Microelectromechanical device, microelectromechanical loudspeaker, microelectromechanical fluid pumping device, and method for operating a microelectromechanical device

Abstract

The invention relates to a microelectromechanical device (1) for generating pressurised fluid pulses (F), comprising a substrate (7) and a vibration-generating unit (2), the vibration-generating unit (2) having a functional unit (13) arranged on a front side (7a) of the substrate (7), which functional unit has a valve function for temporarily forming a fluid opening (14) and a displacement function for displacing fluid, and a through-channel (5) extending from the functional unit (13) through the substrate (7) to a rear side (7b) of the substrate (7), wherein the vibration-generating unit (2) is designed to generate, in the through-channel (5), a pressure oscillation at a predetermined oscillation frequency, and to extract, from the through-channel (5) and via the temporarily formed fluid opening (14) of the functional unit (13), an oscillatory pressure pulse (15a), which is reflected from the through-channel (5) in the direction of the functional unit (13), as a pressurised fluid pulse (F). The invention also relates to a microelectromechanical loudspeaker, a microelectromechanical fluid pumping device, and a method for operating a microelectromechanical device (1).

Description

[0001] Description

[0002] title

[0003] Microelectromechanical device, microelectromechanical loudspeaker, microelectromechanical fluid pumping device and method for operating a microelectromechanical device

[0004] The invention relates to a microelectromechanical device for generating pressurized fluid pulses. The invention further relates to a microelectromechanical loudspeaker, a microelectromechanical fluid pumping device, and a method for operating a microelectromechanical device.

[0005] State of the art

[0006] Microelectromechanical devices, also known as microelectromechanical systems under the term "MEMS", are known from the prior art.

[0007] For example, US patent 2022 / 0224999A1 discloses an air pulse generation device comprising a diaphragm structure, a valve structure, and a cap structure. A chamber is formed between the diaphragm structure, the valve structure, and the cap structure. The valve structure is configured to perform an opening and closing movement to form at least one opening. This opening connects the chamber to the ambient air outside the chamber. A horizontal air oscillation at an operating frequency is generated within the chamber. The opening and closing movement of the valve structure occurs at the operating frequency.

[0008] Disclosure of the invention According to the features of independent claim 1, a microelectromechanical device for generating pressurized fluid pulses is proposed, comprising a substrate and a vibration generator unit, wherein the vibration generator unit has a functional unit arranged on a front side of the substrate with a valve function for temporarily forming a fluid opening and with a displacement function for displacing fluid, as well as a passage extending from the functional unit through the substrate to a rear side of the substrate, wherein the vibration generator unit is configured toto generate a pressure oscillation with a predetermined oscillation frequency in the through-channel and to extract a pressure pulse of this oscillation, reflected from the through-channel towards the functional unit, through the temporarily formed fluid opening of the functional unit from the through-channel as a pressurized fluid pulse.

[0009] In other words, it is proposed to utilize a vertical extension of the substrate to create a pressure oscillation volume and to generate a pressurized fluid pulse from this volume. The pressure oscillation volume can, at least temporarily, form a closed-ended oscillation tube. Within this tube, a reciprocating pressure oscillation can be generated by the functional unit emitting pressure pulses towards the through-channel and reflecting these pulses at an open end of the through-channel on the back side of the substrate.The pressure oscillation can thus be generated and amplified by the displacement function of the functional unit, whereby the pressure pulses propagating along the passage channel towards the rear of the substrate are superimposed with reflected pressure pulses, forming a resulting pressure oscillation. With a suitable design of the microelectromechanical device, it may be possible, in particular, to generate the pressure oscillation in the form of a standing wave, as is known, for example, in an analogous manner from acoustic applications of closed-ended tubes.When an overpressure pulse generated by the functional unit towards the flow channel reaches the open end of the flow channel, a negative pressure pulse is reflected back towards the functional unit. This negative pressure pulse is reflected again at the functional unit when the fluid opening is closed, and then at the open end of the flow channel, it generates another overpressure pulse towards the functional unit. Depending on the control of the functional unit, either an overpressure pulse or a negative pressure pulse can be extracted as a pressurized fluid pulse. For example, the microelectromechanical device can be operated in a pump mode, in which overpressure pulses are extracted as pressurized fluid pulses, and in a suction mode, in which negative pressure pulses are extracted as pressurized fluid pulses. A pressurized fluid pulse can therefore have a positive or negative pressure difference relative to the ambient pressure.In other words, the microelectromechanical device can be configured to generate an overpressure pulse towards the flow channel by displacing fluid via the functional unit, and to discharge a reflected overpressure or underpressure pulse from the flow channel towards the functional unit through the temporarily formed fluid orifice of the functional unit as a pressurized fluid pulse. The valve function of the functional unit can be time-synchronized to the predetermined oscillation frequency such that the functional unit forms a fluid orifice when the reflected overpressure or underpressure pulse reaches the functional unit. This allows the vibrational energy of the pressure oscillation to be advantageously used to extract pressurized fluid pulses.The pressurized fluid pulses can be directed to a target volume or enable at least partial pressure equalization with the target volume. Depending on the design of the vibration generator unit, the reciprocating overpressure and underpressure pulses can experience an increase in their amplitude through interference, which can be advantageously used to increase the power output of the fluid pulse generation. With the described fluid pulse generation principle, the frequency of the generated pressurized fluid pulses can deviate from the predetermined oscillation frequency of the pressure oscillation.In particular, depending on the chosen application of the microelectromechanical device, as will be explained below, the pressure oscillation can have a predetermined oscillation frequency in an ultrasound range that is not perceptible to human hearing, while the generated pressurized fluid pulses can be used to generate a fluid pulse signal to produce a sound signal perceptible in an audible frequency range.

[0010] The microelectromechanical device according to the proposed features has the advantage that pronounced fluid pulses can be generated despite its very small dimensions. Depending on the application, this allows the device to generate high pumping or acoustic power. For example, controlled fluid pulse generation can be used to produce high-power acoustic signals across a wide acoustic frequency range, including pronounced low-frequency acoustic signals with high sound pressure levels. The microelectromechanical device is very compact because the pressure oscillation volume is integrated into its substrate.The through-channel extends vertically, i.e. perpendicular to a substrate surface, through the microelectromechanical device, so that, for example, horizontal pressure oscillation volumes are applied to the horizontal.

[0011] The cap structure limiting the pressure oscillation volume can be dispensed with, and the microelectromechanical device can be designed to be significantly flatter. Through a design analogous to acoustic tone tubes, advantageous pressure oscillation effects can be used to generate pressurized fluid pulses, for example, a so-called clarinet effect, described below, which allows the vibrational properties of standing waves to be advantageously utilized over a very short volume. The vibration generator unit can also be described, for example, as a vertical pipe element. By utilizing the vibrational energy of the generated pressure oscillation and by decoupling the fluid pulse frequency from the pressure oscillation frequency, the microelectromechanical device can be operated very energy-efficiently.As will be described in more detail below, several vibration generator units can be advantageously arranged side by side in the microelectromechanical device, thus not only increasing the pumping or sound power, but also reducing or eliminating secondary sound power radiated into the environment through targeted interference effects. Despite its high effectiveness and efficiency, the microelectromechanical device has a fundamentally simple design and is therefore easy to manufacture.

[0012] Microelectromechanical devices can be, in particular, semiconductor-based devices with microstructures that incorporate, for example, mechanical, optical, physical, and / or chemical components and / or functions, and can be used, for instance, as miniaturized actuators. Due to its microstructural design, the microelectromechanical device may be suitable for implementation as a system-on-a-chip (SoC). The microelectromechanical device can, for example, be used to generate sound signals or fluid pump currents by means of controllable electromechanical components.

[0013] The microelectromechanical device is designed to generate pressurized fluid pulses. A fluid pulse can be a moving volume of gas and / or liquid. The fluid can be, in particular, a gas mixture, especially air. Accordingly, the fluid pulse can be implemented as an air pulse and used, for example, to generate a sound signal. It is also possible to generate a constant or at least quasi-constant fluid flow using the fluid pulses and to deliver it to a target volume. A pressurized fluid pulse can be understood as a fluid pulse with a pressure increased or reduced relative to ambient pressure; thus, the fluid pulse can be pressurized or depressurized. A variable fluid pulse signal, generated from the extracted pressurized fluid pulses, can be used to generate a sound signal.The pressurized fluid pulses can therefore generate sound signals perceptible to the human ear, which can be specifically controlled by varying the fluid pulse signal. The sound pressure can be described by a sound pressure level (SPL).

[0014] Particularly in acoustic applications of microelectromechanical devices, generating a sufficient sound pressure level, especially at low frequencies, presents a technical challenge due to the very small dimensions of the sound-generating structures. The proposed microelectromechanical device, thanks in particular to its specially designed vibration generator unit, makes it possible to generate a high sound pressure level even at low frequencies. The pressurized fluid pulse can, for example, be conveyed into a target volume, which could be a confined space such as an ear canal or a cooling duct.

[0015] A substrate can be a planar semiconductor support structure. The substrate can, for example, be a silicon wafer. Depending on the embodiment, the substrate can also be composed of several wafer elements. For example, the substrate can have at least two wafer elements arranged one above the other. The substrate has two opposing substrate surfaces, which can be referred to as the front and back sides. The front side of the substrate can form a so-called active side of the substrate, on which, for example, movable mechanical microstructures and / or electrical microstructures of the sensor component can be arranged. According to the proposed features, the functional unit, which includes a valve function and a displacement function, is arranged on the front side of the substrate.It is possible that a recess is incorporated into the front surface of the substrate and that the functional unit is positioned within this recess, thus offset from the original substrate surface. It is also conceivable to protect the functional unit from direct environmental influences by means of a cap structure applied to the substrate. The described passageway of the vibration generator unit terminates at the rear of the substrate, so that a corresponding opening exists there, representing the mouth of the passageway. Here, too, it is possible that a recess is incorporated into the rear of the substrate, thus offsetting the passageway from the original substrate surface and providing a protected opening.

[0016] The vibration generator unit of the microelectromechanical device serves to generate a pressure oscillation and to extract pressurized fluid pulses from the generated pressure oscillation. For this purpose, the vibration generator unit comprises the aforementioned functional unit and the through-channel connected to the functional unit. The functional unit includes at least one movable functional element, which, due to its mobility, can act as a valve element for the temporary creation of a fluid opening and / or as a displacement element for the displacement of fluid. The functional unit can be electrically controlled to effect a targeted movement of the functional element. For example, the functional unit can include a functional element that can be deflected capacitively, ferroelectrically, or piezoelectrically.Depending on the chosen embodiment of the functional unit, it is conceivable that a movable functional element can simultaneously function as a valve element and a displacement element. In particular, at least two movable functional elements can interact to jointly fulfill a valve and displacement function. It is also conceivable that the functional unit comprises several movable functional elements, at least one of which can be configured as a valve element and at least one other as a displacement element. Valve elements can be movable functional elements with which a fluid opening can be created and closed again by movement of the functional element or interacting functional elements.The fluid opening can be designed to be periodic with a predetermined valve actuation frequency, which can be implemented, for example, by suitable control of the functional unit with a predetermined drive frequency.

