A MEMS bionic acceleration sensor based on spider web structure

Abstract

The application relates to the technical field of sensors and provides a MEMS bionic acceleration sensor based on a cobweb structure, which comprises a frame, the frame is provided with a cavity, a mass block is arranged in the cavity and located at the center of the cavity, a plurality of variable cross-section cantilever beams are arranged in the cavity and surround the mass block, the middle part of each variable cross-section cantilever beam is a stress-free zone, the two ends of each variable cross-section cantilever beam are stress zones, the stress zones at the two ends of each variable cross-section cantilever beam are connected with the mass block and the frame respectively, piezoelectric films are arranged in the stress zones at the two ends of each variable cross-section cantilever beam, and interdigital electrodes are arranged on the piezoelectric films, a plurality of connecting beams are arranged in the cavity, and the two ends of each connecting beam are connected with the stress-free zones of the adjacent variable cross-section cantilever beams respectively. The application improves the charge sensitivity, reduces the noise, maximally suppresses the cross-axis crosstalk, and reduces the cross-axis sensitivity of the acceleration sensor.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically, to a MEMS biomimetic accelerometer based on a spider web structure. Background Technology

[0002] Piezoelectric accelerometers, also known as piezoelectric accelerometers, are a type of inertial sensor. They offer advantages such as fast response, excellent high-frequency performance, good temperature stability, and high output impedance; however, their sensitivity performance still needs improvement. Summary of the Invention

[0003] The purpose of this invention is to provide a MEMS biomimetic accelerometer based on a spider web structure to solve the technical problem of low sensitivity in existing piezoelectric accelerometers.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] This invention provides a MEMS biomimetic accelerometer based on a spider web structure, comprising:

[0006] A border, the border having a cavity;

[0007] A mass block, wherein the mass block is disposed within the cavity and located at the center of the cavity;

[0008] Multiple variable cross-section cantilever beams are disposed within the cavity and surround the mass block.

[0009] The middle part of the variable cross-section cantilever beam is a stress-free region, and the two ends of the variable cross-section cantilever beam are stress regions. The stress regions at both ends of each variable cross-section cantilever beam are respectively connected to the mass block and the frame. Piezoelectric films are arranged in the stress regions at both ends of the variable cross-section cantilever beam, and interdigitated electrodes are provided on the piezoelectric films.

[0010] Multiple connecting beams are disposed within the cavity, and both ends of each connecting beam are respectively connected to the stress-free zone of the adjacent variable cross-section cantilever beam.

[0011] According to the above-mentioned MEMS biomimetic accelerometer based on spider web structure, multiple variable cross-section cantilever beams are arranged at equal intervals, and the width of the variable cross-section cantilever beam gradually decreases from the middle to both ends of the variable cross-section cantilever beam.

[0012] The stress value for each of the aforementioned variable cross-section cantilever beams is:

[0013]

[0014] Where Z is the height of the neutral layer, E is the elastic modulus of the material, and R is the radius of curvature.

[0015] The amount of charge excited at the piezoelectric film above each of the aforementioned variable cross-section cantilever beams is:

[0016] q x =dσ x

[0017] Where q is the amount of charge excited, and d is the piezoelectric constant;

[0018] The sensitivity calculation formula for a spiderweb-structured MEMS biomimetic accelerometer is as follows:

[0019]

[0020] Among them, S Q - The sensitivity, Q of a piezoelectric MEMS biomimetic accelerometer based on a spiderweb structure 总 -The total charge excited at the piezoelectric film above all variable cross-section cantilever beams, a z -External acceleration.

[0021] According to the above-mentioned MEMS biomimetic accelerometer based on a spider web structure, the ratio of the maximum width of the stress-free region in the middle of the variable cross-section cantilever beam to the minimum width of the stress regions at both ends of the variable cross-section cantilever beam is 1.2 to 3.

[0022] According to the above-mentioned MEMS biomimetic accelerometer based on a spider web structure, the length of the variable cross-section cantilever beam is 200um to 800um.

