DE102020110404A1 - Improved Process for Making a Perforated Membrane - Google Patents

Abstract

The present invention relates to a method for producing a perforated membrane for use in a fluid transfer device, the perforated membrane (1) having a contour (19) and a plurality of continuous nozzles (10), of which an average diameter is 100 μm or less, the A method comprising the shaping of the nozzles (10) by means of laser drilling, laser energy being applied selectively and in a controlled manner to positions on a surface of the membrane on which nozzles (10) are to be molded, the contour (19) of the membrane (1) by means of etching is shaped. Furthermore, a perforated membrane produced by means of the method and a fluid transfer device using this are presented.

Description

The present invention relates to a method of making perforated membranes suitable for use in a fluid transfer device. The fluid transfer or also fluid transport devices discussed here include, for example, nebulizers for atomizing liquids, pumps for generating a pressure difference and / or a directed fluid flow, and filters for filtering out particles from a fluid. The invention also relates to a membrane produced by means of the method according to the invention and its use in a fluid transfer device.

In the prior art, perforated membranes, usually circular in contour, i.e. H. Known outline comprising a variety of fine nozzles. These nozzles usually have a cross-section that changes in their course in order to achieve certain fluid transport properties through the nozzles. Such membranes are used in various fluid transfer devices, such as the aforementioned nebulizers, pumps or filters.

In a pump, an effective fluid transport is to be achieved by means of the membrane. For this purpose, the membrane is usually moved back and forth periodically, or in pumps with a static membrane, the liquid is passed over the membrane by means of a piston that is moved back and forth periodically. When moving in one direction, fluid is pushed back through the nozzles of the membrane and when moving in the opposite direction. In order to achieve an effective fluid transport in a desired direction averaged over the movement cycle, nozzles with a cross-sectional profile that is not symmetrical with respect to the membrane planes are used. In particular nozzles in which the cross-section widens from one side to the opposite side pointing in the desired transport direction. Due to the different flow properties of the nozzles in the two opposite directions, when the nozzles move in the direction of the side with the smaller nozzle cross-section, more fluid is transported through the nozzles than in the opposite direction, which on average results in fluid transport.

Pumps using a moving membrane have the advantage that they are mechanically simpler than rotation-based pumps. Miniaturization is also more easily possible. This is offset by the disadvantage of a higher power consumption per given flow rate. It is important here to optimize the nozzle cross-sections or the cross-sectional progressions along the nozzle, so that the power consumption is minimized.

In filtering, the goal is to retain particles suspended in the fluid. To ensure this, the nozzle must have a diameter that is smaller than all the linear dimensions of the particles to be retained. In order for a perforated membrane to be used effectively as a filter, it is therefore important that the sizes of the individual nozzles differ from one another as little as possible, otherwise uniform and reliable filtering cannot be ensured.

Perforated membranes are also used in the aerosol generators of nebulizers and are usually referred to as mesh membranes. The aim of a nebulizer is to atomize a liquid, which often contains a dissolved active ingredient, i.e. H. to atomize into a mist of fine droplets. Often the goal is for the patient to be able to inhale this mist as deep as possible into the lungs, e.g. into the alveoli. For such respiratory penetration, droplet sizes of 5 µm or less must be achieved.

A perforated or mesh membrane is now used in the aerosol generator of a nebulizer in such a way that the drug liquid is present on a supply side. If the membrane is now set in periodic oscillations in the direction of the surface perpendicular of the membrane, this causes pressure fluctuations in the fluid on the supply side, which pushes it through the nozzles and releases it as a mist of fine droplets on the opposite exit side. The droplet size, and as another important parameter also the efficiency, i.e. H. The energy efficiency as well as the percentage of the drug liquid that is actually released as a mist and not deposited as condensate on the outlet side of the membrane should be as high as possible. These depend on various factors, for example the mean diameter of the nozzles, the change in cross-section in the course of the nozzles and the presence of surface unevenness in the interior of the nozzle or at the nozzle inward or outward openings.

The European published application EP 1 295 647 A1 discloses, for example, a perforated membrane in which the nozzles have two clearly differentiated sections in their course, namely an approximately cylindrical nozzle neck with a smaller diameter, and continuously widening area adjoining the nozzle neck. According to the teaching there, the transition between the nozzle neck and the widening area should not be continuous, but rather have a kink, since this advantageously prevents any liquid still remaining in the nozzle from being completely ejected from the nozzle after the droplet has been dispensed which would result in the nozzle having to be completely filled with liquid again when the membrane springs back.

