Microfluidic interaction element for generating and / or detecting a volume flow of a fluid and an acoustic device having such a microfluidic interaction element
Patent Information
- Application Number
- EP2023744706
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-09-05
- Filing Date
- 2023-07-13
- Publication Date
- 2025-07-16
- Estimated Expiration
- 2043-07-13
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] Microfluidic interaction element for generating and / or detecting a volume flow of a fluid and an acoustic device with such a microfluidic interaction element
[0003] State of the art
[0004] 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.
[0005] MEMS loudspeakers and microphones offer significant advantages over conventional electrodynamic loudspeakers and microphones, including lower latency, lower energy consumption, smaller size, and the ability to be soldered in principle. On the other hand, they currently still have shortcomings with regard to achievable sound levels. To achieve high sound levels, a correspondingly large volume of air must be displaced. The displaced volume can be maximized either by larger deflections of a moving displacement element, such as a membrane or a cantilever beam, and / or by increasing the surface area of the displacement element. Larger deflections are difficult to achieve for micromechanical components due, on the one hand, to the lack of load-bearing capacity of the materials / structures and, on the other hand, to low force generation densities.Another disadvantage is that the bending beams used for actuation are not very robust mechanically and the slight variation in their manufacturing tolerances means that they do not move in phase, which reduces the achievable sound levels.
[0006] Although enlarging the horizontal surface of the displacement element is easier to implement, it is counterproductive in terms of component size and costs.
[0007] The invention is intended to solve the problems mentioned. Disclosure of the invention
[0008] 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 comprises at least one vertically arranged, rigid wall element which is 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 main extension plane of the wall element, wherein the displacement element laterally encloses the respective wall element with its vertical surfaces such that a first sub-chamber and a second sub-chamber are formed within the displacement element by the wall element,wherein the microfluidic interaction element has a first opening from the first subspace to a top side of the substrate and a second opening from the second subspace to a bottom side.,
[0009] The advantage here is that the microfluidic interaction element enables very high conversion efficiency from electrical to acoustic energy, thus achieving correspondingly high sound pressure levels. The displacement element can be set in motion by an actuator element. Further advantages include the solderability of the interaction element, as no magnet is integrated, its low latency due to its low mass, and its compact design. Furthermore, the interaction element is very robust, and the one-piece design of the displacement element allows all vertical surfaces of the displacement element to be moved in phase, making higher sound levels achievable.
[0010] The vertical alignment of the displacement element's surfaces, in conjunction with the vertically arranged wall elements, also allows for an increase in the displaced volume per unit area, which in turn can be equated with an increased sound pressure level per unit area. 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.
[0011] By moving the displacement element horizontally towards a rigid wall element, a partial volume on this side is compressed, while the partial volume on the other side of the rigid wall is rarefied as the displacement element moves away from the wall element. Fluid from the compressed partial volume can flow into the environment through a fluid opening on one substrate surface, while fluid from the environment flows into the rarefied partial volume through another fluid opening on the opposite substrate surface. In this way, a net volume flow of the ambient fluid through the MEMS element occurs 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.
[0012] Depending on the design of the wall element, the main extension plane of the wall element can also be slightly inclined relative to the direction of movement of the displacement element.
[0013] In physics, the term "fluid" refers to liquids and gases. The gas can be, for example, ordinary air, which is moved by the interaction element, thereby generating a volume flow. Volume flow is therefore understood as the movement of the fluid. When implemented appropriately, this volume flow can generate a sound pressure level as an oscillating movement, which is perceptible, for example, to the human ear.
[0014] A substrate can be understood, for example, as a silicon substrate used as a wafer substrate. The substrate is processed accordingly to produce the microfluidic interaction element. A recess is machined into the substrate, forming the cavity with the corresponding openings between the cavity and the substrate exterior. The recess, in turn, defines the interaction volume of the interaction element and is separated from the environment by the substrate.
[0015] In particular, it is conceivable for the interaction element to comprise a plurality of wall elements that are correspondingly enclosed by the displacement element. The wall elements are flat, arranged vertically, 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 arranged to be movable relative to the wall elements along a horizontal direction of movement that is oriented perpendicular to the main extension plane of the wall elements. By moving the displacement element, for example, negative pressure can be generated in the corresponding first sub-spaces and positive pressure can be generated simultaneously in the second sub-spaces.
[0016] A breakthrough is an opening in the substrate which connects the sub-spaces formed in the cavity with the environment of the substrate.
[0017] One embodiment of the invention provides for the displacement element to be connected to the substrate via a particularly resilient suspension. This suspension ensures the mobility of the displacement element. The resilient design also reduces the force required to move the displacement element, as it automatically returns to its original position upon deflection.
[0018] A suspension is understood to be a component by which the displacement element is fixed to the substrate. One embodiment of the invention provides that the suspension is connected to a wall of the cavity.
