Micro-electromechanical device, micro-electromechanical speaker, micro-electromechanical microphone, and micro-electromechanical fluid-conveying device

Abstract

The invention relates to a micro-electromechanical device (1) for generating or detecting a fluid pressure, comprising a functional unit (2), wherein the functional unit (2) has a movable functional element (3) which is coupled to a transmission element (4) in order to deflect the functional element (3) or in order to detect a deflection of the functional element (3), and the device (1) has an electrostatic guide unit (5) for guiding the transmission element (4), comprising a stationary bearing electrode (6) and a sliding electrode (7) which is movable relative to the bearing electrode (6). The invention additionally relates to a micro-electromechanical speaker, to a micro-electromechanical microphone, and to a micro-electromechanical fluid-conveying device comprising such a device.

Description

[0001] Description

[0002] title

[0003] Microelectromechanical device, microelectromechanical loudspeaker, microelectromechanical microphone and microelectromechanical fluid conveying device

[0004] The invention relates to a microelectromechanical device, a microelectromechanical loudspeaker, a microelectromechanical microphone and a microelectromechanical fluid conveying device.

[0005] State of the art

[0006] Microelectromechanical devices, also known as microelectromechanical systems under the term “MEMS”, are known from the state of the art.

[0007] For example, US 2021 / 0297 787 A1 discloses a sound generation chip with a membrane, a coupling plate and a spring structure as well as an actuator for exciting the membrane.

[0008] WO 2021 / 144400 A1 describes a MEMS transducer with an oscillating blade with vertical sections that can be excited to horizontal oscillations.

[0009] WO 2021 / 223 886 A1 relates to a MEMS with a layer structure and a cavity arranged therein, in which an interaction structure arranged to be movable along a plane direction is formed.

[0010] DE 10 2019203 914 B3 describes a MEMS with a movable layer arrangement in a cavity, which is moved along a substrate plane by an electrical potential between two of three beams arranged in the layer arrangement.

[0011] US 2012 / 0 018244 A1 relates to a MEMS loudspeaker with a cavity defined by a lamella and an actuator for displacing or deforming the lamella in order to generate a pressure pulse.

[0012] Disclosure of the invention

[0013] According to the features of independent claim 1, a microelectromechanical device for generating or detecting a fluid pressure with a functional unit is proposed, wherein the functional unit has a movable functional element coupled to a transmission element for deflecting the functional element or for detecting a deflection of the functional element, and wherein the device has an electrostatic guide unit for guiding the transmission element with a stationary bearing electrode and a sliding electrode movable relative to the bearing electrode.

[0014] With an electrostatic guide unit, the transmission element can be stabilized and precisely guided during the deflection of the functional element, enabling precise and accurately definable deflection of the functional element or precise detection of the deflection of the functional element. Using the electrostatic guide unit, for example, a predefined path of motion, a permissible distance of motion, or a permissible plane of motion of the transmission element can be precisely defined and implemented. The functional element can be designed with the lowest possible stiffness in the deflection direction to achieve high deflection amplitudes.The electrostatic guide unit makes it possible to increase the effective electromechanical stiffness of the functional element for degrees of freedom or directions of movement of the functional element that deviate from the deflection direction, thus enabling stabilization of the functional element against, for example, parasitic transverse movements, transverse vibrations, rotational movements, or rotational movements. In other words, the effective electromechanical stiffness can be adjusted directionally using electrostatic forces. Furthermore, the stabilizing guide unit reduces the risk of pull-in effects in the microelectromechanical device, where a critical pull-in voltage is exceeded, which can lead to adhesion of capacitive structures to one another.Furthermore, the electrostatic guide unit can be used to implement a stop function, which allows a predefined movement path of the transmission element and a maximum deflection of the functional element to be precisely limited. Due to the design of the guide unit as an electrostatic guide unit, a contactless and thus friction-free, floating guide structure can be provided for the transmission element, so that the operation of the functional unit of the device is not impaired by friction effects of the guide unit.

[0015] A microelectromechanical device can, for example, be a device produced using semiconductor technology and having microstructures, which is suitable, for example, for implementation of the device as a system-on-chip (SoC). The device is configured to generate or detect a fluid pressure by means of a functional unit. The functional unit can, for example, be designed as a displacement unit for generating a fluid pressure, which can, for example, generate a fluid pressure or promote a fluid flow in a limited displacement space via a targeted volume change using the functional element designed as a movable displacement element. The functional unit can, for example, be designed as a sensor unit for detecting a fluid pressure, which can, for example, detect an absolute or relative fluid pressure or a change in fluid pressure by means of a functional element designed as a movable measuring element.The functional element can be a flat, deflectable lamella structure with a height and length several times greater than its width, wherein the height and length span a lamella plane, which can in particular be aligned vertically in the functional unit. A vertical alignment of the lamella plane can, for example, correspond to an extension of the lamella plane perpendicular to a substrate surface of the semiconductor-produced device. The transmission element for deflecting the functional element or for detecting a deflection of the functional element can, for example, be coupled to the functional element at a lamella edge. The transmission element can, in particular, be movable in a transmission direction that runs essentially orthogonal to the lamella plane in order to deflect the functional element perpendicular to the lamella plane or to detect a deflection of the functional element perpendicular to the lamella plane.Depending on the design, the functional element can be attached laterally to a frame of the device on one or both sides, or can be suspended cantilevered in the functional unit. A deflection of the functional element can be accompanied by an elastic deformation and / or a displacement of the functional element. The functional unit can have a plurality of at least two functional elements, each of which can be deflected individually, in groups, or all together via a respective transmission element, or which can have their deflection detected. The transmission element can also be referred to as a shuttle, particularly for a joint deflection of several functional elements. Using a common transmission element for several functional elements, the number of deflections per transmission element movement can be increased, and simultaneous and uniform fluid pressure generation across the functional unit is promoted.The functional element can enclose a fluid volume with another functional element and / or with a fixed structure, for example a holding structure such as a frame, so that a deflection of the functional element leads to a change in the fluid volume and a fluid pressure is generated or a fluid pressure can be detected. It is conceivable for several functional elements to be arranged, for example, periodically one after the other on a holding structure of the functional unit. The transmission element can, for example, be designed as a measuring electrode for capacitive detection of the deflection of at least one functional element. A movement of the transmission element due to a deflection of the functional element can be detected as a change in capacitance of the measuring electrode relative to a reference electrode.

