DE102021211813A1 - Microfluidic component, corresponding arrangement and corresponding method of operation - Google Patents

Abstract

The present invention creates a microfluidic component, a corresponding arrangement and a corresponding operating method. The microfluidic component is provided with a substrate (S) with a front side (VS) and a back side (RS) and a back side cavern (K), which extends from the back side (RS) to the front side (VS), a first perforated membrane device (M1), which spans the rear side cavern (K) on the front side (VS), a second perforated membrane device (M2), which is arranged above the first membrane device (M1) with respect to the front side (VS) and which has the rear side cavern (K). the front side (VS), a perforated backplate (BP), which is arranged between the first and second membrane device (M1, M2) and spaced apart from the first and second membrane device (M1, M2) and which the rear side cavern (K) on the Front (VS) spanned, a first electric drive device (P1) for oscillating driving of the first membrane device (M 1) and a second electric drive device (P2) for oscillating driving of the second membrane device (M2). The first drive device (P1) and/or the second drive device (P2) has a piezo drive (P1; P2).

Description

The present invention relates to a microfluidic component, a corresponding arrangement and a corresponding operating method.

State of the art

Microfluidics deals with the behavior of liquids and gases in the smallest of spaces. Accordingly, microfluidic components serve to transport or modulate liquids and gases in the smallest of spaces, for example through micromechanical structures.

Although in principle applicable to any microfluidic components, for example loudspeakers and pumps, the present invention and the problems on which it is based are explained using micromechanical loudspeakers based on silicon.

MEMS loudspeakers promise significant advantages over conventional electrodynamic loudspeakers, e.g. in terms of lower latency, lower energy consumption, smaller size, solderability, etc. On the other hand, they still have deficits in terms of the sound level that can be achieved.

An ultrasonic down-conversion principle is proving to be a promising approach. Here, a pump membrane or a modulation membrane is driven at a fixed ultrasonic frequency, while an acoustic signal is modulated onto the other by means of frequency modulation. This results in an imperceptible sum signal at slightly more than twice the ultrasonic frequency and a beat or difference signal that can be in the audible acoustic range.

The advantage here is that very high ultrasonic frequency levels can be achieved with MEMS loudspeakers, which, via down-conversion, ensure high sound levels, especially at low acoustic frequencies.

In the WO 2015/11 96 28 A2 describes the principle of a micromechanical ultrasonic loudspeaker, which provides a constant sound level over the entire audible range and thus enables high sound levels even at low frequencies. The loudspeaker described there has an ultrasound-generating membrane that vibrates at a first frequency, an acoustically transparent backplate (also referred to as a backplate) and an ultrasound-modulating shutter (also referred to as a shutter) that operates at a second, variable frequency close to the first frequency swings. However, the configuration described there on a single substrate leads to a strong fluidic coupling of the movements of the sound-generating membrane and the modulating shutter via the gas spring, which is stiff due to the small volume (between membrane and shutter).

The US 2021/0067865 A1 describes techniques for generating an audio signal with a loudspeaker. In some examples, a speaker device is described that includes a diaphragm and a closure. The membrane can be configured to vibrate along a first directional path and at least one frequency effective to generate an ultrasonic acoustic signal. The shutter is positioned along the propagation of the ultrasonic acoustic signal and configured to modulate the ultrasonic acoustic signal to produce an audio signal.

The DE 10 2016 201 872 discloses a MEMS loudspeaker device with: a first substrate with a first front side and a first rear side, which has a first rear side cavity that is at least partially covered by a sound generating device, a second substrate with a second front side and a second rear side, which has a second rear side cavity which is covered by a first perforated plate means. The second substrate is bonded to the first front side in such a way that the second rear side cavity is arranged above the sound generating device. Also provided is a second perforated plate device, which is attached above the first perforated plate device, wherein at least one of the first perforated plate device and the second perforated plate device can be elastically deflected in such a way that sound from the sound generating device can pass through through interaction of the first perforated plate device and the second perforated plate means can be modulated.

A micromechanical microphone array is from US 2002/0067663 A1 known.

Disclosure of Invention

The present invention creates a microfluidic component according to claim 1, a corresponding arrangement according to claim 12 and a corresponding operating method according to claim 16.

Preferred developments are the subject of the dependent claims.

