MXPA00002458A - Microstructured filter - Google Patents

Abstract

A microstructured filter for a fluid, the filter having an inlet for unfiltered fluid and an outlet for filtered fluid, the filter comprising:a plurality of projections (7) which are arranged in at least two rows (3) in mutually juxtaposed relationship and which project out of a base plate (1) and which are an integral component of the base plate, a plurality of passages (8) between the projections (7), and a cover plate which is securable to the base plate to cover the projections (7) and the passages (8), wherein the passages form a plurality of through paths from the inlet to the outlet, said inlet comprises an elongate inlet slot (5) for the unfiltered fluid, which extends over approximately the entire filter width and which is approximately as high as the projections (7) projecting out of the base plate, on the inlet side of the filter, and said outlet comprises an elongate outlet slot for the filtered fluid, which extends over approximately the entire filter width and which is approximately as high as the projections (7) projecting out of the base plate, on the outlet side of the filter. The filter according to the invention remains operational, even if a part of the filter area is obstructed. The filter is used for example in an atomiser with which an aerosol is produced from a fluid which contains a medicament.

Description

FILTER MICROES RUCTURADO The invention relates to microstructured filters for fluids. Several filters are known, in which the filter medium has micropores below the submicrometer range, the pore size is statistically distributed depending on the material. The external dimensions of the filter medium of this type are powders ten times larger than the diameter of the pore and experience has shown that these can not easily be made as small as desired.

Metal strips with micro-openings which are also known to be used for sifting the stamping, up to a thickness of 100 μm, comprising for example nickel, provided with holes which are evenly distributed on the strip, the diameter of the holes is a few microns. These strips are produced, for example, in a galvanic manner. Metal strips of this type can not be assembled with microstructured components.

REF .: 32674 The specification of European Patent No. 0231 432 describes a microfilter with cross flow where the fluid that is filtered is fed and leaves it with a concentrated flow and a filtered flow is taken. It is placed between the chamber where the fluid flows and the collection chamber for filtering a line of membranes or plates of earth where there are passages. The line of membranes and passages form the microfilter. The direction of the passages is inclined through an angle of 90 ° to 135 ° with respect to the direction of fluid flow / concentrate. The supplied fluid which enters the concentrate flows beyond the line of membranes. The filtrate is collected in a plurality of chambers and leaves the filter perpendicular to the surface of the filter or on the surface of the filter in a plurality of passages extending between the passages for the concentrate.

The specification of the International Patent No. WO 93/11862 discloses a micromechanical filter which is constructed with three layers. Placed in the closed base layer, in given regions is an intermediate layer and placed on it is a coating layer with openings that extend in a certain way in a region. The intermediate layer is absent in the parallel relationship for one or both longitudinal sides of the openings. In these regions, the coating layer is arranged in a corbelled or suspended configuration of the upper part. Positioned under the corbel-shaped part of the covering layer, attached to the opening, is a shallow opening which is as thick as the intermediate layer and as long as the enlarged opening. The filtrate flows through this opening into the filtration collection chamber which is denser than in the intermediate chamber. The coating layer contains a large number of enlarged openings which are arranged in a row fashion parallel to one another. The rows of the openings can be arranged with a serpentine configuration in the coating layer. The fluid flows through a plurality of openings perpendicular to the filter surface in a plurality of inlet chambers and is removed from a plurality of filtrate collection chambers through a plurality of openings perpendicular to the filter surface. The layers of this filter can be made of silicon, plastic or metal and are structured by engraving, embossing or processing or mechanical actuation, since methods involving thin film technology and metal disposition outside the vapor phase can be included.

These, and others, previously proposed devices suffer from several problems. For example, it has been noted that at least one of the previously proposed apparatuses is inappropriately susceptible to blockage whereby the apparatus may then cease to function. In an effort to solve. This problem has been proposed to provide a larger filter, but these larger filters have a large undesirable dead volume. Also, some of the previously proposed devices are inappropriately complicated, and therefore expensive and time consuming in manufacturing. In addition, some of the previously proposed apparatuses are such that they can not be easily assembled with other microstructured components.

