MEMS capacitive plane micro-force sensor based on bistable mechanical structure

Abstract

An MEMS capacitive planar micro-force sensor based on a bistable mechanical structure comprises a bottom silicon layer, a middle oxidation insulating layer and a top silicon structure layer, a sensor sensitive structure is arranged in the top silicon structure layer and comprises a probe structure, the rear end of the probe structure is connected with an internal mass block, the internal mass block is connected with an internal supporting beam, and the internal supporting beam is connected with an external supporting beam. The internal supporting beam is connected with the external mass block, the external mass block is connected with the external supporting beam, and the probe structure, the internal mass block, the internal supporting beam and the external mass block form a sensor movable structure; the external supporting beam is connected with the supporting beam frame; the two sides of the probe structure are differential capacitance comb tooth arrays at the front part of the sensor, the two sides of the internal supporting beam are differential capacitance comb tooth arrays at the middle part of the sensor, the outer side of the external mass block is a differential capacitance comb tooth array at the rear part of the sensor, and the fixed comb tooth array is connected with a comb tooth cantilever frame; according to the invention, precise detection of planar biaxial sub-nN magnitude micro force can be realized at the same time.

Description

Technical Field

[0001] This invention belongs to the field of high-precision micro-force sensor technology, specifically relating to a MEMS capacitive planar micro-force sensor based on a bistable mechanical structure. Background Technology

[0002] In-plane biaxial microforce signals at the micro / nano Newton (μ / nN) level are crucial for studying the mechanical properties of materials and biological cells at the micro / nano scale. These signals allow for the investigation of microscopic mechanical behavior, cell growth and aging, and pathological mechanisms. Furthermore, micromanipulation applications such as micrograsping and microtransfer in the field of micro / nano robotics heavily rely on high-precision in-plane biaxial microforce sensing feedback. This enables micro / nano robots or micro / nano operating systems to automate and perform precise operations such as rotation, transfer, and assembly of micro / nano-scale cellular samples with minimal damage. Therefore, the development of high-precision mechanical sensors is of great significance for the research and preparation of novel micro / nano materials, as well as for the diagnosis and physiological regulation of biological cell diseases.

[0003] The testing environment for samples at the microscale is complex, with high background noise, making high-precision micro-force sensing a significant challenge. Microelectromechanical systems (MEMS) sensors, with their advantages of small size, high stability, and ease of mass production, have been widely used in the field of micro-force measurement and have great development potential. Capacitive MEMS high-precision micro-force sensors utilize the mechanism that changes in the relative position of conductive plates cause changes in capacitance between conductive plates, converting the micro-force load at the measuring probe into a change in the relative position between the plates, thereby achieving high-precision force load detection. Compared to other MEMS micro-force sensors based on piezoelectric or piezoresistive principles, capacitive MEMS force sensors do not require the design and fabrication of stress concentration structures with extreme dimensions, resulting in lower device fabrication difficulty and higher reliability. Employing a comb-like structure with a multi-plate array and differentially arranging the moving and fixed plate arrays, they exhibit higher detection sensitivity. Furthermore, capacitive MEMS sensing chips can be integrated into application-specific integrated circuits (ASICs), resulting in smaller device sizes. Therefore, they have become the mainstream MEMS micro-force measurement technology, suitable for the mechanical measurement and sensing of microstructures.

