Microstructured filter

Microstructured filter

Full description

Background of the invention

This invention relates to microstructured filters for fluids

fluids.

Many filters are known. The filter medium contains micropores with a diameter of less than a micrometer, where the pore size is statistically distributed depending on the material. The external dimensions of filtration media of this type are greater than the mean pore diameter by an amount raised to the power of ten. Experience has shown that it is not possible to easily make these dimensions as small as desired.

Also known as microapertured metal strips, which are used for screen printing, their thickness does not exceed 100 micrometers, and they consist, for example, of nickel. They are provided with holes distributed in an organized manner along the length of the strip, and the diameter of the holes is a few micrometers. These tapes are produced galvanically, for example. Metal strips of this type cannot be assembled with microstructured components.

European Patent Specification No. 432 231 0 describes a cross-flow microfilter that is supplied with the fluid to be filtered and from which a concentrated flow and a filfrate flow are drawn. Between the chamber into which the fluid flows and the collecting chamber is placed a row of webs or two lands with passages between them. It forms a row

Chords and microscopic filter passages. The direction of the passages is inclined to the direction of flow of the fluid/concentrate, at an angle ranging from 90 to 135. The supplied fluid that enters the concentrated material flows through the strings. The leachate is collected in a group of compartments and leaves the filter either perpendicular to the filter surface or at the filter surface in a group of passages that extend between the passages of the concentrated material.

International Patent Specification No. 93/11862 describes a micromechanical filter consisting of three layers. An intermediate layer is placed over the base layer that is covered in specific areas, upon which is placed a covering layer that contains openings that are elongated in specific areas. The intermediate layer is absent along one or both longitudinal sides of the openings. The covering layer in these areas is arranged in a cantilever or overhung manner. Below the cantilevered part of the cover layer, and next to the openings, is a shallow slot whose thickness is the same as the thickness of the middle layer and whose length is also the same as the length of the elongated slot. The leachate flows through that slit into the leachate collection chamber, whose thickness is greater than the thickness of the middle chamber. The covering layer contains a large number of elongated openings arranged in a row and parallel to each other. The rows of cracks can be arranged in a meader configuration in the covering layer. The fluid flows through a group of vertical openings on the surface of the filter into a group of inlet chambers and is removed from the group of leachate collection chambers through a group of vertical openings on the surface of the filter. The layers of this filter can be made of silicon, plastic material, or metal and formed by etching, embossing, mechanical processing or machining, while methods including thin film technology and metal deposition can be used. Vapor phase deposition out of the vapor phase.

These and other previously proposed tools suffer from several problems. It has been observed, for example, that at least some of the previously proposed tools are highly susceptible to clogging.

Thus, the tool may stop working later. In an attempt to alleviate this problem, it was suggested to provide a large filter, but these large filters have an undesirable dead volume. Some of the previously proposed tools are also very complex, and therefore expensive and time-consuming to manufacture. In addition, some previously proposed tools cannot be easily assembled with components with other microstructures.

General description of the invention

Accordingly, the object of the invention is to provide a microstructured filter for a fluid that alleviates one or more of the problems described herein.

According to one aspect of the invention, a filter with a microscopic structure is provided that contains an inlet for the unfiltered fluid and an outlet for the filtered fluid. The filter consists of:

A filtration chamber is provided between said inlet and outlet, said chamber being partially defined by a substantially flat base plate and a cover plate tightly fitted thereon; The filter body is provided inside the filtration chamber, and the enclosed filter body is formed by a group of protrusions, each of which forms an integrated component with the aforementioned base plate, from which each protrusion protrudes. The aforementioned protrusions are separated from each other by passages that form a path for the fluid through the filtration chamber from The vented entrance to the vented outlet, and when the mentioned covering plate is firmly fixed On the base plate it covers the protrusions and passages mentioned;

wherein the said set of protrusions is arranged in at least two rows to extend in a zigzag and alternately contiguous manner across the filtration chamber; And

The inlet and outlet each form an elongated slit for the unfiltered and filtered fluid, respectively, and the width of each of the aforementioned slits is substantially equal to the width of the filtration chamber and its height is substantially equal to the height of the protrusions on either side of the inlet and outlet of the body.

Straight candidate.