[0017] Displacement elements can be movable functional elements that displace fluid from an adjacent volume through their movement. In particular, the local displacement and the resulting fluid pulse can induce pressure oscillations in the flow channel, so the displacement element can also be described as a vibration-generating element. Furthermore, the displacement element can be used to convey pressurized fluid pulses, reflected in the flow channel and directed through the fluid opening, into a target volume.

[0018] The through-channel of the vibration generator unit can be considered a fluid channel that is fluidically connected to an environment or an output volume of the microelectromechanical device via the rear of the substrate. This allows for fluid exchange and pressure equalization with the environment or output volume, and the through-channel is fluid-filled. The through-channel can be viewed as an essentially stationary structure and passive component of the vibration generator unit. Its channel wall acts as a volume boundary, and its exit edge at the open end of the through-channel on the rear of the substrate. This enables the reflection of overpressure and underpressure pulses within the vibration generator unit and the formation of a reciprocating pressure oscillation, which, with a suitable design of the through-channel, can also occur in the form of a standing wave.The through-channel can be easily created in the substrate using known semiconductor manufacturing processes.

[0019] The vibration generator unit is designed to generate a pressure oscillation with a predetermined oscillation frequency in the passage channel and to extract a vibration pressure pulse reflected from the passage channel towards the functional unit through the temporarily formed fluid opening of the functional unit as a pressurized fluid pulse.This allows an overpressure pulse of the pressure oscillation, reflected from the open end of the flow channel towards the functional unit, to be conveyed through the fluid opening of the functional unit and directed to a target volume. Alternatively, an underpressure pulse of the pressure oscillation, reflected from the open end of the flow channel towards the functional unit, can be conveyed through the fluid opening of the functional unit. This enables, on the one hand, at least partial pressure equalization of the target volume and, on the other hand, the generation of an acoustic signal through a variable fluid pulse signal. The vibrational energy of the pressure oscillation is advantageously used to generate pressurized fluid pulses, whereby low-frequency acoustic signals with a high sound pressure level can be generated at the functional unit using high-frequency excitation frequencies.

[0020] According to one embodiment, the vibration generator unit can be designed such that a standing wave can be generated in the through-channel by means of a pressure vibration at the predetermined vibration frequency. This enables particularly energy-efficient operation of the microelectromechanical device. For example, the functional unit of the vibration generator unit can be designed to generate a pressure vibration with a predetermined vibration frequency that is matched to the dimensions of the through-channel. For example, the predetermined vibration frequency and the length of the through-channel from the functional unit to the back of the substrate can be matched such that a standing wave is formed in the through-channel when the pressure vibration is generated at the predetermined vibration frequency.A standing wave is usually created by the interference of two oscillations of the same frequency propagating in opposite directions.

[0021] In the present case, such a standing wave can be created by a pressure oscillation directed towards the open end of the through-channel and by a pressure oscillation reflected at the open end towards the functional unit, which superimpose on each other and, with suitable design, in particular with a suitable length extension of the through-channel, form at least one spatially corresponding node of oscillation.

[0022] According to one embodiment, the length of the passage channel from the functional unit to the rear of the substrate can correspond to essentially one quarter or one quarter and one multiple of one half the wavelength of the pressure oscillation with the predetermined oscillation frequency. This allows a standing wave with the pressure oscillation to be advantageously generated in a tube closed at one end. A pressure oscillation excited by the functional unit in the direction of the open end of the passage channel and a pressure oscillation of the same frequency reflected in the direction of the functional unit can be advantageously superimposed. In particular, high amplitudes of the pressure oscillation are produced by interference of the forward and reflected waves, so that pronounced pressurized fluid pulses can be efficiently extracted.If the length of the through-channel from the functional unit to the back of the substrate corresponds essentially to one-quarter of the wavelength of the pressure oscillation at the specified frequency, a particularly compact microelectromechanical device can be provided. In particular, comparatively thin substrate designs can be used for the microelectromechanical device. The formation of a standing wave is also possible with such a short through-channel, as can be seen analogously in closed-end tubes in acoustic applications. Against this background, the generation of a standing wave with a very short through-channel length, corresponding to one-quarter of the wavelength of the pressure oscillation at the specified frequency, is referred to as the clarinet effect.In a clarinet, only a quarter of the wavelength of the generated air column vibration is contained within the clarinet tube. For this reason, clarinets, with the same tube length, can produce tone vibrations at lower frequencies than other instruments, such as those with a tube structure open at both ends. Nevertheless, even with a through-channel whose length corresponds to a quarter or multiple of a half the wavelength of the pressure vibration at the given frequency, a comparatively efficient vibration generation can be achieved, forming a standing wave. Therefore, it is also conceivable to generate pressure vibrations with wavelengths of three-quarters, five-quarters, or corresponding multiples of the through-channel's length, or conversely, to adapt the through-channel's length to corresponding predetermined vibration frequencies.Such a design can be advantageous, for example, for vibration generator units with high operating frequencies. In a clarinet, these pressure vibrations are used to produce particularly high tones. According to one embodiment, the vibration generator unit can be configured to generate a pressure vibration with a predetermined vibration frequency above 20 kHz (kilohertz). This allows the vibration frequency to lie in an ultrasonic range outside the human hearing range, so that operation of the microelectromechanical device is possible without disturbing harmonics and, depending on the desired application, only the pressurized fluid pulses generated by the pressure vibration and extracted by the functional unit are perceptible to the human ear due to their frequency being decoupled from the vibration generation.Therefore, due to the ultrasonic frequency range, the emission of pressure vibrations into the environment at the open end of the passage does not impair the user comfort of a user operating the microelectromechanical device.

[0023] According to one embodiment, the length of the through-channel can range from 50 pm to 2 mm, and in particular from 200 pm to 800 pm. This allows for the formation of very short to comparatively extended vibration volumes, depending on the application and the specified vibration frequency. The specified lengths can also apply, essentially analogously, to the substrate thickness from a front to a back side. Corresponding substrate thicknesses are available with common wafer elements or can be easily produced. Furthermore, it is conceivable that the length of the through-channel is adapted to a wavelength of the pressure vibration with a specified vibration frequency such that it corresponds essentially to one-quarter or one-quarter and a multiple of one-half of the wavelength of the pressure vibration with the specified vibration frequency, thus enabling the formation of a standing wave in the through-channel.According to a non-restrictive embodiment, for example, with a selected oscillation frequency of 400 kHz and assuming a propagation speed of 330 m / s for ultrasonic waves in air, a wavelength of 825 pm can be determined. With a desired length of the transmission channel of one-quarter of the wavelength, a length of 206.25 pm can be deduced in order to form a standing wave. With such a length of the transmission channel and a corresponding substrate thickness, a very compact microelectromechanical device can also be provided.

[0024] According to one embodiment, the longitudinal extent of the through-channel can be at least twice, and in particular at least 2.5 times or at least three times, the width of the through-channel perpendicular to its longitudinal extent. Accordingly, the through-channel can be designed as a narrow, elongated tube. In other words, the vertical extent of the through-channel can be larger, and in particular several times larger, than its horizontal extent. Since the vertical dimensioning of the through-channel is crucial for the desired vibration generation, a narrow design of the through-channel allows for the use of additional substrate volume, if required, for greater stability of the device or for accommodating additional vibration generator units.For example, in the case of a cylindrically shaped through-channel, the width can correspond to the diameter of the through-channel relative to its cross-section. In the case of a rectangularly shaped, especially slotted, through-channel, the width can correspond to the distance between the longer sides of the through-channel.

[0025] According to one embodiment, the width of the through-channel can be at least half the width of the functional unit. This advantageously adapts the dimensions of the through-channel to the dimensions of the functional unit, ensuring efficient vibration generation with the vibration generator unit. The width of the functional unit can, for example, refer to a diameter or the distance between two opposing anchor points of the functional unit on the substrate. In the case of a rectangular functional unit, this distance can refer to two opposing anchor points on the longer sides of the functional unit. According to one embodiment, the through-channel can have a cylindrical shape. This allows for the formation of a defined, uniform pressure vibration within the through-channel.In particular, the aforementioned clarinet effect can be enhanced by a cylindrical channel shape when a standing wave is formed during pressure oscillation. Furthermore, the through-channel is easy to manufacture and simple to adapt to the functional unit and a predetermined oscillation frequency of the pressure oscillation to be generated. It is also conceivable, in principle, to incorporate a through-channel with a conical shape into the vibration generator unit. For example, the through-channel can have a widening, particularly a steadily increasing cross-sectional expansion, at least in sections towards the rear of the substrate.

[0026] According to one embodiment, the through-channel can have a slot-shaped basic form. A slot-shaped basic form can be understood, for example, as a rectangular cross-sectional contour with a first side length and a second side length, where the second side length is at least twice, and in particular at least three times or at least five times, as long as the first side length. The first side length can correspond to a slot width of the through-channel, and the second side length can correspond to a slot length of the slot-shaped basic form of the through-channel. A slot shape is a comparatively narrow, elongated channel basic form. A slot-shaped through-channel is a structurally advantageous basic form, allowing, for example, several through-channels to be arranged side by side in a very space-saving manner.If the microelectromechanical device is designed as a system-on-chip, the chip area can thus be used particularly efficiently.

[0027] In principle, it is possible to utilize various geometric channel shapes within the microelectromechanical device to combine the advantages of different variants and optimize the device as needed. According to one embodiment, the functional unit can have an outer contour adapted to the basic shape of the channel. This allows the functional unit and the channel to be geometrically matched to optimize vibration generation. For example, the functional unit can have a circular outer contour for a channel with a cylindrical basic shape. Similarly, the functional unit can have a rectangular outer contour for a channel with a slotted basic shape.

[0028] According to one embodiment, the microelectromechanical device can have at least two vibration generator units. These at least two vibration generator units can, in particular, be arranged in a common substrate of the microelectromechanical device. According to an advantageous embodiment, the electromechanical device can have a plurality of more than two vibration generator units. This increases the overall achievable power of the microelectromechanical device for generating pressurized fluid pulses.Furthermore, the vibration generator units can be arranged so close to each other within the device that vibration energy exiting the open ends of the through-channels on the rear side of the substrate can be reduced or eliminated by destructive interference between overpressure or underpressure pulses exiting on the rear side, provided the vibration generator units are operated with a suitable phase shift. This can, for example, reduce secondary sound power, particularly secondary ultrasonic power, which would otherwise be emitted into the environment, thus increasing the efficiency of the microelectromechanical device and reducing any potential environmental impact. The through-channels can, in particular, run parallel to each other along their longitudinal axis through the substrate.

[0029] According to a further development, the at least two vibration generator units can be essentially identical in shape and dimensions. In other words, the vibration generator units can be geometrically similar, in particular essentially congruent. This allows the vibration generator units to be operated essentially in the same way and synchronously with each other, and under comparable control conditions, in a simple and efficient manner. As described previously, however, it is also conceivable in principle to combine different geometric designs of vibration generator units or vibration generator units of different dimensions in a microelectromechanical device.

[0030] According to one embodiment, the distance between the at least two vibration generator units can be smaller than the length and / or width of a passage channel between the vibration generator units. This allows the vibration generator units to be arranged close to one another, resulting in, on the one hand, a higher output of pressurized fluid pulses with efficient utilization of the substrate volume, and on the other hand, improved reduction or elimination of secondary sound power. In particular, the distance between the vibration generator units can be smaller than half the length and / or half the width of a passage channel between the vibration generator units. Here, "distance" can be understood as the shortest distance between two facing outer contours of adjacent vibration generator units.

