System and method of sorting materials using holographic laser steering

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DESCRIPTION

System and procedure of classification of materials using holographic laser direction.

The present invention claims the priority of provisional US patent applications. No.: 60 / 399,386, filed on July 31, 2002 and No.: 60 / 435,541, filed on December 20, 2002.

Background of the invention

The present invention relates to a system and method of classifying materials using laser direction and in particular, using holographic optical entrapment.

In the US industry, there are a great deal of unsatisfactory classification and separation needs related to materials manufactured from particles or units smaller than 50 micrometers. These needs vary in industries from particle sizing and sample preparation in the fields of specialized chemistry and materials, including the manufacture of nanotechnology products, to protein selection and purification in the pharmaceutical and biotechnology industries. Other examples include the classification and selection of cells, in the fields of medicine, diagnosis and agriculture.

The importance of these needs can be observed when examining annual expenditures in areas where specialized or partial solutions have been developed, as well as when calculating the market value of classified / separated / purified production in areas where there is currently not even one partial solution As an example of the above, the biotechnology and pharmaceutical industries annually spend a huge amount on equipment and supplies for protein purification. As an example of the latter, currently in the agriculture sector there is no way to effectively select the genus of the offspring of farm animals; however, it is estimated that only in the area of ​​cattle, value would be added by allowing such sperm selection as part of the current insemination procedure of widespread use in the industry.

Outside the livestock market, the islet cell purification procedure from human pancreas is currently a major concern of medical scientists who develop new treatment procedures for type I diabetes. Significant progress has been made in the procedures of islet transplantation, but the problem of purification is one of the pitfalls that remain. Traditional procedures to purify islet cells are ineffective and result in cell damage.

Islet cell transplantation is important because, in the form of type I diabetes, the islet cells existing in the patient's pancreas are damaged and no longer produce the insulin necessary for human survival. Current treatment for type I diabetes involves insulin injection 1 to 5 times a day. Despite treatment, the disease often leads to complications that include blindness, blood flow problems that require amputations, kidney failure and death. Higher purity and reduction of contaminants for islet cells used in transplantation are expected to reduce the occurrence of these complications.

Of the approximate million current type I diabetes patients in the United States, at least 50,000 patients a year would undergo an islet cell transplant if available. After large-scale acceptance of islet cell transplantation as an effective treatment, the costs could be expected to make a substantial leap. The jump would respond to the difficulty of using the current treatment procedure (frequent injections) and the serious consequences even when the treatment is properly administered.

Therefore, islet purification is nothing more than an important problem that requires highly selective classification of human cells in a non-detrimental and non-invasive manner.

Another problem that needs to be addressed is the purification of healthy cells from bone marrow cancer cells of people undergoing a whole body radiation treatment for cancer.

Another one is the selection of stem cells for research on the causes of and treatments for diseases such as Parkinson's disease.

Another additional concern is the development of new ways of studying large numbers of human cells and selecting those that have characteristics that cannot be subjected to fluorescent labeling, which would greatly expand the scope and power of medical diagnoses.

A conventional technique in the manipulation of microscopic objects is optical entrapment. An accepted description of the effect of optical entrapment is that light with narrow focus, such as light focused by a high numerical aperture microscope lens, has a pronounced intensity gradient. Optical traps use the gradient forces of a beam of light to trap a particle based on its dielectric constant. "Particle" refers to biological material or other chemical material, including, but not limited to, oligonucleotides, polynucleotides, chemical compounds, proteins, lipids, polysaccharides, ligands, cells, antibodies, antigens, cell organelles, lipids, blastomers, cell aggregations, microorganisms, peptides, cDNA, RNA and

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Similar.

To minimize its energy, a particle with a dielectric constant greater than that of the surrounding medium will move towards the region of an optical trap where the electric field is higher. Particles with at least a small differential of the dielectric constant with their environment are sensitive to this gradient and are attracted or repelled from the point of greatest intensity of light, that is, towards or from the focal point of the light beam. When constructing an optical trap, the optical gradient forces of a single beam of light are used to manipulate the position of a dielectric particle immersed in a fluid medium with a refractive index lower than that of the particle, but particles can also be manipulated reflective, absorbent and of low dielectric constant.

The strength of the optical gradient of an optical trap competes with the pressure of the radiation, which tends to displace the trapped particle along the axis of the beam. An optical trap can be placed anywhere within the focal volume of an objective lens by roughly selecting the direction of propagation of the input beam and the degree of collimation. A collimated beam that enters through the lens of the rear aperture of a lens reaches a focus in the center of the focal plane of the lens, while another beam that enters at an angle reaches an off-center focus. A slightly divergent beam focuses beyond the focal plane, while a convergent beam focuses more here.

Each of the multiple beams that enter the lens entrance pupil simultaneously, forms an optical trap in the focal volume at a position determined by its angle of incidence. The holographic optical entrapment technique uses a phase-modifying optical diffractive element to impose the phase pattern for multiple doing on the wavefront of a single input beam, thereby transforming the individual beam into multiple traps.

In the creation of optical traps, the phase modulation of an input beam is preferred because the entrapment is based on the interstices of the beams and not on their relative phases. Amplitude modulations can divert light from traps and decrease their effectiveness.

When a particle is optically trapped, the optical gradient forces exerted by the trap exceed other radiation pressures that arise from dispersion and absorption. In general, for a Gaussian TEM00 input laser beam, this means that the diameter of the beam should substantially coincide with the diameter of the input pupil. A preferred numerical aperture to form a trap is from about 0.9 to about 1.0.

A difficulty in applying optical entrapment technology is that, in general, each trap to be generated requires its own focused beam of light. Many systems of interest require multiple optical traps and several procedures have been developed to achieve multiple trap configurations. An existing procedure uses a single beam of light that is redirected between locations of multiple traps to "share in time" the beam between various traps. However, as the number of traps increases, the intervals during which each trap is in its "off" state can be lengthened so that the particles move away by diffusion from the trap location before the trap is energized again. All these concerns have limited the applications of this procedure to less than approximately 10 traps per system.