A preferred embodiment of the invention provides a fluid microstructure filter having an inlet for the unfiltered fluid and an outlet for the filtered fluid, wherein the direction of fluid flow through the entire filter is superficial and the filter has the following features:

A group of protrusions arranged in alternating rows and protruding from a base plate, preferably flat, and considered an integral component with the base plate. A group of passages located between the protrusions.

A covering plate, preferably flat, located above the protrusions and covering the passages. The passages form an interstitial path from the filter’s entry side to its exit side. The spacing distance between the base plate in the area around the protrusions and the covering plate that is located within the row of protrusions is approximately equal to the width of the passages at The side of the protrusion, along which the fluid passes in the row of passages, and an elongated entry slit for the unfiltered fluid, extending almost along the entire width of the filter and whose height is approximately equal to the height of the protrusions that protrude from the base plate at the entry side of the filter, And

An elongated exit slit for the filter fluid, extending almost along the full width of the filter and having a height approximately equal to the height of the ridges that protrude from the base plate, at the exit side of the filter.

It is preferable that the height to width ratio of the entry slot and the exit slot range from 5:1 to 1000:1. The entry slit preferably traps coarse particles

coarse particles.

A group of rows of protrusions can be arranged in a cascade configuration. It is preferable that the protrusions arranged near the filter entry side be larger than the protrusions arranged at the filter exit side.

It is preferable that the distance between the flat base plate and the flat cover plate be in the area located around each row of protrusions, where these rows are arranged in a manner

Alternate, approximately equal to the width of the passages at the side of the ridges, where the fluid passes in a row of passages. It is preferable that the separation distance be half to two times the width of the corridor. It is preferable that the separation distance from one row to another be reduced, as indicated by the direction of the flow, and therefore, the passages can be made with an approximately square cross-section on the side of their fluid entry.

The distance between the flat base plate in the area around the protrusions and the flat covering plate may be fixed within a row of protrusions. The separation distance for rows of protrusions arranged in a curvilinear or zigzag pattern may be greater in the end-row region located near the filter exit side than in the row-end region located near the filter entry side. It is preferable that the separation distance increases approximately linearly from one end of the row of protrusions to the other.

The mutually opposite sides of two adjacent rows of protrusions can define an interconnected chamber into which the fluid flows from all the passages between the protrusions of the first row, and from which the fluid flows to all the passages that lie between the protrusions of the adjacent row. Before the first row of protrusions, there is a collecting chamber with an elongated cross-section, into which the unfiltered fluid passes and from which the fluid flows into all the passages located between the protrusions of the first row. After the last row of protrusions, there is a collecting chamber with an elongated cross-section, into which the fluid emerging from all the passages of the last row flows and the filtered fluid passes outside of it.

The bulges can be in the form of strings or strands, which - as indicated by the direction of the flow - are straight or curved. The protrusions may also be in the form of columns, preferably straight with any cross-section, and preferably the cross-section be circular or polygonal.

It is preferable that the length of the passages extended between the strings or strings be at least twice greater than their height at the fluid entry side. It is preferable that the cross-section of the corridors be square, barrel-shaped, or approximately trapezoidal;

In the latter case the longer side of the trapezoid can be formed by a covering plate. The length of the lanes ranges, for example, from 5 to 50 micrometers, and their height ranges from

2.5 to 25 micrometers and ranges in width from 2.5 to 25 micrometers. And it can increase

Width of aisles towards exit side.

It is preferable that the distance between the rows of protrusions be twice the width of the corridor on the entry side. The rows of protrusions can extend parallel to each other or in a curved or zigzag manner. The rows arranged in a zigzag manner can be slanted away from each other

At an angle ranging from 2 to 25.

When the filter contains rows of ridges arranged in a curved or zigzag manner,

The particles to be filtered are first deposited in areas on the fluid entry side, which are located near the filter exit side, and the distance between the rows of protrusions located on the inlet side is gradually increased starting from the filter exit side area. The filter does not become almost completely clogged and its capacity is exhausted only when the inlet chamber located between each two rows of protrusions is almost completely filled with particles to be filtered.

It is preferable that the degree of separation in the filter be determined relatively clearly due to slight variations in the dimensions of the passages. The filter may not need a distributor for the flowing feed fluid to be filtered nor a leachate collection device by which the filtered fluid is collected.