[0004] Currently, many institutions have developed micro-force sensors based on MEMS capacitive differential comb arrays (R.Li, et al. Design, modelling and characterization of comb drive MEMS gap-changeable differential capacitive accelerometer[J]. Measurement, 2021, 169: 108377; El Mansouri, Brahim, et al. High-resolution MEMS inertial sensor combining large-displacement buckling behaviour with integrated capacitive readout[J]. Microsystems & nanoengineering, 2019, 5(1): 60; W.Gao, et al. A high-resolution MEMS capacitive force sensor with bionic swallow comb arrays for ultralow multiphysics measurement[J]. IEEE Transactions on Industrial Electronics, 2022, 70(7):7467-7477.), however, the device described above restricts the in-plane degrees of freedom of the movable comb plate, so that the plate can only move in a single direction in the plane, and can only change the distance or area between it and the fixed plate, without causing simultaneous changes. This measurement method can only detect uniaxial micro-force signals and cannot detect biaxial forces in the plane at the same time. Some organizations have also proposed capacitive multi-axis micro-force sensors based on movable structures supported by multi-bend beams (F. Beyeler, S. Muntwyler, et al. A six-axis MEMS force–torque sensor with micro-Newton and nano-Newton meter resolution[J]. Journal of Microelectromechanical Systems, 2009, 18(2): 433-441.), attempting to improve the degree of freedom of motion of movable structures in the two-axis directions in the plane. However, this structure cannot decouple and decompose external planar loads to the corresponding axes, and the sensitive comb array inside the device has obvious inter-axis coupling output, resulting in low linearity and accuracy.Therefore, there is an urgent need to conduct research on MEMS capacitive sensors for high-precision detection of planar biaxial microforces on the μ / nN scale. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a MEMS capacitive planar micro-force sensor based on a bistable mechanical structure. Through the bistable movable structure, the decomposition of planar orthogonal biaxial micro-forces can be achieved without being affected by the coupling of vertical spatial loads. Through the design optimization of the mechanical structure and the corresponding arrangement of the sensing comb teeth, the accurate detection of planar biaxial sub-nN level micro-forces can be achieved simultaneously.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A MEMS capacitive planar micro-force sensor based on a bistable mechanical structure includes a bottom silicon layer, an intermediate oxide insulating layer, and a top silicon structure layer. The top silicon structure layer contains a sensor sensing structure, which includes a probe structure 31. The rear end of the probe structure 31 is connected to an internal mass block 11, the internal mass block 11 is connected to an internal support beam 22, the internal support beam 22 is connected to an external mass block 12, and the external mass block 12 is connected to the external support beam 21. The probe structure 31, the internal mass block 11, the internal support beam 22, and the external mass block 12 constitute a movable sensor structure. Both the internal support beam 22 and the external support beam 21 are flexible straight beams. The external support beam 21 is connected to a first support beam frame 41 and a second support beam frame 42. The probe structure 31 has two... The side of the sensor is the differential capacitor comb array I at the front, and the fixed comb array of the differential capacitor comb array I at the front of the sensor is connected to the first comb cantilever frame 50 and the second comb cantilever frame 51; the two sides of the internal support beam 22 are the differential capacitor comb array II in the middle of the sensor, and the fixed comb array of the differential capacitor comb array II in the middle of the sensor is connected to the third comb cantilever frame 52, the fourth comb cantilever frame 53, the fifth comb cantilever frame 54, and the sixth comb cantilever frame 55; the outside of the external mass block 12 is the differential capacitor comb array III at the rear of the sensor, and the fixed comb array of the differential capacitor comb array III at the rear of the sensor is connected to the seventh comb cantilever frame 56, the eighth comb cantilever frame 57, the ninth comb cantilever frame 58, and the tenth comb cantilever frame 59.

[0008] The differential capacitance comb array I at the front of the sensor includes a first moving comb array 111, a second moving comb array 112, a third moving comb array 113, a fourth moving comb array 114, and corresponding first fixed comb arrays 101, second fixed comb arrays 102, third fixed comb arrays 103, and fourth fixed comb arrays 104. The first moving comb array 111 and the second moving comb array 112 are distributed on the left and right sides of the probe structure 31, respectively, corresponding to the first fixed comb arrays distributed on the left and right sides of the front of the first comb cantilever frame 50 and the second comb cantilever frame 51. The fixed comb tooth array 101 and the second fixed comb tooth array 102 cooperate with each other to form the first comb tooth array 111 / 101 and the second comb tooth array 112 / 102; the third moving comb tooth array 113 and the fourth moving comb tooth array 114 are respectively distributed on the left and right sides of the front part of the internal mass block 11, and cooperate with the third fixed comb tooth array 103 and the fourth fixed comb tooth array 104 distributed on the left and right sides of the rear part of the first comb tooth cantilever frame 50 and the second comb tooth cantilever frame 51, respectively, to form the third comb tooth array 113 / 103 and the fourth comb tooth array 114 / 104.