Another traditional method of creating multi-layer systems is based on the simultaneous passage of multiple light beams through a single high numerical aperture lens. This is done using multiple lasers or using one or more beam splitters in the single laser beam. A problem with this technique is that, as the number of traps increases, the optical system becomes increasingly complex progressively. Due to these problems, the known applications of this procedure are limited to less than about 5 traps per system.

In a third approach to achieve a multi-layer system, an optical diffractive element (DOE) is used (e.g., a phase shift hologram that uses a transmission or reflection geometry) to modify the wavefront of a single beam of laser. This invention is disclosed in US Pat. No. 6,055,106 to Grier et al. The wavefront is modified in such a way that the rear laser beam essentially becomes a larger number of individual laser beams with relative positions and directions of travel set by the exact nature of the optical diffractive element. In effect, the Fourier transform of the DOE produces a set of intensity maxima, each of which acts as an individual trap or “clamp”.

Some applications of the third approach have used a fixed transmission hologram to create between 16 and 400 individual trap centers.

A fixed hologram has been used to demonstrate the principle of holographic optical entrapment, but the use of a liquid crystal grid as a hologram allowed the 'fabrication' of an independent hologram for each new trap distribution. The spatially variable phase modulation imposed on the entrapment laser by the liquid crystal grid can be easily controlled in real time by a computer, thus allowing a variety of dynamic manipulations.

Other types of traps that can be used to optically trap particles include, but are not limited to, optical vortices, optical funnels, optical rotors and light cages. An optical vortex produces a gradient that surrounds an area

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of zero electric field that is useful for handling particles with dielectric constants lower than that of the surrounding medium or that are reflective or other particles that are repelled by an optical trap. To minimize this energy, such a particle will move to the region where the electric field is lowest, namely the zero electric field zone of the focal point of a laser beam appropriately. The optical vortex provides a zero electric field zone very similar to the hole of a donut (toroid). The optical gradient is radial with the highest electric field of the circumference of the donut. The optical vortex stops a small particle inside the donut hole.

The arrest is carried out by sliding the vortex above the small particle along the zero electric field line.

The optical funnel differs from an optical vortex in that it has a zero electric field only in the focus and a non-zero electric field in all other directions surrounding the focus, at one end of the vortex. An optical funnel can be useful for trapping atoms and nano-clusters that may be too small or too absorbent to trap with an optical vortex or optical tweezers. (See J. Arlt and MJ Padgett. “Generation of a beam with a dark focus surrounded by regions of higher intensity: The optical bottle beam”, Opt. Lett. 25,191-193, 2000). The light cage (U.S. Patent No. 5,939,716) is vaguely a macroscopic relative of the optical vortex. A cage of light forms a ring averaged at the time of optical traps to surround a particle that is too large or reflective to trap it with dielectric constants lower than that of the surrounding medium.

When the laser beam is directed through or reflected from the phase pattern optical element, the phase pattern optical element produces a plurality of elementary beams having a modified phase profile. Depending on the number and type of optical traps desired, the modification may include diffraction, wavefront conformation, phase shift, direction, divergence and convergence. Based on the chosen phase profile, the phase pattern optical element can be used to generate optical traps in the form of optical traps, optical vortices, optical funnels, optical rotors, light cages and combinations of two or more of these shapes.

With respect to the manipulation of materials, the clamping of viruses and bacteria has been demonstrated in addition to the clamping of dielectric spheres. In addition to prokaryotes and viruses, a wide variety of protists such as Tetrahymena thermophila have been successfully clamped. In addition, both somatic cells such as leukocytes and carriage epithelial cells, as well as germline cells such as sperm cells, have been trapped and manipulated.

Researchers have sought indirect procedures to manipulate cells, such as marking cells with diamond microparticles and then clamping the diamond particles. Cell manipulations have included cell orientation for microscopic analysis, as well as spreading cells. Tissue cells with tweezers have also been arranged in vitro in the same distribution as in vivo.

In addition to the cells themselves, optical tweezers have been used to manipulate cell organelles, such as vesicles transported along microtubules, chromosomes or globular DNA. Objects have also been inserted into cells using optical tweezers.

A variety of sorting procedures for biological purposes are also possible with optical tweezers. Cell classification has already been demonstrated using traditional optical entrapment for chromosome assays and collection and classification to create collections. Cellular assays for pharmacological screening have also been developed.

Consequently, as an example of new type of classification using laser-directed optical traps, a cell classification procedure using a new technique that isolates valuable cells from other cells, tissues and contaminants is needed. In addition, a way to achieve a unique contribution of optical entrapment to the main industrial classification and purification (cell) needs is necessary. Even more, there is a need to separate sperm in the livestock market.

We are aware that JP3297385 (A) on behalf of the Nippon Steel Corporation that discloses a two cell fusion procedure by trapping each cell in an optical trap generated by a laser, moving the cells together and applying a high voltage pulse to the cells. This requires two lasers and is not suitable for identification and destruction of high speed and high performance cells, which does not arise in cell fusion.

The classification of particles by means of optical cages is disclosed by DE19952322.

Summary of the invention

The present invention relates to an apparatus according to claim 6 and a method according to claim

1.

It will be understood that the invention is not limited in its application to construction details and provisions

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of the components set forth in the following description or illustrated in the drawings. The methods and apparatus consistent with the present invention can be practiced by other embodiments and put into practice and carried out in various ways. In addition, it will be understood that the wording and terminology used in this document, as well as the summary included below, have a descriptive purpose and should not be considered as limiting.

As such, those skilled in the art will appreciate that the conception on which this disclosure is based can be used as a basis for the design of other structures, procedures and systems to carry out the various purposes of the present invention.

Brief description of the drawings

Fig. 1 schematically illustrates a holographic optical entrapment system in accordance with an embodiment consistent with the present invention.

Figs. 2A and 2B are a schematic diagram in side view and a schematic diagram in top view, respectively, showing a sample that is being introduced into the sample holder.

Fig. 3 represents a scanning electron micrograph of a sample chamber.

Fig. 4 shows an enlarged view of the working area of ​​a sample chamber.

Fig. 5 is a schematic diagram of a holographic optical trapping system for classifying objects.

Fig. 6 illustrates an example of lateral deflection for classification.

Figs. 7A and 7B illustrate schematic front and side views, respectively, of pipe traps.