The filter can be made by applying well-known processes using metal, silicon, glass, ceramic or plastic materials, for example. The base plate can be made of the same material as the cover plate or of a different material. The filter is best suited for use in a high-pressure range, for example up to 30 MPa (300 bar).

Other fluidic elements with microstructures are arranged in a microstructured filter according to another embodiment of the invention on the same base plate, for example a nozzle for spraying fluid or for producing aerobic analyzers and also in the range of high pressures.

The microstructured filter according to various embodiments of the invention may exhibit some or all of the following features:

The filter can remain operational even if some of the passages are blocked by impurities in the fluid because the filter contains a large number of passages over a narrow area.

This allows improved usability of the filter when installed with a nozzle for use in an atomizer.

For example, when used in a vaporizer to administer medication, failure of the vaporizer within the specified period of time for its use can lead to fatal consequences for the user;

Passes may be specified within narrow limits with respect to shape, cross-sectional area and length (in the most preferable embodiment all passes within the filter are equally dimensioned);

The cross section of the passage can be adjusted according to additional conditions, for example according to the cross section of the nozzle connected to the passage;

A large surface area can be provided to the filter within a small footprint;

Before the fluid can pass through the passages, the flowing stream of fluid may be directed between rows arranged in a curvilinear or zigzag manner substantially perpendicular to the direction of flow in the passages;

The open filter area (sum of the cross-sectional area of all passes) can be at least 50% of the total filter area,

The filter can have a small dead volume; And

The filter can be assembled in a simple way with other microstructured components.

The microstructured filter described herein finds noteworthy utility when used to filter a drug dissolved in a solvent to produce an aerobic solution for inhalative application. Suitable solvents include, for example, water, ethanol, or mixtures of them. Suitable medications include, for example, Berotec, Atrovent, Berodual, Salbutamol, Combivent, Oxivent, Ba 679, BEA 2108, and others.

The filter according to the present invention may also be used in a nebuliser, such as that described in International Patent Cooperation Treaty Application No. 91/14468 or European Patent Cooperation Treaty Application No. 96/04351.

The microstructured filter described herein may be produced in the following illustrative manner: a set of interconnected base plates, for example in a large number of up to several thousand, are simultaneously converted into microstructured plates over a large surface area and bonded to a large flat covering plate In one step (batch process). This combined assembly can later be divided into several individual pieces.

This manufacturing method has some specific advantages. On the one hand, batch production makes it possible to produce individual parts that are particularly inexpensive and with a high degree of precision and precision of structure on the order of a few micrometres down to the sub-micrometre range, which can only be produced at a very high cost by a serial processing procedure. While on the other hand, batch production allows for a specific, uniform quality with respect to all parts, which can be done reproducibly under the same process conditions and are unlikely to change slowly, as might be the case on For example, in sequential manufacturing procedures due to tool wear.

In addition, the location and placement of parts in the process are also predetermined according to the design and do not have to be adjusted and fixed by expensive sorting and handling mechanisms as is the case with some previously proposed arrangements.

The base plate can be produced, for example, by reactive ion etching, galvano-shaping or, if plastic materials are used

According to the LIGM process using lithographs, galvanoforming and moulding, other forming processes can exist to produce specific path shapes. Passes with a trapezoidal or cylindrical cross section can be produced by over-etching or under-etching

under-etching qualitative. These shapes can be produced by dry etching and wet etching processes as well. Triangular cross-sections of the passages can be produced using anisotropically active etching processes in monocrystalline silicon base sheets. The base plate is preferably formed by isotropic or anisotropic dry or wet etching, or a combination of these processes, and particularly by anisotropic dry etching.

The microstructured base plate and its protrusions can be bonded to the flat cover plate for example by anodic bonding of silicon and glass, for example alkali borosilicate glass. In one example, the glass plate is mounted on a microstructured silicon plate and brought into contact with an electrode.

The total composition is heated to temperatures ranging from 200°C to 500°C (degrees Celsius).