The above document also discloses a manufacturing method for such a perforated membrane by means of laser drilling. This method uses a two-step process, with the widening area being shaped in a first step and, after changing the laser focus, the neck area of the nozzle being shaped in a second step. In order to achieve a possible smooth and even inner nozzle surface, an electropolishing step is then recommended to remove sharp surface structures. The disadvantage here is that the method here is a three-step process, in which, especially during laser drilling, the parameters such as the position of the laser focus and the applied laser energy must be controlled very precisely. Furthermore, this method is also poorly suited to cutting out or working out the contour of the membrane.

Another disadvantage of the use of laser drilling is that it is suitable here for the production of microscopic structures, understood here as structures smaller than approx. 100 μm. Either much more time or significantly higher laser energies are required to produce larger structures. However, higher energies have the consequence that an exact shaping is made more difficult. The macroscopic structures can only be produced with the desired accuracy iso with difficulty. The possible permanent damage to the membrane material in and around the processed areas is even more problematic. Since the thermal load during laser drilling can become very high, the material of the membrane can change disadvantageously, creating weak points that can significantly reduce the service life of the membrane. In the case of metallic membranes, for example, the crystal structure can change in the areas macroscopically processed with the laser, so that fatigue fractures occur more quickly there. Local weakening is also difficult to prevent with polymer membranes.

The present invention is therefore based on the object of finding an alternative method for producing a perforated membrane, which in particular also allows the contour of the membrane and, if necessary, additional macroscopic structures in a material-conserving, simpler and cheaper way.

This object is achieved by a method according to claim 1, which is used to produce a perforated membrane according to claim 8. According to the invention, the perforated membrane is used in a fluid transfer device according to claim 13 or 14.

A first aspect of the present invention is a method of making a perforated membrane, the membrane having a plurality of fine microscopic nozzles. In this context, microscopic or fine should mean that the nozzles have an average diameter of 100 μm or less. In the course of the method according to the invention, the nozzles are introduced into the membrane by means of laser drilling, the laser drilling comprising the fact that laser energy is focused and controlled in a controlled manner at each point at which a nozzle is to be created. This brings about a local ablation of the membrane material, depending on the laser energy, more or less localized heating or direct breaking of the chemical bond.

Essential to the invention is the contour of the membrane, d. H. their outline, and possibly other macroscopic structures that may be present in addition to the microscopic nozzles, produced by means of etching. In this case, the etching comprises, in a manner known per se, a step in which a photosensitive material is applied to a membrane surface and then exposed to light of a wavelength to which this material is sensitive via a mask. The exposed areas are then removed using a chemical bath. The places where the coating material was removed are vulnerable to the actual etching liquid. After the treatment in an etching bath, the contour of the membrane and other macroscopic structures that may be required are created.

Compared to the complete production of the membrane by means of laser treatment methods, for example the above-mentioned laser drilling or laser cutting, this has the advantage of lower energy consumption, greater accuracy of the possible macroscopic structural shapes and lower thermal stress on the membrane material, which is usually a thin metal, ceramic or is a polymer.

Another aspect of the present invention is a perforated membrane with a contour and at least one macroscopic structure, which is present in addition to the microscopic nozzles. Such a structure can consist, for example, of a notch machined into the membrane or a continuous opening. Such a perforated membrane with an additional macroscopic structure can be produced more simply, more cheaply and less stressful for the membrane material by means of the method according to the invention than with known methods.

Another aspect is a fluid transfer device, for example a nebuliser, a pump or a filter, with a perforated membrane with an additional macroscopic structure or with a perforated membrane which was produced by means of the method according to the invention.

Preferred further developments of the present invention, which can be implemented individually or in combination, provided they are not obviously mutually exclusive, are to be presented below.

In embodiments of the method according to the invention, the etching of the contour and possibly the at least one macroscopic structure takes place before the laser drilling of the microscopic nozzles. In these embodiments, however, the inner surface of the nozzles is generally irregularly shaped, so that a subsequent finishing step, for example in the form of electropolishing, is necessary to produce a uniform nozzle shape. Here, sharp surface structures, which have arisen from the thermal heating and re-cooling of the membrane material during laser drilling, are removed by immersion in an electrolyte bath under voltage. Other polishing methods which are suitable, nozzles with a corresponding fineness here in the range of 100 μm or less, in particular 10 μm or less, can also be used.

In particularly preferred embodiments of the present invention, the etching of the contour takes place under macroscopic and optionally one or more macroscopic structures after the laser drilling of the microscopic nozzles. In this case, the nozzles, which are initially irregularly shaped, are first introduced into the membrane blank by means of a laser, and then the blank, which can already be equipped with a photosensitive layer at the beginning, is exposed via a mask and then etched as described above . Carrying out the etching after laser drilling has the advantage that the etching process removes the irregularities and undesired sharp surface structures in the nozzles, so that a subsequent post-treatment step is no longer necessary.