Fig. 8 illustrates a cell sorter with a rotating disk base.

Fig. 9 illustrates optical peristalsis.

Detailed description of the invention

In a holographic optical entrapment apparatus or system 100 as illustrated in fig. 1, the light strikes from a laser system and enters as shown by the down arrow, to power the system 100.

Preferably a phase pattern 101 optical element is a dynamic optical element (DOE), with a dynamic surface, which is also a phase-only spatial light modulator (SLM) <BR> such as "PAL-SLM X7665 series" , manufactured by Hamamatsu of Japan, the "SLM 512SA7" or "SLM 512SA15", both manufactured by Boulder Nonlinear Systems of Lafayette, Colorado. These phase 101 optical elements are computer controlled to generate the elementary beams by a hologram encoded in the medium that can be varied to generate the elementary beams and select the shape of the elementary beams. A phase pattern 102 generated in the lower left part of fig. 1 produces the traps 103 shown in the lower right part filled with silica spheres of diameter measured in µm suspended in water 105. Therefore, the system 100 is controlled by the dynamic hologram shown below on the left.

The laser beam travels through the lenses 106, 107, to a dichroic mirror 108. The beam splitter 108 is constructed of a dichroic mirror, a photonic band gap mirror, an omnidirectional mirror or other similar device. Beam splitter 108 selectively reflects the wavelength of light used to form optical traps 103 and transmits other wavelengths. The portion of light reflected from the area of ​​the beam splitter 108 is then passed through an area of ​​an optical phase phase pattern element arranged substantially in a plane conjugated with a flat rear aperture of a lens (objective) of focus 109.

In single-beam optical entrapment (also called laser or optical tweezers), it was thought that a high numerical aperture lens was necessary for acceptable optical traps. A basis for this belief was that, for optical entrapment, the gradient of the electric field of light that strikes to trap the particle is used. In order to obtain a large trapping force, a large electric field gradient (or numerical density of rays) has been deemed necessary. The way in which this is usually done is by passing the light field through a high numerical aperture lens.

A concern with the observation and entrapment of samples within a large field of view is that such observation and entrapment would involve an objective lens with a low numerical aperture. In contrast to the previous teaching, the present disclosure provides a low numerical aperture lens such as, for example, objective lens 109 of FIG. 1. The ability to observe and catch in this situation could be useful in any application where a large field of view given by a small magnification lens, such as placing microscopic manufactured parts or working with large quantities of objects, such as cells, would be beneficial. example.

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As an example, 3 micrometer silica spheres 104 suspended in water 105 were trapped with lenses 109 with an unprecedented low numerical aperture. The 109 lenses used were manufactured by Nikon:

<dl><dt>(to) </dt><dd>4x plan with an AN of 0.10; and</dd></dl>

<dl><dt>(b) </dt><dd>10x plan with an AN of 0.25. </dd></dl>

Suitable phase pattern optical elements are characterized as transmitters or reflectors depending on how they direct the focused light beam or other energy source. Transmitting optical diffractive elements transmit the light beam or other energy source, while reflective optical diffractive elements reflect the beam.

The phase 101 optical pattern element can also be categorized as static or dynamic surface. Examples of suitable phase pattern optical elements include those with one or more fixed surface regions, such as gratings, including diffraction gratings, reflective gratings and transmitting gratings, holograms, including polychromatic holograms, templates, light-forming holographic filters. , polychromatic holograms, lenses, mirrors, prisms, wave plates and the like. The optical element of the static phase transmitter pattern is characterized by a fixed surface.

However, the phase pattern 101 optical element can be mobile, thereby allowing the selection of one or more of the fixed surface regions by moving the phase pattern 101 optical element relative to the laser beam to select the region. appropriate.

The static phase pattern optical element may be attached to a pivot and rotated with a controlled electric motor (not shown). The static phase pattern optical element has a fixed surface and discrete regions. In other examples of static phase pattern optical elements, whether transmitters or reflectors, the fixed surface has a non-homogeneous surface that contains regions that vary substantially continuously, or a combination of discrete regions and regions that vary substantially continuously. .

Examples of suitable dynamic phase pattern optical elements that have a time-dependent aspect of their function include computer generated diffraction patterns, phase shift materials, phase shift liquid crystal matrices, mirror microarrays, including microarrays of piston mode mirror, spatial light modulators, electro-optical deflectors, acoustic-optical modulators, deformable mirrors, MEMS reflective matrices and the like. With a dynamic phase pattern 101 optical element, the means 105 comprising the phase 101 optical pattern element encodes a hologram that can be modified to confer a pattern phase shift to the focused beam of light resulting in the corresponding change in the phase profile of the focused light beam, such as diffraction or convergence. Additionally, the means 105 can be modified to produce a change in the location of the optical traps 103. An advantage of the dynamic phase pattern 101 optical elements is that the means 105 can be modified to independently move each optical trap 103.

In the examples where the phase profile of the elementary beams is less intense at the periphery and more intense in regions interior to the periphery, it is useful to overload the rear opening by less than about 15 percent to form optical traps with greater periphery intensity than the optical traps formed without overloading the rear opening.

In some examples, the shape of an optical trap can change from its original form to that of a point optical trap, an optical vortex, a Bessel beam, an optical funnel, an optical rotor or a light cage. The optical trap can be moved in two or three dimensions. The phase pattern optical element is also useful for imparting a particular topological mode to the laser light, for example, by converting a Gaussian mode into a Gauss-Laguerre mode. Consequently, an elementary beam can be formed in a Gauss-Laguerre mode at the same time as another elementary beam can be formed in a Gaussian mode. The use of Gauss-Laguerre modes greatly enhances entrapment by reducing the radiation pressure.

1. Imaging system

The present instrument design uses a high resolution CCD camera for the main imaging system 110. The biggest advantage of the CCD camera (see reference number 511 in fig. 5) is the favorable cost / performance ratio, since this is a mature technology.

Another advantage of CCD cameras is its wide dynamic range and the ease of generating digital results.

