Microfluid interaction element for generating and / or detecting a volumetric flow of a fluid and an acoustic device comprising such a microfluidic interaction element

Abstract

The invention relates to a microfluidic interaction element (10, 110, 210, 310, 410) for generating and / or detecting a volume flow of a fluid, wherein the microfluidic interaction element (10, 110, 210, 310, 410) has a substrate (20) with a cavity (30), wherein the cavity (30) has at least one vertically-arranged, rigid wall element (40, 440), which is connected to a ceiling (31) and a floor (32) of the cavity (30), and wherein, in addition, a movable displacement element (50) having vertical surfaces (51) is arranged inside the cavity (30), such that the direction of movement (x) of the displacement element (50) is substantially perpendicular to a main plane of extension of the wall element (40, 440), wherein the displacement element (50) laterally encloses the respective wall element (40, 440) with its vertical surfaces (51), such that a first subspace (41) and a second subspace (42) are formed inside the displacement element (50) by the wall element (40, 440), wherein the microfluidic interaction element (10, 110, 210, 310, 410) has, respectively, a first aperture (61) from the first subspace (41) to an upper side (21) of the substrate (20), and has a second aperture (62) from the second subspace (42) to an underside (22) of the substrate (20). The invention also relates to an acoustic device (500) having at least one microfluidic interaction element (10, 110, 210, 310, 410) according to the invention.

Description

State of the art

[0001] The invention relates to a microfluidic interaction element for generating and / or detecting a volume flow of a fluid, which can be used in particular in a loudspeaker and / or a microphone. DE 10 2017 206766 A1 discloses a microfluidic interaction element for generating and / or detecting a volume flow of a fluid, in particular a MEMS loudspeaker or microphone.

[0002] MEMS loudspeakers and microphones offer significant advantages over conventional electrodynamic loudspeakers and microphones, such as lower latency, reduced energy consumption, smaller size, and their inherent solderability. However, they currently have limitations regarding achievable sound pressure levels. Reaching high sound pressure levels requires displacing a correspondingly large volume of air. This displaced volume can be maximized either by increasing the displacement of a moving displacement element, such as a diaphragm or a bending beam, and / or by increasing the surface area of ​​the displacement element. Larger displacements are difficult to achieve for micromechanical components due to the limited load-bearing capacity of the materials / structures and the low force-generating densities.Furthermore, the bending beams used for actuation are not very robust mechanically, and slight variations in their manufacturing tolerances mean they do not move in phase, which reduces the achievable sound levels. While increasing the horizontal surface area of ​​the displacement element is easier to implement, it is counterproductive in terms of component size and cost.

[0003] The invention is intended to solve the aforementioned problems. Disclosure of the invention

[0004] The invention relates to a microfluidic interaction element for generating and / or detecting a volume flow of a fluid, wherein the microfluidic interaction element comprises a substrate with a cavity, wherein the cavity has at least one vertically arranged, rigid wall element connected to a ceiling and a floor of the cavity, and wherein, in addition, a movable displacement element with vertical surfaces is arranged within the cavity such that the direction of movement of the displacement element is substantially perpendicular to a principal extension plane of the wall element, wherein the displacement element laterally surrounds the respective wall element with its vertical surfaces in such a way that a first sub-space and a second sub-space are formed within the displacement element by the wall element.The microfluidic interaction element has a first opening from the first sub-space to a top surface of the substrate and a second opening from the second sub-space to a bottom surface. A key advantage is that the microfluidic interaction element achieves a very high conversion efficiency from electrical to acoustic energy, enabling correspondingly high sound pressure levels by allowing the displacement element to be set in motion by an actuator. Further advantages include the fact that the interaction element is solderable, as it contains no integrated magnet, has a low latency due to its low mass, and can be manufactured in a very small form. In addition, the interaction element is very robust, and because of the one-piece design of the displacement element, all vertical surfaces can be moved in phase, allowing for higher sound pressure levels.

[0005] Furthermore, the vertical orientation of the surfaces of the displacement element in combination with the vertically arranged wall elements allows the displaced volume per surface to be increased, which in turn can be equated to an increased sound pressure level per surface.

