Microstructural filter

The subject of the invention is a microstructure filter, a method for producing a microstructure filter and an atomizer for inhalation therapy with a microstructure filter. This invention relates to microstructure filters used for liquids.

Various filters are known in which the filter medium has micropores with sizes in the sub-micron compartments, and the size of these pores has a statistical distribution depending on the material. The external dimensions of this type of filtering media are too large compared to the diameter of the average pore (this ratio is expressed by the number ten raised to powers). Experience has shown that they cannot be easily made as small as desired.

Metal belts with micro-holes are also known, which are used in screen printing, with a thickness of up to 100 μηι, containing, for example, nickel, provided with holes evenly distributed throughout the entire belt, with hole diameters expressed in single micrometers. These belts are produced, for example, by galvanic method. Metal belts of this type cannot be assembled with microstructural components.

European Patent No. EP 0 231 432 describes a cross-flow microfilter that is fed with a fluid to be filtered and from which, at the outlet, a concentrate stream and a filter stream are received. Between the fluid chamber and the filter collecting chamber there is a row of shelves or contact surfaces between which there are channels. This row of shelves and channels form a microfilter. The direction of the channels is inclined at an angle of 90 ° to 135 ° relative to the direction of flow of the fluid / concentrate stream. The supplied liquid, which then turns into a concentrate, flows out of the stream next to the row of shelves. The filtrate is collected in numerous chambers and leaves the filter either perpendicular to the filtration surface, or moves in this filtration surface, flowing through numerous channels that extend between the channels for the concentrate.

International patent application number WO 93/11862 discloses a micromechanical filter which is made of three layers. Located on a closed base, the layer in the assumed zones is an intermediate layer and the covering layer with openings is spread on it, which are elongated in the same way as the zone. The intermediate layer does not extend parallel to, and does not bond to, one or both of the longitudinal sides of the holes. In these zones, the cover layer has a cantilever or cantilever configuration. Placed under the cantilever part, the cover layer adjacent to the opening is a shallow groove that has the same dimensions as the thickness of the intermediate layer and is as long as the elongated opening. The filtrate flows through that groove into the filtrate collection chamber, which is larger than the thickness of the intermediate chamber. The cover layer contains a large number of elongated holes that are arranged in rows parallel to each other. These rows of gaps in the cover layer may be in a meandering configuration. The fluid flows through numerous holes perpendicular to the filtration surface, flows into numerous chambers and is removed from many chambers for collecting filtrate, through numerous holes, flowing perpendicular to the filtration surface. The layers of such a filter can be made of silicon, plastic or metal, and are built by etching, embossing, or machining or machining, although methods based on thin coating technology and the precipitation of metal from the vapor phase may also be included. (Vapor Deposition).

These and other devices previously proposed pose many problems. For example, it has been noted that at least some of the previously proposed devices are excessively prone to blocking, after which the device may stop working. In an attempt to alleviate this problem, a larger filter was proposed, but these larger filters had great dead capacity that was undesirable. In addition, some previously proposed devices are not easily assembled with other microstructural components.

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

The microstructure filter having an inlet for unfiltered fluid and an outlet for filtered fluid according to the invention is characterized in that it has a flat base plate and a covering plate attached thereto, and numerous projections, each of which is an integral component of the base plate, each of which protrudes and the performances are

189 969 separated from each other by channels that form fluid passages through the filter from inlet to outlet, the cover plate covering the projections and channels, the multiple projections being arranged in at least two rows along a zigzag line in an interdependent relationship placed side by side and across the filter.

In addition, the filter is distinguished by the fact that both the inlet and outlet respectively contain an elongated slot for unfiltered pflux and for filtered fluid, respectively, and each of the slots has a width of the filter chamber and a height equal to the height of the protrusions on the sides of the filter body, where the inlet and Departure.

The distance between the base plate and the cover plate is approximately equal to the width of the channels between adjacent projections.