[0016] If the functional unit is designed as a displacement unit for generating fluid pressure, the transmission element of the device can be designed to be drivable in order to be able to cause a deflection of the functional element. The transmission element can be driven by a drive device of the device and can serve to transmit force from the drive device to the functional element. The drive device can be configured to be able to drive the functional element in opposite directions of movement in order to be able to deflect the functional element in opposite directions. The drive device can be, for example, an electrostatic, piezoelectric, or other suitable drive device, whereby the drive concept can be based, for example, on comb structures, electrostatic bending actuators (Nanoscopic Electrostatic Drive, NED), or micromuscles.

[0017] If the functional unit is designed as a sensor unit for detecting fluid pressure, the transmission element of the device is movable together with the functional element in order to detect a deflection of the functional element. The transmission element serves to transmit or convert the mechanical movement of the functional element into an electrical signal, for example, through a change in capacitance between the transmission element designed as a measuring electrode and a reference electrode. Furthermore, it is conceivable to use the guide unit to directly stabilize the functional element itself and limit its deflection.

[0018] An electrostatic guidance unit can be understood as a guidance system based on an electrostatic operating principle that utilizes electric fields. In particular, the guidance unit can utilize the property of a capacitive electrode surface pairing to strive for maintaining a capacitive equilibrium and to apply a resistance and restoring force to changes in the distance between the electrode surfaces of the electrode surface pairing that cause capacitance changes, in order to maintain the electric field distribution. Since the capacitance of the electrode surface pairing depends on the distance between the electrode surfaces, a parallel displacement of the electrode surfaces relative to one another can be possible with virtually no resistance, for example, while maintaining a constant distance between the electrode surfaces.In contrast, a reduction or increase in the distance between the electrode surfaces, for example through a translational movement of one electrode surface toward or away from the other electrode surface, or for example through a rotational pivoting movement of an electrode surface about a pivot axis running parallel to the electrode surfaces, can lead to a resistance and restoring force of the electrode surfaces against such a displacement. Thus, a capacitive electrode surface pairing can be used to obtain a self-stabilizing guide system with which a plane of movement of the electrode surfaces can be precisely defined with free mobility. The geometric design and dimensions of the electrode surfaces of an electrode surface pairing can be freely selected and adapted to different applications, so that guide units with differently designed movement paths can be provided.In particular, the electrode surfaces of the electrode surface pairing do not have to be identical to each other, but can have different outer contours and dimensions.

[0019] According to the proposed features, the electrostatic guide unit comprises a stationary bearing electrode and a sliding electrode that is movable relative to the bearing electrode. The stationary bearing electrode can be regarded as a stationary, guiding electrode, and the sliding electrode as a movable, guided electrode. The sliding electrode can also be referred to as a carriage electrode in reference to mechanical guide systems. The bearing electrode and the sliding electrode can have mutually facing, parallel electrode surfaces that form a self-stabilizing guide system according to the capacitive electrode surface pairing described above. The sliding electrode can be displaced along the bearing electrode at a constant distance from the bearing electrode, whereby the sliding movement in this context of an electrostatic guide is regarded as a contactless sliding movement.The stationary bearing electrode and the movable sliding electrode can be designed differently in their shape and dimensions. For example, the electrode surface of the sliding electrode facing the bearing electrode can have a smaller surface area than the electrode surface of the bearing electrode facing the sliding electrode, in order to easily enable sufficient freedom of movement of the sliding electrode along the bearing electrode. For simplicity, the electrode surface of the sliding electrode facing the bearing electrode is referred to below as the sliding surface, and the electrode surface of the bearing electrode facing the sliding electrode is referred to as the bearing surface.

[0020] Accordingly, according to one embodiment, the stationary bearing electrode can have a bearing surface facing the sliding electrode, and the sliding electrode can have a sliding surface facing the bearing electrode, wherein the bearing surface and the sliding surface extend parallel to each other. The sliding surface can have a smaller surface area than the bearing surface. The bearing surface and the sliding surface are spaced apart from each other and have a substantially constant orthogonal distance from each other along their surfaces.

[0021] According to one embodiment, the bearing surface can define a permissible movement distance or plane of movement of the sliding electrode, and a boundary of the bearing surface can define a stop region of the sliding electrode. This allows a permissible movement distance or plane and at least one stop region for the transmission element to be defined via the sliding electrode, which, depending on the embodiment, can, for example, directly form the transmission element or be mechanically coupled to it. The permissible movement planes of the sliding electrode and the transmission element do not have to be arranged in the same plane, but can be spaced from each other, for example, by a mechanical coupling between the transmission element and the sliding electrode.When the sliding surface of the sliding electrode reaches a boundary of the bearing surface, the aforementioned resistance and restoring forces begin to counteract an incipient change in capacitance, resulting in an electrostatic stopping effect. This stopping effect is transferred to the transmission element, so that the mobility of the transmission element in different spatial directions can be defined and limited by a suitable design of the bearing surface.