[0031] According to one embodiment, the at least two vibration generator units can be arranged linearly in a row. In other words, the geometric centers of the functional units can, for example, lie on a common imaginary line parallel to a substrate surface. If the functional units have a substantially rectangular shape, their longer sides can be arranged parallel to each other. A linear arrangement can be particularly advantageous for vibration generator units with through-channels that have a slot-shaped base, where the functional units have a rectangular base adapted to this shape. This allows for a particularly space-saving arrangement and, due to the resulting small spacing, efficient interaction of the vibration generator units for secondary noise reduction.In principle, it is also conceivable to arrange vibration generator units with cylindrically designed through channels linearly next to each other.

[0032] According to one embodiment, the at least two vibration generator units can be arranged hexagonally relative to each other. This allows for a particularly space-saving arrangement and, due to the resulting small spacing, efficient interaction of the vibration generator units for secondary noise reduction. A hexagonal arrangement can be particularly advantageous for vibration generator units with through-channels that have a cylindrical base shape, with the functional units having a circular base shape adapted to this. In other words, viewed from the front of the substrate with the functional units arranged on it, the vibration generator units can form a hexagonal circular packing.

[0033] According to one embodiment, the functional unit can have a first diaphragm and a second diaphragm that are movable relative to each other, wherein the microelectromechanical device has a drive unit that is configured to excite the first diaphragm to a first oscillation at a first frequency and to excite the second diaphragm to a second oscillation at a second frequency that differs from the first frequency. In simplified terms, this makes it possible to deliberately utilize different phase angles of the oscillating diaphragms by means of oscillations of the first and second diaphragms at different frequencies to temporarily create a fluid opening and to displace fluid, for example, to generate the pressure oscillation described above and to extract pressurized fluid pulses.Accordingly, the first and second diaphragms can form movable functional elements of the functional unit, which, in conjunction, can perform the valve and displacement functions of the unit. Due to the relative mobility of the first and second diaphragms, they can, depending on their phase, oscillate past each other, for example, creating a fluid opening for extracting the reflected pressure pulse, or oscillate in the same direction to direct the fluid pulse towards a target volume. By appropriately exciting the first and second diaphragms, the oscillation patterns can be influenced, thus allowing for the simple variation of various parameters of pressure oscillation and / or fluid pulse generation.Fluid pulse generation with a variable fluid pulse signal can, for example, be used for sound signal generation and can be implemented by varying the phase shift between the vibrations of the first and second membrane.

[0034] In principle, it is conceivable that the functional unit has further movable structural elements, in particular additional membranes besides the first and second membranes. A membrane can be a substantially planar, deflectable structural element with a height and length several times greater than its width. The first and second membranes can each be attached to a fixed support structure, for example, the substrate of the microelectromechanical device, and thus be held movable in space by it. A fluid opening can be formed between the first and second membranes by a relative movement of the membranes to each other in at least one phase segment, so that the first and second membranes can be considered valve elements. In particular, in one phase segment of a unidirectional oscillation, the first and second membranes can be considered displacement elements.

[0035] The drive unit can be a controllable microelectromechanical unit for actuating the first and second diaphragms. A drive element of the drive unit can be assigned to the first and / or second diaphragm, for example, and configured to excite vibrations at the diaphragm, for instance, by being mechanically coupled to it. Depending on the embodiment, for example, one drive element per diaphragm can be provided on the drive unit, or a common drive element can be provided for the first or second diaphragm, whereby the excitation of the other diaphragm can be achieved, for example, by a superimposed drive signal and a mechanical coupling of the first and second diaphragms. The drive element can, for example, be configured to compress and / or stretch the respective diaphragm in certain areas, thereby causing a deflection of the diaphragm.Depending on the embodiment, the drive element can be bidirectional, meaning it can deflect the respective diaphragm either in a first direction of deflection and in a second direction opposite to the first, or it can be unidirectional, meaning it can deflect the respective diaphragm in only one predetermined direction. The drive element can be, for example, a capacitive, ferroelectric, or piezoelectric drive element. In principle, it is also conceivable to use alternative drive concepts for the electromechanical actuation of the diaphragm. According to the features described above, the drive device is configured to excite the first diaphragm to a first vibration at a first frequency and to excite the second diaphragm to a second vibration at a second frequency that differs from the first.The first oscillation at the first frequency and the second oscillation at the second frequency can be considered mechanical, for example, at least approximately sinusoidal, vibrations of the membranes. The second frequency of the second oscillation can be considered a frequency that differs from the first frequency of the first oscillation. In particular, the second frequency can be higher than the first frequency. The first and second frequencies can, in particular, differ from the frequency of the generated fluid pulses, since the generation of pressure oscillations and fluid pulses depends on the vibration behavior of the membranes and not directly on the excitation frequency. Due to this frequency decoupling, low-frequency sound signals with high sound power can be generated despite the very small dimensions of the microelectromechanical device.To generate different frequencies, it is generally possible to subject the diaphragms to different excitation frequencies using different drive elements of the drive unit. Alternatively or additionally, it is conceivable to design the natural frequencies of the diaphragms differently through suitable geometric design and dimensioning. Even small diaphragm deflections are effective and efficient in generating a pressure oscillation, allowing the microelectromechanical device to be operated efficiently and with low energy consumption.

[0036] According to one embodiment, the second diaphragm can have a natural frequency that is essentially twice that of the first diaphragm. For example, the natural frequency of the second diaphragm can be essentially twice the natural frequency of the first. For example, the natural frequency of the second diaphragm can be essentially twice the natural frequency of the first diaphragm plus or minus at most 25 percent of the first frequency. This allows a favorable phase relationship between the first and second diaphragms to be achieved when the diaphragms are excited at or near their natural frequencies, enabling efficient pressure oscillation and fluid pulse generation. At the diaphragms' natural frequencies, larger amplitudes can be generated for the same excitation energy than outside the natural frequency range.The natural frequency of the first and second membranes can be influenced, for example, by their geometric design and dimensions.

[0037] According to one embodiment, the first membrane can have a recess and / or the second membrane can have a stiffening structure. The natural frequency can therefore also be influenced by changing the stiffness of the membranes. For example, a stiffening structure, such as a stiffening lip, can be molded onto the second membrane to increase its stiffness and thus its natural frequency. Conversely, a recess can be incorporated into the first membrane to reduce its stiffness and thus its natural frequency. Stiffening structures or recesses can also be used to selectively influence the movement pattern of the membranes, for example, to enable the movement of a larger fluid volume. According to another embodiment, a sealing lip can be provided between the first and second membranes.This allows for a favorable seal, resulting in improved displacement behavior of the functional unit, without impairing the mechanical properties of the membranes. Alternatively or additionally, it may be possible, for example, to thin the first and second membranes at their facing ends or at their transition zone to favorably influence the displacement behavior of the functional unit. Such thinning can be advantageous, for instance, depending on the properties of the fluid being pumped or the base thickness of the membrane.

[0038] According to one embodiment, the natural frequency of the first diaphragm and / or the natural frequency of the second diaphragm can be at least 20 kHz. This allows for efficient excitation of the first and / or second diaphragm in an ultrasonic frequency range inaudible to the human ear. This applies analogously to the ultrasonic vibrations generated in the passageway by the excitation of the first and second diaphragms. Consequently, the device can operate without audible pumping noise or disruptive harmonics. Furthermore, at such high frequencies, many vibrations per unit of time can be generated, enabling the proposed device to achieve a high energy conversion per unit of time and, for example, high pumping power or high sound power.

[0039] According to one embodiment, the drive device can have a drive element arranged on the first diaphragm and another on the second diaphragm. This allows the first and second diaphragms to be excited to individual vibrations independently of each other in a simple and direct manner.

[0040] According to one embodiment, the first and second membranes can be mechanically coupled. This allows the vibrations of one membrane to be at least partially transmitted to the other. The mechanical coupling of the first and second membranes can be achieved, for example, by appropriately structuring a membrane layer of the device. The mechanical coupling can be formed, for example, by coupling points flanking a separation gap between the membranes. Depending on the design of the mechanical coupling, for example, by using different elasticities of the coupling, the relative vibration behavior of the membranes can also be specifically influenced.

[0041] According to one embodiment, the first and second diaphragms can be configured to be excited by a superimposed drive signal from a drive element assigned to either the first or second diaphragm. This allows for the provision of an efficient and simply constructed microelectromechanical device. Furthermore, a high pumping or acoustic power output can be achieved with just one drive element for both the first and second diaphragms.

[0042] According to one embodiment, the microelectromechanical device can have at least two first diaphragms configured to be excited by the first vibration at the first frequency by means of the drive unit, and / or at least two second diaphragms configured to be excited by the second vibration at the second frequency by means of the drive unit. This allows for the provision of an efficient microelectromechanical device suitable, for example, for generating high pumping or sound power. The first and second diaphragms can, for example, be arranged alternately next to each other in order to optimally utilize the dynamic relative vibration behavior of the first and second diaphragms.

[0043] According to one embodiment, two secondary diaphragms can be mechanically coupled to a first diaphragm arranged between them. The secondary diaphragms and the first diaphragm are configured to be excited by a superimposed drive signal from drive elements of the drive unit assigned to the secondary diaphragms. This forms a seesaw-like structure, enabling the provision of an efficient microelectromechanical device. The secondary diaphragms can be designed to be excited at approximately twice the frequency of the first diaphragm; for example, the secondary diaphragms can be given a natural frequency twice that of the first diaphragm through suitable geometric design and dimensioning.The functional unit can be designed such that the two secondary diaphragms, relative to the fluid volume displaced by their movement, have a higher displacement than the first diaphragm positioned between them. The secondary diaphragms can be configured to be excited at a second frequency that is essentially twice the frequency of the first diaphragm. It can be advantageous for the first diaphragm to be suspended from, and thus coupled to, the secondary diaphragms and to exhibit their fundamental frequency. In such an arrangement, the combined surface area of ​​the first and second diaphragms is advantageously used to excite the pressure oscillation.

[0044] According to one embodiment, the through-channel can have a first channel section and a second channel section, wherein the first channel section adjoins the functional unit and has a larger cross-section than the second channel section. In other words, the through-channel can have a widening below the functional unit. The first channel section can form an expanded clearance at the functional unit to increase its range of motion. This allows movable functional elements of the functional unit, such as the aforementioned first and second diaphragms of the functional unit, to be deflected further and thereby achieve, for example, a higher displacement capacity. The generation of the pressure oscillation in the through-channel, as well as any associated effects such as the aforementioned clarinet effect, are only minimally affected by the cross-sectional expansion.It is advantageous if the cross-section of the first channel section is at most three times, and in particular at most twice, the size of the cross-section of the second channel section. Conceptually, the cross-section can refer specifically to the cross-sectional area of ​​the channel space in a plane parallel to the front of the substrate. The first channel section can, for example, transition into the second channel section via a step or a conical profile. However, it is also possible for the channel to have no change in cross-section from the functional unit to the back of the substrate.