[0009] The differential capacitance comb array II in the middle of the sensor includes a fifth moving comb array 211, a sixth moving comb array 212, a seventh moving comb array 213, an eighth moving comb array 214, and corresponding fifth fixed comb arrays 201, sixth fixed comb array 202, seventh fixed comb array 203, and eighth fixed comb array 204. The fifth moving comb array 211 and the seventh moving comb array 213 are distributed on the left front end of the external mass block 12, respectively, and are distributed on the third comb cantilever frame 52 and the fifth comb cantilever frame 54. The fifth fixed comb tooth array 201 and the seventh fixed comb tooth array 203 cooperate with each other to form the fifth comb tooth array 211 / 201 and the seventh comb tooth array 213 / 203; the sixth moving comb tooth array 212 and the eighth moving comb tooth array 214 are distributed on the front right side of the external mass block 12, and cooperate with the sixth fixed comb tooth array 202 and the eighth fixed comb tooth array 204 distributed on the fourth comb tooth cantilever frame 53 and the sixth comb tooth cantilever frame 55, respectively, to form the sixth comb tooth array 212 / 202 and the eighth comb tooth array 214 / 204.

[0010] The differential capacitance comb array III at the rear of the sensor includes a ninth moving comb array 311, a tenth moving comb array 312, an eleventh moving comb array 313, a twelfth moving comb array 314, a thirteenth moving comb array 315, a fourteenth moving comb array 316, and corresponding ninth fixed comb arrays 301, tenth fixed comb array 302, eleventh fixed comb array 303, twelfth fixed comb array 304, thirteenth fixed comb array 305, and fourteenth fixed comb array 306; the ninth moving comb array 311, tenth moving comb array 312, eleventh moving comb array 313, twelfth moving comb array 314, and thirteenth moving comb array are located at the rear end of the external mass block 12. 315 and the fourteenth moving comb tooth array 316 respectively cooperate with the ninth fixed comb tooth array 301, the tenth fixed comb tooth array 302, the eleventh fixed comb tooth array 303, the twelfth fixed comb tooth array 304, the thirteenth fixed comb tooth array 305 and the fourteenth fixed comb tooth array 306 located on the seventh comb tooth cantilever frame 56, the ninth comb tooth cantilever frame 58, the tenth comb tooth cantilever frame 59 and the eighth comb tooth cantilever frame 57 to form the ninth comb tooth array 311 / 301, the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, the twelfth comb tooth array 314 / 304, the thirteenth comb tooth array 315 / 305 and the fourteenth comb tooth array 316 / 306.

[0011] When the probe structure 31 is loaded, the internal support beam 22 and the external support beam 21 deform, the movable structure and the moving comb teeth on it are displaced, while the fixed comb teeth fixed on the comb tooth cantilever frame do not move, so that the relative positions of the moving and fixed comb teeth in the overall capacitance comb tooth array of the sensor change, the relative spacing or relative area of ​​the moving and fixed comb teeth changes, and thus the capacitance changes.

[0012] The differential capacitor comb array I at the front of the sensor has the same comb width, the same comb length, and the same overlap area. The distance d between each moving comb tooth and its adjacent fixed comb tooth on the first comb array 111 / 101 is... 11 and spacing d 12 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the second comb tooth array 112 / 102 is not equal. 13 and spacing d 14 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the third comb tooth array 113 / 103 is not equal. 15 and spacing d 16 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the fourth comb tooth array 114 / 104 is not equal. 17 and spacing d 18 They are not equal; in the initial state, the distance d between the moving and stationary comb plates in the comb array is... 11 =d 13=d 15 =d 17 The distance d between the moving and fixed comb teeth plates 12 =d 14 =d 16 =d 18 .