[0022] If the functional unit is designed as a displacement unit and has a drive device, it is conceivable for the electrostatic guide unit to have a guide drive separate from the drive device of the transmission element or to be coupled to the drive device of the transmission element, so that the drive device can be configured to displace the transmission element and the sliding electrode of the guide unit. It is also possible for the sliding electrode not to have a dedicated drive, but rather to be mechanically coupled to the transmission element and to execute its movement, while exerting a stabilizing effect on the transmission element through the capacitive coupling with the bearing electrode.Furthermore, it is conceivable that a drive function for the transmission element is integrated into the guide unit, i.e., the electrostatic guide unit for the transmission element simultaneously provides an electrostatic drive for the transmission element. This allows for a particularly compact device with precisely controllable deflection of the functional element. If the functional unit is designed as a sensor unit, it is conceivable that the electrostatic guide unit primarily exerts a stabilizing effect on the transmission element without a drive device being provided for the functional unit or the guide unit.

[0023] According to one embodiment, the transmission element can be designed as a sliding electrode. This allows the transmission element to be guided directly and precisely by the electrostatic guide unit. For example, the transmission element can be designed as an electrode and have a side surface designed as a sliding surface, which faces a bearing surface of the bearing electrode and runs parallel to it.

[0024] According to an alternative embodiment, the transmission element can be mechanically coupled to a separate sliding electrode. This allows the guide unit and the transmission element to be arranged spatially spaced from one another in the device, so that the available installation space can be functionally divided and individually optimized, and mutual interference between displacement and guide structures can be reliably excluded. According to one embodiment, the electrostatic guide unit can have a plurality of bearing electrodes and / or a plurality of sliding electrodes. A plurality can mean at least two bearing electrodes or at least two sliding electrodes. A plurality of bearing and / or sliding electrodes can increase the functional density and design freedom of the guide unit.For example, several transmission elements can be guided with the guide unit or different guide paths can be realized in the device.

[0025] In principle, the number of bearing electrodes can correspond to the number of sliding electrodes. In other words, the same number of bearing electrodes as sliding electrodes can be provided. According to one embodiment, it can be advantageous if the number of bearing electrodes is different from the number of sliding electrodes. For example, more bearing electrodes can be provided than sliding electrodes, for example to stabilize a sliding electrode from multiple sides. For example, more sliding electrodes can be provided than bearing electrodes, for example to be able to guide multiple transmission elements on a bearing electrode. If the number of bearing electrodes differs from the number of sliding electrodes around an electrode, a balanced arrangement is achieved with which the forces acting between the bearing and sliding electrodes can be completely canceled out.

[0026] According to a configuration with a plurality of bearing or sliding electrodes, at least two bearing electrodes and at least one sliding electrode, or at least one bearing electrode and at least two sliding electrodes, can be arranged alternately one after the other. In such an arrangement, the bearing electrodes and sliding electrodes can be arranged alternately one after the other and, for example, extend above and below one another or next to one another. In this arrangement, the bearing surfaces of the bearing electrodes and the sliding surfaces of the sliding electrodes can each extend parallel to one another. In an alternating arrangement, for example, at least one sliding electrode can be arranged between two bearing electrodes, whereby such a sandwich arrangement can increase the stability and precision of the guide unit.If, however, a bearing electrode with two bearing surfaces is flanked by a sliding electrode on each bearing surface, these can, for example, serve to guide two adjacent transmission elements. The described arrangements can be continued as desired for more than two sliding and / or bearing electrodes.

[0027] According to one embodiment, the transmission element can be mechanically coupled to at least two sliding electrodes, which are arranged along different spatial axes from the transmission element. This allows the transmission element to be stabilized in multiple spatial orientations and precisely guided or stopped. For example, the spatial axes can be orthogonal to one another, so that a 90° angle is formed between two coupling structures connecting the transmission element to the sliding electrodes. Accordingly, several sliding electrodes assigned to a transmission element can be distributed at different angles around the transmission element. The transmission element can, for example, have a basic geometric shape with six outer surfaces, wherein, according to the embodiment, at least two different outer surfaces of the transmission element can be used for coupling to a respective sliding electrode.Based on a three-dimensional coordinate system, the spatial axes can, for example, form an x-axis, a y-axis, and a z-axis that are perpendicular to each other. For example, with different spatial axes, a sliding electrode in the x-direction and a sliding electrode in the y-direction are coupled to the transmission element. The term "different spatial axes" can also refer to different spatial directions of the same spatial axis, for example, -x and +x starting from the transmission element.

[0028] For example, sliding electrodes coupled to the transmission element in opposite directions can be provided, starting from two opposing outer surfaces of the transmission element, so that two sliding electrodes arranged parallel to one another accommodate the transmission element between them and are arranged in opposite spatial directions relative to the transmission element. According to one embodiment, the guide unit can have a plurality of sliding electrodes assigned to a common bearing electrode, wherein the sliding electrodes are arranged in different spatial axes starting from the bearing electrode. This allows several sliding electrodes to be guided with one bearing electrode without mutual interference, and a particularly compact guide unit is provided.Furthermore, the self-stabilization of the electrostatic guide unit is further improved with such an arrangement by preventing any incipient non-parallel displacement of the electrodes relative to one another due to field forces from multiple sliding electrodes in different spatial directions through resistance and restoring forces. The bearing electrode can have several bearing surfaces around its circumference, each of which has an associated sliding electrode. For example, the spatial axes can be orthogonal to one another, so that two sliding electrodes are arranged at an angle of 90° to each other on the circumference of the bearing electrode.Based on a three-dimensional coordinate system, the spatial axes can, for example, form an x-axis, a y-axis, and a z-axis that are perpendicular to one another, so that with different spatial axes, for example, starting from the bearing electrode, a sliding electrode is arranged in the x-direction and a sliding electrode in the y-direction. The term “different spatial axes” can also refer to different spatial directions of the same spatial axis, for example -x and +x starting from the bearing electrode. For example, sliding electrodes can be provided on two opposite bearing surfaces of the bearing electrode, so that two sliding electrodes arranged parallel to one another accommodate the bearing electrode between them. In one embodiment, the bearing electrode can have a cross-shaped cross-section with four cross sections, along each of which a sliding electrode can be guided.