[0006] The microfluidic interaction element can, for example, be designed as a so-called MEMS element. A MEMS element is a micro-electromechanical system that combines or integrates electronic and mechanical components in a very small space.

[0007] A horizontal movement of the displacement element towards a rigid wall element compresses the volume on that side, while the volume on the other side of the rigid wall becomes less dense, as the displacement element moves away from the wall element. Fluid from the compressed volume can flow out into the surroundings through a fluid orifice on one substrate surface, while fluid from the surroundings flows into the less dense volume through another fluid orifice on the opposite substrate surface. In this way, the MEMS element results in a net volume flow of fluid from the surroundings in a direction perpendicular to the main plane of extension of the substrate. If the displacement element moves in the opposite direction, the fluid flow direction is reversed.In other words, the interaction element can be used to generate an acoustic sound wave with positive and negative pressure half-waves in a fluid.

[0008] Depending on the design of the wall element, the main extension plane of the wall element can also be slightly oblique to the direction of movement of the displacement element.

[0009] In physics, the term "fluid" encompasses both liquids and gases. The gas could be, for example, ordinary air, which is moved by the interaction element, thereby generating a volume flow. Volume flow, therefore, refers to the movement of the fluid. This volume flow, if appropriately converted into an oscillating motion, can generate a sound pressure level that is perceptible, for example, to the human ear.

[0010] A substrate can be, for example, a silicon substrate used as a wafer substrate. The substrate undergoes appropriate processing to produce the microfluidic interaction element. This involves machining a cavity into the substrate, forming the cavity with the corresponding openings between the cavity and the substrate's outer surface. The cavity defines the interaction volume of the interaction element and is delimited from its surroundings by the substrate.

[0011] In particular, it is conceivable that the interaction element comprises several wall elements, which are enclosed by the displacement element. The wall elements are planar, vertically arranged, and together with the vertical surfaces of the displacement element, form corresponding first and second sub-spaces within the space enclosed by the displacement element. The displacement element is movably arranged relative to the wall elements along a horizontal direction of movement, which is oriented perpendicular to the main plane of extension of the wall elements. A movement of the displacement element can, for example, generate negative pressure in the corresponding first sub-spaces and simultaneously positive pressure in the second sub-spaces.

[0012] A breakthrough is understood to be an opening in the substrate, which connects the sub-spaces formed in the cavity with the environment of the substrate.

[0013] One embodiment of the invention provides that the displacement element is connected to the substrate via a suspension, in particular a spring-loaded one. An advantage of this is that the suspension ensures the mobility of the displacement element. Furthermore, the spring-loaded design reduces the force required to move the displacement element, as it returns to its original position automatically after being deflected.

[0014] A suspension is a component by which the displacement element is fixed to the substrate.

[0015] One embodiment of the invention provides that the suspension is connected to a wall of the cavity.

[0016] The advantage here is that this provides a simple and robust way to suspend the displacement element laterally within the cavity. The suspension can be arranged either on the walls perpendicular to the direction of movement of the displacement element and / or on the walls in the direction of movement of the displacement element.

[0017] Another embodiment of the invention provides that the suspension is connected to the ceiling and the floor of the cavity.

[0018] An advantage of this type of suspension is that it requires little lateral space, which allows the base area of ​​the microfluidic interaction element to be reduced or kept small.

[0019] In this case, the suspension is designed in a columnar shape and extends from the floor of the cavity to its ceiling.

[0020] According to one embodiment of the invention, the suspension is laterally enclosed by the displacement element.

[0021] The advantage here is that it offers a simple way to achieve vertical suspension. Such a suspension is particularly robust.

[0022] According to a further embodiment of the invention, the suspension is integrated vertically into the displacement element.

[0023] The advantage here is that the space required for the suspension can be further reduced, which allows the microfluidic interaction element itself to be manufactured in a smaller size.

[0024] The term "integrated" here means that the suspension forms part of the displacement element.

[0025] According to a further embodiment of the invention, the microfluidic interaction element comprises an actuator area with an actuator element configured to drive the displacement element along the direction of movement, wherein the actuator element is configured in particular as an electrostatic drive and / or as a piezoelectric drive. It is advantageous that such an actuator element can drive the displacement element uniformly, thereby achieving phase-coherent movement of all vertical surfaces of the displacement element, in order to optimize the generation of the sound pressure level.