[0045] The invention also relates to a microelectromechanical loudspeaker comprising a microelectromechanical device according to one of the features described above, wherein the vibration generator unit of the microelectromechanical device is configured to generate a sound signal, and a signal processing unit for applying and processing signals from the microelectromechanical device. Due to the design of the device described above, the proposed microelectromechanical loudspeaker enables efficient and powerful sound pressure generation despite the device's very small dimensions. In particular, the frequency of the sound signal generated with a variable fluid pulse signal deviates from the predetermined vibration frequency of the pressure oscillation.In particular, the pressure oscillation can have a predetermined oscillation frequency in an ultrasonic range inaudible to the human ear, while the frequency of the generated sound signal lies within an audible frequency range. For example, a variable fluid pulse signal with alternating increasing and decreasing suction pulses and subsequent increasing and decreasing pump pulses can be generated to produce a sound signal. The proposed loudspeaker can also generate low-frequency sound signals with high sound power. Therefore, for example, efficient and powerful use of the loudspeaker as a bass speaker is conceivable. By utilizing the vibrational energy of the generated pressure oscillation and decoupling the sound signal frequency from the pressure oscillation frequency, the microelectromechanical loudspeaker can be operated very energy-efficiently.Furthermore, secondary sound power from the loudspeaker during vibration generation can be advantageously reduced or eliminated by destructive interference through the adjacent arrangement of several vibration generator units. A signal processing unit can be considered a control circuit, which can be designed as an integrated circuit, for example, as an ASIC (application-specific integrated circuit). The signal processing unit is configured to apply and process signals from the microelectromechanical device and can, in particular, control the electromechanical actuation of the functional unit, for example, the electrical control of a drive unit for deflecting the diaphragms of the functional unit.

[0046] The invention also relates to a microelectromechanical fluid pumping device comprising a microelectromechanical device according to one of the features described above, wherein the vibration generator unit of the device is configured to generate a pumping current, and a signal processing unit for applying and processing signals from the microelectromechanical device. The microelectromechanical device can therefore be used, for example, as a fluid pump. The pumping current can be generated by the pressurized fluid pulses and simulated as a quasi-constant fluid flow. When used in a fluid pumping device, the fluid pulse frequency of the microelectromechanical device can be constant. The proposed fluid pumping device enables powerful, efficient, and low-noise fluid pumping, for example, for cooling systems in electrical or mobile devices.

[0047] In principle, a microelectromechanical combination component can also be formed using the microelectromechanical device. For this purpose, the microelectromechanical combination component comprises a microelectromechanical device according to one of the preceding features and a signal processing unit for applying and processing signals from the microelectromechanical device, wherein the functional unit of the device is configured to selectively generate either an acoustic signal or a pump current. The proposed combination component can, for example, be advantageously used in a mobile device to be operated selectively or as a loudspeaker, either as needed or as a cooling device.

[0048] The invention also relates to a method for operating a microelectromechanical device according to one of the features described above, wherein a pressure oscillation with a predetermined oscillation frequency is generated in the through-channel by means of the vibration generator unit, and a vibration pressure pulse reflected from the through-channel towards the functional unit is extracted from the through-channel as a pressurized fluid pulse through the temporarily formed fluid opening of the functional unit. The proposed method also achieves the advantages described above of efficient fluid pulse generation with high achievable sound or pumping power in a very small space.

[0049] According to one embodiment, a variable fluid pulse signal can be generated from the pressurized fluid pulses to produce a sound signal. For this purpose, the microelectromechanical device can, for example, be operated alternately in a pumping mode and a suction mode, with the microelectromechanical device operating in a neutral mode without significant fluid pulse generation during the transitions. The extracted fluid pulses can form a fluid pulse signal with increasing and decreasing pulse intensity, which can be varied, for example, by a continuous phase change when controlling the diaphragms of the functional unit. A sound signal, for example, with sinusoidal tone vibrations, can be simulated using the fluid pulse signal.The sound signal can have a significantly lower frequency compared to the fluid pulse signal and can therefore be generated, for example, in an audible, low frequency range with high amplitudes, while the vibration generator units are operated at high vibration frequencies.

[0050] According to one embodiment, a standing wave can be generated in the through-channel by means of a pressure oscillation at a predetermined oscillation frequency. This enables particularly energy-efficient operation of the microelectromechanical device. For example, the functional unit of the vibration generator can generate a pressure oscillation with a predetermined oscillation frequency that is matched to the dimensions of the through-channel. For example, the predetermined oscillation frequency can be such that the length of the through-channel from the functional unit to the back of the substrate is such that a standing wave is generated in the through-channel when the pressure oscillation is generated at the predetermined oscillation frequency.

[0051] According to one embodiment, the microelectromechanical device can have at least two vibration generator units, and the vibration generator units can be operated with a phase shift, so that overpressure pulses or underpressure pulses of the pressure vibration propagating from the rear of the substrate into the environment of the microelectromechanical device are reduced or eliminated by destructive interference. This can, for example, reduce secondary sound power, in particular secondary ultrasonic power, that would otherwise be emitted into the environment, thus increasing the efficiency of the microelectromechanical device and reducing any potential environmental impact.

[0052] According to further training, linearly arranged vibration generator units can be operated with a phase shift of 180° between adjacent units, and / or hexagonally arranged vibration generator units can be operated with a phase shift of 120° between adjacent units. This allows the previously described effect of reducing secondary sound power through destructive interference to be specifically optimized depending on the arrangement of the vibration generator units relative to each other.

[0053] According to one embodiment, the functional unit can have a first diaphragm and a second diaphragm that are movable relative to each other. To generate the pressurized fluid pulses, the first diaphragm is excited to a first oscillation at a first frequency, and the second diaphragm is excited to a second oscillation at a second frequency that differs from the first, by means of a drive unit of the microelectromechanical device. This allows the functional unit to perform both a valve and a displacement function in a simple and efficient manner. Within a very small installation space, the first and second diaphragms enable the generation of the pressure oscillation, the temporary creation of a fluid orifice, and the extraction of pressurized fluid pulses through this orifice.

[0054] According to a further development, the second frequency of the second oscillation can be essentially twice as high as the first frequency of the first oscillation. For example, the second frequency can be essentially twice the first frequency. For example, the second frequency can be essentially twice the first frequency plus or minus at most 25 percent of the first frequency. The second membrane can therefore complete approximately two periods during one period of the first membrane, i.e., oscillate at least approximately twice as fast as the first membrane. This allows for a favorable phase relationship between the membranes, enabling efficient fluid pulse generation. According to one embodiment, the first frequency and / or the second frequency can be at least 20 kHz. This allows for excitation of the first and / or second membrane outside the human audible frequency range.Furthermore, such high frequencies generate a large number of oscillations per unit of time, resulting in a high energy conversion per unit of time and enabling, for example, high pumping power or high sound power during operation of the device. It is conceivable, for instance, to select frequency ranges of 50 to 450 kHz, particularly 350 to 450 kHz, and especially 400 kHz, at least for the second frequency of the second oscillation. This allows for the use of very small and rigid microelectromechanical structures for the device. This results in high efficiency and space utilization of the microelectromechanical device.

[0055] According to one embodiment, a fixed phase relationship can be established between the first vibration of the first diaphragm and the second vibration of the second diaphragm. This allows for at least quasi-constant fluid flow generation. A fixed phase relationship can be advantageous, for example, for operating the device for ventilation and cooling purposes. Due to the compact and flat design of the microelectromechanical device, it is conceivable, for instance, to use it as a cooling device in electronic equipment, particularly in mobile electronic devices. By operating the vibration generator unit at excitation frequencies of at least 20 kHz, above the human hearing range, as proposed as an advantageous option, quiet and energy-efficient operation of the device as a cooling unit can be achieved.

[0056] According to one embodiment, the phase relationship between the first oscillation of the first diaphragm and the second oscillation of the second diaphragm can be varied to generate a variable fluid pulse signal for sound production using the extracted pressurized fluid pulses. By varying the phase relationship between the first oscillation of the first diaphragm and the second oscillation of the second diaphragm, the generated pressure oscillation and the timing of the fluid opening can be adjusted according to predefined conditions to vary the frequency of the generated fluid pulses and thereby produce a sound signal. According to one embodiment, the first diaphragm and the second diaphragm can each be excited by a drive element of the drive unit. This allows the first and second diaphragms to be excited to individual oscillations in a simple and direct manner.According to a further embodiment, the first and second diaphragms can be excited by a superimposed drive signal from a drive element assigned to either the first or second diaphragm. This allows for a more efficient process and eliminates the need for a separate drive element for each diaphragm. The first and second diaphragms can be mechanically coupled. According to another embodiment, the device can have at least two first diaphragms that are excited to the first vibration at the first frequency by means of the drive unit, and / or at least two second diaphragms that are excited to the second vibration at the second frequency by means of the drive unit.By exciting more than one first diaphragm to a first vibration at a first frequency and / or more than one second diaphragm to a second vibration at a second frequency, the generation of pressurized fluid pulses can be improved, and, for example, pumping or sound power can be increased. The first and second diaphragms can, for instance, be arranged alternately next to each other to optimally utilize the dynamic relative vibration behavior of the first and second diaphragms.

[0057] According to one embodiment, two secondary diaphragms can be mechanically coupled to a first diaphragm arranged between them. The secondary diaphragms and the first diaphragm are excited by a superimposed drive signal from the drive elements of the drive unit assigned to the secondary diaphragms. This creates a seesaw-like structure with which the device can be operated efficiently. The second frequency of the second oscillation of the secondary diaphragms can be essentially twice as high as the first frequency of the first oscillation of the first diaphragm. The excitation of the secondary diaphragms can be effected by a symmetrical signal applied to a drive element of the drive unit assigned to each secondary diaphragm.The first diaphragm can be excited by a superimposed differential signal, which is additionally applied to the drive elements of the second diaphragm and transmitted to the first diaphragm via the mechanical coupling between the second and first diaphragms. The resulting seesaw-like structure optimizes the operation of the vibration generator unit. For example, a large fluid volume can be pumped per stroke of the vibration generator unit.Furthermore, the opposing movements of the first and second membranes, which oscillate in opposite directions, can achieve an increased number of pumping movements per oscillation cycle. This is because, for example, with a second frequency of the second membranes approximately twice as high as the first frequency of the first membrane, the proposed membrane arrangement can produce several oscillation phases per cycle in which the first and second membranes oscillate in the same direction and can thus pump a fluid volume. One oscillation cycle can, for example, correspond to one period of the first oscillation of the first membrane. Generally speaking, in the context of this application, the words "a / an" are not to be understood as numerals, unless expressly defined otherwise, but rather as indefinite articles meaning "at least one / an".