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

According to one aspect of the invention there is provided a microstructured filter having an inlet for the unfiltered fluid and an outlet for the filtered fluid, the filter comprising: a filtering chamber provided between the inlet and the outlet, the chamber is partially defined by a flat base plate and a cladding plate that is secured thereto; and a filtering body within the filtering chamber, the filtering body is formed by a plurality of projections where each comprises an integral component of the base plate and each is projected from it, the projections are spaced one from the other. another by means of passages forming a fluid path through the filtering chamber from the entrance to the exit, the covering plate when secured to the base plate covers the projections and the passages; wherein the plurality of projections is arranged in at least two rows extending with a zigzag configuration and a mutually juxtaposed relationship through the filtering chamber; and the inlet and outlet of each comprises an elongated slot for the unfiltered and filtered fluid respectively, each of the slots being substantially as wide as the filtering chamber and substantially as high as the projections on the inlet and inlet sides. output of the filter body respectively.

A preferred embodiment of the invention provides a microstructured filter for a fluid 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 on the surface, which it has the following characteristics: a plurality of projections that are arranged in the form of mutually juxtaposed and projecting rows away from a preferably flat base plate and which are an integral component of the plate. a plurality of passages between the projections, a preferably flat coating plate which is placed on the projections and which covers the passages, where the passages form a path of passage from the inlet side to the outlet side of the filter, and the spacing between the base plate in the area around the projections and the liner plate within a row of projections is approximately as large as the width of the passages on the side of the projections, where the fluid passes within the row of passages, and an entry point attached to a unfiltered fluid, which extends over approximately the width of the filter and which is about as high as the projections projecting out of the base plate, on the inlet side of the filter, and an elongated outlet opening for a filtered fluid, which extends over approximately the width of the filter and which is approximately as high as the projections projecting away from the base plate, on the outlet side of the filter.

Preferably, the ratio of height to width of the opening. of entry and exit opening is from 1: 5 to 1: 1000. The entry opening preferably retains the granular particles.

A plurality of rows of projections can be arranged in a cascade configuration. The projection arrangements closest to the filter inlet are larger than the projections that are arranged more toward the filter output side.

The spacing between the flat base plate and the flat facing plate in the region around each of the rows of projections, this row is arranged in a cascaded configuration, is preferably as large as the width of the passages on the side of the projections, where the fluid passes within the row of passages. The spacing is preferably between half and twice the width of the passage. The spacing preferably decreases from one row to another, as seen in the direction of flow. Therefore, the passages can be of a square cross section at their inlet sides for the fluid.

The spacing between the flat base plate in the area around the projections and the flat coating plate may be constant within a row of projections. In the case where the rows of projections are arranged with a serpentine configuration or a zigzag configuration, the spacing may be greater in the region of the end of the row which is in the vicinity of the outlet side of the filter than in the region of the end of the row which is in the vicinity of the input side of the filter. The spacing preferably increases approximately linearly from one end of the row of projections to the other.

The mutually facing sides of two adjacent rows of projections can define an interconnected chamber wherein the fluid flows through all the passages between the projections of a first row, and outside of this fluid flows into all passages between the rows. projections of the adjacent row. Positioned upstream of the first row of projections is a collection chamber of the elongated cross section, wherein the unfiltered fluid passes and out of this fluid flows into all passages between the projections of the first row. Positioned downstream of the first row of projections is a collection chamber of elongated cross-section, where the fluid flows out of all the passages of the first row, and out of this passes the filtered fluid.

The projections can be in the form of membranes or plates of earth that as you can see the direction of the flow is straight or curved. The projections may also preferably be in the form of straight columns of any cross section, preferably a round or polygonal cross section.

The length of the passages extending between the membranes or ground plates is preferably at least twice as large as their heights at the fluid inlet side.

Preferably the cross section of the passages is approximately square or cylindrical or trapezoidal; in. In the latter case the larger side of the trapezoid can be formed by a lining plate. The passages are for example from 5 to 50 μm in length, from 2.5 to μm high and from 2.5 to 25 μm wide. The width of the passages can be larger towards the exit side.