[0019] The advantage here is that this represents a simple and robust way to suspend the displacement element laterally within the cavity. It is conceivable that the suspension is 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.
[0020] A further embodiment of the invention provides that the suspension is connected to the ceiling and the floor of the cavity.
[0021] The advantage here is that this type of suspension requires little lateral space, which means that the footprint of the microfluidic interaction element can be reduced or kept small.
[0022] In this case, the suspension is column-shaped and extends from the floor of the cavity to its ceiling.
[0023] According to one embodiment of the invention, it is provided that the suspension is laterally enclosed by the displacement element.
[0024] The advantage here is that it offers a simple way to implement a vertical suspension. This type of suspension is particularly robust.
[0025] According to a further embodiment of the invention, it is provided that the suspension is integrated vertically into the displacement element.
[0026] The advantage here is that the space required for the suspension can be further reduced, which means that the microfluidic interaction element itself can be made smaller.
[0027] Integrated here means that the suspension is part of the displacement element.
[0028] According to a further embodiment of the invention, the microfluidic interaction element comprises an actuator region 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. Advantageously, such an actuator element can drive the displacement element uniformly, thereby achieving in-phase movement of all vertical surfaces of the displacement element, in turn optimizing the generation of the sound pressure level.
[0029] The electrostatic drive can be designed, for example, as a comb drive or as an NED (Nanoscopic Electrostatic Drive). Furthermore, such an actuator element can either be arranged directly on the suspension or integrated into it, or it can be designed as a separate structure. With a piezoelectric drive, it is advisable to arrange the actuator element directly on the suspension or on the displacement element itself 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 corresponding structure within or on the suspension.
[0030] 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.
[0031] In principle, it is also conceivable that an externally driven volume flow of the fluid, 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 by the actuator element as a sensor element. Thus, a volume flow of a fluid can also be detected accordingly. According to a further embodiment of the invention, the first opening and / or the second opening are each less than 200 μm wide, in particular less than 100 μm, and more than 100 μm long, in particular more than 500 μm.
[0032] The advantage here is that there is low fluid resistance between the subspaces and the environment of the interaction element, allowing for easy volume flow of the fluid. This is important for the acoustic performance of the interaction element and, in turn, enables high sound pressure levels.
[0033] The width is defined in the direction of movement of the displacement element, whereas the length is defined horizontally across the direction of movement of the displacement element.
[0034] According to a further embodiment of the invention, it is provided that the distance between the wall element and the displacement element on both end faces of the wall element is less than 20 pm, in particular less than 10 pm.
[0035] The advantage here is that there is a high fluid resistance between the subchambers, which reduces fluid leakage due to the necessary gaps between the displacement element and the wall element. This enables a high sound pressure level at low frequencies.
[0036] The distance is to be understood as the lateral distance between the wall element and the displacement element transverse to the direction of movement of the displacement element.
[0037] According to a further embodiment of the invention, the wall element has at least one transverse segment perpendicular to the main extension plane of the wall element on at least one end face, in particular on both end faces. This is advantageous in that the fluid resistance between the subchambers can be further increased, thus correspondingly reducing fluid leakage due to the gaps between the wall element and the displacement element.
[0038] A further advantage is that the at least one transverse segment can serve as a mechanical stop or also to dampen movements of the displacement element in undesirable directions or with undesirably large movement amplitudes.
[0039] According to a further embodiment of the invention, it is provided that the vertical distance between the displacement element and the floor of the cavity and / or between the displacement element and the ceiling of the cavity is less than 5pm, in particular less than 2pm.
[0040] The advantage here is that there is a high fluid resistance between the subchambers, which reduces fluid leakage due to the necessary gaps between the cavity ceiling or floor and the displacement element. This, in turn, enables a high sound pressure level at low frequencies.
[0041] According to a further embodiment of the invention, it is provided that the wall element is designed to be wave-shaped and / or bent.
[0042] The advantage here is that an increase in the fill factor of the interaction element can be achieved, whereby a higher sound pressure level can be achieved with the same base area of the interaction element or the same sound pressure level with a smaller base area of the interaction element.
[0043] A wall element is to be understood as wavy or kinked if, when viewed from above, it has, for example, an undulating shape or is designed in a meandering manner.
[0044] The invention also relates to an acoustic device, in particular a loudspeaker and / or microphone, comprising at least one microfluidic interaction element according to the invention. Loudspeakers are sound transducers that generate sound from an electrical input signal. Microphones, in turn, 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 component, these can differ from one another in their lateral dimension and, for example, form a matrix arrangement. The control or evaluation of the interaction elements can then be carried out via shared or separately designed control lines.In particular, the control is carried out in such a way that, in order to generate an optimal sound pressure level, a deflection of the respective displacement elements that is in phase with all interaction elements can be achieved.