Numerous rows of projections are arranged in the shape of a cascade, the cross-section of the channels made perpendicular to the direction of the fluid stream, looking in the direction of flow, decreases going from one row to the next, the projections that are located closer to the inlet side of the filter are larger than the projections that are arranged more on the outlet side of the filter, the distance between the base plate and the cover plate, in the area around each row of projections, with rows arranged in the shape of a cascade, is approximately equal to the width of the channels on the side of the projections through which the fluid passes into the row of channels.

The cover plate is preferably flat.

The inlet slot has a height to width ratio of 1: 5 to 1: 1000, the outlet slot has a height to width ratio of 1: 5 to 1: 1000.

The distance between the base plate in the area around the protrusions and the covering plate inside the row of the protrusions has a size comprised between half the channel width and double the channel width on the side of the projections, where the fluid passes into the cymbals, the sides facing each other of two adjacent rows of projections, defining internally connected space, in which fluid flows from all channels between the first row projections and from which fluid flows into all channels between the next row projections, going in the direction of flow of the stream.

In addition, the filter includes a collection chamber with an elongated cross section, located between the inlet slot and the first row of projections, into which unfiltered fluid enters and from which this fluid exits flowing into all channels located between the projections in the first row, a collection chamber with an elongated cross section, the outlet gap between the last row of projections, into which fluid flows out of all the last-order channels and from which it exits as filtered fluid.

The projections are either in the form of a contact surface, which when viewed in the direction of flow of the stream, are straight or curved, or are in the form of columns.

The channels are of constant cross-section and have a length at least equal to their double height from the fluid inlet side.

The channels are a constant cross-section over the entire length of the channel and have the following dimension range and length from 5pm to 50pm, height from 2.5pm to 25pm, and width from 2.5pm to 25pm.

The channels have a square cross section.

In another embodiment, the channels have a barrel-shaped or trapezoidal cross-section, the longer trapezoidal base in the trapezoidal channels being formed by a cover plate

In yet another embodiment, the channels have approximately a square cross-section on the inlet side of the filter, which widens going towards the outlet side of the filter.

The distance between the rows of protrusions is preferably equal to twice the width of the channel on the input side of the filter.

The projections are arranged in rows extending parallel to each other.

The configuration of the rows is zigzag, with the rows of protrusions inclined to each other at an angle and in the size range from 2 ° to 25 °.

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The distance between the base plate in the area around the protrusions and the cover plate within the row of protrusions is constant.

The distance between the base plate in the area around the protrusions and the cover plate inside the row of the protrusions is greater in the end zone of the row adjacent to the filter outlet than in the end zone of the row which is adjacent to the filter inlet.

In another embodiment, the distance between the flat base plate in the area around the protrusions and the flat covering plate inside the row of the protrusions increases linearly from the end zone of the row located adjacent to the inlet side of the filter towards the end zone of the row which is adjacent to the outlet side of the filter. towards the end zone of the row, which is adjacent to the outlet side of the filter.

The method for producing a microstructure filter with an unfiltered fluid inlet and a filtered fluid outlet according to the invention is characterized in that the base plate is made by wet or dry isotropic or anisotropic etching, or a combination of these processes.

The base plate is made of silicon and the cover plate is made of glass, the base plate being connected to the cover plate by anodic bonding.

Inhalation therapy atomizer with a micro-structured fluid filter with an inlet for unfiltered fluid, characterized by the fact that it has numerous projections, arranged in at least two rows and in mutual arrangement, are next to each other, protruding outwards from the base plate and form an integral all with a base plate, numerous channels between the projections, a cover plate located above the projections and channels, which is attached to the base plate according to the invention is characterized in that the channels form a plurality of through passages extending from the inlet to the outlet, the inlet having an elongated inlet slot for the unfiltered fluid which extends across the entire width of the filter and which has the height of the protrusions protruding from outside of the base plate on the inlet side of the filter, the outlet having an elongated inlet slot for the filtered fluid, which extends across the entire width of the filter, and which has the height of the projections protruding outwardly from the base plate on the outlet side of the filter.

In addition, the atomizer includes a nozzle fitted to the filter.

In the microstructural filter according to another embodiment of the invention, further microstructural jet elements also operating at high pressures are installed on the same base plate, e.g.