[0026] The electrostatic drive can be designed, for example, as a comb drive or as a nanoscopic electrostatic drive (NED). Furthermore, such an actuator element can either be arranged directly on or integrated into the suspension, or it can be designed as a separate structure. With a piezoelectric drive, arranging the actuator element directly on the suspension or on the displacement element itself is advantageous in order to enable direct force transmission from the actuator element to the suspension and thus to the displacement element, or directly to the displacement element. The electrical contact of the actuator element is then achieved, for example, by means of a suitable structure within or on the suspension.

[0027] In particular, the wall elements can also be designed to be electrically insulated from the displacement element, whereby an electrostatic force can be generated by applying a voltage between the wall element and the displacement element, since the wall element and the displacement element act as electrodes and attract or repel each other accordingly.

[0028] In principle, it is also conceivable that an externally driven fluid flow, acting as an external sound pressure level, sets the interaction element, or more precisely the displacement element, in motion. This can then be detected using the reverse actuator principle, with the actuator element acting as a sensor element. Thus, the fluid flow can also be measured accordingly.

[0029] According to a further embodiment of the invention, the first breakthrough and / or the second breakthrough is each less than 200µm, in particular less than 100µm, wide and more than 100µm, in particular more than 500µm, long.

[0030] An advantage here is the low fluid resistance between the sub-chambers and the environment of the interaction element, which allows for a smooth flow of fluid. This is important for the acoustic performance of the interaction element and, in turn, enables high sound pressure levels.

[0031] The width is defined in the direction of movement of the displacement element, whereas the length is defined horizontally perpendicular to the direction of movement of the displacement element.

[0032] According to a further embodiment of the invention, the distance between the wall element and the displacement element on both end faces of the wall element is less than 20µm, in particular less than 10µm.

[0033] An advantage here is the high fluid resistance between the compartments, which reduces fluid leakage due to the necessary gaps between the displacement element and the wall element. This allows for a high sound pressure level at low frequencies.

[0034] The distance here is to be understood as the lateral distance between the wall element and the displacement element perpendicular to the direction of movement of the displacement element.

[0035] According to a further embodiment of the invention, it is provided that the wall element has at least one transverse segment perpendicular to the main extension plane of the wall element at least on one end face, in particular on both end faces.

[0036] The advantage here is that the fluid resistance between the sub-spaces is further increased, and thus the fluid leakage due to the gap between the wall element and the displacement element can be reduced accordingly.

[0037] A further advantage is that at least one transverse segment can serve as a mechanical stop or to dampen movements of the displacement element in undesired directions or with undesirably large movement amplitudes.

[0038] According to a further embodiment of the invention, the vertical distance between the displacement element and the bottom of the cavity and / or between the displacement element and the ceiling of the cavity is less than 5µm, in particular less than 2µm.

[0039] An advantage here is the high fluid resistance between the compartments, which reduces fluid leakage caused by the necessary gaps between the cavity ceiling or floor and the displacement element. This, in turn, allows for a high sound pressure level at low frequencies.

[0040] According to a further embodiment of the invention, the wall element is designed to be wavy and / or bent.

[0041] The advantage here is that an increase in the fill factor of the interaction element can be achieved, which allows for a higher sound pressure level with the same base area of ​​the interaction element or the same sound pressure level with a smaller base area of ​​the interaction element.

[0042] A wall element described as wavy or bent is one which, in plan view, has an undulating shape or is designed in a meandering shape.

[0043] The invention also relates to an acoustic device, in particular a loudspeaker and / or microphone, with at least one microfluidic interaction element according to the invention.