[0023] According to the above-mentioned MEMS biomimetic accelerometer based on a spider web structure, the number of variable cross-section cantilever beams is 2 to 20, and correspondingly, the number of connecting beams is 2 to 20.

[0024] According to the above-mentioned MEMS biomimetic accelerometer based on a spider web structure, the ratio of the length of the piezoelectric thin film to the length of the variable cross-section cantilever beam is 0.2 to 0.4.

[0025] According to the above-mentioned MEMS biomimetic accelerometer based on a spider web structure, the thickness of the piezoelectric film is 1µm to 5µm.

[0026] According to the above-mentioned MEMS biomimetic accelerometer based on a spider web structure, the width of the interdigitated electrodes is 2µm to 10µm, and the spacing between the interdigitated electrodes is 5µm to 10µm.

[0027] According to the aforementioned MEMS biomimetic accelerometer based on a spider web structure, the width of the connecting beam is 5µm to 50µm.

[0028] According to the above-mentioned MEMS biomimetic accelerometer based on a spider web structure, the mass block is circular with a diameter of 100um to 1000um;

[0029] Alternatively, the mass block may be polygonal, and the diameter of the inscribed circle or the circumscribed circle of the polygon may be 100µm to 1000µm.

[0030] The beneficial effects of the spiderweb-structure-based MEMS biomimetic accelerometer provided by this invention are at least as follows:

[0031] The MEMS biomimetic accelerometer based on a spider web structure provided by this invention adopts a variable cross-section cantilever beam structure, which greatly improves the stress on the surface of the cantilever beam, thereby improving the charge sensitivity. Furthermore, the combination of the variable cross-section cantilever beam and interdigitated electrodes also reduces noise. Inspired by the horizontal filament structure of a spider web, connecting beams are set at adjacent variable cross-section cantilever beams to form a spider web structure, which limits the horizontal crosstalk to the greatest extent and greatly reduces the horizontal axis sensitivity of the accelerometer, making the overall system stable and reliable. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of the structure of the accelerometer provided in the embodiment of the present invention. Figure 1 ;

[0034] Figure 2 A schematic diagram of the variable cross-section cantilever beam provided in an embodiment of the present invention. Figure 1 ;

[0035] Figure 3 A schematic diagram of the structure of the accelerometer provided in the embodiment of the present invention. Figure 2 ;

[0036] Figure 4 A schematic diagram of the variable cross-section cantilever beam provided in an embodiment of the present invention. Figure 2 .

[0037] The following are the labeling elements in the figure:

[0038] 100. Accelerometer; 110. Frame; 111. Cavity; 120. Mass block; 130. Variable cross-section cantilever beam; 131. Stress-free zone; 132. Stress zone; 140. Piezoelectric film; 150. Interdigitated electrode; 160. Connecting beam. Detailed Implementation

[0039] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0040] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it may be directly or indirectly located on that other component. When a component is referred to as "connected to" another component, it may be directly or indirectly connected to that other component. The terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate orientations or positions based on the accompanying drawings, and are for ease of description only, and should not be construed as limiting the technical solution. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. "A plurality" means two or more, unless otherwise explicitly defined.

[0041] Please see Figures 1 to 4 This embodiment provides a MEMS biomimetic accelerometer 100 based on a spiderweb structure, including: a frame 110 having a cavity 111; a mass block 120 disposed within the cavity 111 and located at the center of the cavity 111; and multiple variable cross-section cantilever beams 130 disposed within the cavity 111 and surrounding the mass block 120; the middle portion of each variable cross-section cantilever beam 130 is a stress-free region 131. The two ends of the variable cross-section cantilever beam 130 are stress zones 132. The stress zones 132 at both ends of each variable cross-section cantilever beam 130 are respectively connected to the mass block 120 and the frame 110. Piezoelectric films 140 are arranged in the stress zones 132 at both ends of the variable cross-section cantilever beam 130. Interdigitated electrodes 150 are provided on the piezoelectric films 140. Multiple connecting beams 160 are arranged in the cavity 111, and the two ends of each connecting beam 160 are respectively connected to the stress-free zone 131 of the adjacent variable cross-section cantilever beam 130.