A negative voltage of about 1000 volts is applied between the silicon plate and the glass plate. Because of this voltage, the positively charged alkaline ions pass through the glass to the cathode, where they are neutralized there. A negative space charge is formed in the glass at the transition point between the glass and the silicon, which provides electrostatic attraction between the two surfaces, and also leads, through oxygen bridge bonds, to the formation of a strong chemical bond between the glass surface and the silicon surface.

silicon

According to the illustrative process described above, the glass covering plate is particularly useful for quality assurance because of the bond connection on the one hand and on the other hand because defects or inlet particles that lead to filter failure can be easily identified by visual inspection.

After the bonding process, the composition can be broken down into individual filters, preferably with a high-speed rotary diamond circular saw, with side exposure.

Entry and exit for each candidate, if neither of them is already exposed. The position of the severing cut can be determined with an accuracy of up to a few micrometres.

In addition to using the anodic bonding process, the microstructured base plate can be attached to the flat cover plate by ultrasonic welding, laser welding, glueing, soldering or by any other means known to those skilled in the technique.

Embodiments of the present invention will now be described by example only by reference to the attached drawings, where:

Brief explanation of fees

Figure 1: shows a schematic representation of one embodiment of the filter;

Figure 2: A magnified view showing the arrangement of the protrusions in rows in the filter shown in Figure 1;

Figure 3: A cross-section view along line A-A in Figure 2;

Figure 4: A schematic illustration of different types of protrusions.

Figure 5: A schematic illustration of other protrusions;

Figure 6: is a schematic illustration of a number of illustrative patterns in which it is possible

Arrangement of ridges;

Figure 7: shows an illustrative example of routing bumps; And

Figure 8: An image produced by a scanning electron microscope

scanning electron microscope of the filter at the end of its validity period.

Detailed description

As mentioned above, Figure 1 shows an illustrative embodiment of a filter, as viewed from the initially open side, which is then covered by a cover plate 20. The base plate 1 of the filter is formed microscopically between edge regions 2a and 2b. Microscopic formation is ensured in

This example has 3 rows of bumps arranged in a zigzag manner. It can also be seen that the 3 rows are inclined from each other at an angle of alpha.

In this example, the base plate, in addition to the filter and its predecessor, is provided with another row of protrusions 4 to form a large coarse filter that mixes the fluid flowing through it. The entry slot 5 is located before the other row of protrusions through which the unfiltered fluid passes into the filter. In this embodiment, a nozzle 6 is arranged adjacent to the filter at its outlet 10 from which the filtered fluid can exit. The nozzle 6 in this illustrative example is formed as an integral component with the base plate 1. It is understood that the filter can be formed without the nozzle 6 and without the wide-hole filter 4.

Figure 2 is an enlarged view of part of Figure 1, showing an illustrative arrangement of the protrusions in rows 3. In this case, the protrusions 7 are in the form of rectangular tendons or ridges, but, as will be described later, the protrusions can have an alternative shape. It can be seen that rows 3 have a set of ridges 7 extending from the base plate 1 and spaced apart to provide a fine fluid filter.

Figure 3 is a cross-section view taken through a row of ridges along line A-A in Figure 2. In this illustrative embodiment, the protrusions have 7 concave-curved longitudinal sides, between which are located 8 passages of cylindrical cross-section.

Figure 4 shows a set of embodiments of the bumps, each viewed from the initially open side of the filter (i.e. from above). Any or any combination of the protrusions described (or any other protrusion) may be used in the filter described herein. Figure 4 shows a rectangular board 11, an elongated board 12 of fixed width and round narrow sides, a wing-shaped board 13, a board 14 of fixed width and a narrow side extending diagonally, and a board 15 that is curved in the form of part of a circle. . Also shown in the figure are a square column 16, a triangular column 17, a circular column 18, and an octagonal column 19. As mentioned above, any material or any combination of these materials is suitable for use in the filter.

Figure 5 shows different cross-sectional views taken through a variety of different protrusions, specifically a protrusion of cross-section 22 with concave longitudinal sides, a protrusion of trapezoidal cross-section 3 2 where the long side of the trapezoid connects to the base plate 1, a protrusion with Cross section of a trapezoid 4 2 where the short side of the trapezoid connects to the base plate 1, and a protrusion 25 with two long, rounded edges.

Figure 6 shows different arrangements of the bumps, where the bumps - regardless of their shape - appear as dots of different sizes. The protrusions can be arranged in the form of a matrix 31, linearly in a row 32, in a curved form 33, or zigzag 34. The group of protrusions may be arranged in a row 35 or in a curve or zigzag 36 successively.