[0044] Loudspeakers are sound transducers that generate sound from an electrical input signal. Microphones, on the other hand, can convert sound into electrical output signals. The sound can be generated or detected by the respective interaction element. In the case of multiple interaction elements in a MEMS device, these can differ in their lateral dimensions and, for example, form a matrix arrangement. The control or evaluation of the interaction elements can then be carried out via shared or separate control lines. In particular, the control is such that, in order to generate an optimal sound pressure level, a phase-coherent displacement of the respective displacement elements can be achieved for all interaction elements. Drawings

[0045] Fig. 1a A first embodiment of a microfluidic interaction element according to the invention is shown in a sectional view as a top view. Fig. 1b shows the first embodiment of a microfluidic interaction element according to the invention. Fig. 1a in a side sectional view. Fig. 2 A second embodiment of a microfluidic interaction element according to the invention is shown in a sectional view as a top view. Fig. 3 A third embodiment of a microfluidic interaction element according to the invention is shown in a sectional view as a top view. Fig. 4 Figure 4 shows a fourth embodiment of a microfluidic interaction element according to the invention in a sectional view as a top view. Fig. 5 Figure 5 shows a fifth embodiment of a microfluidic interaction element according to the invention in a sectional view as a top view. Fig. 6 shows an acoustic device with several microfluidic interaction elements according to the invention. Description of exemplary implementations

[0046] Fig. 1a Figure 1 shows a first embodiment of a microfluidic interaction element according to the invention in a sectional view as a top view. The microfluidic interaction element 10 for generating a volume flow of a fluid (not shown) is depicted, cut along a section plane B and shown in a top view. The exact position of the section plane B is shown in the figure. Fig. 1b visible.

[0047] The microfluidic interaction element 10 has a substrate 20 with a cavity 30.

[0048] The cavity 30 has three vertically arranged, rigid wall elements 40, which are firmly connected to a ceiling 31 and a floor 32 of the cavity 30.

[0049] Furthermore, within the cavity 30 a movable displacement element 50 with vertical surfaces 51 is arranged such that the direction of movement x of the displacement element 50 is essentially perpendicular to the main extension planes of the wall elements 40.

[0050] The displacement element 50 laterally encloses the respective wall element 40 with its vertical surfaces 51 such that each of the wall elements 40 forms a first subspace 41 and a second subspace 42 within the displacement element 50. The distance d between the respective wall element 40 and the displacement element 50 at both end faces 45 of the wall element 40 is less than 20 µm, in particular less than 10 µm.

[0051] Furthermore, each wall element 40 has a transverse segment perpendicular to the main extension plane of the wall element 40 on both end faces 45.

[0052] Furthermore, the microfluidic interaction element 10 has a first opening 61 from the first subspace 41 to a top surface 21 of the substrate 20 and a second opening 62 from the second subspace 42 to a bottom surface 22 of the substrate 20, which is particularly evident in Fig. 1b This is illustrated more clearly. The first breakthrough 61 and / or the second breakthrough 62 can each be less than 200 µm wide, in particular less than 100 µm, and more than 100 µm long, in particular more than 500 µm.

[0053] The displacement element 50 is connected to the substrate 20 via a suspension 70, which is particularly spring-loaded. The suspension 70 is connected to the walls 33 of the cavity 30, and is designed as a transverse beam oriented transversely to the direction of movement x of the displacement element 50. The suspension 70 is arranged on two sides of the displacement element 50 and is connected to the displacement element 50 at its center.

[0054] Furthermore, the microfluidic interaction element 10 has actuator areas 80, each with an actuator element that drives the displacement element 50 along the direction of movement x. The actuator elements can be designed, for example, as electrostatic drives and / or as piezoelectric drives. The actuator element can be arranged on the suspension 70.

[0055] If the displacement element 50 is moved to the right by the actuator elements, for example, the volume in the first sub-chambers 41 is compressed, and the volume in the second sub-chambers 42 is correspondingly increased. Through the first openings 61, fluid from the compressed first sub-chambers 41 can flow out into the vicinity of the interaction element 10, while through the second openings 62 on the opposite substrate surface, fluid from the surroundings flows into the less dense second sub-chambers 42. In this way, a net volume flow of the surrounding fluid is obtained in a direction perpendicular to the main plane of extension of the substrate 20. If the displacement element 50 moves in the opposite direction, the fluid flow direction is reversed. In other words, an acoustic sound wave with positive and negative pressure half-waves can be generated in a fluid using the interaction element 10.