[0042] The MEMS biomimetic accelerometer 100 based on a spiderweb structure provided in this embodiment is based on the principle of ultra-sensitive capture of micro-vibrations and ultra-stable characteristics of a spiderweb structure. Since the stress zone 132 of the variable cross-section cantilever beam 130 is provided with a piezoelectric thin film 140, and interdigitated electrodes 150 are provided on the piezoelectric thin film 140, the charge excited by the piezoelectric effect is collected by the interdigitated electrodes 150. The interdigitated electrodes 150 are connected to form a closed loop through methods such as differential circuits. When subjected to an external acceleration signal, the variable cross-section cantilever beam 130 will undergo bending or other deformations, causing the piezoelectric thin film 140 to generate charge. Therefore, the greater the external acceleration signal, the greater the amount of charge generated on the piezoelectric thin film 140, thereby completing the detection of the external acceleration signal. Furthermore, the use of a variable cross-section cantilever beam 130 structure greatly improves the stress on the surface of the cantilever beam, thereby improving the charge sensitivity. In addition, the combination of the variable cross-section cantilever beam 130 and the interdigitated electrode 150 also reduces noise. Inspired by the spider web structure, a connecting beam 160 is set at adjacent variable cross-section cantilever beams 130 to form a spider web structure, which limits the transverse crosstalk to the greatest extent and greatly reduces the transverse sensitivity of the accelerometer 100, making the whole system stable and reliable.

[0043] In one embodiment, a plurality of variable cross-section cantilever beams 130 are arranged at equal intervals, and the width of the variable cross-section cantilever beam 130 gradually decreases from the middle to both ends of the variable cross-section cantilever beam 130.

[0044] The stress value of each of the variable cross-section cantilever beams 130 is:

[0045]

[0046] Where Z is the height of the neutral layer, E is the elastic modulus of the material, and R is the radius of curvature.

[0047] The amount of charge excited at the piezoelectric film 140 above each of the variable cross-section cantilever beams 130 is:

[0048] q x =dσ x

[0049] Where q is the amount of charge excited, and d is the piezoelectric constant;

[0050] The sensitivity calculation formula for the MEMS biomimetic accelerometer 100 based on a spider web structure is as follows:

[0051]

[0052] Among them, S Q -The sensitivity, Q of the piezoelectric MEMS biomimetic accelerometer 100 based on a spiderweb structure 总-The total charge excited at the piezoelectric thin film 140 above all variable cross-section cantilever beams 130, a z -External acceleration.

[0053] By reducing the width W at the ends, the variable cross-section cantilever beam 130 increases the surface stress. Furthermore, the piezoelectric film 140, arranged at the ends of the variable cross-section cantilever beam 130, excites more charges, thereby improving charge sensitivity.

[0054] In one embodiment, the noise of the accelerometer 100 mainly consists of two parts: low-frequency (below 10kHz) electrical thermal noise and high-frequency (above 10kHz) mechanical thermal noise. The test bandwidth of this embodiment is primarily in the low-frequency range; therefore, the focus is on reducing low-frequency noise.

[0055] Where, k B C S D, w, S Q These are Boltzmann constant, sensor capacitance, piezoelectric material dissipation factor, operating frequency, and charge sensitivity.

[0056] By flexibly adjusting the spacing between the two interdigital electrodes 150 (i.e., the spacing between the interdigital electrodes to b), the sensor capacitance C can be reduced. S The variable cross-section cantilever beam 130 improves the sensor's charge sensitivity S. Q This reduces noise.

[0057] In one embodiment, the ratio of the maximum width of the stress-free zone in the middle of the variable cross-section cantilever beam 130 to the minimum width of the stress zones at both ends of the variable cross-section cantilever beam 130 is 1.2 to 3.