[0058] The invention allows for various embodiments and is explained in more detail below with reference to exemplary embodiments and the accompanying drawings. These show, in schematic form:

[0059] Fig. 1 - a basic principle of a microelectromechanical device according to a first embodiment in a cutaway side view;

[0060] Fig. 2 - a microelectromechanical device according to a second

[0061] Design shown in a top view;

[0062] Fig. 3 - a microelectromechanical device according to a third

[0063] Design shown in a top view;

[0064] Fig. 4 - a functional unit of a microelectromechanical

[0065] Device according to a first embodiment variant in a cutaway side view;

[0066] Fig. 5 - the functional unit according to the first embodiment variant in a top view;

[0067] Fig. 6-14 - a functional principle of the functional unit according to the first embodiment variant based on a vibration cycle;

[0068] Fig. 15 - a functional unit of a microelectromechanical

[0069] Device according to a second embodiment variant in a cutaway side view;

[0070] Fig. 16 - the functional unit according to the second design variant in a top view;

[0071] Fig. 17 - a functional principle of the functional unit according to the second

[0072] Implementation variant with a first dimensioning of a through-channel of the microelectromechanical device and operation of the same in a pumping mode;

[0073] Fig. 18 - a functional principle of the functional unit according to the second

[0074] Design variant with the first dimensioning of the through-channel of the microelectromechanical device and its operation in a suction mode;

[0075] Fig. 19 shows a more detailed illustration of the operating principle illustrated in Fig. 17, including intermediate states of the functional unit;

[0076] Fig. 20a / b shows a functional principle of the functional unit according to the second embodiment variant with a second dimensioning of the through-channel of the microelectromechanical device and operation of the same in a suction mode;

[0077] Fig. 21 shows a simplified operating principle for generating a sound signal using the microelectromechanical device;

[0078] Fig. 22 shows a functional unit of a microelectromechanical device according to a third embodiment in a cutaway side view;

[0079] Fig. 23 shows the functional unit according to the third design variant in a top view;

[0080] Fig. 24 shows a functional unit of a microelectromechanical

[0081] Device according to a fourth embodiment variant in a cutaway side view;

[0082] Fig. 25 shows the functional unit according to the fourth design variant in a top view;

[0083] Fig. 26 shows a functional unit of a microelectromechanical

[0084] Device according to a fifth embodiment variant in a cutaway side view;

[0085] Fig. 27 shows the functional unit according to the fifth design variant in a top view;

[0086] Fig. 28 shows a functional unit of a microelectromechanical

[0087] Device according to a sixth embodiment variant in a cutaway side view;

[0088] Fig. 29 shows the functional unit according to the sixth design variant in a top view;

[0089] Fig. 30 shows a functional unit of a microelectromechanical device according to a seventh embodiment in a sectional side view; Fig. 31 shows the functional unit according to the seventh embodiment in a top view;

[0090] Fig. 32 - a functional unit of a microelectromechanical

[0091] Device according to an eighth embodiment variant in a cutaway side view;

[0092] Fig. 33 - the functional unit according to the eighth design variant in a top view;

[0093] Fig. 34 - a functional unit of a microelectromechanical

[0094] Device according to a ninth embodiment variant in a cutaway side view;

[0095] Fig. 35 - the functional unit according to the ninth design variant in a top view;

[0096] Fig. 36 - a microelectromechanical device according to a fourth

[0097] embodiment in a cutaway side view;

[0098] Fig. 37 - a schematic diagram of a microelectromechanical component with a microelectromechanical device; and

[0099] Fig. 38 - a simplified representation of a functional principle of a

[0100] Vibration generator unit of a microelectromechanical device.

[0101] Fig. 1 shows a schematic diagram of a microelectromechanical device 1 for generating pressurized fluid pulses F according to a first embodiment. The microelectromechanical device 1 has a substrate 7 with a front side 7a and a back side 7b. Furthermore, the microelectromechanical device 1 has several, in total four, vibration generator units 2, which serve to generate pressure oscillations and to extract pressurized fluid pulses F from the generated pressure oscillations. According to the embodiments shown in the figures, the vibration generator units 2 are essentially identical in shape and dimensions. Each vibration generator unit 2 has a functional unit 13 arranged on the front side 7a of the substrate and a through-channel 5 extending from the functional unit 13 to the back side of the substrate 7.

[0102] The functional unit 13 in the vibration generator unit 2 has a valve function for temporarily creating a fluid opening 14 and a displacement function for displacing fluid, for example, air. A vibration pressure pulse 15 can be generated in the direction of the flow channel 5 by means of the displacement function. In addition, a reflected vibration pressure pulse 15a can be extracted from the flow channel 5 as a fluid pulse F. According to the state shown in Fig. 1, the vibration generator unit 2 can be controlled such that, when the fluid opening 14 is created, a vacuum pulse 34 reaches the functional unit 13, so that the fluid pulse F is subjected to a vacuum and forms a suction pulse. The direction of the fluid pulse F indicates an average flow direction of the fluid pulse F, which here is directed towards the functional unit 13, corresponding to the suction pulse.By adapting the control of the functional unit 13, the vibration generator unit 2 can also be controlled such that, upon opening of the fluid orifice 14, an overpressure pulse 33 reaches the functional unit 13, so that the fluid pulse F is pressurized and forms a pump pulse. This will be explained in more detail below in connection with Figures 17 to 20a / b.

[0103] The vibration generator units 2 are designed to generate a pressure oscillation with a predetermined oscillation frequency in the through-channels 5 and to discharge vibration pressure pulses 15a reflected from the through-channels 5 towards the functional unit 13 through the temporarily formed fluid openings 14 of the functional units 13 as pressurized fluid pulses F.With the vertically extending passage channels 5 through the substrate 7, a pressure oscillation volume is formed in the form of a vibration tube that is at least temporarily closed on one side, in which a reciprocating pressure oscillation with superposition of the vibration pressure pulses 15, 15a can be formed in the passage channel 5 by means of the displacement function of the functional unit 13 by emitting vibration pressure pulses 15 or amplifying reflected vibration pressure pulses 15a towards the open end of the passage channel 5 on the back 7b of the substrate 7 and by vibration pressure pulses 15a reflected towards the functional unit 13.The vibrational energy of the pressure oscillation can advantageously be used to generate pressurized fluid pulses F by opening a valve 14 using the functional unit 13 upon arrival of a reflected vibrational pressure pulse 15a and extracting the reflected vibrational pressure pulse 15a as a pressurized fluid pulse F. The valve function of the functional unit 13 can therefore be temporally synchronized with the oscillation frequency of the generated pressure oscillation. While the pressure oscillation can advantageously oscillate in an ultrasonic frequency range, an acoustic signal in an audible frequency range can be generated using the extracted fluid pulses F, as will be explained in more detail below in connection with Fig. 21. Alternatively or additionally, a quasi-constant fluid flow generation using the pressurized fluid pulses F is also feasible.

[0104] The proposed principle enables the generation of pronounced fluid pulses F in the microelectromechanical device 1 with extremely small dimensions, whereby the limited installation space is utilized particularly efficiently by creating vertical vibration volumes in the substrate 7 of the microelectromechanical device 1. Thus, the microelectromechanical device 1 can generate sound signals with high sound pressure levels over a wide frequency range. Furthermore, the microelectromechanical device 1 can be operated with exceptional energy efficiency.

[0105] The microelectromechanical device 1 can be operated according to a method in which a pressure oscillation with a predetermined oscillation frequency is generated in the through-channel 5 by means of the vibration generator unit 2, and a vibration pressure pulse 15a reflected from the through-channel 5 towards the functional unit 13 is extracted as a pressurized fluid pulse F through the temporarily formed fluid opening 14 of the functional unit 13. The vibration generator units 2 shown by way of example in Fig. 1 can be designed, in particular, to generate standing waves in the through-channels 5 by means of the pressure oscillations according to the predetermined oscillation frequency in order to achieve particularly energy-efficient operation of the microelectromechanical device 1.Accordingly, during operation of the microelectromechanical device 1, standing waves can be generated in the through-channels 5 by means of pressure oscillations at the predetermined oscillation frequency. For this purpose, a length LD of the through-channels 5 from the respective functional unit 13 to the rear side 7b of the substrate 7 can correspond to essentially one-quarter or one-quarter and multiples of one-half of the wavelength of the pressure oscillations at the predetermined oscillation frequency. Due to the design of the vibration generator units 2 as temporarily closed-end vibration tubes, it is already possible to form a standing wave with a length LD of one-quarter of the wavelength of the generated pressure oscillation. Stable and high oscillation amplitudes can be generated with standing waves, which can be advantageously used to obtain pressurized fluid pulses F.The length LD of the through-channels 5 can, for example, range from 50 pm to 2 mm, and in particular from 250 pm to 800 pm. Therefore, depending on the application and the specified vibration frequency, very short to comparatively extended vibration volumes can be achieved with readily available or manufacturable substrate dimensions.

[0106] The longitudinal extent LD of the through-channels 5 can be at least twice as large as the lateral extent BD of the through-channels 5 perpendicular to the longitudinal extent LD, as shown. In this context, the vertical extent of the through-channels 5 is paramount for vibration generation, and their elongated, narrow shape allows for the arrangement of multiple through-channels 5 side by side. The lateral extent BD of the through-channels 5 can be at least half as large as the lateral extent BF of the functional units 13, as shown, so that the dimensions of the through-channels 5 and the functional units 13 are advantageously matched to each other, ensuring efficient vibration generation.

[0107] By having several vibration generator units 2 in the microelectromechanical device 1 according to the illustrated embodiment, the achievable total power of the microelectromechanical device 1 can be advantageously increased. Furthermore, the vibration generator units 2 can be arranged in the device 1 at such a small distance A from each other that vibrations emerging at the open ends of the through-channels 5 on the rear side 7b of the substrate 7 can be reduced or eliminated by destructive interference between the emerging vibration pressure pulses 15 if the vibration generator units are operated with a suitable phase shift. As shown in Fig.As can be seen in Figure 1, to achieve such a reduction in vibration, in particular a distance A between the vibration generating units 2 can be smaller than the length LD and smaller than the width BD of the passage channels 5 of the vibration generating units 2.

[0108] The vibration generator units 2 can be configured, in particular, to generate pressure vibrations with a predetermined vibration frequency above 20 kHz. This makes the generated pressure vibrations for obtaining pressurized fluid pulses F imperceptible to the human ear, thus enabling the microelectromechanical device 1 to be operated with a high degree of user comfort.

[0109] Furthermore, as can be seen in Fig. 1, the functional units 13 each have a first diaphragm 3 and two second diaphragms 4, which are movable relative to each other. The microelectromechanical device 1 has, for example, a capacitive, ferroelectric, or piezoelectric drive unit 6, which is configured to excite the first diaphragm 3 to a first oscillation at a first frequency fi and to excite the second diaphragms 4 at a second frequency f2 that differs from the first frequency fi. For this purpose, the drive unit 6 has a drive element 6b arranged on each of the second diaphragms 4.The two second diaphragms 4 are mechanically coupled to the first diaphragm 3 located between them, such that the second diaphragms 4 and the first diaphragm 3 are configured to be excited by a superimposed drive signal from the drive elements 6b of the drive unit 6 assigned to the second diaphragms 4. This allows for the provision of highly efficient functional units 13 with valve and displacement elements, which can be deflected with minimal energy expenditure to generate oscillatory pressure pulses 15, to temporarily create valve openings 14, and to extract pressurized fluid pulses F. By appropriately exciting the first diaphragm 3 and the second diaphragms 4, the oscillation patterns of the diaphragms 3 and 4 can be advantageously influenced and used to vary the generation of pressure oscillations and fluid pulses.A functional principle of the functional unit 13 with a first membrane 3 and two second membranes 4 is described below with reference to Figs. 17 to 20a / b.