[0013] The differential capacitor comb array II in the middle of the sensor has equal comb widths, and the fifth comb array 211 / 201, the sixth comb array 212 / 202, the seventh comb array 213 / 203, and the eighth comb array 214 / 204 have the same moving and fixed comb spacing; in the initial state, the moving and fixed combs in the comb array are aligned with a length l. o1 =l o2 =l o3 =l o4 The length of the moving and fixed comb teeth is l g1 =l g2 =l g3 =l g4 .

[0014] The ninth comb array 311 / 301, the twelfth comb array 314 / 304, and the thirteenth comb array 315 / 305 in the differential capacitor comb array III at the rear of the sensor have the same comb tooth arrangement, wherein the distance d between each moving comb tooth and its adjacent fixed comb tooth is... 21 and spacing d 22 They are not equal; the comb teeth of the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, and the fourteenth comb tooth array 316 / 306 have the same comb tooth arrangement, wherein the spacing d between each moving comb tooth and its adjacent fixed comb tooth is... 23 and spacing d 24 They are not equal; in the initial state, the distance d between the moving and stationary comb plates in the capacitor comb array is... 21 =d 23 The distance d between the moving and fixed comb teeth plates 22 =d 24 .

[0015] The twelfth comb array 314 / 304 and the thirteenth comb array 315 / 305 in the differential capacitance comb array III at the rear of the sensor have the same comb tooth arrangement, wherein the distance d between each moving comb tooth cantilever and its adjacent fixed comb tooth cantilever is... a1 and spacing d a2 They are not equal; the comb teeth of the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, and the fourteenth comb tooth array 316 / 306 have the same comb tooth arrangement, wherein the distance d between each moving comb tooth cantilever and its adjacent fixed comb tooth cantilever is... a3 and spacing d a4They are not equal; the cantilever arms of each comb tooth in the differential capacitor comb array III at the rear of the sensor have equal widths. In the initial state, the distance d between the moving and stationary comb tooth cantilever arms is equal. a1 =d a3 The distance d between the movable and fixed comb teeth small cantilever is... a2 =d a4 The ninth comb tooth array 311 / 301, the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, the twelfth comb tooth array 314 / 304, the thirteenth comb tooth array 315 / 305, and the fourteenth comb tooth array 316 / 306 have the same moving and fixed comb tooth spacing and comb tooth width; in the initial state, they have the same moving and fixed comb tooth facing length l. oa1 =l oa2 and the same comb tooth length l ga1 =l ga2 .

[0016] By setting different spacing between moving and fixed plates, overlap length of comb plates, total length of comb array, length of inner and outer flexible support beams, and thickness of structural layer, planar micro-force linear sensing, precise sensing of decoupled axial components of planar micro-force, and decoupling and precise measurement of sub-nN planar micro-force can be achieved within different measurement ranges.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1) Compared with optical, magnetic micro-force sensors and other types of MEMS micro-force sensors such as piezoresistive and piezoelectric sensors, this invention adopts the principle of capacitive sensing, which transforms the changes in load and small displacement into changes in plate capacitance that are easier to measure. Furthermore, the comb-tooth capacitance obtained through the sensing electrode plate array is more sensitive to capacitance changes and has extremely high micro-force measurement sensitivity.

[0019] 2) This invention employs a dual-axis measurement sensing structure, which can orthogonally decouple the measured planar load and then measure the load components on the x and y axes. This invention connects the internal and external mass blocks through an internal support beam, decoupling and decomposing the planar displacement of the sensor mass block into single-axis motions on two orthogonal axes. Furthermore, since both the internal and external support beams have high stiffness in the z-direction, the sensor can also effectively decouple spatially when subjected to spatial loads, accurately measuring the magnitude of the dual-axis component of the planar force of the load on the working plane.

[0020] 3) This invention adopts a bistable structural design, which can decouple the coupling of electric field and mechanical force field to the sensitive displacement of each axis of the sensor. It also uses multi-region, multi-row capacitive comb teeth for differential measurement, which greatly improves the measurement accuracy of the sensor under limited device size and overcomes the constraints between sensitivity, accuracy and linearity in capacitive MEMS micro-force sensors. Attached Figure Description

[0021] Figure 1-1 This is a top view of the planar micro-force sensor of Example 1.