A microstructural filter according to various embodiments of this invention may have some or all of the following advantages in that the filter can maintain performance even if some channels are blocked by impurities in the fluid. This is possible because it has a large number of channels per small area. This may allow the use of a filter when it is combined with the nozzle used in the atomizer, and thus improves the atomizer, especially when it is a medication atomizer, when a malfunctioning atomizer over a certain period of use may have fatal consequences for the user .

Channels can be defined within strict boundaries, in terms of shape, cross-sectional area and length (in the most preferred form, the dimensions of all channels inside the filter are the same).

The cross-section of the channel can be adapted to the conditions imposed by further devices, for example to the cross-section of the nozzle which is connected to the channel at the outlet of it.

A large area of ​​the filter surface may be contained within a small filter volume.

Fluid flow can be directed between rows arranged in a meandering configuration or in a zigzag configuration, essentially perpendicular to the direction of flow in the channels, where the fluid flows before it can enter inside the channels.

The filter opening area (the sum of the cross-sectional areas of all channels) can be at least 50% of the total overall filter area.

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The filter may have a small dead capacity, and it can also be easily assembled with other microstructural components.

The microstructure filter described here finds particular application when used to filter medicine dissolved in an aerosol-forming solvent for inhalation applications. Suitable solvents are, for example, water or ethyl alcohol, or a mixture thereof. Suitable medicaments are, for example, Berotec, Atrovent, Berodual, Salbutamol, Combivent, Oxivent, Ba 679, BEA2108, and others.

The filter of this invention can also be used in an atomizer as described in EP 521061.

The microstructural filter described here can be produced in the following exemplary manner: a plurality of base plates joined together, the number of which, for example, is of the order of a thousand, are simultaneously subjected to the production of a microstructure extending over a large surface area and combined in one treatment with a large flat cover plate ( batch process). This combined set can then be divided into many individual pieces.

This production method has some specific advantages. On the one hand, periodic production makes it possible to produce particularly inexpensive individual parts, with a high degree of precision in making exact dimensions of the structure, on the order of several micrometers, with tolerances in the sub-micron compartments, which, using the serial production procedure, could only be carried out at significantly higher costs and, on the other hand, batch production gives the opportunity to achieve the same specified quality of all parts, which can be achieved repeatedly while maintaining the same technological conditions, and there is no likelihood of slow changes, as would be the case, for example, with the manufacturing procedures used in mass production due to wear of the tool.

In addition, the position and location of parts during the process are also predetermined by their design and do not need to be set up and assembled using expensive sorting and conveying equipment, as is the case with some previously proposed systems.

The base plate can be made, for example, by negative ion etching, electroplating, or, in the case of plastics, according to the LGM process, by lithography, electroplating or pressing. There may be further processes that process the structure, aimed at making channels of specific shapes. Trapezoidal and barrel-shaped ducts can be made using specific pickling or pickling methods. Such shapes can be made both by dry etching and wet etching processes. In monocrystalline silicon base plates, the triangular cross-section can be made in multi-directional etching processes. It is recommended that the base plate has a structure made by etching, isotropic or anisotropic, wet or dry, or when using a combination of these processes, dry anisotropic etching is recommended.

The base plate with the microstructure and its protrusions can be combined with a flat plate covering, for example, by anodic bonding of silicon and glass, for example basic borosilicate glass. In one example, a flat glass plate is laid on a silicon plate with a microstructure, which is in contact with the electrode. The whole set is heated to a temperature in the range from 200 ° C to 500 ° C, and a negative voltage of about 1000V is applied at the interface between the silicon plate and the glass plate. Under the influence of this voltage, positively charged alkaline ions pass through the glass to the cathode and there they are neutralized. With this transition, a spatial negative charge is formed between the glass and silicon, which causes electrostatic attraction on these two surfaces and which, in addition, by means of oxygen link bridges, results in a permanent chemical bond between the glass surface and the silicon surface.

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With the reference process described above, the cover plate made of glass is particularly convenient for quality assurance because, on the one hand, the quality of the bond in combination, and on the other hand defects or contained particles causing malfunctioning of the filter can be easily recognized by visual inspection.