[0045] Drawings
[0046] Fig. 1a shows a first embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view.
[0047] Fig. lb shows the first embodiment of a microfluidic interaction element according to the invention according to Fig. la in a side sectional view.
[0048] Fig. 2 shows a second embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view.
[0049] Fig. 3 shows a third embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view.
[0050] Fig. 4 shows a fourth embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view.
[0051] Fig. 5 shows a fifth embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view. Fig. 6 shows an acoustic device with several microfluidic interaction elements according to the invention.
[0052] Description of implementation examples
[0053] Fig. 1a shows a first embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view. It depicts microfluidic interaction element 10 for generating a volume flow of a fluid (not shown in the image), which is cut open along a sectional plane B and shown in a plan view. The exact position of sectional plane B is shown in Fig. 1b.
[0054] The microfluidic interaction element 10 has a substrate 20 with a cavity 30.
[0055] 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.
[0056] In addition, a movable displacement element 50 with vertical surfaces 51 is arranged within the cavity 30 such that the direction of movement x of the displacement element 50 is substantially perpendicular to the main extension planes of the wall elements 40.
[0057] 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 on both end faces 45 of the wall element 40 is less than 20 μm, in particular less than 10 μm.
[0058] Furthermore, the respective wall elements 40 each have a transverse segment perpendicular to the main extension plane of the wall element 40 on both end faces 45.
[0059] Furthermore, the microfluidic interaction element 10 has a first opening 61 from the first subspace 41 to a top side 21 of the substrate 20 and a second opening 62 from the second subspace 42 to a bottom side 22 of the substrate 20, which is shown more clearly in particular in Fig. 1b. The first opening 61 and / or the second opening 62 can each be less than 200 μm, in particular less than 100 μm, wide and more than 100 μm, in particular more than 500 μm, long.
[0060] The displacement element 50 is connected to the substrate 20 via a particularly resilient suspension 70. The suspension 70 is connected to the walls 33 of the cavity 30, wherein the suspension 70 is designed as a crossbar oriented transversely to the direction of movement x of the displacement element 50 and arranged on two sides of the displacement element 50, each centrally connected to the displacement element 50.
[0061] In addition, the microfluidic interaction element 10 has actuator regions 80, each with an actuator element, which drive the displacement element 50 along the direction of movement x. The actuator elements can be configured, for example, as an electrostatic drive and / or as a piezoelectric drive. In this case, the actuator element can be arranged on the suspension 70.
[0062] If the displacement element 50 is moved to the right, for example by the actuator elements, the volume in the first sub-chambers 41 is compressed and the volume in the second sub-chambers 42 is correspondingly increased. Fluid can flow out of the compressed first sub-chambers 41 into the environment of the interaction element 10 through the first openings 61, while fluid from the environment flows into the rarefied second sub-chambers 42 through the second openings 62 on the opposite substrate surface. This results in a net volume flow of the fluid in the environment in a direction perpendicular to the main extension plane of the substrate 20. If the displacement element 50 moves in the opposite direction, the flow direction of the fluid 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. Fig.lb shows the first embodiment of a microfluidic interaction element according to the invention according to Fig. la in a side sectional view.
[0063] The interaction element 10 from Fig. 1a is again shown, but this time in a lateral cross-section taken along the section plane A shown in Fig. 1a.
[0064] Here, the substrate 20 is again shown with the cavity 30, in which the rigid wall elements 40 and the displacement element 50, which is movable in the direction of movement x and has its vertical surfaces 51, are arranged. Also visible are the first sub-chambers 41 and second sub-chambers 42 formed by the corresponding design and arrangement of the wall elements 40 and the displacement element 50, which have the first openings 61 to the top side 21 of the substrate 20 and the second openings 62 to the bottom side 22 of the substrate 20, respectively.
[0065] The vertical distance h between the displacement element 50 and the floor 32 of the cavity 30 and / or between the displacement element 50 and the ceiling 31 of the cavity 30 is less than 5pm, in particular less than 2pm.
[0066] If, for example, the displacement element 50 is moved to the right by the actuator element, as described in Fig. 1a, 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 flow direction is reversed. In other words, the interaction element 10 can generate an acoustic sound wave with positive and negative pressure half-waves in a fluid, which is illustrated by the corresponding double arrows.
[0067] Fig. 2 shows a second embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view. It shows a microfluidic interaction element 110, which differs from the interaction element 10 of Fig. 1a only in the design of the suspension 170. In this case, the suspension 170 has a longitudinal beam, which is in contact with the walls 33 of the cavity 30.
[0068] Longitudinal direction to the direction of movement x of the displacement element 50.