[0022] Figure 1-2 This is a schematic diagram of the distribution of the differential capacitor comb array in the planar micro-force sensor of Example 1.

[0023] Figure 1-3 This is a schematic diagram of the differential comb array, consisting of a moving comb array and a fixed comb array, located at the front of the sensor in Example 1.

[0024] Figure 1-4 This is a schematic diagram of the differential comb array, consisting of a moving comb array and a fixed comb array, located in the middle of the sensor in Example 1.

[0025] Figure 1-5 This is a schematic diagram of the differential comb array, consisting of a moving comb array and a fixed comb array, located at the rear of the sensor in Example 1.

[0026] Figure 2-1 This is a top view of the planar micro-force sensor in Example 2.

[0027] Figure 2-2 This is a schematic diagram of the distribution of the differential capacitor comb array in the planar micro-force sensor of Example 2.

[0028] Figure 2-3 This is a schematic diagram of the differential comb array, consisting of a moving comb array and a fixed comb array, located at the rear of the sensor in Example 2. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0030] Example 1, referring to Figure 1-1 , Figure 1-2A MEMS capacitive planar micro-force sensor based on a bistable mechanical structure is described. The sensor is a pitch-changing type, comprising a bottom silicon layer, an intermediate oxide insulating layer, and a top silicon structure layer. The top silicon structure layer contains a sensor sensing structure, which includes a probe structure 31. The rear end of the probe structure 31 is connected to an internal mass block 11, which is connected to an internal support beam 22. The internal support beam 22 is connected to an external mass block 12, which is connected to the external support beam 21. The probe structure 31, internal mass block 11, internal support beam 22, and external mass block 12 constitute the movable structure of the sensor. Both the internal and external support beams 22 and 21 are flexible straight beams. The external support beam 21 is connected to a first support beam frame 41 and a second support beam frame 42. On both sides of the probe structure 31 are differential capacitor comb arrays I at the front of the sensor. The fixed comb array of the differential capacitor comb array I at the front of the sensor and the first comb cantilever frame 50 and the second comb cantilever frame 50 are described. The arm frame 51 is connected; the two sides of the internal support beam 22 are the differential capacitor comb array II in the middle of the sensor. The fixed comb array of the differential capacitor comb array II in the middle of the sensor is connected to the third comb cantilever frame 52, the fourth comb cantilever frame 53, the fifth comb cantilever frame 54, and the sixth comb cantilever frame 55; the outer side of the external mass block 12 is the differential capacitor comb array III at the rear of the sensor. The fixed comb array of the differential capacitor comb array III at the rear of the sensor is connected to the seventh comb cantilever frame 56, the eighth comb cantilever frame 57, the ninth comb cantilever frame 58, and the tenth comb cantilever frame 59; after the probe structure 31 is loaded, the internal support beam 22 and the external support beam 21 deform, the movable structure and the moving comb on it are displaced, while the fixed comb on the comb cantilever frame does not move. This causes the relative position of the moving and fixed comb in the overall capacitor comb array of the sensor to change, the relative distance between the moving and fixed comb changes, and thus the capacitance changes.

[0031] Reference Figure 1-2The differential capacitance comb array I at the front of the sensor includes a first moving comb array 111, a second moving comb array 112, a third moving comb array 113, a fourth moving comb array 114, and corresponding first fixed comb arrays 101, second fixed comb arrays 102, third fixed comb arrays 103, and fourth fixed comb arrays 104. The first moving comb array 111 and the second moving comb array 112 are distributed on the left and right sides of the probe structure 31, respectively corresponding to the first moving comb array 111 and the second moving comb array 112 distributed on the left and right sides of the front of the first comb cantilever frame 50 and the second comb cantilever frame 51. The fixed comb tooth array 101 and the second fixed comb tooth array 102 cooperate with each other to form the first comb tooth array 111 / 101 and the second comb tooth array 112 / 102; the third moving comb tooth array 113 and the fourth moving comb tooth array 114 are respectively distributed on the left and right sides of the front part of the internal mass block 11, and cooperate with the third fixed comb tooth array 103 and the fourth fixed comb tooth array 104 distributed on the left and right sides of the rear part of the first comb tooth cantilever frame 50 and the second comb tooth cantilever frame 51 to form the third comb tooth array 113 / 103 and the fourth comb tooth array 114 / 104.