After completing the binding procedure, the assembly can be divided into individual filters, preferably using a high-speed diamond circular saw, so that the entry and exit sides of each filter are exposed, if they have not already been exposed. The separating cut can be positioned with a degree of accuracy that is within a few micrometres.

In addition to using an anode bond, the base plate with microstructure can be combined with a flat cover plate by ultrasonic welding, laser welding, gluing or soldering, or some other method obvious to those skilled in the art.

Forms of the invention will now be described, merely as examples, with reference to the accompanying drawings.

The subject of the invention will be seen in the examples of the drawing, in which Fig. 1 is an illustration of an example of a filter, Fig. 2 - an enlarged view showing the arrangement of the protrusions in the rows in the filter of Fig. 1, Fig. 3 - cross section taken along the line AA in Fig. 2, Fig. 4 is a schematic illustration of variations of the various projections, Fig. 5 is a schematic illustration of further projections, Fig. 6 - schematic representation of many sample patterns according to which the protrusions can be arranged, Fig. 7 - illustrative example showing the angular orientation of the protrusions, Fig. 8 - the image of the filter, at the end of its usefulness, produced in a scanning electron microscope.

As mentioned above, Fig. 1 is an illustration of an example of a filter seen from the initially open side, which is then covered with a cover plate (not shown). The filter base plate 1 has a microstructure between the edge sectors 2a and 2b. The microstructure contains, in this case, rows of 3 projections that are arranged in a zigzag configuration. It can also be seen that the rows 3 are inclined to each other, relative to each other, at an angle a.

In this example, the base plate 1 is equipped, in addition to this filter and on the entry side thereof, with a further row of protrusions 7 that form a very coarse filter for gagging the fluid flowing through it. At the access to the protrusions 7 there is an inlet slot 5 through which the unfiltered fluid passes inside the filter. In this example, there is a nozzle 6, which is in a system with the filter, through which the filtered fluid can go out. The nozzle 6 was formed, in this illustrative example, as an integral component forming one whole with the base plate 1. In another version, the filter can also be formed without the nozzle 6 and without the coarse filter 4.

Figure 2 is an enlarged view of a fragment of Fig. 1 showing an exemplary arrangement of projections in rows. In this case, the protrusions 7 are shelves, or contact surfaces, of rectangular cross section, but as will be described later, they may have an alternative configuration. Rows 3 comprise a plurality of projections 7 that protrude upwardly from the base plate 1 and which are spaced apart relative to each other so as to form a filter for thorough cleaning of the fluid.

Figure 3 is a cross-section in a plane passing through the row of projections taken along the line AA in Figure 2. In this exemplary embodiment, the projections 7 have concave curved longitudinal sides, between which there are channels 8 with a barrel cross section.

Figure 4 shows numerous examples of projections, each of which is shown from the initially open side of the filter, i.e. from above. Each of these exemplary performances, or any combination thereof (or any other performance yet), may be used in the filter described herein. Fig. 4 shows a rectangular one. contact surface 11, elongated contact surface 12 of constant width with rounded narrow sides, contact surface 13 of wing shape, contact surface 14 of fixed width and narrow side running obliquely, and contact surface 15 which is curved in the shape of a ring segment. Given

189 969 are also, as examples, a square column 16, a triangular column 17, a round column 18 and an octagonal column 19. As mentioned above, each of these contact surfaces, or any combination thereof, are suitable for use in the filter.

Figure 5 shows various longitudinal sections through various different projections, more specifically: a projection with a rectangular section 21, a projection with a concave section with concave curved longitudinal sides 22, a projection with a trapezoidal section 23 in which the longer trapezoid base is in contact with the base plate 1 , a trapezoidal cross section 24 in which the shorter trapezoid base is in contact with the base plate 1, and a projection 25 with two rounded longitudinal edges.