[0029] According to one embodiment, the guide unit can have a linear guide section. A linear guide section can enable translation of the sliding electrode along a straight line, so that the guide unit can support straight movement paths of the transmission element. Alternatively or additionally, the guide unit can have a rotational guide section. A rotational guide section can enable rotation of the sliding electrode along a circular path, so that the guide unit can support arcuate or circular movement paths of the transmission element. Such rotational guides can be advantageous, for example, for functional units designed as displacement units based on rotary displacement principles, for example for fluid conveying devices similar to centrifugal pumps.

[0030] In principle, it is conceivable to combine linear and rotary guide sections in the guide unit. Furthermore, it is also possible to freely define geometrically irregular guideways, which can be individually tailored to the application-specific movement paths of the transmission element. The geometric design of the bearing surface, as well as the selected shape and dimensions of the sliding surface, can influence the executed guide movement.

[0031] According to one embodiment, the bearing surface of the bearing electrode and / or the sliding surface of the sliding electrode can have a regular geometric basic shape. This allows a regular movement path or permissible movement plane for the sliding electrode to be specified depending on the application, whereby more complex movement sequences can also be implemented. A regular geometric basic shape can, for example, be a point- or axis-symmetric shape or a shape with several sides of equal length. Examples of regular geometric shapes are squares, crosses, or rings.

[0032] Alternatively, the bearing surface of the bearing electrode and / or the sliding surface of the sliding electrode can have an irregular geometric basic shape. This also allows for irregular movement paths, which can be freely defined depending on the required deflection, guidance, or measurement tasks. For example, for acoustic devices designed as sound transducers, it may be conceivable to implement complex movement paths of the transmission element that go beyond regular geometric shapes to optimize vibration.

[0033] Furthermore, it is conceivable that the bearing electrode has regular geometric shape sections and irregular geometric shape sections in combination.

[0034] According to one embodiment, the bearing electrode and the sliding electrode can be arranged crosswise relative to each other. The stabilizing capacitance is generated in the intersection area of ​​the electrodes, and stop areas are formed by the boundary of the bearing surface and the boundary of the sliding surface, thus providing a multi-axis stop. Furthermore, a material- and space-saving arrangement of the guide unit can be provided.

[0035] The device can, for example, be manufactured as a layered structure with multiple functional layers generated between two cover layers or wafers. For example, the functional element can be arranged in a first functional layer and the transmission element in a second functional layer. The second functional layer can be arranged above and / or below the first functional layer. Coupling points can extend between the first and second functional layers, connecting the functional element to the transmission element, thereby forming, for example, an intermediate coupling layer. The functional element and / or the transmission element can advantageously be made of a semiconductor material such as silicon or silicon compounds.

[0036] The fluid pressure generated or detected by the functional unit can, for example, be a sound pressure, making the device suitable for use as an acoustic MEMS component. Accordingly, according to one embodiment, the device can be designed as a sound transducer, for example, as a loudspeaker component or as a microphone component. According to other embodiments, the device can be designed as a fluid conveying device for generating and / or controlling a fluid flow, for example, as a miniaturized pump or valve for microfluidic applications.

[0037] The invention also relates to a microelectromechanical loudspeaker comprising a microelectromechanical device according to at least one of the above-described features, wherein the functional unit is configured to generate sound pressure as fluid pressure, and which comprises a signal processing unit for applying and processing signals from the microelectromechanical device. The proposed guide unit enables precise guidance and stabilization of the transmission element of the functional unit, which is designed as a displacement unit, so that precise deflection of the functional element of the functional unit can be achieved. Therefore, low mechanical rigidity of the functional element in the deflection direction and, at the same time, high electromechanical rigidity in spatial directions deviating from the deflection direction can be achieved.This allows for the provision of a microelectromechanical loudspeaker with a high and constant sound pressure level (SPL) across a wide frequency range, for example, between 20 Hz and 20 kHz, as well as with high efficiency. Furthermore, high sound quality is achieved for the loudspeaker, which can be reflected, for example, by low total harmonic distortion (THD). Low transverse and torsional stiffness, which could be associated with unsafe operation or a pull-in risk, are avoided thanks to the proposed guide unit. The proposed loudspeaker is robust and functions reliably even under strong mechanical forces such as external shocks. The signal processing unit can be implemented, for example, as an ASIC.

[0038] The invention also relates to a microelectromechanical microphone comprising a microelectromechanical device according to at least one of the above-described features, wherein the functional unit is configured to detect sound pressure as fluid pressure, and which comprises a signal processing unit for applying and processing signals from the microelectromechanical device. The proposed guide unit enables precise guidance and stabilization of the transmission element of the functional unit, which is configured as a sensor unit, so that a precise measurement of the deflection of the functional element of the functional unit is achievable. This allows for low mechanical rigidity of the functional element in the deflection direction and, at the same time, high electromechanical rigidity in spatial directions deviating from the deflection direction.This makes it possible to create a robust yet sensitive microelectromechanical microphone. The signal processing unit can be implemented, for example, as an ASIC.

[0039] The invention also relates to a microelectromechanical fluid conveying device comprising a microelectromechanical device according to at least one of the above-described features, wherein the functional unit of the device is configured to generate and / or control a fluid flow, and which comprises a signal processing unit for applying and processing signals from the microelectromechanical device. The proposed guide unit enables precise guidance and stabilization of the transmission element of the functional unit, so that precise deflection of the functional element of the functional unit, which is configured as a displacement unit, can be achieved. This makes it possible to provide a microelectromechanical fluid conveying device with a high and constant fluid flow rate and with high efficiency. The fluid conveying device can be configured, for example, as a pump or valve.The signal processing unit can, for example, be designed as an ASIC.