The images are displayed on a computer monitor (see reference number 510 in fig. 5) to provide a frame of reference both to select the location of the traps and to minimize the possibility of accidental exposure of the operator to the To be.

two. User interface

to. Object presentation

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The user interface consists of a computer monitor that presents the field of vision taken by the CCD camera. The user indicates the trap sites with a mouse. There is also an option to delete a location.

As described in more detail below, the user can also specify the power per trap in order to avoid damaging the sample. In addition, it is desirable to be able to vary the potency of the trap because the entrapment depends on the difference between the refractive index of the sample and the suspension medium, which can be expected to vary from one sample to another.

b. Hologram

The purpose of indicating the trap sites is to provide input data for hologram calculation. In essence, the hologram is a function whose Fourier transform produces the desired trap array. However, in the case of the liquid crystal display, this function is a phase object (that is, an object that changes the phase of the wavefront without absorbing any energy).

c. Election procedures

When a large number of traps are needed, the time to indicate their location with a computer mouse can be extremely high. Therefore, there are several options to reduce the time needed.

Frequently, it is desired to use the traps to move an object in a particular direction. This can be done using the mouse to create a line (dragging). The computer program interprets a line as a request to deploy a series of traps sequentially and close enough to each other to move the target in small stages without losing the target lock.

This text also includes the ability to change the height of the traps. If a laser beam is parallel to the optical axis of the objective lens 109, then a trap is formed at the same height as the focal plane of the lens 109. Changing the height of a trap is carried out by adjusting of the hologram so that the beam of light that forms the trap converges (or diverges) slightly when it enters the objective lens 109 of the microscope. The height of a trap can be adjusted using lenses, but only a holographic optical trap (HOT) allows the height of each individual trap to be adjusted independently of any other trap. This is done by adjusting the computer program of the phase modulation caused by the liquid crystal hologram.

3. Sample holder

to. general

Sample chamber 200 (see Figs. 2A and 2B) is cheap and disposable. Although the sample chamber 200 of the present invention is described below, another object of the present invention is a flexible design that can be changed for different applications.

The sample chamber 200 rests on the surface of a microscope slide 201. Sample chamber 200 contains a series of channels 203 for entering samples or objects. Channels 203 are connected to supply and collection tanks by a thin tube 204 (commercially available). Samples or objects will be suspended in a liquid medium and will be introduced into the work area through channels 203. The sample chamber 200 is covered by a coverslip 205.

b. Sample chamber manufacturing

A poly (dimethylsiloxane) resin (PDMS) is used to make the chamber 200. The procedure involves creating the desired channel pattern 203 on a computer using ordinary CAD / CAM procedures and transferring the pattern to a photomask using conventional photoresist / engraving techniques. The photomask is then used as a negative mask to create an inverse pattern of the channels that are etched on a silicon wafer. The depth of the channels 203 is controlled by the engraving time. The silicon wafer is a negative replica of the actual sample chamber 200. The final stage consists in creating the positive sample chamber 200 by pouring PDMS on the wafer and polymerizing it. This results in a PDMS mold that is attached to a glass slide 201 and covered with a coverslip 205. The glass is attached to the PDMA with an oxygen etch that activates the exposed surfaces.

To ensure consistent quality, a series of additional stages are necessary. For example, the PDMS / hardener solution is maintained under vacuum in order to avoid the formation of bubbles. The silicon wafer is silanized to prevent the PDMS from sticking to the wafer. There are a variety of stages that involve cleaning the replicas and maintaining appropriate environmental controls. They represent ordinary technology.

Channels 203 are connected to microscopic gauge tube 204 using small syringe needles 206 attached using glue 214, which are inserted through the PDMS mold into small circular wells 207 that connect to each channel 203. Sample solutions are introduced on channel 203 using micropumps

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208.

Fig. 2B shows a diagram of a typical arrangement for the introduction of a sample through the syringe pump 208 at 210. The medium is introduced at 211 and the waste is collected at 212 and the desired collections at 213.

Fig. 3 presents a representation of an electronic scanning micrograph of the diagram of fig. 2B as actually created from the procedure described above. The channels are approximately 50 micrometers wide and 50 micrometers deep. Fig. 4 presents a representation of a scanning electron micrograph of the 'work' volume where manipulations of the sample under study would occur. The diagrams clearly show that channels 203 are smooth and clean. Although channels 203 are rectangular in cross-section, other shapes are also provided. Channels 203 are designed to allow samples to flow into the "work zone", the shape of which can be tailored to the experimental requirements.

c. Holographic optical traps

Unlike the scanned optical traps, which direct multiple entrapment points in sequence and therefore, are timeshare, the holographic optical traps illuminate each of their traps continuously. For a scanned optical trap to achieve the same trapping force as a continuously illuminated trap, it must provide at least the same intensity averaged over time. This means that the scanned trap must have a maximum intensity greater by a factor proportional to at least the number of entrapment regions. This higher intensity maximum increases the chances of optically induced damage to the trapped material. This damage can arise by at least three mechanisms: (1) monophotonic absorption that results in local heating, (2) monophotonic absorption that results in photochemical transformations and (3) multifotonic absorption that results in photochemical transformations. The events (1) and

(2) can be mitigated by choosing a wavelength of light that the entrapment material and the surrounding fluid medium weakly absorb. Event (3) is a more general problem and is partially mitigated by working with light of greater wavelength. Thus, holographic optical traps can manipulate delicate materials more smoothly with greater efficiency by distributing smaller amounts of force continuously between a series of points on an object instead of potentially damaging the object by exerting total force on a single point or higher intensity over a period of time.

The design is flexible in that any desired channel pattern 203 can be designed with an ordinary CAD / CAM computer program. The complexity of the pattern is not a factor as long as the channels 203 are separated enough to not invade each other. As you can see in figs. 2B and 3, multiple sets of channels 203 can be easily accommodated so that a single chip can be used for more than one experiment. In addition, once a mold is manufactured, it can be used to manufacture thousands of sample chambers, so that the methodology easily adapts to mass production techniques. It is estimated that the marginal cost of a single chamber would be of the order of a few cents when mass produced.