[0058] The ratio of the maximum width of the stress-free zone in the middle of the variable cross-section cantilever beam 130 to the minimum width of the stress zones at both ends of the variable cross-section cantilever beam 130 is 1.2 to 3. This not only ensures that the surface stress of the variable cross-section cantilever beam 130 is strong enough, but also avoids the fracture of the variable cross-section cantilever beam 130.

[0059] In one embodiment, the length of the variable cross-section cantilever beam 130 is 200µm to 800µm. Setting the length of the variable cross-section cantilever beam 130 to 200µm not only ensures charge sensitivity but also ensures that the test bandwidth is not reduced.

[0060] In one embodiment, the number of variable cross-section cantilever beams 130 is 2 to 20, and correspondingly, the number of connecting beams 160 is 2 to 20. Setting the number of variable cross-section cantilever beams 130 to 2 to 20 can achieve higher sensitivity. Correspondingly, setting the number of connecting beams 160 to 2 to 20 results in less lateral effect, reduces cross-axis crosstalk, and enables multi-axis measurement, i.e., measurement of the X, Y, and Z axes.

[0061] Optionally, the number of variable cross-section cantilever beams 130 is 4, and correspondingly, the number of connecting beams 160 is 4. Optionally, the number of variable cross-section cantilever beams 130 is 8, and correspondingly, the number of connecting beams 160 is 8. It should be understood that the number of variable cross-section cantilever beams 130 and the number of connecting beams 160 are not limited to the above situations, and other situations are also possible, which are not limited here.

[0062] In one embodiment, the ratio of the length of the piezoelectric film 140 to the length of the variable cross-section cantilever beam 130 is 0.2 to 0.4. This ratio ensures that the piezoelectric film 140 is deposited at the location of maximum stress.

[0063] In one embodiment, the thickness of the piezoelectric film 140 is 1µm to 5µm, which facilitates the formation of the piezoelectric film through processes such as deposition, sputtering, or sol-gel method.

[0064] Optionally, the piezoelectric film 140 is made of zinc oxide, aluminum nitride, or lead zirconate titanate. It should be understood that the material of the piezoelectric film 140 is not limited to the above-mentioned materials and may be other materials, which are not limited here.

[0065] In one embodiment, see Figure 4 The width a of the interdigital electrode 150 is 2um to 10um, and the spacing b of the interdigital electrodes is 5um to 10um.

[0066] Setting the width a of the interdigital electrode 150 to 2µm to 10µm ensures charge sensitivity. Optimizing the spacing b of the interdigital electrodes to 5µm to 10µm reduces capacitance and thus reduces noise.

[0067] Optionally, the electrode material of the interdigital electrode 150 may be gold, platinum, or silver. It should be understood that the material of the interdigital electrode 150 is not limited to the above-mentioned cases, and may also be other materials, which are not limited here.

[0068] In one embodiment, the width of the connecting beam 160 is 5µm to 50µm. Setting the width of the connecting beam 160 to 5µm does not increase the overall mass of the structure and ensures that the test bandwidth of the accelerometer 100 is not reduced.

[0069] In one embodiment, the mass block 120 is circular with a diameter of 100µm to 1000µm;

[0070] In one embodiment, the mass block 120 is polygonal, and the diameter of the inscribed circle or the circumscribed circle of the polygon is 100µm to 1000µm.

[0071] When the mass block 120 is circular, its diameter is set to 100um to 1000um. When the mass block 120 is polygonal, its inscribed circle diameter or circumscribed circle diameter is set to 100um to 1000um. This not only ensures the sensitivity of the charge.