[0040] The invention permits various embodiments and is explained in more detail below using exemplary embodiments with the accompanying drawings. Figures 1a-1b show a schematic basic principle of an electrostatic guide unit with a bearing electrode and a sliding electrode in a side view and a top view;

[0041] Fig. 2a-2c schematic diagrams of a capacity, resistance force and effective stiffness curve of the guide unit along the y-direction shown in Fig. 1b;

[0042] Fig. 3a-3c schematic diagrams of a capacity, resistance force and effective stiffness curve of the guide unit along the x-direction shown in Fig. 1b;

[0043] Fig. 4 is a schematic representation of an electrostatic guide unit according to a first embodiment in a perspective view;

[0044] Fig. 5 is a schematic representation of an electrostatic guide unit according to a second embodiment in a perspective view;

[0045] Fig. 6 is a schematic representation of an electrostatic guide unit according to a third embodiment in a perspective view;

[0046] Fig. 7 is a schematic representation of an electrostatic guide unit according to a fourth embodiment in a perspective view;

[0047] Fig. 8 is a schematic representation of an electrostatic guide unit according to a fifth embodiment in a perspective view;

[0048] Fig. 9 is a schematic representation of an electrostatic guide unit according to a sixth embodiment in a perspective view;

[0049] Fig. 10 is a schematic representation of an electrostatic guide unit according to a seventh embodiment in a plan view;

[0050] Fig. 11a-11c show examples of different bearing surface shapes of bearing electrodes for an electrostatic guide unit in schematic plan views; Fig. 12a-12b show schematic representations of an electrostatic guide unit according to an eighth embodiment in two variants in a sectional side view;

[0051] Fig. 13a-13b - schematic representations of an electrostatic guide unit according to a ninth embodiment in two variants in a sectional side view;

[0052] Fig. 14 - a schematic representation of a microelectromechanical device with an electrostatic guide unit in a perspective view;

[0053] Fig. 15 - a schematic diagram of a microelectromechanical system with a microelectromechanical device.

[0054] Figures 1a and 1b show a schematic basic principle of an electrostatic guide unit 5 with a bearing electrode 6 and a sliding electrode 7, wherein Fig. 1a shows a side view and Fig. 1b a top view of the guide unit 5. According to the exemplary embodiment shown, the bearing electrode 6 forms a stationary bearing electrode 6, to which the sliding electrode 7 is movable relative. The stationary bearing electrode 6 has a bearing surface 6a facing the sliding electrode 7, and the movable sliding electrode 7 has a sliding surface 7a facing the bearing electrode 6. The bearing surface 6a and the sliding surface 7a are spaced apart and parallel to one another. The bearing electrode 6 and the sliding electrode 7 are connected to a voltage source 14 to generate electrostatic forces.In principle comparable to a plate capacitor, the bearing electrode 6 and the sliding electrode 7 form an electrostatic system with an electrical capacitance C when subjected to a potential difference. Such an electrostatic system has the property of striving to maintain the capacitance C and, depending on the applied electrical voltage and the dimensions of the bearing surface 6a and the sliding surface 7a, of applying a resistance and restoring force F when a capacitance change occurs, which can be caused by a change in the distance between the bearing surface 6a and the sliding surface 7a. In contrast, a displacement of the sliding surface 7a parallel to the bearing surface 6a is possible with virtually no resistance at a constant distance and correspondingly constant capacitance C. According to the illustrations in Figs. 1a and 1b, such a resistance-free parallel displacement can occur in the x-direction.Such unobstructed directions of movement and movement distances are referred to below as the guide direction RF. In Figs. 1a and 1b, the guide direction RF is marked as a double arrow for bidirectional mobility. Depending on the design of the bearing surface 6a and the sliding surface 7a, two-dimensional planes of movement can also be defined instead of the illustrated one-dimensional mobility of the sliding electrode 7, within which a parallel displacement or parallel rotation of the sliding surface 7a to the bearing surface 6a is possible, as will be explained below with reference to further figures. Fig. 1b also shows two stop directions Rs, in which a displacement of the sliding surface 7a to the bearing surface 6a is prevented by the equilibrium effort of the electrostatic guide unit 5. The bearing surface 6a is defined circumferentially by a boundary 6b, which establishes a stop area of ​​the sliding electrode 7.If the sliding electrode 7 moves perpendicular to the guide direction RF, here in the y-direction as shown, the guide unit 5, upon exceeding the limit 6b, develops a resistance and restoring force F due to electrostatic conservation forces, which stops the sliding electrode 7. This behavior of the guide unit 5 applies analogously to a rotational or pivoting movement of the sliding electrode 7, also designated as the stop direction Rs, which would lead to a partial exceeding of the limit 6b. Thus, the electrode surface pairing of sliding surface 7a and bearing surface 6a forms a self-stabilizing guide system with a geometrically predefined mobility of the sliding electrode 7 relative to the bearing electrode 6. For sufficient mobility, the sliding surface 7a can have a smaller surface area than the bearing surface 6a. In Fig.1b shows that, for example, with the same width b1, b2 of the bearing electrode 6 and the sliding electrode 7, the length 11 of the sliding electrode 7 can be smaller than the length 12 of the bearing electrode 6.