The spacing between the rows of projections is preferably twice the width of the passage on the entry side. The rows of projections may extend parallel to one another or with a serpentine configuration or a zigzag configuration. The rows arranged in a zigzag configuration can be inclined in relation to one another through an angle from 2 ° to 25 °.

When the filter has rows of projections that are arranged in a serpentine or zigzag configuration, the particles that are filtered first are deposited in the regions on the inlet side of the fluid, which are in the vicinity of the outlet side of the filter, The space between the rows of projections on the input side increases progressively, starting in the region on the output side of the filter. The filter approximately only becomes completely clogged and the capacity of the filter becomes impoverished when the entrance chamber between each of the rows of projections is almost filled with particles that are fi lled.

The degree of separation of the filter is preferably relative to the defined shape due to the smaller fluctuations in the dimensions of the passages. The filter may not require a distributor of the feed flow for the fluid to be filtered and a filter collection apparatus for the filtered fluid.

The filter can be produced using known processes for metal, silicon, glass, ceramic or plastic material for example. The base plate can be made of the same material as, or of different material to, the lining plate. The filter is preferably suitable for a high pressure range, for example up to 30 MPa (300 bar).

A microstructured filter according to another embodiment of the invention, other microstructured flow elements are arranged in the same base plate, for example a nozzle for spraying a fluid or for producing an aerosol, also in the high pressure range.

The microstructured filter according to various embodiments of the invention may exhibit some or all of the following advantages: - because the filter has a large number of passages over a small area this may be operational even if some passages are blocked by contaminating impurities the fluid. This allows the usability to improve the filter when it is assembled with a nozzle for use with an atomizer, as well as when an atomizer is used for the administration of a medication, the failure of the atomizer within the specific period of use may have fatal consequences for the user; - The passages can be defined within narrow limits with respect to the shape, cross-sectional area and length (in the most preferred mode the dimensions of all the passages within the filter are the same); - the passage cross section can be adapted for other conditions, for example for the cross section of a nozzle that is connected downstream of this; - a larger surface area of the filter can be placed within a small volume of the filter; - before the fluid passes into the passages the flow of the fluid can be directed between the rows arranged with a serpentine or zigzag configuration substantially perpendicular to the flow in the passages; - the open area of the filter (sum of the cross-sectional area of all the passages) can be at least 50% of the total area of the filter; the filter can have a small dead volume; and - the filter can be assembled in a simple manner with other microstructured components.

The microstructured filter disclosed herein finds particular utility when used to filter a drug dissolved in a solvent to produce an aerosol for application by inhalation. Suitable solvents are, for example, water or ethanol or mixtures thereof. Suitable medicaments are for example Berotec, Atrovent, Berodual, Salbutanol, Conbivent, Oxívent, Ba 679, BEA 2108 and others.

The filter according to the invention can also be used in a nebulizer, as described in PCT application W091 / 14468 or PCT / EP96 / 04351.

The microstructured filter described here can be produced in the following illustrative manner; a plurality of interconnected base plates, for example the order of magnitude of a few thousand, are simultaneously squeezed into a larger surface area and connected in one step with the larger flat slab plate (batch process). This combined assembly can then be divided into several individual pieces.

This mode of manufacturing has some specific advantages. On the one hand batch production provides the possibility of producing particularly individual parts that are not expensive with a high degree of accuracy with structure accuracy of a few micrometres below within the submicrometer range, which could only produce a substantially higher cost in a series of procedures for processing, which on the other hand batch production provides a defined uniform quality with respect to all parts, which can be reproduced under the same conditions of the process and a slow change is unlikely, as This would be the case, for example, in the series of procedures for processing due to wear of the tool.

In addition, the position and location of the parties in the process are also predetermined by the design and do not have to be adjusted and placed by means of separation and expensive handling mechanisms as in the case, with some of the previously proposed arrangements.