Figure 7 shows an illustrative orientation of the pressure in relation to the direction of the inlet fluid flow 41.

As shown in the figure, some of the two blocks (indicated by the reference number 42) are arranged parallel to the direction of the inlet fluid flow, some of the other two blocks (indicated by the reference number 43) are arranged perpendicular to the direction of the inlet fluid flow, and the remaining two blocks (indicated by the reference number 44) are arranged. Inclined to the direction of flow of the incoming fluid at different angles. We should realize from Figure 7 that the two streams do not need to be directed in the same direction as the inlet fluid flow. In fact, providing two different orientations is a distinct advantage because the different orientation improves the degree of agitation of the fluid as it travels through the filter.

Figure 8 shows a scanning electron microscope image of a microstructured filter, such as the filter shown in Figure 1, at the end of its life. The image was recorded through the glass cover plate (not shown in the drawing). The image shown shows a filter containing rows of bumps arranged in a zig-zag pattern, but the bumps themselves cannot be seen at this chosen magnification.

The fluid flowed through the filter in the direction of the arrows while the filter was in use, and particles suspended in the fluid were trapped by the adjacent ridges. As shown in the figure, the rows

The protrusions are covered by filter particles, and specifically, they are covered to a greater extent in the region near the edge regions 2a and 2b than in the central region of the filter. There are almost no particles in the space between the rows of ridges located on the flow side of the fluid entering the filter. Thus the filter is still fully operable in that area (i.e. the fluid can still flow through it). As can be seen from Figure 8, the boundary line between the free filter region and the blocked filter region extends in the form of an approximately parabola. As shown in Figure 8, the unfiltered fluid entering the inlet slot can still pass through the filter to exit the outlet slot 10, even though a large portion of the filter surface area has previously been clogged.

On this basis, it can be inferred that the filter described in this statement is less susceptible to clogging than previously proposed filters, because it can still operate adequately even when a relatively large portion of the filter surface is clogged. As a result of this improvement, the life of the filter (and therefore of any tools containing the filter) can be greatly extended, in stark contrast to previously proposed arrangements where relatively small blockages cause the tool to stop operating properly.

Example: A microstructured filter used in an atomizer

As mentioned above, the filter described in this statement finds many uses in atomizers,

Especially in nebulizers used to produce an aerobic solution from a fluid carrying a drug.

An illustrative example of such an atomizer will now be described. In this illustrative example, the filter is formed on a base plate with a number of other microstructured components. The base plate is 2.6 mm wide and about 5 mm long. The plate, about 2 mm wide, contains 40 rows of protrusions arranged in a zigzag pattern. The length of each row is 1.3 mm. The protrusions are in the form of two rectangular tubes, 10 micrometers long and 2.5 micrometers wide, protruding from the base plate at a distance of 5 micrometers. Corridors are provided

Between the two nations, it is 5 micrometers high and 3 micrometers wide.

On the fluid entry side of the filter is a row of 10 rectangular tubes, 200 micrometers long and 50 micrometers wide, protruding from the base plate at a distance of 100 micrometers and providing passages between these two tubes that are 100 micrometers high and 150 micrometers wide. These ten rectangular filters provide a wide-perforated filter and a means of agitating the fluid flowing through it. The fluid entry gap is provided at a distance of about 300 micrometers in front of the bracket row, with a width of about 2 mm and a height of about 100 micrometers. Referring to Figure 1, a collecting chamber 9A with an elongated cross-section is provided before the first row of rectangular tubes, through which the unfiltered fluid passes and from which the fluid flows to all passages between the two tubes of the first row.

The leachate collection chamber 9B is provided behind the rows of tents arranged in a zigzag pattern.

The leachate collection chamber is 5 µm high, tapers from a width of 2 mm and connects to a nozzle with a rectangular cross-section, 5 µm high and 8 µm wide. The nozzle opening in this example was manufactured at the same time as the base plate microstructure.

The 1.5 mm thick base plate contains nickel and is produced by galvano-shaping of plastic molding insert containing the complementary structures of 1083 filters. It is covered with a flat 0.8 mm thick nickel plate which is welded onto Base plate.