[0069] Fig. 3 shows a third embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view. Shown is a microfluidic interaction element 210, which again differs from the interaction element 10 of Fig. 1a in the design of the suspension 270. The suspension 270 is centrally arranged and columnar and is correspondingly connected to the ceiling 31 and the floor 32 of the cavity 30, which is not visible in the image, and is also laterally enclosed by the displacement element 50. In terms of arrangement, the suspension 270 virtually replaces the central wall element 40 compared to the interaction element 10 according to Fig. 1a. The centrally arranged, columnar design of the suspension 270 is connected to the displacement element 50 via corresponding springs, on which the actuator region 80 is arranged.
[0070] Fig. 4 shows a fourth embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view. Shown is a microfluidic interaction element 310, which again differs from the interaction element 10 of Fig. 1a in the design of the suspension 370. The suspension 370, like the suspension 270 in Fig. 3, is columnar and connected to the ceiling 31 and the floor 32 of the cavity 30, which is not visible in the image. Unlike the suspension 270 in Fig. 3, the suspension 370 is vertically integrated into the displacement element 50. Here, the actuator region 80 with the actuator element is arranged directly on the displacement element 50, for example, as a piezoelectric layer.
[0071] Fig. 5 shows a fifth embodiment of a microfluidic interaction element according to the invention in a sectional view as a plan view. Shown is a microfluidic interaction element 410 which differs from the interaction element 10 of Fig. 1a in the design of the wall elements 440. Thus, the wall element 440 is bent, whereby four wall elements 440 instead of just three wall elements 40 can be arranged on the same base area as in the interaction element 10 of Fig. 1a. 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.
[0072] Fig. 6 shows an acoustic device with several microfluidic interaction elements according to the invention.
[0073] Shown is an acoustic device 500, which can be configured, for example, as a loudspeaker and / or microphone. The acoustic device 500 has a plurality of microfluidic interaction elements 10, 110, 210, 310, 410, which are arranged next to one another in a plane. By means of these microfluidic interaction elements 10, 110, 210, 310, 410, the loudspeaker can generate corresponding sound pressure levels. 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 control of the interaction elements 10, 110, 210, 310, 410 can then be carried out via common or separately formed control lines (not shown in the image).
Claims
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) comprises a substrate (20) with a cavity (30), wherein the cavity (30) comprises 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) with vertical surfaces (51) is arranged within the cavity (30) such that the direction of movement (x) of the displacement element (50) is substantially perpendicular to a main extension plane 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) a first subspace (41) and a second subspace (42) are formed within the displacement element (50), wherein the microfluidic interaction element (10, 110, 210, 310, 410) has a first opening (61) from the first subspace (41) to a top side (21) of the substrate (20) and a second opening (62) from the second subspace (42) to a bottom 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) via a particularly resilient suspension (70, 170, 270, 370).
3. Microfluidic interaction element (10, 110, 410) according to claim 2, characterized in that the suspension (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 suspension (270, 370) is connected to the ceiling (31) and the floor (32) of the cavity (30). The microfluidic interaction element (210, 410) according to claim 4, characterized in that the suspension (270) is laterally enclosed by the displacement element (50). The microfluidic interaction element (310, 410) according to claim 4, characterized in that the suspension (370) is vertically integrated into the displacement element (50). The microfluidic interaction element (10, 110, 210, 310, 410) according to one of the preceding claims, characterized in that the microfluidic interaction element (10, 110, 210, 310, 410) has an actuator region (80) with an actuator element that 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.Microfluidic interaction element (10, 110, 210, 310, 410) according to one of the preceding claims, characterized in that the first opening (61) and / or the second opening (62) are each less than 200 μm, in particular less than 100 μm, wide and more than 100 μm, in particular more than 500 μm, long. Microfluidic interaction element (10, 110, 210, 310, 410) according to one of the preceding claims, characterized in that the distance (d) between the wall element (40, 440) and the displacement element (50) on both end faces (45, 445) of the wall element (40, 440) is less than 20 μm, in particular less than 10 μm. Microfluidic interaction element (10, 110, 210, 310, 410) according to one of the preceding claims, characterized in that the wall element (40, 440) has at least one transverse segment perpendicular to the main extension plane of the wall element (40, 440) on at least one end face (45, 445), in particular on both end faces (45, 445). Microfluidic interaction element (10, 110, 210, 310, 410) according to one of the preceding claims, characterized in that the vertical distance (h) between the displacement element (50) and the floor (32) of the cavity (30) and / or between the displacement element (50) and the ceiling (31) of the cavity (30) is less than 5 μm, in particular less than 2 μm. Microfluidic interaction element (410) according to one of the preceding claims, characterized in that the wall element (440) is wave-shaped and / or kinked. Acoustic device (500), in particular loudspeaker and / or microphone, with at least one microfluidic interaction element (10, 110, 210, 310, 410) according to one of the preceding claims.