The base plate can be produced, for example, by engraving by reactive ion exchange, galvanoforming or in the case of plastic materials, according to the LIGM process by lithography, galvanoforming and molding. There may be other processes for the production of specific forms of passages. The cross section of the trapezoidal or cylindrical shaped passages can be produced by specific over-engraving or sub-engraving. These forms can be produced by dry etching processes and also with wet taxing. The triangular cross sections of the passage can be produced with anisotropically engraved processes on silicon monocrystalline base plates. The base plate is preferably structured by isotropic or anisotropic wet or dry etching or a combination of these processes, particularly preferred by dry anisotropic etching.

The micro-structured base plate and the projections thereof can be joined to the flat coating plate by anodic bonding of silicon and glass, for example an alkaline borosilicate glass. In one example, the glass plate is placed on the micro-structured silicon plate and connected with an electrode. The entire assembly is heated to temperatures between 200 to 500 ° C and a negative voltage of approximately 1000V between the silicon plate and the glass plate. Due to the voltage the positively charged alkaline ions pass through the glass to the cathode where they are neutralized. In the transition between the glass and the silicon, a negative space charge is formed in the glass, which is provided by electrostatic attraction of the two surfaces, and also by means of links with oxygen bridges, it causes a durable chemical bond between the surface of the glass and the surface of silicon.

With the illustrative process described above a glass lining plate is particularly advantageous to ensure the quality due, on the one hand, to the quality of the connection of the link and, on the other hand due to the defects or particles included which causes malfunctioning. of the filter that can be easily recognized by means of optical inspection.

After the assembly procedure it can be divided into individual filters, preferably with a high speed rotary diamond circular saw, with the internal part and the external part of each filter exposed if they are not previously exposed. The cut can be placed with a degree of accuracy within a few micrometers.

However using the anodic link, the microstructured base plate can be attached to the flat coating plate by means of ultrasonic welding, laser welding, gluing or welding or any other apparent means to persons skilled in the art.

The embodiments of the inventions will now be described as a means of example only, with reference to the accompanying figures, wherein: Figure 1 illustrates a schematic representation of a filter mode; Figure 2 is a view on an enlarged scale showing the arrangement of the projections in lines of the filter of Figure 1; Figure 3 is a cross-sectional view along line A-A of Figure 2; Figure 4 is an illustration of a variety of different projections; Figure 5 is a schematic illustration of other projections; Figure 6 is a schematic illustration of various illustrative patterns in how the projections can be arranged; Figure 7 shows an illustrative example of the orientation of the projections; Y Figure 8 is an image produced in a microscope by electron scanning of a filter at the end of its useful life.

As mentioned, Figure 1 shows an illustrative embodiment of a filter, seen from the initial opening side, which is then covered with the coating plate (not shown). A base plate 1 of the filter is microstructured between the edge regions 2a and 2b. The microstructure provides, in this example, the projection lines 3 which are arranged in a zigzag configuration. It can also be seen that the lines 3 are relatively inclined to one another through an angle alpha.

In this example, the base plate is provided, in addition to the filter and upstream thereof, with another line of projections 4 which form a very rough filter and which serves to agitate the fluid flowing through the filter. An inlet slot 5 is placed upstream of the lines 4 through this the unfiltered fluid passes into the filter. In this mode, the arrangement that joins the filter is the nozzle 6 out of which the filtered fluid can exit. The nozzle 6 has been formed. in this illustrative example, as an integral component of the base plate 1. It will be appreciated that the filter can be formed without the nozzle 6 and the rough filter 4.

Figure 2 is an enlarged view of a portion of Figure 1 showing an array of projections on the lines 3. In this case the projections 7 are membranes or ground plates but, will be described below, these may have an alternate configuration. It can be seen that the lines 3 comprise a plurality of projections 7 which ascend from the base plate 1 and which are separated from one another to provide a fine fluid filter.

Figure 3 is a cross-sectional view through a line of projections taken along the line AA in Figure 2. In this embodiment, the projections 7 have longitudinal sides curved concavely, between these are the passages 8 with cylinder-shaped cross section.

Figure 4 shows a plurality of projection modes, each seen from the initial opening side of the filter (for example from above). Any, or some combination of, the illustrated projections (or any other projection) can be used in the filter described here. Figure 4 shows a plate with rectangular earth 11, a plate with elongated earth 12 of constant width surrounded by narrow sides, a plate in the shape of a frame 13, a ground plate 14 of constant width and with a narrow side extending from inclined way, and a ground plate 12 which is curved with a segment with a circle shape. Also illustrated are a column 16, a triangular column 17, a round column 18 and an octagonal column 19. As mentioned above, any or any combination of these plates with earths are suitable for use in the filter.