[0072] In summary, this embodiment provides a MEMS biomimetic accelerometer 100 based on a spiderweb structure, comprising: a frame 110 having a cavity 111; a mass block 120 disposed within the cavity 111 and located at the center of the cavity 111; and a plurality of variable cross-section cantilever beams 130 disposed within the cavity 111 and surrounding the mass block 120; the middle portion of each variable cross-section cantilever beam 130 is a stress-free region 131. Both ends of the beam 130 are stress zones 132. The stress zones 132 at both ends of each variable cross-section cantilever beam 130 are respectively connected to the mass block 120 and the frame 110. Piezoelectric films 140 are arranged in the stress zones 132 at both ends of the variable cross-section cantilever beam 130. Interdigitated electrodes 150 are provided on the piezoelectric films 140. Multiple connecting beams 160 are arranged in the cavity 111, and both ends of each connecting beam 160 are respectively connected to the stress-free zone 131 of the adjacent variable cross-section cantilever beam 130. The MEMS biomimetic accelerometer 100 based on a spider web structure provided in this embodiment adopts a variable cross-section cantilever beam 130 structure, which greatly improves the stress on the surface of the cantilever beam, thereby improving the charge sensitivity. Furthermore, the combination of the variable cross-section cantilever beam 130 and the interdigitated electrodes 150 also reduces noise. Inspired by the horizontal filament structure of a spider web, connecting beams 160 are set at adjacent variable cross-section cantilever beams 130 to form a spider web structure, which limits the horizontal crosstalk to the greatest extent and greatly reduces the horizontal axis sensitivity of the accelerometer 100, making it stable and reliable overall.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A MEMS biomimetic accelerometer based on a spiderweb structure, characterized in that, include: A border, the border having a cavity; A mass block, wherein the mass block is disposed within the cavity and located at the center of the cavity; Multiple variable cross-section cantilever beams are disposed within the cavity and surround the mass block. The middle part of the variable cross-section cantilever beam is a stress-free region, and the two ends of the variable cross-section cantilever beam are stress regions. The stress regions at both ends of each variable cross-section cantilever beam are respectively connected to the mass block and the frame. Piezoelectric films are arranged in the stress regions at both ends of the variable cross-section cantilever beam, and interdigitated electrodes are provided on the piezoelectric films. Multiple connecting beams are disposed within the cavity, and both ends of each connecting beam are respectively connected to the stress-free zone of the adjacent variable cross-section cantilever beam.

2. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, Multiple variable cross-section cantilever beams are arranged at equal intervals, and the width of the variable cross-section cantilever beam gradually decreases from the middle to both ends of the variable cross-section cantilever beam; The stress value for each of the aforementioned variable cross-section cantilever beams is: Where Z is the height of the neutral layer, E is the elastic modulus of the material, and R is the radius of curvature. The amount of charge excited at the piezoelectric film above each of the aforementioned variable cross-section cantilever beams is: q x =dσ x Where q is the amount of charge excited, and d is the piezoelectric constant; The sensitivity calculation formula for a spiderweb-structured MEMS biomimetic accelerometer is as follows: Among them, S Q - The sensitivity, Q of a piezoelectric MEMS biomimetic accelerometer based on a spiderweb structure 总 -The total charge excited at the piezoelectric film above all variable cross-section cantilever beams, a z -External acceleration.

3. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The ratio of the maximum width of the stress-free zone in the middle of the variable cross-section cantilever beam to the minimum width of the stress zones at both ends of the variable cross-section cantilever beam is 1.2 to 3.

4. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The length of the variable cross-section cantilever beam is 200µm to 800µm.

5. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The number of variable cross-section cantilever beams is 2 to 20, and correspondingly, the number of connecting beams is 2 to 20.

6. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The ratio of the length of the piezoelectric film to the length of the variable cross-section cantilever beam is 0.2 to 0.

4.

7. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The thickness of the piezoelectric film is 1µm to 5µm.

8. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The width of the interdigitated electrodes is 2µm to 10µm, and the spacing between the interdigitated electrodes is 5µm to 10µm.

9. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The width of the connecting beam is 5µm to 50µm.

10. The MEMS biomimetic accelerometer based on a spiderweb structure according to claim 1, characterized in that, The mass block is circular with a diameter of 100µm to 1000µm; Alternatively, the mass block may be polygonal, and the diameter of the inscribed circle or the circumscribed circle of the polygon may be 100µm to 1000µm.

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