[0032] The differential capacitance comb array II in the middle of the sensor includes a fifth moving comb array 211, a sixth moving comb array 212, a seventh moving comb array 213, an eighth moving comb array 214, and corresponding fifth fixed comb arrays 201, sixth fixed comb array 202, seventh fixed comb array 203, and eighth fixed comb array 204. The fifth moving comb array 211 and the seventh moving comb array 213 are distributed on the left front end of the external mass block 12, respectively, and are distributed on the third comb cantilever frame 52 and the fifth comb cantilever frame 54. The fifth fixed comb tooth array 201 and the seventh fixed comb tooth array 203 cooperate with each other to form the fifth comb tooth array 211 / 201 and the seventh comb tooth array 213 / 203; the sixth movable comb tooth array 212 and the eighth movable comb tooth array 214 are distributed on the front right side of the external mass block 12, and cooperate with the sixth fixed comb tooth array 202 and the eighth fixed comb tooth array 204 distributed on the fourth comb tooth cantilever frame 53 and the sixth comb tooth cantilever frame 55 respectively to form the sixth comb tooth array 212 / 202 and the eighth comb tooth array 214 / 204.

[0033] The differential capacitance comb array III at the rear of the sensor includes a ninth moving comb array 311, a tenth moving comb array 312, an eleventh moving comb array 313, a twelfth moving comb array 314, a thirteenth moving comb array 315, a fourteenth moving comb array 316, and corresponding ninth fixed comb arrays 301, tenth fixed comb array 302, eleventh fixed comb array 303, twelfth fixed comb array 304, thirteenth fixed comb array 305, and fourteenth fixed comb array 306; the ninth moving comb array 311, tenth moving comb array 312, eleventh moving comb array 313, twelfth moving comb array 314, and thirteenth moving comb array are located at the rear end of the external mass block 12. 315 and the fourteenth moving comb tooth array 316 respectively cooperate with the ninth fixed comb tooth array 301, the tenth fixed comb tooth array 302, the eleventh fixed comb tooth array 303, the twelfth fixed comb tooth array 304, the thirteenth fixed comb tooth array 305 and the fourteenth fixed comb tooth array 306 located on the seventh comb tooth cantilever frame 56, the ninth comb tooth cantilever frame 58, the tenth comb tooth cantilever frame 59 and the eighth comb tooth cantilever frame 57 to form the ninth comb tooth array 311 / 301, the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, the twelfth comb tooth array 314 / 304, the thirteenth comb tooth array 315 / 305 and the fourteenth comb tooth array 316 / 306.

[0034] Reference Figure 1-3 The differential capacitor comb array I at the front of the sensor has the same comb width, the same comb length, and the same overlap area. The distance d between each moving comb tooth and its adjacent fixed comb tooth on the first comb array 111 / 101 is... 11 and spacing d 12 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the second comb tooth array 112 / 102 is not equal. 13 and spacing d 14 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the third comb tooth array 113 / 103 is not equal. 15 and spacing d 16 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the fourth comb tooth array 114 / 104 is not equal. 17 and spacing d 18 They are not equal; in the initial state, the distance d between the moving and stationary comb plates in the comb array is... 11 =d 13 =d 15 =d 17 The distance d between the moving and fixed comb teeth plates 12 =d 14 =d 16 =d 18 .