[0110] Fig. 2 shows a microelectromechanical device 1 according to a second embodiment in a top view. The illustrated microelectromechanical device 1 has several, here a total of six, functional units 13, which can be used for vibration generation and fluid pulse extraction. Viewed from above, through-channels 5 extend behind the functional units 13 through the substrate 7 analogous to the basic principle illustrated in Fig. 1. In Fig. 2, it can be seen that the functional units 13 have a rectangular outer contour 13a, which is adapted to a basic shape of the through-channels 5 extending behind them. The elongated rectangular outer contour 13a of the functional units 13 thus results in a slot-shaped basic shape of the through-channels 5. In addition, the vibration generator units 2 are arranged linearly one after the other, as can be seen in the illustration. In Fig.Figure 2 shows that in this way several vibration generator units 2 can be arranged side by side in a space-saving manner, resulting in optimized chip area utilization. Furthermore, the compact arrangement allows pressure pulses of the pressure vibration propagating from the rear side 7b of the substrate 7 into the environment 16 of the microelectromechanical device 1 to be reduced or eliminated by destructive interference when the vibration generator units 2 are operated with a phase shift. Due to the linear arrangement of the vibration generator units 2, such an effect can be advantageously optimized with a phase shift of 180° between adjacent vibration generator units 2.

[0111] Fig. 3 shows a top view of a microelectromechanical device 1 according to a third embodiment. The illustrated microelectromechanical device 1 has several, here a total of eighteen, functional units 13, which can be used for generating vibrations and extracting fluid pulses. Viewed from above, corresponding through-channels 5 extend behind the functional units 13 through the substrate 7, analogous to the basic principle illustrated in Fig. 1. Fig. 3 shows that the functional units 13 have a circular outer contour 13a, which is adapted to a basic shape of the through-channels 5 extending behind them. The circular outer contour 13a of the functional units 13 thus results in a cylindrical basic shape for the through-channels 5.With cylindrically shaped through-channels 5, a defined, uniform pressure oscillation can be generated in the through-channels 5, and any clarinet effect resulting from the closed-ended, tube-like character of the through-channels 5 can be better utilized. Furthermore, it can be seen that the vibration generator units 2 are arranged hexagonally to one another, which allows for a particularly space-saving arrangement of the vibration generator units 2. This compact arrangement also enables pressure pulses of the pressure oscillation propagating from the rear side 7b of the substrate 7 into the environment 16 of the microelectromechanical device 1 to be reduced or eliminated by destructive interference.Due to the hexagonal arrangement of the vibration generator units 2, such an effect can be advantageously optimized with a phase offset of 120° between adjacent vibration generator units 2.

[0112] Figures 4 and 5 show in more detail a functional unit 13 of a microelectromechanical device 1 according to a first embodiment in a sectional side view and a top view. The functional unit 13 has a first diaphragm 3 and a second diaphragm 4, which are arranged above the passage 5. According to the illustrated embodiment, the diaphragms 3 and 4 are laterally anchored and project beyond the passage 5. For sealing and improved pumping performance, a sealing lip 12 is formed on both the first diaphragm 3 and the second diaphragm 4.

[0113] The first diaphragm 3 and the second diaphragm 4 are movable relative to each other. The diaphragms 3 and 4 can, for example, oscillate together in one direction or oscillate past each other. A separating gap 8 can be provided between the first diaphragm 3 and the second diaphragm 4 to allow the relative movement of the diaphragms 3 and 4. The device 1 has a drive unit 6 with a drive element 6a for the first diaphragm 3 and a drive element 6b for the second diaphragm 4. The drive elements 6a and 6b are coupled to their respective assigned diaphragms 3 and 4 and are configured to excite the diaphragms 3 and 4 to oscillate independently of each other.The drive unit 6 is designed to excite the first diaphragm 3 to a first vibration with a first frequency h and the second diaphragm 4 to a second vibration with a second frequency f2, the second frequency f2 differing from the first frequency h. This creates a phase shift between the vibrating diaphragms, which can be used to form a fluid opening 14 as shown in Fig. 8. The vibration patterns of the diaphragms 3 and 4 can be varied by means of control technology, thereby influencing various parameters of the vibration generation, the formation of the fluid opening, and the extraction of pressurized fluid pulses F.

[0114] In the example according to the first embodiment, the second frequency f2 of the second oscillation can be essentially twice as high as the first frequency h of the first oscillation, so that the second diaphragm 4 oscillates approximately twice as fast as the first diaphragm 3. For this purpose, the second diaphragm 4 can be dimensioned with a smaller width b2 compared to the width bi of the first diaphragm 3, as shown in Fig. 5, in order to effect a higher natural frequency of the second diaphragm 4. The frequency doubling results in a phase relationship between the oscillations of the diaphragms 3 and 4 that is favorable for generating the oscillations.

[0115] Figures 6 to 14 schematically illustrate the operating principle of the functional unit 13 according to the first embodiment, using a vibration cycle as an example. The microelectromechanical device 1 is designed such that the length LD of the through-channel 5 from the functional unit 13 to the rear side 7b of the substrate 7 corresponds essentially to one-quarter of the wavelength of the pressure vibrations with the predetermined vibration frequency. The vibration cycle is depicted in maximum power operation, in which zero crossings of the first vibration of the first diaphragm 3 coincide with zero crossings of the second vibration of the second diaphragm 4. According to the illustrated embodiment, the second frequency f2 of the second vibration of the second diaphragm 4 is essentially twice as high as the first frequency fi of the first vibration of the first diaphragm 3, so that the second diaphragm 4 vibrates approximately twice as fast as the first diaphragm 3.One period of the first oscillation of the first membrane 1, which corresponds to one oscillation cycle according to the example here, is denoted by T below. A first direction Ri of the membranes 3, 4 corresponds to a deflection direction of the membranes 3, 4 in the direction of the passage channel 5, while a second direction R2 of the membranes 3, 4 corresponds to a deflection direction of the membranes 3, 4 in a deflection direction opposite to the first direction Ri.

[0116] In Fig. 6, a vibration cycle of the functional unit 13 begins. The first diaphragm 3 and the second diaphragm 4 oscillate together in the first direction Ri, thereby moving a fluid volume in the passage 5, generating a vibration pressure pulse 15 in the form of an overpressure pulse 33. At this point, the first diaphragm 3 and the second diaphragm 4 oscillate in phase; there is no phase shift between the first diaphragm 3 and the second diaphragm 4, and the separation gap 8 between the first diaphragm 3 and the second diaphragm 4 is at least approximately closed. Fig. 7 shows a state of the functional unit 13 at 1 / 8 T. In this state, the faster-oscillating second diaphragm 4 has already reached its maximum displacement in the first direction Ri and begins to oscillate back in the second direction R2, while the first diaphragm 3 continues to oscillate in the first direction Ri.Due to the different deflection states of the membranes 3, 4, the separation gap 8 opens and begins to form a fluid opening 14 as shown in Fig. 8. In addition, the generated vibration pressure pulse 15 is converted into a negative pressure pulse 34 at the open end of the passage channel 5 by a phase shift and reflected back towards the functional unit 13.

[0117] Figure 8 shows a state of the functional unit 13 at 2 / 8 T. In this state, the faster-oscillating second diaphragm 4 has reached its zero crossing, while the first diaphragm 3 has reached its maximum displacement in the first direction Ri and begins to oscillate back in the second direction R2. In this state, the fluid opening 14 between the diaphragms 3 and 4 reaches its maximum. Shortly before the fluid opening 14 reaches its maximum, the reflected vibration pressure pulse 15a approaches in the form of the vacuum pulse 34. The first diaphragm 3, oscillating towards the passage channel 5, reflects the vacuum pulse 34 back towards the open end of the passage channel 5 and amplifies it. However, a portion of the vacuum pulse 34 can be extracted via the fluid opening 14 as a pressurized fluid pulse F, with the fluid pulse F forming a suction pulse.

[0118] Figure 9 shows a state of the functional unit 13 at 3 / 8 T. In this state, the faster-oscillating second diaphragm 4 has reached its maximum displacement in the second direction R2 and begins to oscillate again in the first direction Ri. The first diaphragm 3 continues to oscillate in the second direction R2. The fluid opening 14 between the diaphragms 3 and 4 begins to close. The extraction of the negative pressure pulse 34 can still continue in this state. Meanwhile, the portion of the negative pressure pulse 34 reflected back towards the passage channel 5 can be converted into a positive pressure pulse 33 at an open end of the passage channel 5 and reflected back towards the functional unit 13. Figure 10 shows a state of the functional unit 13 at 4 / 8 T, in which half a period has elapsed.In this state, the first diaphragm 3 and the second diaphragm 4 each reach their zero crossing, but with different directions of oscillation, so that almost no fluid volume is conveyed. The fluid opening 14 between the diaphragms 3 and 4 is largely closed. If the first diaphragm 3 is larger than the second diaphragm 4, a vibration pressure pulse 15 is generated or amplified as a negative pressure pulse 34 in this state. While the fluid opening 14 is closed, the reflected positive pressure pulse 33 reaches the functional unit 13, but is not extracted due to the closed fluid opening 14; instead, it is reflected back towards the open end of the passage channel 5.

[0119] Figure 11 shows a state of the functional unit 13 at 5 / 8 T. In this state, the faster-oscillating second diaphragm 4 has reached its maximum displacement in the first direction Ri for the second time, while the first diaphragm 3 continues to oscillate in the second direction R2. The fluid opening 14 between the diaphragms 3 and 4 begins to open again. Meanwhile, the portion of the overpressure pulse 33 reflected back towards the passage 5 can be converted into an underpressure pulse 33 at an open end of the passage 5 and reflected back towards the functional unit 13.

[0120] Figure 12 shows a state of the functional unit 13 at 6 / 8 T. In this state, the faster-oscillating second diaphragm 4 has again reached its zero crossing, while the first diaphragm 3 has reached its maximum displacement in the second direction R2 and begins to oscillate back in the first direction Ri. In this state, the fluid opening 14 between the diaphragms 3 and 4 is again at its maximum. A vibration pressure pulse 15a, reflected from the passage 5 towards the functional unit 13 in the form of a negative pressure pulse 34, can again be extracted via the fluid opening 14 as a pressurized fluid pulse F.

[0121] Figure 13 shows a state of the functional unit 13 at 7 / 8 T. In this state, the second diaphragm 4 has reached its maximum deflection in the second direction R2 for the second time, while the first diaphragm 3 continues to oscillate in the first direction Ri. The fluid opening 14 between the diaphragms 3 and 4 begins to close again. Meanwhile, the negative pressure pulse 34 is converted back into a positive pressure pulse 33 at the open end of the passage channel 5 and reflected back towards the functional unit 13.

[0122] Figure 14 shows a state of the functional unit 13 at 8 / 8 T, which again corresponds to the initial state shown in Figure 6. At 8 / 8 T, one full period of the first oscillation has elapsed. The first diaphragm 3 and the second diaphragm 4 oscillate together in the first direction Ri, thereby generating a pressure oscillation pulse 15 in the passage channel 5. At this point, the first diaphragm 3 and the second diaphragm 4 oscillate in phase; there is no phase shift between the first diaphragm 3 and the second diaphragm 4, and the fluid opening 14 between the first diaphragm 3 and the second diaphragm 4 is at least approximately closed. The overpressure pulse 33 reaching the functional unit 13 is reflected back towards the passage channel 5, but is not extracted due to the closed fluid opening 14.