Four. Optical system

to. Hologram Synthesis

The first versions of the holographic optical traps used fixed holograms made from a variety of materials. They were adequate to demonstrate the principle of using holograms to create several hundred traps. However, the main defect of these holograms was that they were static and that it took hours to manufacture a single hologram. With the advent of equipment to create computer-controlled liquid crystal displays capable of forming holograms many times per second, the use of optical traps as a dynamic device has become a reality in practice. The principle for calculating the hologram is described below.

b. The microscope

The optical system 110 consists of an ordinary high quality optical microscope. The objective is a high numerical aperture lens 109 coupled with a long working distance condensing lens. The high numerical aperture objective lens 109 is used for entrapment. Although the long working distance condenser lens can reduce the resolution of the images to a certain extent, it does not jeopardize entrapment and provides extra space near the sample slide to accommodate pipes and receptacles. The objects can be moved by holding them with traps and moving the microscope stage vertically or laterally.

Approximately 2 mW of laser power is used to produce 200 microwatts in the trap. The power level provided by a 2 W laser is suitable to create approximately 1000 traps. A green laser (532 nm) is used, but other wavelengths can also be used, including, for example, a far red laser to work with materials that absorb near the value of 532 nm.

The entrapment depends on the refractive index gradient, so that materials with indexes of

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Refraction close to the surrounding environment need traps with higher power levels. In addition, the tolerance of materials to damage will vary with the power of the traps, so it is desirable that the operator can control this parameter. The user can increase the power level of any particular trap using a 'power regulator' shown in the graphical interface.

c. The liquid crystal hologram (also called spatial light modulator or SLM)

The spatial light modulator 108 is essentially a liquid crystal matrix controlled by an electrostatic field which, in turn, can be controlled by a computer program. The liquid crystal matrix has the property that it retards the phase of light in different amounts depending on the strength of the applied electric field.

Nematic liquid crystal devices are used for screens or applications where a large depth of phase-only modulation (2Π or greater) is necessary. The nematic liquid crystal molecules are usually parallel to the surface of the device, giving the maximum delay due to the birefringence of the liquid crystal. When an electric field is applied, the molecules slope parallel to the electric field. As the voltage increases, the refractive index along the extraordinary axis effectively decreases and therefore the birefringence, causing a reduction of the device delay.

d. She is

Useful lasers include solid-state lasers, diode-pumped lasers, gaseous lasers, dye lasers, alexandrite lasers, free electron lasers, VCSEL lasers, diode lasers, Ti-sapphire lasers, doped YAG lasers, doped YLF lasers , YAG lasers pumped by diodes and YAG lasers pumped by flash lamps. Nd: YAG lasers pumped by diodes operating at 10 mW to 5 W. are preferred. Preferred wavelengths of the laser beam used to form matrices to investigate biological material include infrared, near infrared, visible red, green and visible blue wavelengths, with wavelengths from about 400 nm to about 1060 nm being preferred .

5. Operating procedure

An optical entrapment system 500 (see Fig. 5) (such as the BioRyx system marketed by Arryx, Inc., Chicago, Illinois) includes a 501 microscope of the Nixon TE 2000 series in which a mount for form the optical traps using a holographic optical entrapment unit 505. The slide 502 to which a housing is attached, fits directly into the microscope 501 by means of the mount. For imaging, a light source 503 is provided above the objective lens 504 to illuminate the sample 506.

The optical trap system 100 (see Figs. 1 and 5) includes one end of the first light channel, which is very close to the optical element and the other end of the first light channel, which cuts through and communicates with a second channel. of light formed perpendicular to it. The second light channel is formed within a base of a microscope lens mount tower or "slide". The slide is adapted to fit in a microscope of the Nixon TE 200 series. The second light channel communicates with a third light channel that is also perpendicular to the second light channel. The third light channel crosses from the upper surface of the slide through the base of the slide and is parallel to a focusing lens of the objective lens 109. The focusing lens 109 has upper and lower portions that form a rear aperture. . Interposed in the third light channel between the second light channel and the rear aperture of the focusing lens is a dichroic mirror beam splitter 108.

Other components inside the optical trap system to form the optical traps include a first mirror, which reflects the elementary beams emanating from the phase pattern optical element 101 through the first light channel, a first set of transfer optics 106 arranged within the first light channel, aligned to receive the elementary beams reflected by the first mirror, a second set of transfer optics 107 disposed within the first light channel, aligned to receive the elementary beams passing through the first set of transfer lenses and a second mirror 108 located at the intersection of the first light channel and the second light channel, aligned to reflect the elementary beams that pass through the second set of transfer optics and through the third light channel.

To generate the optical traps, a laser beam is directed from a laser 507 (see Fig. 5) through a collimator and through an optical fiber end 508 and is reflected from the dynamic surface of the optical diffractive element 509. The light beam leaving the collimator end of the optical fiber is diffracted by the dynamic surface of the optical diffractive element in a plurality of elementary beams. The number, type and direction of each elementary beam can be controlled and varied by modifying the hologram encoded in the dynamic surface medium. The elementary beams are then reflected from the first mirror through the first set of transfer optics down the first light channel through the second set of reference optics to the second mirror; and they are directed to the dichroic mirror 509 to the rear opening of the objective lens 504, converge through the objective lens 504, thereby producing the optical gradient conditions necessary to form the optical traps. That portion of the light that is divided through the dichroic mirror 509, for the formation of

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images, pass through the bottom of the third light channel forming a stream of optical data (see fig. 1).

The spectroscopy of a sample of biological material can be carried out with an illumination source 503 for imaging suitable for inelastic spectroscopy or backscatter of polarized light, the former being useful for assessing chemical identity and the latter being suitable for measuring dimensions of internal structures such as core size. With the use of these spectroscopic procedures, in all embodiments, the cells are studied. A computer 510 may be used to analyze the spectral data and to identify cells carrying an X or Y chromosome, or cell types suspected to be cancerous, precancerous and / or non-cancerous. The computer program can then apply the information to direct optical traps to contain selected cell types. Then, the cells contained can be identified based on the reaction or the binding of the cells contained with chemical compounds.

The present procedure and system lend themselves to a semi-automatic or automatic procedure to track the movement and content of each optical trap. The movement can be monitored by means of a 511 video camera, spectra or an optical data stream and that provides a computer program that controls cell selection and the generation of optical traps. The movement of the cells is traced based on the predetermined movement of each optical trap caused by the coding of the phase pattern optical element. Additionally, a computer program is used to keep a record of each cell contained in each optical trap.