[0035] Reference Figure 1-4 The differential capacitor comb array II in the middle of the sensor has equal comb widths for its capacitive comb teeth. The fifth comb array 211 / 201, the sixth comb array 212 / 202, the seventh comb array 213 / 203, and the eighth comb array 214 / 204 have the same moving and fixed comb tooth spacing. In the initial state, the moving and fixed comb teeth in the comb array are aligned with a length l. o1 =l o2 =l o3 =l o4 The length of the moving and fixed comb teeth is l g1 =l g2 =l g3 =l g4 .

[0036] Reference Figure 1-5 The ninth comb array 311 / 301, the twelfth comb array 314 / 304, and the thirteenth comb array 315 / 305 in the differential capacitor comb array III at the rear of the sensor have the same comb tooth arrangement, wherein the distance d between each moving comb tooth and its adjacent fixed comb tooth is... 21 and spacing d 22 They are not equal; the comb teeth of the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, and the fourteenth comb tooth array 316 / 306 have the same comb tooth arrangement, wherein the spacing d between each moving comb tooth and its adjacent fixed comb tooth is... 23 and spacing d 24 They are not equal; in the initial state, the distance d between the moving and stationary comb plates in the capacitor comb array is... 21 =d 23 The distance d between the moving and fixed comb teeth plates 22 =d 24 .

[0037] Example 2, refer to Figure 2-1 , Figure 2-2 A MEMS capacitive planar micro-force sensor based on a bistable mechanical structure is an area-changing type. The overall structure is the same as the embodiment, except that the relative positions of the moving and fixed comb teeth in the overall capacitive comb array of the sensor change, causing the relative area of ​​the moving and fixed comb teeth to change, thereby generating a change in capacitance.

[0038] Reference Figure 2-2 The overall structure and distribution of the differential capacitor comb array I at the front of the sensor, the differential capacitor comb array II in the middle of the sensor, and the differential capacitor comb array III at the rear of the sensor are the same as in Example 1.

[0039] Reference Figure 2-2 , Figure 2-3The twelfth comb array 314 / 304 and the thirteenth comb array 315 / 305 in the differential capacitor comb array III at the rear of the sensor have the same comb tooth arrangement, wherein the distance d between each moving comb tooth cantilever and its adjacent fixed comb tooth cantilever is... a1 and spacing d a2 They are not equal; the comb teeth of the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, and the fourteenth comb tooth array 316 / 306 have the same comb tooth arrangement, wherein the distance d between each moving comb tooth cantilever and its adjacent fixed comb tooth cantilever is... a3 and spacing d a4 They are not equal; the cantilever arms of each comb tooth in the differential capacitor comb array III at the rear of the sensor have equal widths. In the initial state, the distance d between the moving and stationary comb tooth cantilever arms is equal. a1 =d a3 The distance d between the movable and fixed comb teeth small cantilever is... a2 =d a4 The ninth comb tooth array 311 / 301, the tenth comb tooth array 312 / 302, the eleventh comb tooth array 313 / 303, the twelfth comb tooth array 314 / 304, the thirteenth comb tooth array 315 / 305, and the fourteenth comb tooth array 316 / 306 have the same moving and fixed comb tooth spacing and comb tooth width; in the initial state, they have the same moving and fixed comb tooth facing length l. oa1 =l oa2 and the same comb tooth length l ga1 =l ga2 .

[0040] The above description is only one embodiment of the present invention, and not all or the only embodiment. Any equivalent modifications made by those skilled in the art to the technical solution of the present invention by reading the present invention specification are covered by the claims of the present invention.

Claims

1. A MEMS capacitive planar micro-force sensor based on a bistable mechanical structure, comprising a bottom silicon layer, an intermediate oxide insulating layer, and a top silicon structure layer, wherein a sensor sensing structure is provided in the top silicon structure layer, characterized in that: The sensor sensing structure includes a probe structure (31), the rear end of the probe structure (31) is connected to the internal mass block (11), the internal mass block (11) is connected to the internal support beam (22), the internal support beam (22) is connected to the external mass block (12), and the external mass block (12) is connected to the external support beam (21). The probe structure (31), the internal mass block (11), the internal support beam (22), and the external mass block (12) constitute the movable structure of the sensor. The internal support beam (22) and the external support beam (21) are both flexible straight beams. The external support beam (21) is connected to the support beam frame. The probe structure (31) has differential capacitor comb tooth arrays (Ⅰ) on both sides of the front of the sensor, the internal support beam (22) has differential capacitor comb tooth arrays (Ⅱ) on both sides of the middle of the sensor, and the external mass block (12) has differential capacitor comb tooth arrays (Ⅲ) on the outside of the rear of the sensor. The fixed comb tooth array is connected to the comb tooth cantilever frame.