[0055] 2a to 2c show schematic diagrams of a capacitance, resistance force and effective stiffness curve of the guide unit 5 along the y-direction shown in Fig. 1b. In Fig. 2a, the capacitance C is shown relative to a deflection of the sliding electrode 7 in the y-direction starting from the O-position shown in Fig. 1b. It can be seen that a deflection in the y-direction leads to a change in capacitance which, depending on the deflection, causes a resistance and restoring force F on the sliding electrode 7 as shown in Fig. 2b. Derived from the resistance and restoring force F, the deflection of the sliding electrode 7 in the y-direction can be described with an effective electromechanical stiffness S as shown in Fig. 2c. The guide unit 5 shown in Figs. 1a and 1b thus has a high stiffness S transverse to the guide direction RF.The stiffness S can be regarded as the differential of the resistance and restoring force F, which in turn corresponds to the differential of the capacity C.

[0056] 3a to 3c show schematic diagrams of a capacitance, resistance force, and effective stiffness curve of the guide unit 5 along the x-direction shown in Fig. 1b. In Fig. 3a, the capacitance C is shown relative to a deflection of the sliding electrode 7 in the x-direction, starting from the O-position shown in Fig. 1b. It can be seen that a movement of the sliding electrode 7 in the x-direction up to a boundary 6b of the bearing surface 6a, which defines a stop region of the sliding electrode 7, is associated with a constant capacitance C corresponding to the plateau shown. However, if the sliding electrode 7 exceeds the boundary 6b in the x-direction, a resistance and restoring force F occurs at the sliding electrode 7, as shown in Fig. 3b. Analogously, a rotation in the stop direction Rs, as shown in Fig. 1b, would result in a resistance and restoring moment.Derived from the resistance and restoring force F, the deflection of the sliding electrode 7 in the y-direction can be described with an effective stiffness S as shown in Fig. 3c. The guide unit 5 shown in Figs. 1a and 1b thus has a low stiffness S in the guide direction RF until the limit 6b is reached, with the stiffness S increasing abruptly at the limit 6b. Accordingly, the guide unit 5 makes it possible to define precise stop regions for the sliding electrode 7 and the transmission element 4 connected thereto or formed integrally. The stiffness S can be viewed as the differential of the resistance and restoring force F, which in turn corresponds to the differential of the capacitance C. Fig. 4 shows a schematic representation of an electrostatic guide unit 5 according to a first embodiment.The guide unit 5 has a bearing electrode 6 and a sliding electrode 7, which are shown in simplified form as cuboid structures. The bearing electrode 6 has a bearing surface 6a facing the sliding electrode 7, the circumferential boundary 6b of which defines stop positions for the sliding electrode 7 due to the electrostatic effects described above. The sliding electrode 7 has a sliding surface 7a facing the bearing electrode 6, which runs parallel to the bearing surface 6a. Due to the effects of electric field forces at a potential difference between the bearing electrode 6 and the sliding electrode 7, the sliding electrode 7 can be displaced parallel to the bearing electrode 6 until it reaches the boundary 6b. The guide unit 5 stabilizes itself in this process according to the above description.Due to the essentially identical width of the bearing electrode 6 and the sliding electrode 7, a substantially one-dimensional mobility of the sliding electrode 7 is provided in the guide direction RF along a permissible movement path, i.e., up to the boundary 6b of the bearing surface 6a. Outside the permissible movement path, as well as in translational and rotational directions transverse to the guide direction RF, a deflection of the sliding electrode 7 is electrostatically prevented, so that the other movement directions are represented as stop directions Rs. In other words, the sliding electrode 7 has limited longitudinal mobility along the bearing electrode 6.

[0057] Fig. 5 shows an electrostatic guide unit 5 according to a second embodiment. The guide unit 5 has a plurality of bearing electrodes 6 and a plurality of sliding electrodes 7, which are arranged alternately one after the other. This allows several transmission elements 4 (not shown in detail) to be guided by the sliding electrodes 7, and the sliding electrodes 7 are stabilized by the sandwich structure on two opposite sides. Analogous to the embodiment shown in Fig. 4, the sliding electrodes 7 are longitudinally movable to a limited extent along the bearing electrodes 6, i.e., they can be guided in the guide direction RF along a permissible movement distance until they reach the limits 6b of the bearing surfaces 6a of the bearing electrodes 6, and are prevented from deflecting beyond the limits 6b and in stop directions Rs transverse to the guide direction RF. In Fig.Figure 5 shows an equal number of bearing electrodes 6 and sliding electrodes 7 as an example. However, it is also conceivable to provide an unequal number of bearing electrodes 6 and sliding electrodes 7 in order to create a force-balanced arrangement in which the electrostatic forces between the electrodes are mutually canceled. As indicated by the dotted line at the edge of the image in Figure 5, the consecutive alternating arrangement can be continued as desired with additional bearing electrodes 6 and sliding electrodes 7.

[0058] Fig. 6 shows an electrostatic guide unit 5 according to a third embodiment. The guide unit 5 has an arrangement formed from a plurality of bearing electrodes 6 and sliding electrodes 7, in which each sliding electrode 7 is mechanically coupled to a transmission element 4 via a coupling structure 8, wherein the sliding electrodes 7 are arranged in different spatial axes y, z starting from the transmission element 4. Thus, as shown, one sliding electrode 7 is aligned in the z direction and another sliding electrode 7 in the y direction to the transmission element 4. Due to the multiple electrode surface pairings, the stopping effect of the transmission element 4 in the stopping directions Rs is further increased and the transmission element 4 is even more balanced, while the permissible movement distance of the transmission element 4 in the x direction or in the guide direction RF is not impaired.In other words, additional effective electromechanical stiffnesses S are added to the transmission element 4 at five of the six possible rigid body degrees of freedom. The coupling structure 8 can, for example, be designed as a substantially rigid connecting web, but in principle, other coupling forms for mechanically coupling the transmission element 4 to the sliding electrodes 7 are also conceivable.