Figure 5 shows several cross-sectional views through a variety of different projections, more specifically a projection of a rectangular cross section 21, a projection of a cross section 22 with concavely curved longitudinal sides, a projection of trapezoidal cross-section 23 wherein the long side of the trapezoid is connected to the base plate 1, a projection of the trapezoidal cross section 24 wherein the short side of the trapezoid is connected to the base plate i, and a projection 25 with two rounded longitudinal edges.

Figure 6 shows several arrangements of the projections where the projections - without taking into account the shape of these - are indicated by points of different sizes. The projections may be arranged in the form of array 31 or just in a row 32 or in a serpentine configuration 33 or in a zigzag configuration 34. A plurality of projections arranged in a row configuration 35 or in a serpentine or zigzag configuration 36 may be arranged in succession in relation to a cascad.

Figure 7 shows an illustrative orientation of the plates with. ground relative to the inlet direction of the flow 41 of the fluid.

As shown, some of the plates with ground (indicated with the reference number 42) are arranged in parallel to the flow inlet direction, others of the plates with ground (indicated with the reference numeral 43 are arranged perpendicular to the direction of flow entry and the rest of the plates with ground (indicated with the reference number 44) are arranged in an inclined manner with different angles to the flow inlet direction It should be understood from Figure 7 that the plates with ground do not have to have the same orientation with respect to the direction of flow in. In fact, the provision of ground plates oriented in different ways is a distinctive advantage while the Different orientation serves to improve the degree of fluid agitation as the fluid moves through the filter.

Figure 8 shows an image produced in an electron-scanning microscope of a microstructured filter tai as shown in Figure 1 at the end of its useful life. service. The image was engraved through the glass lining plate (not visible). The image shown illustrates a filter with lines of projections arranged in a zigzag configuration; however, the same projections can not be seen in the selected extension.

The fluid has flowed through the filter in the direction of the arrows during the use of the filter. The particles suspended in the fluid have begun to be trapped by the adjacent projections. As shown, the projection lines are covered with filtered particles, more specifically to a greater degree in the vicinity of the edge regions 2a and 2b than in the central region of the filter. There are no particles in the space between the projection lines, which is on the filter's inlet side of flow; and thus the filter is fully operational in this region (for example, the fluid can still pass through it). As can be seen from Figure 8, the limiting line between the free region of the filter and the clogged region of the filter extends approximately parabolically. As shown in Figure 8, the fluid can still pass through the filter even though a considerable part of the surface area of the filter has already become clogged.

It can therefore be seen that the filter described here is less prone to blockage than the previously proposed filters, whereas this can work properly even when a relatively large portion of the filter surface has become clogged. As a result of this improvement, the useful life of the filter (and thus any device including the filter) can be greatly increased. This is a direct contrast to the previously proposed arrangements where a relatively small amount of filter clogging causes the apparatus to stop functioning correctly.

Example: Microstructured filter for an atomizer As mentioned above, the filter described here finds great utility in the atomizers to produce a .aerosol of a fluid that carries medication.

An illustrative example of an atomizer will now be described. In this illustrative example, the filter is formed on a base plate together with several microstructured components. The base plate is 2.6 mm wide and approximately 5 mm long. In a width of approximately 2 mm it contains 40 rows of projections, with rows arranged in a zigzag configuration. Each row is 1.3 mm long. The projections are rectangular plates with earth, which are 10 μm long and 2.5 μm wide; and these are projected out of the base plate by 5 μm. provided between the plates are the passages which are 5 μm high and 3 μm wide.

Placed on the input side of the filter is a line of 10 rectangular ground plates which are 200 μm long and 50 μm wide; and these are projected out from the base plate by 100 μm. Provided between these plates of earth are the passages which are of iOOμm of high and 150 μm of width. The ten rectangular plates provide a filter flow pattern and a medium for agitating the fluid fluid through it. At a spacing of approximately 300 μm in front of the ground plate line a fluid entering the hole is provided which is approximately 2 mm wide and 100 μm high.