Then, the optical data stream can be visualized, converted into a video signal, monitored or analyzed by an operator's visual inspection, spectroscopically and / or by video tracking. The optical data stream can also be processed by a photodetector to track the intensity, or any suitable device to convert the optical data stream into a digital data stream adapted for use by a computer.

In an approach that does not employ an SLM, the movement is carried out by transferring the objects from a first set of optical traps to a second, a third and then a fourth, etc. To move the objects from the first position to a second position, a static phase pattern optical element is rotated around a pivot to align the laser beam with a second region that generates the second set of optical traps to a corresponding second set of predetermined positions. By constructing the second set of optical traps at the appropriate proximity of the first position, the probes can be passed from the first set of optical traps to the second set of optical traps. The sequence can continue passing the probes from the second set of predetermined positions to a third set of predetermined positions, from the third set of positions to a fourth set of predetermined positions and from the fourth set of predetermined positions and so on, by rotating of the phase pattern optical element to align the appropriate region corresponding to the desired position. The time interval between the completion of a set of optical traps and the generation of the next one is of a duration that ensures that the probes are transferred to the next set of optical traps before they are deflected.

In a staggered movement of objects from a wide proximity to a narrow one, the staggered movement of the cells occurs in a similar way. However, as the objects pass from a first set of optical traps to a second set and move to a second and subsequent positions, the stepped arrangement of the traps allows a dense packaging of the objects without placing a set of traps too next to two objects at the same time, which could cause the objects to be contained in the wrong optical trap.

Once an object or cell has interacted with a trap, spectral procedures can be used to study the cell. The spectrum of cells that had positive results (i.e., cells that reacted with or joined a brand) can be obtained by using illumination for imaging such as adequate for inelastic spectroscopy or backscatter of polarized light. A computer can analyze the spectral data to identify the desired objectives and direct the phase pattern optical element to separate those desired objectives. After the end of the test, the selection can be made, by computer or by an operator, of which cells to discard and which ones to collect.

Optical peristalsis (see Fig. 9) is an existing procedure that uses parallel trap lines 400 in a fluidic microchannel 401 arranged so that the spacing between the lines allows particles 402 trapped in a line to be absorbed into traps of the another line when the first line of traps is turned off. Optical peristalsis can be used as an alternative to and together with fluorescent labels (as described below with reference to applications). The procedure works by synchronizing the extinction of the synchronized trap lines so that the particles move in the desired directions specified by the arrangement of the trap lines. By choosing if a line of traps on one side or the other of a particle are lit

or off, the particle can be moved forward or backward in one direction. Therefore, by employing large numbers of traps, large quantities of particles can be moved together in a given direction. Thus, the particles attracted to the traps can be moved to a given area and if desired, collect them there.

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Similarly, by gradually reducing the spacing between the traps of the lines towards a given direction and / or by varying the curvature of the trap lines, the particles can be barrier in a focus pattern to concentrate them. The inversion of this pattern would disperse the particles.

The spacing between lines can be relatively greater to accelerate the movement of the particles, or relatively narrower to slow them down. Similarly, the variation of the intensity of selected traps or lines and therefore their effect on the particles can also be used. By converging or diverging the flows, particles can be combined or separated. In addition, optical peristalsis can be combined with differential effects of viscous drag or electric fields to produce complex and specific sets of parameter values ​​to separate materials accurately, for example. By opposing the entrapment and other forces, the equilibrium point of the two forces determines whether a particle moves with the trap or with the other force.

Optical peristalsis can be applied with a holographic system that cycles through a sequence of phase patterns to apply a corresponding sequence of holographic optical entrapment patterns. These patterns can be encoded on the surface relief of reflective optical diffractive elements mounted on the face of a prism, in which a motor rotates each pattern to its site. Similarly, optical diffractive transmitting elements can be placed on the perimeter of a disk and rotated so that they cycle through the patterns. Switchable phase grids and phase holograms encoded on films can also be used.

For particles conducted beyond a rectilinear matrix by an oblique external force, such as fluid flow, when the entrapment force is considerably greater than the external guide force, the particles are trapped. When the oblique force is greater, the particles flow beyond the matrix.

Between these extremes, the oblique force exceeds the entrapment force in different measure for different fractions of the particles, causing the particles to jump from trap to trap along the direction of the main axis of the matrix. When the matrix is ​​rotated at 45 °, a zero network deflection can be observed because: (1) positive and negative displacements occur with equal probability; or (2) the particles are blocked in the direction [11], jumping diagonally through the matrix.

The particles affected to a greater extent by a matrix can be deflected at greater angles than the particles affected to a greater extent by the oblique force. The optical gradient force exerted on the particles varies approximately as a3, where a = radius. Stokes drag on particles varies as "a". Therefore, larger particles are disproportionately affected by trap matrices, while smaller particles experience less deflection. By orienting the matrix near the optimum deflection angle and adjusting the intensity, the larger particles are placed in jump conditions and therefore, with a greater deflection than the smaller particles. Particles with different deflections can be collected or fractionated further by additional matrices after the first.

Some conventional techniques for fractionation achieve separation in the direction of an applied force. However, these techniques work on batches of samples instead of continuously.

Other conventional techniques for microfracing employ microfabricated sieves consisting of a two-dimensional network of obstacles or barriers. For example, an asymmetric arrangement of barriers rectifies the Brownian movement of the particles that pass through the sieve, causing the particles to follow paths that depend on the diffusion coefficients of the particles. However, the microfabricated fabrics used are clogged and cannot be adapted to the particle size and type.

In fig. 6, an example of particle classification is exemplified. Although the illustrated example exemplifies lateral deflection, optical peristalsis can be obtained in the same system. A representation of a video image shows the separation of light-based material, in this case adapted to separate objects based on particle size. The flow of the upper left channel contains particles of 1, 2.25 and 4.5 μm and another flow enters from the lower left. The overlapping lines respectively indicate the flow of each channel when the laser system power is turned off. When the laser power is on, the light from the interaction region (indicated by the superimposed green box), extracts the 4.5 μm particles from the upper flow and takes them to the lower right channel as indicated by the superimposed white path.