[0059] Fig. 7 shows an electrostatic guide unit 5 according to a fourth embodiment. In this exemplary embodiment, the bearing surface 6a of the bearing electrode 6 is larger in both surface dimensions x, y than the sliding surface 7a of the sliding electrode 7, so that no one-dimensional permissible movement path is defined, but rather a two-dimensional permissible movement plane of the sliding electrode 7. The sliding surface 7a can be moved in several guide directions RF parallel to the bearing surface 6a until the sliding electrode 7 reaches the boundary 6b of the bearing surface 6a. This allows a high degree of freedom of movement of the sliding electrode 7 with a reliable stopping effect in the edge regions of the bearing surface 6a.

[0060] Such an electrode arrangement with a two-dimensional permissible plane of movement can also be provided in an alternating arrangement with a plurality of support electrodes 6 and sliding electrodes 7, as shown in Fig. 8 according to a fifth embodiment. As indicated by the dotted line at the edge of the image, the consecutive alternating arrangement can be continued as desired with additional support electrodes 6 and sliding electrodes 7.

[0061] Fig. 9 shows an electrostatic guide unit 5 according to a sixth embodiment. Here, the bearing electrode 6 and the sliding electrode 7 are arranged crosswise relative to one another. With a suitable geometric design and dimensioning, the boundaries 6b, 7b of the bearing surface 6a and the sliding surface 7a can be used for a stopping effect, thus providing a biaxial stopper. The capacitance S relevant for the effective stiffness S is generated in the intersection area of ​​the bearing surface 6a and the sliding surface 7a. Furthermore, the guide unit 5 according to the sixth embodiment can be manufactured in a material- and space-saving manner.

[0062] Fig. 10 shows an electrostatic guide unit 5 according to a seventh embodiment. Here, the bearing surface 6a and the sliding surface 7a have an irregular geometric basic shape, which also allows for the implementation of irregular movement planes and paths of the transmission element 4, as well as different direction-dependent stop areas, which can be freely defined depending on the required deflection and guidance tasks.

[0063] Figs. 11a to 11c show examples of different bearing surface shapes of bearing electrodes 6 for an electrostatic guide unit 5. Here, the bearing surfaces 6a and sliding surfaces 7a are shown with regular geometric basic shapes, through which more complex movement paths of the sliding electrode 7 can be realized. For example, with the electrode pairing shown in Fig. 11a, linear guide sections 9 with movement paths along a quadrilateral shape can be implemented. With the electrode pairing shown in Fig. 11b, for example, linear guide sections 9 with movement paths along a cross shape can be implemented, so that, for example, the implementation of locking and unlocking tasks with the sliding electrode 7 is also conceivable.For example, the electrode pairing shown in Figure 11c allows for the realization of rotational guide sections 10 with arcuate or circular movement paths, which can be applied, for example, to rotary displacement principles. Using the predefined movement paths and a suitable design of the sliding electrode, for example, a sliding electrode that corresponds to the width of the bearing electrode, very precise movement sequences of the sliding electrode can be implemented and parasitic movement patterns can be avoided.

[0064] 12a and 12b show two variants of an electrostatic guide unit 5 according to an eighth embodiment in a sectional view transverse to the guide direction. The guide unit 5 has a plurality of sliding electrodes 7 which are assigned to a common bearing electrode 6, wherein the sliding electrodes 7 are arranged in different spatial axes y, z starting from the bearing electrode 6. Thus, as shown in Fig. 12a, one sliding electrode 7 is aligned in the z direction and another sliding electrode 7 is aligned in the y direction to the bearing electrode 6. In Fig. 12b, two sliding electrodes 7 are aligned on either side of the bearing electrode 6 in the z direction and two further sliding electrodes 7 are aligned on either side of the bearing electrode 6 in the y direction to the bearing electrode 6.According to the exemplary embodiment shown, the bearing electrode 6 has a cross-shaped cross-section and guides the sliding electrodes 7 along the cross sections so that they are sufficiently spaced from one another and do not interfere with one another. With the selected arrangement, the sliding electrodes 7 and the bearing electrode 6 stabilize each other in their positions, enabling robust and precise guidance of the sliding electrodes 7. The electrode pairs each generate effective electromechanical stiffnesses S in the different spatial directions y, z and each protect a pair of electrodes aligned orthogonally thereto against a pull-in effect. The arrangement shown in Fig. 12b provides a guide unit 5 that is balanced with regard to the electrostatic forces.

[0065] Figs. 13a and 13b show two variants of an electrostatic guide unit 5 according to a ninth embodiment in a sectional view transverse to the guide direction. As shown in Figs. 13a and 13b, the transmission element 4 in this embodiment is mechanically coupled via coupling structures 8 to sliding electrodes 7 in several spatial axes y, z. This allows for precise and stable guidance for the transmission element 4.