Figure 6 shows the various arrangements of the projections, where the projections, regardless of their shape, are marked with dots of varying sizes. The projections can be arranged in a matrix form 31, either linearly in row 32, or in the meandering configuration 33, or in the zigzag configuration 34. The multiple protrusions arranged in rows 35, or in the meander or zig-zag configuration 36, can also be arranged in a cascade arrangement .

Figure 7 shows an exemplary orientation of the contact surface relative to the direction of the fluid inlet stream 41. As shown, some contact surfaces (indicated by reference number 42) are arranged parallel to the direction of the inlet stream, other contact surfaces (indicated by reference number 43) are arranged perpendicular to the direction of the inlet stream, and the other contact surfaces (indicated by reference number 44) are deflected under different angles to the inlet stream direction. From fig. 7 it should be concluded that the contact surfaces need not have the same orientation relative to the direction of the inlet stream. In fact, establishing differently oriented contact surfaces is a discernible advantage, as orientation differentiation serves to improve the degree of fluid mixing as it travels through the filter.

Figure 8 is a picture of a microstructural filter such as that shown in Figure 1 at the end of its life-span produced in a scanning electron microscope. The image was recorded by a cover plate (invisible) made of glass. The image shown shows a filter having rows of protrusions arranged in a zigzag configuration, however the protrusions themselves cannot be seen at this selected magnification.

When using the filter, the fluid flowed through the filter in the direction of the arrows, and the particles suspended in the fluid were caught by the adjacent projections. As shown, the rows of projections are covered with filtered particles, and more precisely, this is done more in the vicinity of the edge segments 2a and 2b than in the middle region of the filter. In the space between the rows of protrusions, which is located in the filter from the stream inlet side, there are almost no filtered particles, and thus the filter is fully able to work in this region (that is, fluid can still pass through it). As can be seen in Figure 8, the boundary line between the free region in the filter and the clogged region of the filter extends approximately in the form of a parabolic line. As can be seen from fig. 8, although a significant portion of the filter's surface area has already been clogged, the fluid may even then still pass through the filter.

Thus, it can be seen that the filter described here is less prone to blocking than previously proposed filters because it can still function properly even when a relatively large portion of the filtering surface has been clogged. As a result of this improvement, the service life of the filter (and thus of all devices containing this filter) can increase dramatically. This is a direct contrast to the previously proposed systems, where the relatively small clogging of the filter causes the device to stop functioning properly.

Example: a microstructure filter for an atomizer.

As mentioned above, the filter described here is widely used in atomizers, and especially atomizers for producing an aerosol from a liquid medicament carrier.

One of these nozzles will be described below as an illustrative example. In this illustrative example, the filter is formed on the base plate along with a certain amount

189 969 other microstructural components. The base plate has a width of 2.6 mm and about 5 mm in length. At a width of about 2 mm it contains 40 rows of projections arranged in a zigzag configuration. Each row has a length of 1.3 mm. The projections are rectangular contact surfaces, 10 pm long and 2.5 pm wide, and protrude outwards from the 5 pm base plate. Between the contact surfaces are provided channels that are 5 pm high and 3 pm wide.

On the inlet side of the filter fluid, a row of 10 rectangular contact surfaces are arranged, which are 200 pm long and 50 pm wide, they protrude outwards from the 100 pm base plate. Between these contact surfaces are provided channels that are 100 pm high and 150 pm wide. These ten rectangular contact surfaces form a coarse filter and a system for gagging the fluid flowing through it. At a distance of about 300 pm in front of this row of contact surfaces, there is a fluid entry slot provided which is approximately 2 mm wide and 100 pm high.

In addition to the rows of contact surfaces arranged in a zigzag configuration, a filtrate collection chamber is provided. The filtrate collecting chamber is 5 pm high and narrows gradually starting from 2 mm wide, this chamber has a communication connection with a rectangular cross-section nozzle, which has a height of 5 pm and a width of 8 pm. In this example, the nozzle opening was made simultaneously with the microstructure. base plates.

The base plate, which is 1.5 m thick, contains nickel and is made by electroplating technology of the plastic molded insert, this insert includes complementary structures for 1083 filters. It is covered with a 0.8 mm flat nickel plate, which is soldered to the base plate.

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