Advantages of the Invention

The idea on which the present invention is based is that the first drive device for driving the first membrane device in an oscillating manner and/or the second drive device for driving the second membrane device in an oscillating manner has a piezo drive.

The microfluidic component according to the invention thus enables a very high conversion efficiency from electrical to acoustic energy. It can be soldered, has a low latency time and can be built very small. It has no limitation of the piezoelectrically driven membrane device due to electrostatic attraction, which allows larger deflections and larger distances than with electrostatically operated membrane devices.

According to a preferred development, the first membrane device, the second membrane device and the backplate span the rear side cavern essentially completely and essentially have the same surface area. In this way, fluid leakage can be minimized or avoided.

According to a further preferred development, the first membrane device has a first plurality of perforations with a first extent, the second membrane device has a second plurality of perforations with a second extent, and the backplate has a third plurality of perforations with a third extent, and the first and second perforations substantially unrelated to the third perforations. This enables a very efficient valve action.

According to a further preferred development, the first and second extents are smaller than the third extent. In this way, the pump performance can be increased.

According to a further preferred development, a degree of perforation of the backplate is greater than a degree of perforation of the first and second membrane device. The pumping power can also be increased in this way.

According to a further preferred development, the piezo drive is arranged in an edge area or a central area of the associated membrane device. This ensures even fluid distribution.

According to a further preferred development, the backplate has a greater thickness than the first and second membrane device. Thus, when using the same material for the backplate and the first and second membrane device, the required rigidity of the backplate can be adjusted.

According to a further preferred development, the first drive device and the second drive device have a respective first and second piezo drive. This creates even more energy efficiency combined with larger deflections of the membrane devices.

According to a further preferred development, the first and second piezo drive have a common ground connection. This saves space.

According to a further preferred development, the first or second membrane device itself serves as an electrical electrode for the first or second piezo drive. In this way, the stress balance of the membranes can be set in a more defined manner and a temperature drift of the component can be reduced.

According to a further preferred development, the first membrane device and/or the second membrane device has a stiffening element, in particular a thickened area. This reduces deformation in the membrane center of the membrane devices and minimizes distortion effects.

character list

The present invention is explained in more detail below with reference to the exemplary embodiments given in the schematic figures of the drawings.

• 1 eine schematische Querschnittsdarstellung eines mikrofluidischen Bauelements gemäß einer ersten Ausführungsform der vorliegenden Erfindung;
• 2 eine schematische Querschnittsdarstellung eines mikrofluidischen Bauelements gemäß einer zweiten Ausführungsform der vorliegenden Erfindung; und
• 3 eine schematische Querschnittsdarstellung eines mikrofluidischen Bauelements gemäß einer dritten Ausführungsform der vorliegenden Erfindung.

Show it:

• 1 a schematic cross-sectional representation of a microfluidic component according to a first embodiment of the present invention;
• 2 a schematic cross-sectional representation of a microfluidic component according to a second embodiment of the present invention; and
• 3 a schematic cross-sectional representation of a microfluidic component according to a third embodiment of the present invention.

Embodiments of the invention

In the figures, the same reference symbols denote the same elements or elements with the same function.

1 shows a schematic cross-sectional illustration of a microfluidic component according to a first embodiment of the present invention.

In 1 Reference numeral 10 generally designates a MEMS speaker device as a microfluidic device according to the first embodiment of the present invention.

The MEMS speaker device 10 has a substrate S with a front side VS and a back side RS and is a silicon substrate, for example.

A rear side cavern K is provided in the substrate S, which extends from the rear side RS to the front side VS and provides a rear volume (back volume) or access to a rear volume. It is required to reduce the influence of the fluidic return spring.

A first insulation layer L1, for example made of silicon oxide, is provided on the front side VS, which is interrupted in the region of the rear side cavity K in order to allow sound to pass through. A first membrane device M1 is provided on the first insulation layer L1, which is formed from a micromechanical functional layer made of polysilicon, for example. The first membrane device M1 has a multiplicity of perforations PF1, which have an extent b1.

A first conductive electrode layer E11 is applied and structured on the first membrane device M1. A first piezo layer PZ1, e.g. made of PZT or AIN, is applied and structured on the first conductive electrode layer E11. A second conductive electrode layer E12 is applied and structured on the first piezo layer PZ1. The first and second electrode layers E11, E12 can be formed from Pt or from polysilicon.

