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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

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 projection (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 atomizer with which an aerosol is produced from a fluid which contains a medicament.

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1. A microstructured filter having an inlet for unfiltered fluid and an outlet for filtered fluid, the filter comprising:a substantially flat base plate and a cover plate that is securable thereto; a plurality of projections, each of which is an integral component of said base plate and each of whic

1. A microstructured filter having an inlet for unfiltered fluid and an outlet for filtered fluid, the filter comprising:a substantially flat base plate and a cover plate that is securable thereto; a plurality of projections, each of which is an integral component of said base plate and each of which projects therefrom, said projections being spaced from one another by passages that form a fluid path through the filter from said inlet to said outlet, said cover plate when secured to the base plate covering said projections and said passages; wherein said plurality of projections are arranged in at least two rows to extend in a zig-zag configuration and in a mutually juxtaposed relationship across the filter; and the inlet and the outlet each comprise an elongate slot for unfiltered and filtered fluid respectively, each of said slots being substantially as wide as the filter and substantially as high as the projections on an inlet side and an outlet side of the filter respectively. 2. A filter according to claim 1, wherein a spacing between the base plate and the cover plate is approximately as large as a width of the passages between adjacent projections.3. A filter according to claim 1, wherein:a plurality of rows of projections are arranged in cascade form, a cross-section of the passages perpendicular to a direction of flow of the fluid, as viewed from the direction of flow, decreases from row to row, the projections which are arranged closer to the inlet side of the filter are larger than the projections which are arranged more at the outlet side of the filter, and a spacing between the base plate and the cover plate in an area around each row of projections, which row is arranged in a cascade form, is approximately as large as a width of the passages on a side of the projections, on which the fluid passes into the row of passages. 4. A filter according to claim 1, wherein said cover plate is substantially flat.5. A filter according to claim 1, wherein said inlet slot has a ratio of height to width from 1:5 to 1:1000, and said outlet slot has a ratio of height to width from 1:5 to 1:1000.6. A filter according to claim 1, wherein:a spacing between the base plate in an area around the projections and the cover plate within a row of projections is between half and double a passage width on a side of the projections on which the fluid passes into the row of passages. 7. A filter according to claim 1, wherein mutually facing sides of two adjacent rows of projections define an interconnected space into which the fluid flows from all passages between the projections of a first row and out of which the fluid flows into all passages between the projections of the row following in a the direction of flow.8. A filter according to claim 1, comprising:a collecting chamber of elongate cross-section between the inlet slot and a first row of projections, into which the unfiltered fluid is passed and out of which the fluid flows into all passages between the projections of the first row, and a collecting chamber of elongate cross-section between a last row of projections and the outlet slot, into which the fluid flows out of all passages of the last row and out of which the filtered fluid is passed. 9. A filter according to claim 1, wherein said projections are either in the form of lands which, as viewed in the flow direction, are straight or curved or are in the form of columns.10. A filter according to claim 1, wherein said passages are of substantially constant cross-section, and have a length that is at least twice as great as their height on an entry side of the fluid.11. A filter according to claim 1, wherein said passages are of an approximately constant cross-section over a passage length, and are of a length of 5 μm to 50 μm, a height of 2.5 μm to 25 μm and a width of 2.5 μm to 25 μm.12. A filter according to claim 11, wherein said passages have a substantially square cross-section.13. A filter according to claim 1, wherein said passages have a barrel-shaped or trapezoidal cross-section.14. A filter according to claim 13, wherein a longer side of each of a trapezoidal cross-section passage is formed by the cover plate.15. A filter according to claim 1, wherein the passages have an approximately square cross-section on the inlet side of the filter that becomes wider towards the outlet side of the filter.16. A filter according to claim 1, wherein a spacing between the rows of projections is preferably twice as great as a passage width on an entry side.17. A filter according to claim 1, wherein said projections are arranged in rows extending parallel to each other.18. A filter according to claim 1, wherein said zig-zag configuration comprises rows of projections inclined relative to each other through an angle alpha of between 2° to 25°.19. A filter according to claim 1, wherein a spacing between the base plate in an area around the projections and the cover plate within a row of projections is substantially constant.20. A filter according to claim 1, wherein a spacing between the base plate in an area around the projections and the cover plate within a row of projections is greater in a region of the end of the row which is in a proximity of the outlet of the filter than in a region of the end of the row which is in a proximity of the inlet of the filter.21. A filter according to claim 1, wherein a spacing between the flat base plate in an area around the projections and the flat cover plate within a row of projections linearly increases from a the region of end of the row which is in a proximity of the inlet side of the filter in a direction towards a region of the end of the row which is in a proximity of the outlet side of the filter.22. A filter according to claim 1, wherein said base plate has been structured by isotropic or anisotropic wet or dry etching or a combination of those processes, preferably by anisotropic dry etching.23. A filter according to claim 1, wherein said base plate is of silicon and said cover plate is of glass, said base plate being joined to said cover plate by anodic bonding.24. A nebulizer for inhalation therapy, the nebulizer comprising a microstructured filter for fluid having an inlet for unfiltered fluid and an outlet for filtered fluid, the filter comprising:a plurality of projections which are arranged in at least two rows in mutually juxtaposed relationship and which project out of a base plate and which are an integral component of the base plate; a plurality of passages between the projections; and a cover plate that is securable to the base plate to cover the projections and the passages wherein, the passages form a plurality of through paths from the inlet to the outlet, said inlet comprises an elongate slot for the unfiltered fluid which extends over substantially an entire filter width and which is substantially as high as the projections projecting out of the base plate on an inlet side of the filter, and said outlet comprises an elongate outlet slot for the filtered fluid which extends over substantially the entire filter width and which is substantially as high as the projections projecting out of the base plate on an outlet side of the filter. 25. A nebulizer according to claim 24, comprising a nozzle connected to said outlet.