[0056] Fig. 1b The first embodiment of a microfluidic interaction element according to the invention is shown. Fig. 1a in a side sectional view.

[0057] The interaction element 10 is shown again. Fig. 1a , however, this time in a lateral cross-section, which runs along the in Fig. 1a The sectioning plane A shown has been carried out.

[0058] Here, the substrate 20 with the cavity 30 is again shown, in which the rigid wall elements 40 and the displacement element 50, movable in the direction of movement x, with its vertical surfaces 51, are arranged. Furthermore, the first sub-spaces 41 and second sub-spaces 42 formed by the corresponding design and arrangement of the wall elements 40 and the displacement element 50 are shown, which have the first openings 61 to the top 21 of the substrate 20 and the second openings 62 to the bottom 22 of the substrate 20, respectively.

[0059] The vertical distance h between the displacement element 50 and the bottom 32 of the cavity 30 and / or between the displacement element 50 and the ceiling 31 of the cavity 30 is less than 5µm, in particular less than 2µm.

[0060] For example, if the displacement element 50 is, as in Fig.1a As described, when the actuator element moves to the right, this generates a volume flow of the fluid from bottom to top relative to the substrate 20. If the displacement element 50 moves in the opposite direction, the fluid flows in the opposite direction. In other words, the interaction element 10 can generate an acoustic sound wave with positive and negative pressure half-waves in a fluid, as illustrated by the corresponding double arrows.

[0061] Fig. 2 Figure 1 shows a second embodiment of a microfluidic interaction element according to the invention in a sectional view as a top view. A microfluidic interaction element 110 is shown, which differs from the interaction element 10 only in the configuration of the suspension 170. Fig. 1a differs. In this case, the suspension 170 has a longitudinal beam which is connected to the walls 33 of the cavity 30 in the longitudinal direction to the direction of movement x of the displacement element 50.

[0062] Fig. 3 Figure 1 shows a third embodiment of a microfluidic interaction element according to the invention in a sectional view as a top view. A microfluidic interaction element 210 is shown, which in turn is differentiated from the interaction element 10 by the configuration of the suspension 270. Fig. 1a The suspension 270 is centrally located and designed in a column-like manner, and is accordingly connected to the ceiling 31 and the floor 32 of the cavity 30, which is not visible in the illustration, and is also laterally enclosed by the displacement element 50. In this arrangement, the suspension 270 essentially replaces the central wall element 40 in comparison to the interaction element 10. Fig. 1a The centrally arranged, column-like design of the suspension 270 is connected to the displacement element 50 via corresponding springs, on which the actuator area 80 is arranged.

[0063] Fig. 4 Figure 1 shows a fourth embodiment of a microfluidic interaction element according to the invention in a sectional view as a top view. Shown is a microfluidic interaction element 310, which in turn is differentiated from the interaction element 10 by the configuration of the suspension 370. Fig. 1a The suspension 370 is like the suspension 270 in Fig. 3 designed in a column-like manner and connected to the ceiling 31 and the floor 32 of the cavity 30, which is not apparent in the image, whereby the suspension 370, unlike the suspension 270, is made of Fig. 3 The actuator area 80 is vertically integrated into the displacement element 50. The actuator element is arranged directly on the displacement element 50, for example as a piezoelectric layer.

[0064] Fig. 5 Figure 5 shows a fifth embodiment of a microfluidic interaction element according to the invention in a sectional view as a top view. Shown is a microfluidic interaction element 410, which, in the configuration of the wall elements 440, differs from the interaction element 10. Fig. 1a This differs. For example, wall element 440 is designed with an angled shape, resulting in the same base area as interaction element 10. Fig. 1a Four wall elements 440 can be arranged instead of only three wall elements 40. The wall elements 440 again have transverse segments on their end faces 445, wherein the lateral distance d between the end faces 445 of the wall elements 440 and the displacement element 50 is again less than 20 µm, in particular less than 10 µm.

[0065] Fig. 6 shows an acoustic device with several microfluidic interaction elements according to the invention.