The structuring is such that the first electrode layer E11 and the second electrode layer E12 together with the intervening first piezo layer PZ1 form a first piezo drive P1 for piezoelectrically exciting the first membrane device M1, which is essentially located in an edge area outside the area of the rear side cavern K.

The first electrode layer E11 can be contacted externally via a first contact K11 and the second electrode layer E12 can be electrically contacted externally to a voltage supply (not shown) via a second contact K12.

A second insulation layer I2, for example made of silicon oxide, is provided on the second electrode layer E12, which is also interrupted in the region of the rear side cavity K in order to allow sound to pass through. A backplate BP is provided on the second insulation layer I2, which is also formed, for example, from a micromechanical functional layer made of polysilicon. The backplate BP has a multiplicity of perforations PFB, which have an extent b3. The perforations PFB of the backplate BP are arranged offset laterally with respect to the perforations PF1 of the first membrane layer M1.

A third insulation layer I3, for example made of silicon oxide, is provided on the backplate BP, which is interrupted in the region of the rear side cavity K in order to allow sound to pass through. A second membrane device M2 is provided on the third insulation layer I3, which is formed from a micromechanical functional layer made of polysilicon, for example. The second membrane device M2 also has a multiplicity of perforations PF2, which have an extent b2. The perforations PF2 of the second membrane device M2 are arranged offset laterally with respect to the perforations PFB of the backplate BP.

A third conductive electrode layer E21 is applied and structured on the second membrane device M2. A second piezo layer PZ2, e.g. made of PZT or AIN, is applied and structured on the third conductive electrode layer E21. A fourth conductive electrode layer E22 is applied and structured on the second piezo layer PZ2. The third and fourth electrode layers E21, E22 can be formed from Pt or from polysilicon.

The structuring is such that the third electrode layer E21 and the fourth electrode layer E22 together with the intervening second piezo layer PZ2 form a second piezo drive P2 for piezoelectrically exciting the second membrane device M2, which is essentially located in an edge area outside the area of the rear side cavern K.

The third electrode layer E21 can be contacted externally via a third contact K21 and the fourth electrode layer E22 can be electrically contacted to a voltage supply (not shown) via a fourth contact K22. The third and fourth contacts K21, K22 are routed through a fourth insulating layer I4, made of silicon oxide, for example.

The two piezoelectrically driven membrane devices M1, M2, in fluid interaction with the backplate BP, ensure that a high-frequency, pulsed fluid flow is generated with a beat frequency in the acoustically audible range.

In order to achieve this, the membrane devices M1, M2 are flexible, whereas the backplate BP is relatively rigid, ie it cannot be excited or driven to cause the high-frequency vibrations of the membrane devices M1, M2.

The pump membrane device, here for example the second membrane device M2, generates a pressure change in the space between the membrane devices M1, M2, while the modulation membrane device, here for example the first membrane device M1, together with the backplate BP allows pressure surges to pass through a valve.

The drive frequencies of the membrane devices M1, M2 are both in the ultrasonic range (>40 kHz), but differ by frequencies <20 kHz. A beat frequency in the acoustic frequency range is thus generated by the frequency detuning (20 Hz to 20 kHz) of the membrane devices M1, M2 with one another. Beat frequencies or tones in the entire audible range can now be generated by modulating the drive frequency of one of the modulation membrane devices M1, M2.

In order to minimize or avoid a fluid-acoustic short circuit, both membrane devices M1, M2 span the rear side cavern K as completely as possible. The piezo drives P1, P2 are particularly energy-efficient and can drive the membrane devices M1, M2 with a sufficiently high frequency.

The membrane devices M1, M2 and the backplate BP are the same in the present example, as if b1=b2=b3, but they can also have different perforations PF1, PF2, PFB. This applies to both the arrangement and the degree of the perforations PF1, PF2, PFB. These differences can serve to achieve better pump performance. For example, the backplate BP can have a higher degree of perforation (perforated area/total area) and thus a lower fluidic resistance than the two driven membrane devices M1, M2.

In order to realize the valve effect, it is necessary that the perforations PF1, PF2 of the membrane devices M1, M2 and the perforations PFB of the backplate BP essentially do not overlap.

