publications and patents or patent applications referenced herein contradict the disclosure contained in the specification, the specification is intended to supersede and/or take precedence over any such contradictory material.

0566Unless otherwise defined, all terms (including technical and scientific terms) are to be given their ordinary and customary meaning to a person of ordinary skill in the art, and are not to be limited to a special or customized meaning unless expressly so defined herein. It should be noted that the use of particular terminology when describing certain features or aspects of the disclosure should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or aspects of the disclosure with which that terminology is associated. Terms and phrases used in this application, and variations thereof, especially in the appended claims, unless otherwise expressly stated, should be construed as open ended as opposed to limiting.

0567While certain example embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions disclosed herein. Thus, nothing in the foregoing description is intended to imply that any particular feature, characteristic, step, module, or block is necessary or indispensable. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the methods and systems described herein may be made without departing from the scope of the inventions as defined by the appended claims.