[0066] The illustration shows an acoustic device 500, which can be configured, for example, as a loudspeaker and / or microphone. The acoustic device 500 has several microfluidic interaction elements 10, 110, 210, 310, 410, which are arranged side by side in a plane. The loudspeaker can generate corresponding sound pressure levels by means of these microfluidic interaction elements 10, 110, 210, 310, 410. The interaction elements 10, 110, 210, 310, 410 can differ from one another in their lateral dimension and, for example, form a matrix arrangement. The interaction elements 10, 110, 210, 310, 410 can then be controlled by common or separate control lines, which are not shown in the illustration.

Claims

1. Microfluidic interaction element (10, 110, 210, 310, 410) for generating and / or detecting a volume flow of a fluid, wherein the microfluidic interaction element (10, 110, 210, 310, 410) has a substrate (20) with a cavity (30), wherein the cavity (30) has at least one vertically arranged, rigid wall element (40, 440) which is connected to a top (31) and a bottom (32) of the cavity (30), and wherein a movable displacement element (50) with vertical surfaces (51) is additionally arranged within the cavity (30) in such a way that the direction of movement (x) of the displacement element (50) is substantially perpendicular to a main plane of extent of the wall element (40, 440), wherein the displacement element (50) laterally encloses the respective wall element (40, 440) with its vertical surfaces (51) in such a way that the wall element (40, 440) in each case forms a first subspace (41) and a second subspace (42) within the displacement element (50), wherein the microfluidic interaction element (10, 110, 210, 310, 410) in each case has a first aperture (61) from the first subspace (41) to an upper side (21) of the substrate (20) and a second aperture (62) from the second subspace (42) to a lower side (22) of the substrate (20).

2. Microfluidic interaction element (10, 110, 210, 310, 410) according to Claim 1, characterized in that the displacement element (50) is connected to the substrate (20) by way of an in particular resilient mount (70, 170, 270, 370).

3. Microfluidic interaction element (10, 110, 410) according to Claim 2, characterized in that the mount (70, 170) is connected to a wall (33) of the cavity (30).

4. Microfluidic interaction element (210, 310, 410) according to Claim 2, characterized in that the mount (270, 370) is connected to the top (31) and the bottom (32) of the cavity (30).

5. Microfluidic interaction element (210, 410) according to Claim 4, characterized in that the mount (270) is laterally enclosed by the displacement element (50).

6. Microfluidic interaction element (310, 410) according to Claim 4, characterized in that the mount (370) is vertically integrated into the displacement element (50).

7. Microfluidic interaction element (10, 110, 210, 310, 410) according to any of the preceding claims, characterized in that that the microfluidic interaction element (10, 110, 210, 310, 410) has an actuator region (80) with an actuator element which drives the displacement element (50) along the direction of movement (x), wherein the actuator element is designed in particular as an electrostatic drive and / or as a piezoelectric drive.

8. Microfluidic interaction element (10, 110, 210, 310, 410) according to any of the preceding claims, characterized in that the first aperture (61) and / or the second aperture (62) are / is in each case less than 200 µm, in particular less than 100 µm, wide and more than 100 µm, in particular more than 500 µm, long.

9. Microfluidic interaction element (10, 110, 210, 310, 410) according to any of the preceding claims, characterized in that the distance (d) between the wall element (40, 440) and the displacement element (50) on both end sides (45, 445) of the wall element (40, 440) is less than 20 µm, in particular less than 10 µm.

10. Microfluidic interaction element (10, 110, 210, 310, 410) according to any of the preceding claims, characterized in that the wall element (40, 440) has at least one transverse segment perpendicular to the main plane of extent of the wall element (40, 440) on at least one end side (45, 445), in particular on both end sides (45, 445).

11. Microfluidic interaction element (10, 110, 210, 310, 410) according to any of the preceding claims, characterized in that the vertical distance (h) between the displacement element (50) and the bottom (32) of the cavity (30) and / or between the displacement element (50) and the top (31) of the cavity (30) is less than 5 µm, in particular less than 2 µm.

12. Microfluidic interaction element (410) according to any of the preceding claims, characterized in that the wall element (440) is wavy and / or folded.

13. Acoustic device (500), in particular loudspeaker and / or microphone, having at least one microfluidic interaction element (10, 110, 210, 310, 410) according to any of the preceding claims.

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