[0123] To transition from generating negative pressure pulses 34 as pressurized fluid pulses F in a suction mode to generating positive pressure pulses 33 as pressurized fluid pulses F in a pumping mode, only a phase shift is required when exciting the first diaphragm 3 and the second diaphragm 4. This ensures that the fluid opening 14 is at its maximum when a positive pressure pulse 33, as a reflected vibrational pressure pulse 15a, reaches the diaphragms 3 and 4, and that the diaphragms 3 and 4 are at their zero crossings, meaning the fluid opening 14 is largely closed, when a negative pressure pulse 34, as a reflected vibrational pressure pulse 15a, reaches the diaphragms 3 and 4. To generate a negative pressure pulse 34 as a vibrational pressure pulse 15a, the diaphragms 3 and 4 can be deflected together in the opposite direction compared to the positive pressure pulse generation, i.e., upwards instead of downwards in the figures shown.

[0124] Figures 15 and 16 show a functional unit 13 of a microelectromechanical device according to a second embodiment. The second embodiment shown corresponds in its essential structure and operating principle to the functional unit 13 of the microelectromechanical device 1 shown in Figures 1 to 3. In this embodiment, the functional unit 13 has a first diaphragm 3, which is arranged between two second diaphragms 4 and mechanically coupled to them via coupling points 9. The first diaphragm 3 and the second diaphragms 4 form a seesaw-like structure. Between the first diaphragm 3 and the second diaphragms 4 are two separation gaps 8 and four coupling points 9. The coupling points 9 can form or enclose a pivot axis of the first diaphragm 3.Each of the second diaphragms 4 is assigned a drive element 6b of the drive unit 6, which is designed to excite the second diaphragms 4 at the second frequency f2. According to the illustrated embodiment, the first diaphragm 3 is not assigned a separate drive element. Instead, the first diaphragm 3 is excited by a differential signal superimposed on the drive signal of the drive elements 6b and by the mechanical coupling between the second diaphragms 4 and the first diaphragm 3, so that the movement of the second diaphragms 4 is at least partially transmitted to the first diaphragm 3. The drive signal of the drive unit 6 can be applied to the drive elements 6b as a symmetrical signal and superimposed on the differential signal. The drive signal of the drive elements 6b then leads to a second vibration of the second diaphragms 4 at the second frequency f2 and to a first vibration of the first diaphragm 3 at the first frequency f1.Due to the seesaw-like structure and the plurality of membranes 3, 4, a particularly high fluid volume can be displaced and more pulse energy can be extracted through the two fluid openings 14 formed in between.

[0125] Fig. 17 shows a functional principle of the functional unit 13 according to the second embodiment with a first dimensioning of the through-channel 5 of the microelectromechanical device 1 and its operation in a pumping mode. The first dimensioning of the through-channel 5 means that the length LD of the through-channel 5 from the respective functional unit 13 to the rear side 7b of the substrate 7 corresponds essentially to one quarter of the wavelength of the pressure oscillations with the specified oscillation frequency. To illustrate the pumping mode, four vibration generator units 2 with different phase angles are shown side by side, with a phase difference of 180° at the open end of the through-channel 5 between the vibration generator units 2 shown in Fig. 17 a) and c).Figure 17 a) shows that a oscillation pressure pulse 15, generated as a negative pressure pulse 34, generates a positive pressure pulse 33 at the open end of the flow channel 5 due to a phase shift, which propagates back towards the functional unit 13. Figure 17 b) shows that the positive pressure pulse 33 is reflected at the functional unit 13, but at the same time, a positive pressure pulse 33 can also be extracted as a pressurized fluid pulse F, in the sense of a pump pulse, through the maximally developed fluid openings 14. Figure 17 c) shows that the reflected positive pressure pulse 33 generates a negative pressure pulse 34 at the open end of the flow channel 5, which propagates towards the functional unit 13. In Fig. 17 d) it can be seen that the vacuum pulse 34 reaches the functional unit 13 when the fluid openings 14 are closed, so that the vacuum pulse 34 is reflected at the membranes 3, 4, but no fluid pulse F is extracted.Accordingly, the microelectromechanical device 1 is in a pumping mode in which overpressure pulses 33 can be extracted as pressurized fluid pulses F.

[0126] Fig. 18 shows essentially the same structure and function of the microelectromechanical device 1 analogous to Fig. 17, except that here it is operated in a suction mode. Accordingly, the fluid openings 14 are closed at a time shown in Fig. 18 b) when an overpressure pulse 33 reaches the functional unit 13, and open at a time shown in Fig. 18 d) when a negative pressure pulse 34 reaches the functional unit 13, so that this can be extracted from the passage 5 as a pressurized fluid pulse F in the sense of a suction pulse.

[0127] Fig. 19 shows a more detailed illustration of the operating principle illustrated in Fig. 17, including intermediate states of the functional unit 13. This makes it even easier to understand the vibration state of the first diaphragm 3 and the second diaphragms 4 while overpressure pulses 33 and underpressure pulses 34 propagate up or down the passage 5. It is evident that the microelectromechanical device 1 operates in a pump mode, since the overpressure pulses 33 are extracted as pressurized fluid pulses F.

[0128] Figures 20a and 20b show an illustration of the operating principle comparable to Figure 19, with intermediate states of the functional unit 13 during the negative and positive pressure pulse movements through the passage channel 5, where a second dimensioning of the passage channel 5 differs from the first dimensioning, in which the length extent LD of the passage channel 5 from the respective functional unit 13 to the back side 7b of the substrate 7 corresponds essentially to three quarters of the wavelength of the pressure oscillations with the specified oscillation frequency.Due to the longer distance that the overpressure pulses 33 and the underpressure pulses 34 must travel through the passage channel 5 before being converted into the other pulse type at the open end and reflected back to the functional unit 13, an underpressure pulse 34 is extracted as fluid pulse F only every second time the fluid openings 14 are at their maximum extent, and an overpressure pulse 33 is almost completely reflected at the functional unit 13 only every second time the fluid openings 14 are closed. The last state in Fig. 20b corresponds to the first state in Fig. 20a, so the sequence shown can be continuously repeated from the beginning.

[0129] Fig. 21 shows a schematic diagram of a functional principle for generating a sound signal 39 using the microelectromechanical device 1. For this purpose, the microelectromechanical device 1 is operated alternately in a pumping mode 35 and a suction mode 36, whereby the microelectromechanical device 1 can be operated in a neutral mode 37 without significant fluid pulse generation during the transitions. The extracted fluid pulses F form a fluid pulse signal 38 with increasing and decreasing fluid pulses F, which can be varied, for example, by a continuous phase change in the control of the diaphragms 3, 4 of a functional unit 13. A sound signal 39, illustrated here by a sinusoidal oscillation, can be simulated using the fluid pulse signal 38.It can be seen that the sound signal 39 has a significantly lower frequency compared to the fluid pulse signal 38 and can therefore be generated, for example, in an audible, low frequency range with high amplitudes, while the vibration generator units 2 are operated at high vibration frequencies.

[0130] Figures 22 and 23 show a functional unit 13 of a microelectromechanical device 1 according to a third embodiment. According to this third embodiment, the functional unit 13 has several, here two, first diaphragms 3 and several, here two, second diaphragms 4. This allows for the generation of high pumping or sound power. The first and second diaphragms 3, 4 are arranged alternately next to each other. In the illustrated embodiment, the first diaphragms 3 and the second diaphragms 4 are arranged above the passage 5. According to other embodiments, it is conceivable, for example, to arrange a first diaphragm 3 and a second diaphragm 4 in pairs above a respective passage 5. Each first diaphragm 3 is assigned a drive element 6a and each second diaphragm 4 is assigned a drive element 6b of the drive unit 6.The first membranes 3 are configured for excitation at a first frequency fi, and the second membranes 4 are configured for excitation at a second frequency f2. For this purpose, for example, the thickness di of the first membrane 3 can be smaller than the thickness d2 of the second membranes 4, in order to shape the natural frequencies of membranes 3 and 4 according to the intended excitation.

[0131] Figures 24 and 25 show a functional unit 13 of a microelectromechanical device 1 according to a fourth embodiment. The fourth embodiment corresponds to a modification of the third embodiment in which the different natural frequencies of the first diaphragms 3 and the second diaphragms 4 are not determined by different thicknesses di and d2, but rather the second diaphragms 4 have a stiffening structure 10, which in this case is formed as an integral stiffening lip 10a or, as shown, as several integral stiffening lips 10a per diaphragm 4. This allows the natural frequency of the second diaphragms 4 to be increased in a targeted and simple manner. Figures 26 and 27 show a functional unit 13 of a microelectromechanical device 1 according to a fifth embodiment.The fifth embodiment corresponds to a modification of the third and fourth embodiments, in which the different natural frequencies of the first membranes 3 and the second membranes 4 are not determined by a different thickness di and d2 or by a stiffening structure 10, but rather the stiffness and thus the natural frequency of the first membranes 3 is specifically reduced by recesses 11. The recess 11 can be produced, for example, by structuring the first membranes 3.

[0132] Figures 28 and 29 show a functional unit 13 of a microelectromechanical device 1 according to a sixth embodiment. In the sixth embodiment, a first diaphragm 3 and a second diaphragm 4 are provided for the functional unit 13, wherein the first diaphragm 3 and the second diaphragm 4 are fundamentally movable relative to each other by means of separating gaps 8, but are additionally mechanically coupled to each other via coupling points 9. The first diaphragm 3 and the second diaphragm 4 are excited by a superimposed drive signal from a drive element 6a assigned to the first diaphragm 3. With the illustrated sixth embodiment, a very simply designed functional unit 13 with a compact form can be provided.

[0133] Figures 30 and 31 show a functional unit 13 of a microelectromechanical device 1 according to a seventh embodiment. The seventh embodiment corresponds to a modification of the first embodiment, in which, however, a sealing lip 12 is provided between the first diaphragm 3 and the second diaphragm 4. This allows for a favorable seal to be achieved for improved pumping performance of the functional unit 13 without impairing the mechanical properties of the diaphragms 3 and 4. Alternatively or additionally, it may be possible, for example, to thin the first diaphragm 3 and the second diaphragm 4 at their facing ends or at their transition area to favorably influence the pumping performance of the functional unit 13.

[0134] Figures 32 and 33 show a functional unit 13 of a microelectromechanical device 1 according to an eighth embodiment. The eighth embodiment corresponds to a variant of the sixth embodiment, wherein the mechanical coupling area with coupling points 9 is geometrically designed and positioned differently in order to vary the relative dynamic behavior of the first diaphragm 3 and the second diaphragm 4 with respect to each other. By means of an asymmetrically offset mounting of the center of gravity with respect to the pivot point of the second diaphragm 4 compared to the sixth embodiment, the second diaphragm 4 and the first diaphragm 3 can be favorably driven by a superimposed drive signal.

[0135] Figures 34 and 35 show a functional unit 13 of a microelectromechanical device 1 according to a ninth embodiment. This embodiment is arranged in which the first diaphragm 3 is positioned between two wider diaphragms 4 and mechanically coupled to them, but has at least one, or in this case two, drive elements 6a of its own. This allows movements between the diaphragms 3 and 4 to be at least partially transmitted to one another, while at the same time the separate drive elements 6a and 6b allow frequency differences between the first diaphragm 3 and the second diaphragms 4 to be generated simply and directly.