On the one hand, to achieve high sound pressure levels, the largest possible membrane surfaces and deflections of the membrane devices M1, M2 are necessary. On the other hand, the membrane size of the membrane devices M1, M2 must not exceed a critical size so that the membrane devices M1, M2 can still be operated with a high deflection around or below their natural frequency.

In order to nevertheless achieve higher sound pressure levels, a plurality of the fluidic components 10 can therefore be arranged next to one another on a common substrate S and form one or more matrix arrangements which can be controlled together by a parallel connection or separately by an electrical control device (not shown). In this case, several of the fluidic components 10 can share a common rear side cavern K.

An electrical parallel circuit simplifies the simultaneous, in-phase control of all fluidic components 10 and prevents acoustic distortions due to phase differences of individual fluidic components 10.

In order to achieve the advantages of piezoelectric excitation, at least one of the two membrane devices M1, M2 must have a piezo drive P1, P2 with piezo layer PZ1, PZ2 and with electrode layers E11, E12, E21, E21 at least in a partial area, here periphery. In an embodiment that is not shown, such a piezo drive can also be located in another area of the membrane devices M1, M2, for example in the middle.

If the two membrane devices M1, M2 are both driven via a piezo drive P1, P2, they can share a common ground connection, e.g. contact K11.

The two membrane devices M1, M2 have essentially the same thickness. This is a prerequisite for similar resonant frequencies required for low beat frequencies in the lower audible range using the same material. The backplate BP is thicker than the two membrane devices M1, M2. The backplate BP should be as stiff as possible against deformation so that it does not make any evasive movements and can fulfill the valve function as well as possible.

2 shows a schematic cross-sectional representation of a microfluidic component according to a second embodiment of the present invention.

In 2 Reference numeral 10' generally designates a MEMS speaker device as a microfluidic device according to the second embodiment of the present invention.

The MEMS speaker device 10' according to the second specific embodiment differs from the MEMS speaker device 10 according to the first specific embodiment in the structure of the first and second membrane devices M1', M2'.

As in the first embodiment, the membrane devices M1', M2' have respective perforations PF1', PF2', which have the same extent b1' or b2' and are arranged offset to the perforations PFB of the backplate BP.

The membrane devices M1', M2' of the MEMS loudspeaker device 10' have a stiffening element, such as a respective thickened area V1' or V2', in the central area above the rear side cavity K.

Such stiffening elements reduce deformation in the membrane center of the membrane devices M1′, M2′ and promote a desirable low-distortion sound generation in the so-called cylinder mode (“piston mode”).

Otherwise, the second embodiment is designed in exactly the same way as the first embodiment.

3 shows a schematic cross-sectional representation of a microfluidic component according to a third embodiment of the present invention.

In 3 Reference numeral 10'' generally designates a MEMS speaker device as a microfluidic component according to the third embodiment of the present invention.

The MEMS speaker device 10" according to the third specific embodiment differs from the MEMS speaker device 10 according to the first specific embodiment in that the first diaphragm device M1" is driven".

As in the first embodiment, the membrane devices M1", M2" have respective perforations PF1", PF2" which have the same dimensions b1" or b2" and are arranged offset to the perforations PFB of the backplate BP.

The first membrane device M1" has an electrostatic drive device P1', the first piezo drive P1 with the electrode layers E11, E12 and the first piezo layer PZ1 being omitted.

The first membrane device M1" can be electrically connected to a power supply (not shown) via a first contact K11" and forms a first capacitor plate. The backplate BP can be connected to a ground connection via a second contact K2". The first membrane device M1" can thus be driven to oscillate at high frequencies via a corresponding external AC voltage.

Otherwise, the third embodiment is designed in exactly the same way as the first embodiment.

Although the present invention has been fully described above on the basis of preferred exemplary embodiments, it is not restricted to them, but rather can be modified in a variety of ways.

In particular, the geometries and materials listed are only examples and can be varied as desired depending on the application.