In order to avoid that the microscopic nozzles are enlarged too much by the etching, either as an intermediate step a thin layer of a layer protecting the membrane material in the area of the large number of microscopic nozzles from the etching liquid can be applied, which is separated comparatively more slowly than during the etching the membrane material itself. It is important to ensure that this layer is not so thick that the nozzles completely escape the etching liquid. Alternatively, the photosensitive layer can also be applied by laser drilling after the nozzles have been produced. Due to the fineness of the nozzles, less photosensitive material is generally deposited inside the nozzle than on the unprocessed, smooth surface of the membrane blank. As a result, the suitably selected photosensitive material in the area of the nozzles dissolves more quickly through the etching liquid than on the untreated and unexposed smooth surface.

In preferred embodiments, several membranes are advantageously machined from a flat membrane blank.

The perforated membrane according to the invention preferably has one or more continuous openings as an additional macroscopic structure. The radius of the preferred cylindrical openings is in particular more than 100 μm, particularly preferably more than 200 μm, very particularly preferably more than 500 μm.

The contour of the membrane is preferably circular, which makes it particularly suitable for use in nebulizers. Here, the microscopic nozzles are arranged, in particular, in an inner region of the membrane surface, for example within a circle of approximately half the membrane contour radius. Furthermore, more than one passage opening is preferably arranged in an edge region of the membrane surface, it being particularly preferred that these are distributed evenly over the edge region.

The fluid transfer device according to the invention is preferably a nebulizer with an aerosol generator which, in addition to the perforated membrane according to the invention or a perforated membrane produced using the method according to the invention, has a circular piezoelectric crystal, which can be used to set the membrane in oscillation with circularly symmetrical waveforms.

Further properties, features and advantages of the present invention emerge from the preferred exemplary embodiments explained in more detail below with reference to the figures. These are only intended to illustrate the invention and in no way limit its generality.

• 1: Eine erste bevorzugte Ausführungsform des erfindungsgemäßen Verfahrens, bei dem das Ätzen der Konturen nach dem Laserbohren der mikroskopischen Düsen erfolgt.
• 2: Eine zweite bevorzugte Ausführungsform des erfindungsgemäßen Verfahrens, bei dem das Laserbohren der mikroskopischen Düsen nach dem Ätzen der Konturen und einer makroskopischen Struktur erfolgt.
• 3: Ein Beispiel einer Ausführungsform einer erfindungsgemäßen perforierenden Membran mit einer Vielzahl durchgängiger Öffnungen als makroskopische Strukturen.

Show it:

• 1 : A first preferred embodiment of the method according to the invention, in which the etching of the contours takes place after the laser drilling of the microscopic nozzles.
• 2 : A second preferred embodiment of the method according to the invention, in which the laser drilling of the microscopic nozzles takes place after the etching of the contours and a macroscopic structure.
• 3 : An example of an embodiment of a perforating membrane according to the invention with a large number of continuous openings as macroscopic structures.

1 shows in five sub-figures AE, all of which show the membrane schematically in cross section, a first preferred embodiment of a method according to the invention for manufacturing a perforated membrane.

After a membrane blank 1' with a top layer 2 Photosensitive material has been provided, in a first step, as shown in part A, the desired number of microscopic nozzles by means of laser drilling 10 (here two) of a desired cross-section and cross-sectional progression in the blank 1' brought in. The process of laser drilling is indicated here at a point 10 ', at the laser energy by means of the lens 3 is focused on the membrane surface. In the process, more or less pronounced surface irregularities remain almost inevitably 13th back after the membrane material has cooled and solidified again after laser drilling, during which it was locally liquefied by the laser energy.
This is followed, as illustrated in part B, that exposure to light 5 a wavelength for which the photosensitive material 2 is sensitive. This causes a chemical reaction in the exposed areas, here 20 'and 20 ", which makes the material removable by means of a developer liquid. The exposure takes place via masks 4th , 4 ', 4 ", which, in addition to the contours of the individual perforating membrane to be produced, also shows any macroscopic structures present therein.
In C. the situation after developing the exposed membrane blank is shown. The photosensitive layer was removed by the development in the exposed areas 20 ', 20 "shown in dotted lines in part B.
D. shows the membrane 1 after etching. As can be seen, the inner walls of the nozzles were made 10 advantageously smoothed by the etching process. Furthermore, the contour 19th the membrane 1 worked out.
Finally, part E shows the state after the removal of the photosensitive layer, either mechanically or chemically, and thus the finished membrane 1 shown. Left and right are further, neighboring and from the same blank 1' molded membranes 1 indicated. These further membranes can be designed in the same way or differently.