A filtering collection chamber is provided behind the rows of ground plates arranged in a zigzag configuration. The collection chamber of the filtrate is 5 μm high and gradually narrow from a width of 2 μm and which communicates with the rectangular cross-section nozzle which is 5 μm high and 8 μm wide. In this example, the opening of the nozzle occurred at the same time as the base plate was microstructure.

The base plate is 1.5 mm thick comprised of nickel and is prod by electroplating-formed from an insert by plastic molding which contains the complementary structures for 1083 filters. This is coated with a flat nickel plate with 0.8 thickness which is welded to the base plate.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present invention.

Having described the invention as above, it is claimed as property and content in the following.

Claims (25)

Claims

1. A microstructured filter having an inlet for the unfiltered fluid and an outlet for the filtered fluid, characterized in that the filter comprises: a filtration chamber provided between the inlet and outlet, the chamber is partially defined by a substantially flat plate and a cover plate that is secured to this; and a filter body provided within the filter chamber; the filter body is formed by a plurality of projections wherein each comprises an integral component of the base plate and from where each is projected, the projections are spaced from each other by means of passages forming a fluid path through from the filtering chamber from the entrance to the exit, the lining plate is then secured to the base plate covering the projections and the passages; wherein the plurality of projections is arranged in at least two rows extending in a zigzag configuration and with a mutually juxtaposed relationship through the filter chamber; and the inlet and outlet each comprise an elongated slot for the unfiltered fluid and the filtrate respectively, each of the slots is substantially as wide as the filter chamber and substantially as high as the projections on the inlet and outlet sides. of the filter body respectively.

2. A filter according to claim 1, characterized in that the spacing between the base plate and the cover plate is approximately as large as the width of the passages between the adjacent projections.

3. A filter according to claim 1, characterized in that: - a plurality of rows of projections is arranged in cascade form, the cross section of the passages perpendicular to the direction of fluid flow - as seen in the flow direction - decreases from row to row, - The projections that are arranged closer to the inlet side of the filter are larger than the projections that are arranged closer to the filter outlet, and the spacing between the base plate and the liner plate in the area around each of the rows of projections, this row is arranged in the form of a waterfall, is approximately as large as the width of the passages on the side of the projections, where the fluid passes in the row of the passages .

4. A filter according to any of claims 1 to 3, characterized in that the base plate and the coating plate are substantially planar.

5. A filter according to any of claims 1 to 4, characterized in that the inlet opening has a height ratio with a width of 1: 5 to 1: 1000, and the outlet opening has a height-to-width ratio of 1: 5 to 1: 1000.

6. A filter according to any of claims 1 to 5, characterized in that: a spacing between the base plate in the area around the projections and the coating plate within a row of projections is between half and twice the width of the passage on the side of the projections, where the fluid passes within the row of passages.

7. A filter according to any of claims 1 to 6, characterized in that the mutually spaced opposite faces of two rows of adjacent projections define an interconnected space within which the fluid flows through all the passages between the projections of the first row and outside it the fluid flows into all the passages between the projections of the row following the direction of the flow.

8. A filter according to any of claims 1 to 7, characterized in that it comprises: a collection chamber of elongated section between the entrance opening and a first row of projections, inside which passes the unfiltered fluid and leaves it the flow of the fluid in all the passages between the projections of the first row, and a collection chamber of elongated cross section between the last row of projections and the outlet slot, where the flow of the fluid exits from all the passages of the last row and out of this passes the filtered fluid.

9. A filter according to any of claims 1 to 8, characterized in that the projections < = are in the form of plates with earth which - as seen in the direction of flow - are straight or curved; or it is in the form of columns.

10. A filter according to any of claims 1 to 9, characterized in that the passages are of a substantially constant cross section, and have a length that is at least twice as great as their height on the fluid inlet side.

11. A filter according to any of claims 1 to 10, characterized in that the passages are of an approximately constant cross section over the length of the passage, and are of a length of 5μm to 50μm, a height of 2.5μm to 25μm and a width of 2.5 μm to 25 μm.