6. Application in sperm classification

to. Background

In one application, a classification of high performance high performance cells is implemented by using optical entrapment technology. The need to implement this technology as a new basis for cell classification is evidenced by the failure of traditional flow cytometers when making high resolution determinations of the cellular characteristics necessary in many classification problems. In this example of separation of sperms carrying X and Y chromosomes from each other in the livestock industry, flows are scaled substantially from the current speeds of state-of-the-art systems.

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The reason is that traditional flow cytometry is better for a fluorescence / non-fluorescence determination and in this mode, it can operate at speeds that provide results of 30,000 cells / second. Since the problem lies in discriminating between different levels of fluorescence (as it is in the problem of sperm separation ), these procedures become very ineffective. In the problem of sperm separation, when sperm carrying X and Y chromosomes differ in fluorescence by approximately 4%, the rate slows down to approximately 4,000 result cells per second (see JL Schenk, et al., Proceedings, The Range Beef Cow Symposium XVI, 1999).

b. Classification using holographic optical traps

The procedure for applying the high performance high performance cell classification has the following components: microfluidic development, development of an optical trap system (entrapment component for the channeling system and the trap component for the separation system ), high resolution fluorescence measurement, system control (including hologram calculation) and mechanical design.

The first component is a flow cell that has a fluid inlet channel, which carries the inlet sample and two outlet channels that carry separate cells outside the inlet channel. The second component is a set of traps that perform the "channeling" function (this "channeling function" is the equivalent of the nozzle that forms the droplet flow in a traditional flow cytometer). The third component is the detection system and finally, the fourth component is the classification system. Figs. 7A-7B illustrate the relationship between these four components.

In this example, sperm is used as the sample target for separation. The traditional method of differentiation between X and Y chromosome-bearing sperm employs Hoechst 33342, a dye that specifically binds to DNA so that the total fluorescence present is a measure of the total DNA present. The measurement of this fluorescence provides an estimate of the nature of the underlying chromosomal load. (Schenk, 1999; also, Erik B. van Munster, Cytometry, volume 47, page 192, 2002).

The essential feature that allows to achieve high yields is its inherent ability to move material in parallel lines simultaneously and close to each other. For this initial application, a flow system is created with 10 input lines 300, separated from each other by 10 micrometers. This determines a total width for the flow from the 110 micrometer inlet reservoir. The output channels 302, 303 are each the same 110 micrometers wide as the input channel 301 and run parallel to the input channel 301 as shown in figs. 7A and 7B. Within the "output channels" 302, 303 is a buffer solution that is introduced into these channels at the same flow rate that is maintained in the input channel 301. These three channels 301, 302, 303 are designed to maintain the laminar flow. in the flow intervals of interest. In the classification region, where specific cells are transferred from the input channel 301 to one of the output channels 302, 303, the three flows are adjacent, without mechanical separation between them. Laminar flows maintain any material in its corresponding flow unless a specific external force is introduced to transfer that material from one flow channel to another.

The channeling traps 305 act on the input cells 306 so that both move along well-defined flow lines and therefore, the input cells 306 are separated from each other by a minimum distance 306 to be set by the operator. The flow rates of the channels 301, 302, 303 are set for this minimum distance 306, for the "update" speed of the device that performs the separation function and for the desired overall processing speed of the cells. Assuming that the minimum distance in the case of the present sample is 20 micrometers (enough to completely separate the heads of the sperm, but a distance that will allow an overlap without consequences of the tails) and a processing speed of 1,500 cells / second , this system uses a flow rate of 3 mm / second [(15,000 cells / second) x (20 micrometers / cell line)  (10 lines)].

The channeling system is composed of a low intensity trap pattern 305 established by a set of static holograms that are mounted on a rotating wheel so that the pattern changes as a function of the rotation pattern. The most later channeling traps are of fixed intensity and position, so they only serve to maintain the separation between cell flow lines. The earlier traps 305 can change both intensity and position over time to act so that they alter the flow in clustered cells and pass through individual, ungrouped cells.

The measurement after which the classification determination is made can be produced in the region after the pipeline traps 305 or it can be produced in a region beyond the pipeline system. For this initial system, the measurement will consist of high resolution fluorescence detection. However, other criteria for active classification, such as dispersion measures, may be applied in the future, or passive techniques such as those using optical deflection can be used as explained above.

The final component of the device is the separation system in which the classification criteria are used to divert the cells to one of the output channels 302, 303 or to allow them to remain in the flow of the input channel 301. The crucial parameter for this component is the field of view of the objective lens 304 of

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high numerical aperture used to apply the array of dynamic traps 305 that control the separation. The width of this field of view is the same 110 micrometers of the widths of the individual channels. The length, however, depends on the flow rates, the depths of the channels and the update speeds of the optical device used to control these traps.

Currently, a configuration includes spatial light modulators to create phase masks that are very effective in directing optical entrapment systems. These devices have update speeds of 30 Hz or more. With an estimated channel depth of 10 micrometers and assuming that the sperm should move in stages of 1 micrometer, 10 updates of the spatial light modulator are used to move a cell from the center of the input channel 301 to the center of any of the output channels 302, 303. With an update value of 30 Hz, the application of these 10 stages will take place in 1/3 of a second. At a flow rate of 3 mm / second, these 10 stages are applied in a length of 1 mm in the direction of flow. Therefore, the objective lens 304 for the separation component would have a working area of ​​110 micrometers x 1000 micrometers. An important development area of ​​this project is the design of this lens assembly. In general, the compensation of the lens design is between the field of view and the numerical aperture. That is, for a lens assembly of a particular complexity, a significant increase in the performance of one of these areas will lead to a decrease in performance in the other area. This is why the high performance lenses used in areas such as high resolution lithographic production of electronic products with integrated circuits are quite complex. However, the present disclosure is at significantly lower performance levels than those of these lens mounts.