In 2 similar to in 1 In five sub-figures AE, the membrane according to the invention is shown after the individual steps of a second embodiment of the production method according to the invention, which first knows the contour by etching, as shown in sub-figures A to C 19th as well as continuous openings 11 shaped and then, as in the C. -E shown the microscopic nozzles 10 created and the inner walls are smoothed. The relative size of the nozzles 10 and the macroscopic through openings 11 is not true to scale here.

Partial figure A shows the exposure of the membrane blank 1' via the mask (s) 4 with light 5 , which exposes the areas 20, 20 'and 20 ". In part B, the exposed areas 20, 20', 20" were removed by the development.
C. shows the state after etching through which the contour 19th as well as the macroscopic openings 11 the membrane 1 have already been created. A microscopic nozzle is also shown as an example in the partial figure 10 by means of laser drilling in the central area of the membrane 1 molded. The result of this step is in D. shown, which still with bumps on their inner walls 13th damaged nozzle 10 shows. In this form, the membrane is usually not (well) usable because of the unevenness 13th lead to significant disadvantages, such as loss of efficiency or an increase in the mean droplet size and worsening of the droplet size distribution of the mist produced when used in nebulisers.
That's why the bumps become 13th in a subsequent post-treatment step, such as electropolishing or another brief immersion in the etching bath. The result is the finished membrane shown in part E. 1 with contour 19th , microscopic nozzles 10 and macroscopic continuous openings 11 . As in 1 are also here other neighboring ones, from the same blank 1' molded membranes 1 indicated.

3 shows a schematic plan view of an example of a preferred embodiment of a perforated membrane according to the invention with a circular contour 19th which in a central area 12th a variety of microscopic nozzles 10 and in the edge area a large number of macroscopic through-openings distributed evenly and circumferentially 11 having.

List of reference symbols

1'

Membrane blank

1

membrane

10

microscopic nozzle

11

macroscopic opening

12th

inner area

13th

Surface irregularities

19th

contour

2

photosensitive layer

3

Laser lens

4th

Exposure mask

5

Light for exposure

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 1295647 A1 [0008]

Claims (15)

A method of manufacturing a perforated membrane for use in a fluid transfer device, the perforated membrane (1) having a contour (19) and a plurality of continuous nozzles (10), of which an average diameter is 100 µm or less, the method comprising Shaping the nozzles (10) by means of laser drilling, with laser energy being applied selectively and in a controlled manner to positions on a surface of the membrane on which nozzles (10) are to be formed, characterized in that the contour (19) of the membrane (1) by means of Etching is shaped. Procedure according to Claim 1 , characterized in that the etching is carried out before the laser drilling. Procedure according to Claim 2 , characterized in that a post-treatment step for removing surface unevenness (13), in particular surface unevenness remaining in the nozzles (10) after laser drilling, is carried out. Procedure according to Claim 1 , characterized in that the etching is carried out after the laser drilling. Procedure according to Claim 4 , characterized in that no post-treatment takes place. Method according to one of the preceding claims for producing a membrane with an additional macroscopic structure, in particular a notch or a continuous opening (11) which has an average diameter of greater than 100 µm, in particular greater than 200 µm, characterized in that the at least a macroscopic structure is also formed by means of etching. Perforated membrane for use in a fluid transfer device, the membrane (1) having a contour (19) and a plurality of continuous nozzles (10), of which an average diameter is 100 µm or less, characterized by at least one macroscopic structure formed by etching (11). Membrane after Claim 7 , characterized in that the at least one macroscopic structure (11) is one or more continuous openings (11) with an average diameter of more than 100 µm, in particular more than 200 µm. Membrane according to one of the Claim 7 or 8th , characterized in that the nozzle (10) is arranged in an inner region (12) of the membrane surface and the at least one macroscopic structure (11) is arranged in an edge region of the membrane surface. Membrane according to one of the Claims 7 until 9 , characterized by a large number of macroscopic structures (11), in particular through openings. Membrane after Claim 10 , characterized by a circular contour (19) with macroscopic structures distributed over the circumference, in particular through openings (11). Membrane according to the previous one Claim 11 , characterized in that the macroscopic structures (11) are evenly distributed over the circumference of the contour (19) of the membrane (1). Fluid transfer device with a perforated membrane according to one of the Claims 7 until 12th . Fluid transfer device with a according to one of the Claims 1 until 7th manufactured perforated membrane. Fluid transfer device according to one of the Claims 13 or 14th , characterized in that the fluid transfer device is a nebulizer with an aerosol generator.

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