The microfluidic component 10, 10', 10" can be not only a loudspeaker, but also a fluid pump. In contrast to the loudspeaker, the operation of the fluidic component 10, 10', 10" as a fluid pump requires the same drive frequency and a fixed phase offset of the two membrane devices M1, M2.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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

• WO 2015/119628 A2 [0007]
• US 2021/0067865 A1 [0008]
• DE 102016201872 [0009]
• US 2002/0067663 A1 [0010]

Claims (16)

Microfluidic component (10; 10'; 10") with: a substrate (S) with a front side (VS) and a back side (RS) and a back side cavern (K) which extends from the back side (RS) to the front side (VS); a first perforated membrane device (M1; M1'; M1"), which spans the rear side cavern (K) on the front side (VS); a second perforated membrane device (M2; M2'; M2"), which is arranged above the first membrane device (M1; M1'; M1") with respect to the front side (VS) and which spans the rear side cavern (K) on the front side (VS). ; a perforated backplate (BP) sandwiched between the first and second membrane means (M1, M2; M1', M2'; M1", M2") and from the first and second membrane means (M1, M2; M1', M2'; M 1", M2") is arranged at a distance and which spans the rear side cavern (K) on the front side (VS); a first electrical drive device (P1; P1') for driving the first membrane device (M1; M1'; M1") in an oscillating manner; and a second electric drive device (P2) for driving the second membrane device (M2; M2'; M2") in an oscillating manner; wherein the first drive device (P1; P1') and/or the second drive device (P2) has a piezo drive (P1; P2). Microfluidic component (10; 10';10") claim 1 , wherein the first membrane device (M1; M1';M1"), the second membrane device (M2; M2';M2") and the backplate (BP) essentially completely span the rear side cavern and essentially have the same surface area. Microfluidic component (10; 10';10") claim 1 or 2 , wherein the first membrane means (M1; M1';M1") has a first plurality of perforations (PF1; PF1';PF1") having a first extent (b1; b1`; b1"), the second membrane means (M2; M2';M2") a second plurality of perforations (PF2; PF2';PF2") having a second extent (b2; b2`; b2") and the backplate (BP) has a third plurality of perforations (PFB) having a third extent ( b3) and the first and second perforations (PF1, PF2; PF1', PF2`; PF1", PF2") essentially do not overlap with the third perforations (PFB). Microfluidic component (10; 10';10") claim 3 , where the first and second dimensions (b1, b2; b1', b2`; b1", b2") are smaller than the third dimension (b3). Microfluidic component (10; 10'; 10") according to one of the preceding claims, wherein a degree of perforation of the backplate (BP) is greater than a degree of perforation of the first and second membrane device (M1, M2; M1', M2'; M1", M2" ) is. Microfluidic component (10; 10'; 10") according to one of the preceding claims, wherein the piezo drive (P1; P2) is in an edge region and/or a central region of the associated membrane device (M1, M2; M1', M2`; M1", M2") is arranged. Microfluidic component (10; 10'; 10") according to one of the preceding claims, wherein the backplate (BP) has a greater rigidity and/or thickness than the first and second membrane device (M1, M2; M1', M2`; M1", M2"). Microfluidic component (10; 10'; 10") according to one of the preceding claims, wherein the first drive device (P1; P1') and the second drive device (P2) have a respective first and second piezo drive (P1; P2). Microfluidic component (10; 10'; 10") according to one of the preceding claims, wherein the first or second membrane device itself serves as an electrical electrode for the first or second piezo drive. Microfluidic component (10; 10';10") claim 9 , wherein the first and second piezo drive (P1; P2) have a common ground connection (K11). Microfluidic component (10') according to one of the preceding claims, wherein the first membrane device (M1') and/or the second membrane device (M2`) has a stiffening element, in particular a thickened region (V1'; V2`). Arrangement of a plurality of microfluidic components (10; 10'; 10'') on a common substrate (S) in one or more matrix arrangements, it being possible for the microfluidic components to have different sizes in particular. arrangement according to claim 12 , wherein the microfluidic components (10; 10';10'') have a common rear side cavern (K). arrangement according to claim 12 or 13 , wherein the electrical drive devices (P1, P2; P1', P2) of the plurality of microfluidic components (10; 10';10") are electrically connected in parallel. Microfluidic component (10; 10';10") according to one of Claims 1 until 11 or arrangement according to one of Claims 12 until 14 , designed as a loudspeaker device or as a fluid pump. Operating method for operating a microfluidic component (10; 10';10") according to one of Claims 1 until 11 or an arrangement according to one of Claims 12 until 14 by means of an electrical control device as a loudspeaker device or as a fluid pump.

Images