7. Broadfield Vortex Clamping Disclosure

The grip with a wide field of view involves microscope objective lenses that have a relatively low numerical aperture. The ability to optically trap objects in the axial direction is based on focusing a beam of light downward so that it has the greatest gradients in the axial direction. This implies that a cone of light with the widest possible radius is formed. The radius of the cone is determined directly by the numerical aperture of the target, that is, a high numerical aperture means a broad cone radius. This is in direct conflict with the requirements of broad fields of vision. Traditionally, this has made it difficult to grip with a wide field of view in the axial direction. One of the main contributions to the difficulty of axial clamping is the radiation pressure of the focused beam of light. Especially for particles that have a good combination of density with the surrounding medium, for example, polystyrene microspheres, the radiation pressure can expel the particles from the trap. With a low numerical aperture target, it is difficult to overcome the radiation pressure with a sufficient clamping force in the axial direction. However, holographic optical traps have the ability to form unusual modes of light that greatly reduce the radiation pressure of the light beam. Vortex traps, for example, have a dark center because the variable phases of light cancel in the center of the trap. This dark center means that most of the rays of light that travel down the center of the beam cease to exist. It is exactly these beams that harbor most of the light radiation pressure, so that their elimination greatly mitigates the difficulty in axial entrapment. Other modes, p. eg, donut modes, have the same advantage.

The manipulation (push, direction, classification) of objects or cells in general is made safer by having multiple beams available. As a bed of skewers, the multiple clamps ensure that less power is introduced at any particular cell point. This eliminates hot spots and reduces the risk of damage. Any biphotonic destructive process benefits greatly, since the absorption is proportional to the square of the laser power. The simple addition of a second clamp reduces biphotonic absorption at a particular point by a factor of four. Large cells, such as those in Tetrahymena, that are held in place by a pincer array, involve a large amount of laser power for effective entrapment. The arrangement of power in a single trap would cause immediate damage to the cell.

Finally, even single cell manipulation is greatly enhanced by the use of holographic optical entrapment. A single carrion epithelial cell can be manipulated by a line of tweezers, which lift the cell along the perimeter of one side. The resulting rotation allows a 360 degree view of the cell. In addition to the advantage of viewing the biological samples, there is also the ability to orient the samples in a stable manner, which has a clear benefit for studies such as dispersion experiments that have a high dependence on the orientation of the sample.

8. Rotary disk based cell sorter

Due to the large amount of sperm of a typical bovine ejaculation and the small amount of time available before the sperm ceases to be functional, a large amount of sperm per second is classified for a commercially viable sperm sorter (of the order of a million). The classification with holographic optical traps confers a huge one through its ability to process a large number of cells in parallel.

The technology to use lasers to access a large number of sites quickly already exists in the form of a rotating laser disk, CD player or DVD player. These devices combine the rotational movement of the disc with the radial movement of the laser to access sites at incredibly high speeds. For example, him

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Typical DVD player can access approximately 4 billion independent "bits" on the disk in approximately two hours. The combination of this rotating disk approach with the optical entrapment (see Fig. 8) allows the cells to be accessed at similar speeds and the holographic optical entrapment increases these speeds by factors of 100 or even greater.

As shown in fig. 8, the objects or cells are introduced into the sample inlet 700 and by using an appropriate sample delivery system 701, the cells are arranged in the sample distribution disk 702 that is rotated by the control of an engine . The trapping and imaging system 703, which is connected to a control and analysis system 704, classifies the cells and is collected in sample chambers 705 and 706.

There are many mechanisms to distribute cells throughout the surface of the disk. Fluid chambers that house individual cells, gels that immobilize the cells, sticky or waxy surfaces that bind the cells, or even the freezing of the cells in a solid mass, are procedures that can be employed. Once the cells are positioned so that they maintain their relative positions, they can be measured correctly. The optical entrapment can then be used to release the desired or unwanted cells from the surface or volume. In situations where you want to classify in more than two groups, you can release each group in a single step and you can execute multiple steps.

9. Classification of cells and non-biological material through the use of meltable substrates

Technologies such as fluorescence activated cell classification (FACS), although well established, suffer from the fact that they are serial processing procedures. Due to the ubiquity of the marker dyes in biology, classification based on these dyes is possible. Frequently, these dyes create an absorption difference of some wavelength or wavelength range between stained and unstained samples, assuming that the groups to be classified no longer inherently exhibit this absorption difference. Holographic optical traps can then be used both to heat and to manipulate the sample in a substrate that melts by the elevated temperature of the sample. The sample that is embedded can then be released with an increase in the mass temperature. In addition, an even faster parallel processing procedure is possible in which the cells are illuminated with a broad light source of high power that processes the entire array of samples simultaneously. The same set of procedures can be applied to non-biological samples that differ in absorption spectra, or can be selectively prepared for that purpose.

10. Gel based classification

Holographic optical laser traps are a great advantage for the manipulation of objects in that they can access and move objects in three dimensions. As the applications of biological classification progress, it is necessary to classify larger quantities of samples, often in small amounts of time. Three-dimensional access to holographic optical traps means that these classification applications can be made. Quantities of cells and other samples of biological interest that would be cumbersome or impossible to classify in series or on a two-dimensional substrate can be efficiently classified.

An application of this three-dimensional classification is based on a reversible gelation procedure. The cells are gelled in a network and then the desired or unwanted cells are removed from the gel using holographic optical traps. The heat of the traps can be used to melt the gel and provide exit paths.

Alternatively, cells are selectively destroyed, based on some criteria, holographic optical laser traps. Then, the entire gel is melted and the living cells are separated from the dead ones. Instead of simply destroying them, a more destructive thermal explosion can be generated, which disintegrates the cell into much smaller components and then classification can be made based on size, grouping or connecting certain cells together again.

eleven. Destruction of biological samples

A wide variety of applications benefit from the ability to destroy biological samples selectively. One of these applications is the elimination of pathogens from the blood. Another application is cell classification. The cells are identified, one or more groups of cells are destroyed and then the dead cells are removed. The destruction is carried out by the light energy of the lasers themselves and does not necessarily require optical traps to perform this function.

Essentially, the cells or the environment surrounding the cells are heated with the laser beam, damaging and destroying the cell. Holographic optical traps, due to their versatility and three-dimensional control, allow the destruction of selective massive parallel cells.

12. Fixing electronic components

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It should be noted that many of the above techniques can be used to move small electronic components or to fix electronic components in place.