12. A filter according to claim 11, characterized in that the passages have a substantially square cross section.

13. A filter according to any of claims 1 to 11, characterized in that the passages have a trapezoidal or cylinder-shaped cross section.

14. A filter according to claim 13, characterized in that a longer side of the trapezoidal passage is formed by the lining plate.

15. A filter according to any of claims 1 to 11, characterized in that the passages have an approximately square cross-section on the input side of the filter that becomes wider towards the outlet side of the filter.

16. A filter according to any of claims 1 to 15, characterized in that a spacing between the rows of projections is preferably twice as large as the width of the passage on the input side.

17. A filter according to any of claims 1 to 16, characterized in that the projections are arranged in rows that extend parallel to one another.

18. A filter according to any of the preceding claims, characterized in that the zigzag configuration comprises rows of projections inclined relative to each other through an angle alpha of between 2o to 25 °.

19. A filter according to any of claims 1 to 18, characterized in that the spacing between the base plate in the area around the projections and the coating plate within the row of projections is substantially constant.

20. A filter according to any of claims 1 to 18, characterized in that the spacing between the base plate in the area around the projections and the coating plate within the row of projections is greater in the region of the end of the row. which is in the vicinity of the filter outlet in the region of the end of the row which is in the vicinity of the filter inlet.

21. A filter according to any of claims 1 to 18, characterized in that a spacing between the flat base plate in the area around the projections and the flat coating plate within a row of projections is linearly increased from the end region of the screen. the row which is in the vicinity of the input side of the filter with an address towards the end region of the row which is in the vicinity of the outlet side of the filter.

22. A filter according to any of claims 1 to 21, characterized in that the base plate is structured by isotropic or anisotropic wet or dry etching or a combination of these processes, preferably by dry anisotropic etching.

23. A filter according to any of claims 1 to 22, characterized in that the base plate is silica and the coating plate is made of glass, the base plate is joined to the coating plate by anodic bond.

24. A nebulizer for inhalation therapy, the nebulizer comprises a microstructured filter for the fluid having an inlet for the unfiltered fluid and an outlet for the filtered fluid, characterized in that the filter comprises: a plurality of projections which are arranged in at least one two rows in mutually juxtaposed relation and which are projected outside the motherboard and which are an integral component of the motherboard; a plurality of passages between the projections, and a covering plate that is secured to the base plate to cover the projections and the passages; wherein: the passages form a plurality of trajectories from the entrance to the exit; the inlet comprises an elongated inlet slot for the unfiltered fluid which extends substantially over the entire width of the filter and is substantially as large as the projections projecting outwardly from the base plate on the inlet side of the filter, and the outlet comprises an elongated outlet slot for the filtered fluid that extends substantially over the entire width of the filter and is substantially as large as the projections projecting outwardly from the base plate on the outlet side of the filter.

25. A nebulizer according to claim 24, characterized in that it comprises a nozzle connected to the outlet. »* MICROSTRUCTURED FILTER Summary of the Invention A microstructured filter for a fluid, the filter has an inlet for the fluid without 5 filtering and an output for the filtered fluid, the filter comprises: a plurality of projections (7) that are arranged in at least two rows (3) in mutually juxtaposed relation and which project outside the base plate (i) and the 10 which are an integral component of the base plate, a plurality of passages (8) between the projections (7), and a cover plate which is secured to the base plate to cover the projections (7) and the passages (8) , where The passages form a plurality of paths from the entrance to the exit, the entrance comprising an elongated entrance opening (5) for an unfiltered fluid, which extends for approximately all the The width of the filter and which is approximately as high as the projections (7) projecting out of the plate, on the inlet side of the filter, and the outlet comprises an elongated outlet opening for a fluid. 25 filtering, that is. It extends for approximately the entire width of the filter and is approximately as high as the projections (7) projecting away from the base plate on the outlet side of the filter. The filter according to the invention remains operational, even if a part of the area is obstructed. The filter is used for example in an atomizer where an aerosol of a fluid is produced which contains a medicament.