[0136] Fig. 36 shows a microelectromechanical device 1 according to a fourth embodiment, with only one vibration generator unit 2 of the microelectromechanical device 1 being shown by way of example. According to the illustrated embodiment, the vibration generator unit 2 has a functional unit 13 with a first diaphragm 3 and a second diaphragm 4, which are movable relative to each other. The microelectromechanical device 1 also has a drive unit 6, which is configured to excite the first diaphragm 3 to a first vibration with a first frequency f1 and to excite the second diaphragm 4 to a second vibration with a second frequency f2 that differs from the first frequency f1.For this purpose, a drive element 6a is assigned to the first membrane 3 and a drive element 6b to the second membrane 4, so that the first membrane 3 and the second membrane 4 can be excited to individual vibrations independently of each other in a simple and direct way.

[0137] According to the embodiment shown in Fig. 40, the through-channel 5 has a first channel section 5a and a second channel section 5b, wherein the first channel section 5a adjoins the functional unit 13 and has a larger cross-section than the second channel section 5b. Such a widening of the through-channel 5 below the functional unit 13 allows for increased freedom of movement of the first diaphragm 3 and the second diaphragm 4, enabling them to deflect over a wider area and thus be more efficient.

[0138] Fig. 37 schematically shows a microelectromechanical component 20 with a microelectromechanical device 1 according to the features described above and a signal processing unit 21, for example an ASIC, which is connected to the microelectromechanical device 1 by a signal connection 22 and is configured for applying and processing signals from the microelectromechanical device 1. The micromechanical component 20 can be configured, in particular, as a loudspeaker, as a fluid pump device, or as a combination component. In an application of the microelectromechanical component 20 as a fluid pump device, a fixed phase relationship can be established between the first vibration of the first diaphragm 3 and the second vibration of the second diaphragm 4.In an application of the microelectromechanical component 20 as a loudspeaker, the phase relationship between the first vibration of the first diaphragm 3 and the second vibration of the second diaphragm 4 can be varied in order to generate a variable fluid pulse signal 38 with the extracted pressurized fluid pulses F, which can then be used to generate a sound signal 39. Fig. 38 illustrates in a simplified way a functional principle of a vibration generator unit 2 of a microelectromechanical device 1 according to the features described above, analogous to a closed-end acoustic tube 30. Here, an overpressure pulse 33 is generated at the closed end 31 in the direction of the open end 32 of the acoustic tube 30.Applied to the previously described microelectromechanical device 1, the clay tube 30 corresponds to the through-channel 5, the functional unit 13 to the closed side 31, and the opening of the through-channel 5 on the rear side 7b of the substrate 7 to the open side 32 of the clay tube 30. The overpressure pulse 33 moves from the closed side 31 to the open side 32, as shown in Figures 42A to 42C. At the open side 32, the overpressure pulse 33 exits, and a phase shift occurs in the clay tube 30, generating an underpressure pulse 34 that moves towards the closed side 31, as shown in Figures 42D to 42F. At the closed side 31, the negative pressure pulse 34 is reflected back towards the open side 32 and exits at the open side 32, cf. Figs. 42G and 42H. Upon exiting the negative pressure pulse 34, another phase shift occurs, resulting in the following as shown in the Figs.Figures 42I and 42J show that an overpressure pulse 33 is generated, propagates towards the closed side 32, and is reflected and amplified there. A pressure oscillation can be generated by the back-and-forth oscillating pressure pulses 15, 15a, the vibrational energy of which can be advantageously used to generate pressurized fluid pulses F.

Claims

Claims 1. Microelectromechanical device (1) for generating pressurized fluid pulses (F) with a substrate (7) and a vibration generator unit (2), comprising the vibration generator unit (2): - a functional unit (13) arranged on a front side (7a) of the substrate (7), which has a valve function for temporarily forming a fluid opening (14) and a displacement function for displacing fluid; and - a through channel (5) extending from the functional unit (13) through the substrate (7) to a rear side (7b) of the substrate (7), wherein the vibration generator unit (2) is configured to generate a pressure oscillation with a predetermined oscillation frequency in the through channel (5) and to extract a vibration pressure pulse (15a) reflected from the through channel (5) in the direction of the functional unit (13) through the temporarily formed fluid opening (14) of the functional unit (13) from the through channel (5) as a pressurized fluid pulse (F).

2. Microelectromechanical device (1) according to claim 1, wherein the vibration generator unit (2) is designed such that a standing wave can be formed in the through channel (5) by means of the pressure vibration according to the predetermined vibration frequency.

3. Microelectromechanical device (1) according to claim 1 or 2, wherein a length extent (LD) of the passage channel (5) from the functional unit (13) to the rear side (7b) of the substrate (7) corresponds substantially to one quarter or one quarter and one multiple of half the wavelength of the pressure oscillation with the predetermined oscillation frequency.

4. Microelectromechanical device (1) according to one of the preceding claims, wherein the vibration generator unit (2) is configured to generate a pressure vibration with a predetermined vibration frequency above 20 kHz.

5. Microelectromechanical device (1) according to one of the preceding claims, wherein the length extent (LD) of the through-channel (5) is between 50 pm and 2 mm, in particular between 250 pm and 800 pm.

6. Microelectromechanical device (1) according to one of the preceding claims, wherein the length extent (LD) of the passage channel (5) is at least twice, in particular at least 2.5 times or at least three times as large as a width extent (BD) of the passage channel (5) perpendicular to the length extent (LD).

7. Microelectromechanical device (1) according to one of the preceding claims, wherein the width extent (BD) of the through channel (5) is at least half as large as a width extent (BF) of the functional unit (13).

8. Microelectromechanical device (1) according to one of the preceding claims, wherein the through-channel (5) has a cylindrical basic shape.

9. Microelectromechanical device (1) according to one of the preceding claims, wherein the through-channel (5) has a slot-shaped basic form.

10. Microelectromechanical device (1) according to one of the preceding claims, wherein the functional unit (13) has an outer contour (13a) adapted to the basic shape of the through-channel (5).

11. Microelectromechanical device (1) according to one of the preceding claims, wherein the microelectromechanical device (1) comprises at least two vibration generator units (2).

12. Microelectromechanical device (1) according to claim 11, wherein the at least two vibration generator units (2) are substantially identical in shape and dimensions.

13. Microelectromechanical device (1) according to claim 11 or 12, wherein a distance (A) between the at least two vibration generator units (2) is smaller than the length extent (LD) and / or smaller than the width extent (BD) of a through-channel (5) of the vibration generator units (2).

14. Microelectromechanical device (1) according to one of claims 11 to 13, wherein the at least two vibration generator units (2) are arranged linearly next to each other.

15. Microelectromechanical device (1) according to one of claims 11 to 14, wherein the at least two vibration generator units (2) are arranged hexagonally to each other.

16. Microelectromechanical device (1) according to one of the preceding claims, wherein the functional unit (13) comprises a first diaphragm (3) and a second diaphragm (4) which are movable relative to each other, and wherein the microelectromechanical device (1) comprises a drive unit (6) which is configured to excite the first diaphragm (3) to a first vibration with a first frequency (fi) and to excite the second diaphragm (4) to a second vibration with a second frequency (f2) which differs from the first frequency (fi).

17. Microelectromechanical device (1) according to claim 16, wherein the second membrane (4) has a natural frequency which is substantially twice as high as the natural frequency of the first membrane (3).

18. Microelectromechanical device (1) according to claim 16 or 17, wherein the drive device (6) has a drive element (6a, 6b) arranged on the first membrane (3) and on the second membrane (4).

19. Microelectromechanical device (1) according to one of claims 16 to 18, wherein the first membrane (3) and the second membrane (4) are mechanically coupled to each other.

20. Microelectromechanical device (1) according to claim 19, wherein the first membrane (3) and the second membrane (4) are arranged to be excited by a superimposed drive signal of a drive element (6a, 6b) associated with the first membrane (3) or the second membrane (4).

21. Microelectromechanical device (1) according to one of the preceding claims, wherein the through-channel (5) has a first channel section (5a) and a second channel section (5b) and wherein the first channel section (5a) is adjacent to the functional unit (13) and has a larger cross-section than the second channel section (5b).

22. Microelectromechanical loudspeaker comprising a microelectromechanical device (1) according to any one of claims 1 to 21, wherein the vibration generator unit (2) of the microelectromechanical device (1) is configured to generate a sound signal, and a signal processing unit (21) for applying and processing signals of the microelectromechanical device (1).

23. Microelectromechanical fluid pumping device comprising a microelectromechanical device (1) according to any one of claims 1 to 21, wherein the vibration generator unit (2) of the device (1) is configured to generate a pump current, and a signal processing unit (21) for applying and processing signals of the microelectromechanical device (1).

24. Method for operating a microelectromechanical device (1) according to one of claims 1 to 21, wherein a pressure oscillation with a predetermined oscillation frequency is generated in the through-channel (5) by means of the vibration generator unit (2) and a vibration pressure pulse (15a) reflected from the through-channel (5) in the direction of the functional unit (13) is extracted from the through-channel (5) as a pressurized fluid pulse (F) through the temporarily formed fluid opening (14) of the functional unit (13).

25. Method according to claim 24, wherein a variable fluid pulse signal (38) is generated with the pressurized fluid pulses (F) to generate a sound signal (39).

26. Method according to claim 24 or 25, wherein a standing wave is formed in the passage channel (5) by means of the pressure oscillation according to the predetermined oscillation frequency.

27. Method according to any one of claims 24 to 26, wherein the microelectromechanical device (1) has at least two vibration generator units (2) and wherein the vibration generator units (2) are operated with a phase shift, such that overpressure pulses (33) or underpressure pulses (34) of the pressure vibration propagating on the rear side (7b) of the substrate (7) into an environment (16) of the microelectromechanical device (1) are reduced or eliminated by destructive interference.

28. Method according to claim 27, wherein linearly arranged vibration generator units (2) are operated with a phase offset of 180° between adjacent vibration generator units (2) and / or wherein hexagonally arranged vibration generator units (2) are operated with a phase offset of 120° between adjacent vibration generator units (2).

29. Method according to one of claims 24 to 28, wherein the functional unit (13) has a first diaphragm (3) and a second diaphragm (4) which are movable relative to each other, and wherein, to generate the pressurized fluid pulses (F), the first diaphragm (3) is excited to a first oscillation with a first frequency (fi) and the second diaphragm (4) is excited to a second oscillation with a second frequency (f2) that differs from the first frequency (fi) by means of a drive device (6) of the microelectromechanical device (1).

30. Method according to claim 29, wherein the second frequency (f2) of the second oscillation is substantially twice as high as the first frequency (fi) of the first oscillation.

31. Method according to one of claims 29 or 30, wherein a fixed phase relationship is established between the first vibration of the first membrane (3) and the second vibration of the second membrane (4).

32. Method according to one of claims 29 or 30, wherein a phase relationship between the first vibration of the first membrane (3) and the second vibration of the second membrane (4) is varied in order to generate a variable fluid pulse signal (38) with the extracted pressurized fluid pulses (F) for generating a sound signal (39).

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