[0066] Fig. 14 shows a microelectromechanical device 1 according to an embodiment for generating a fluid pressure with a functional unit 2 designed as a displacement unit. As shown, the functional unit 2 has two functional elements 3 which are movable in a guide direction RF and designed as vertically arranged lamellae, which can be deflected to generate the fluid pressure by means of a common transmission element 4 designed as a shuttle, which is coupled to the functional elements 3. The device 1 has an electrostatic guide unit 5 with two stationary bearing electrodes 6 and a sliding electrode 7 which is movable relative to the bearing electrodes 6, wherein according to the embodiment shown, the transmission element 4 is designed directly as a sliding electrode 7.The transmission element 4 has two sliding surfaces 7a, each arranged opposite a bearing surface 6a of the bearing electrodes 6 and running parallel. By applying a potential difference to the bearing electrodes 6 and the sliding electrode 7, an electrostatic guidance system can be provided with which the transmission element 4 can be precisely and safely guided along the bearing surfaces 6a of the bearing electrodes 6 by electrostatic forces. The transmission element 4 is reliably stopped at the boundaries 6b of the bearing surfaces 6a, so that the movement of the functional elements 3 is specifically limited. To drive the transmission element 4, it is connected via an actuator 15 to a drive device (not shown in detail), so that a drive force can be transmitted to the transmission element 4 via the actuator 15, and the transmission element can be moved within the provided guide by the guide unit 5.Furthermore, the transmission element 4 is coupled to a frame 17 of the device 1 via at least one connecting element 16, which is particularly elastic. The illustration in Fig. 14 can also be applied analogously to a microelectromechanical device 1 with a functional unit 2 designed as a sensor unit, wherein the device 1 is configured to detect a fluid pressure acting on the movable functional elements 3. The transmission element 4 can be designed as a measuring electrode for capacitive detection of the deflection of the functional elements 3, and the previously described actuator 15 would be designed as a sensor 15 in this embodiment. A movement of the transmission element 4 due to a deflection of the functional elements 3 can be detected, for example, as a change in capacitance of the measuring electrode relative to a reference electrode (not shown in detail).Furthermore, it is conceivable that a functional unit 2 designed as a sensor unit has only a single functional element 3, the deflection of which is limited and stabilized by means of the guide unit 5.

[0067] Fig. 15 schematically shows a microelectromechanical system 11, which can be embodied, for example, as a microelectromechanical loudspeaker, a microelectromechanical microphone, or a microelectromechanical fluid conveying device. The microelectromechanical system 11 comprises a microelectromechanical device 1, embodied, for example, as a sound transducer or fluid conveying device, according to one of the features described above, and a signal processing unit 13, which is connected to the device 1 by a signal connection 12 and is designed to apply and process signals from the microelectromechanical device 1. The microelectromechanical system 11 can be implemented, for example, as a system-on-chip.

Claims

Claims 1 . Microelectromechanical device (1) for generating or detecting a fluid pressure with a functional unit (2), wherein - the functional unit (2) has a movable functional element (3) which is coupled to a transmission element (4) for deflecting the functional element (3) or for detecting a deflection of the functional element (3), and - the device (1) has an electrostatic guide unit (5) for guiding the transmission element (4) with a stationary bearing electrode (6) and a sliding electrode (7) movable relative to the bearing electrode (6).

2. Device (1) according to claim 1, wherein the stationary bearing electrode (6) has a bearing surface (6a) facing the sliding electrode (7) and the sliding electrode (7) has a sliding surface (7a) facing the bearing electrode (6), and wherein the bearing surface (6a) and the sliding surface (7a) run parallel to one another.

3. Device (1) according to claim 2, wherein the bearing surface (6a) defines a permissible movement distance or movement plane of the sliding electrode (7) and a boundary (6b) of the bearing surface (6a) defines a stop region of the sliding electrode (7).

4. Device (1) according to one of the preceding claims, wherein the transmission element (4) is designed as a sliding electrode (7).

5. Device (1) according to one of claims 1 to 3, wherein the transmission element (4) is mechanically coupled to a separate sliding electrode (7).

6. Device (1) according to one of the preceding claims, wherein the electrostatic guide unit (5) has a plurality of bearing electrodes (6) and / or a plurality of sliding electrodes (7).

7. Device (1) according to claim 6, wherein the number of bearing electrodes (6) is not equal to the number of sliding electrodes (7).

8. Device (1) according to claim 6 or 7, wherein at least two bearing electrodes (6) and at least one sliding electrode (7) or at least one bearing electrode (6) and at least two sliding electrodes (7) are arranged alternately one after the other.

9. Device (1) according to one of claims 6 to 8, wherein the transmission element (4) is mechanically coupled to at least two sliding electrodes (7) which are arranged in different spatial axes (x, y, z) starting from the transmission element (4).

10. Device (1) according to one of claims 6 to 9, wherein the guide unit (5) has a plurality of sliding electrodes (7) which are assigned to a common bearing electrode (6), wherein the sliding electrodes (7) are arranged in different spatial axes (x, y, z) starting from the bearing electrode (6).

11. Device (1) according to one of the preceding claims, wherein the guide unit (5) has a linear guide section (9).

12. Device (1) according to one of the preceding claims, wherein the guide unit (5) has a rotation guide section (10).

13. Device (1) according to one of the preceding claims, wherein the bearing surface (6a) of the bearing electrode (6) and / or the sliding surface (7a) of the sliding electrode (7) have a regular geometric basic shape.

14. Device (1) according to one of claims 1 to 12, wherein the bearing surface (6a) of the bearing electrode (6) and / or the sliding surface (7a) of the Sliding electrode (7) has an irregular geometric basic shape.

15. Device (1) according to one of the preceding claims, wherein the bearing electrode (6) and the sliding electrode (7) are arranged crosswise to one another.

16. Device (1) according to one of the preceding claims, wherein the device (1) is designed as a sound transducer. [Loudspeaker component, microphone component] 17. Device (1) according to one of claims 1 to 15, wherein the device (1) is designed as a fluid conveying device for generating and / or controlling a fluid flow.

18. A microelectromechanical loudspeaker comprising a microelectromechanical device (1) according to one of claims 1 to 16, wherein the functional unit (2) is configured to generate sound pressure as fluid pressure, and a signal processing unit (13) for applying and processing signals of the microelectromechanical device (1).

19. A microelectromechanical microphone comprising a microelectromechanical device (1) according to one of claims 1 to 16, wherein the functional unit (2) is configured to detect sound pressure as fluid pressure, and a signal processing unit (13) for applying and processing signals of the microelectromechanical device (1).

20. Microelectromechanical fluid conveying device, comprising a microelectromechanical device (1) according to one of claims 1 to 17, wherein the functional unit (2) of the device (1) is configured to generate and / or control a fluid flow, and a signal processing unit (13) for applying and processing signals of the microelectromechanical device (1).

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