2. The planar micro-force sensor according to claim 1, characterized in that: The differential capacitance comb array (Ⅰ) at the front of the sensor includes a first moving comb array (111), a second moving comb array (112), a third moving comb array (113), a fourth moving comb array (114), and corresponding first fixed comb arrays (101), second fixed comb arrays (102), third fixed comb arrays (103), and fourth fixed comb arrays (104). The first moving comb array (111) and the second moving comb array (112) are distributed on the left and right sides of the probe structure (31), respectively corresponding to the first moving comb array (111) and the second moving comb array (112) distributed on the left and right sides of the front part of the first comb cantilever frame (50) and the second comb cantilever frame (51). The fixed comb tooth array (101) and the second fixed comb tooth array (102) cooperate with each other to form the first comb tooth array (111 / 101) and the second comb tooth array (112 / 102); the third moving comb tooth array (113) and the fourth moving comb tooth array (114) are respectively distributed on the left and right sides of the front part of the internal mass block (11), and cooperate with the third fixed comb tooth array (103) and the fourth fixed comb tooth array (104) distributed on the left and right sides of the rear part of the first comb tooth cantilever frame (50) and the second comb tooth cantilever frame (51) to form the third comb tooth array (113 / 103) and the fourth comb tooth array (114 / 104).

3. The planar micro-force sensor according to claim 1, characterized in that: The differential capacitance comb array (II) in the middle of the sensor includes a fifth moving comb array (211), a sixth moving comb array (212), a seventh moving comb array (213), an eighth moving comb array (214), and corresponding fifth fixed comb arrays (201), sixth fixed comb arrays (202), seventh fixed comb arrays (203), and eighth fixed comb arrays (204). The fifth moving comb array (211) and the seventh moving comb array (213) are distributed on the left front end of the external mass block (12), respectively, and are distributed on the cantilever frame (52) of the third comb and the cantilever frame (54) of the fifth comb. The fifth fixed comb tooth array (201) and the seventh fixed comb tooth array (203) cooperate with each other to form the fifth comb tooth array (211 / 201) and the seventh comb tooth array (213 / 203); the sixth moving comb tooth array (212) and the eighth moving comb tooth array (214) are distributed on the right side of the front end of the external mass block (12), and cooperate with the sixth fixed comb tooth array (202) and the eighth fixed comb tooth array (204) distributed on the fourth comb tooth cantilever frame (53) and the sixth comb tooth cantilever frame (55) respectively to form the sixth comb tooth array (212 / 202) and the eighth comb tooth array (214 / 204).

4. The planar micro-force sensor according to claim 1, characterized in that: The differential capacitance comb array (Ⅲ) at the rear of the sensor includes a ninth moving comb array (311), a tenth moving comb array (312), an eleventh moving comb array (313), a twelfth moving comb array (314), a thirteenth moving comb array (315), a fourteenth moving comb array (316), and corresponding ninth fixed comb arrays (301), tenth fixed comb arrays (302), eleventh fixed comb arrays (303), twelfth fixed comb arrays (304), thirteenth fixed comb arrays (305), and fourteenth fixed comb arrays (306); the ninth moving comb array (311), tenth moving comb array (312), eleventh moving comb array (313), twelfth moving comb array (314), and thirteenth moving comb array are located at the rear end of the external mass block (12). (315) The fourteenth moving comb tooth array (316) cooperates with the ninth fixed comb tooth array (301), tenth fixed comb tooth array (302), eleventh fixed comb tooth array (303), twelfth fixed comb tooth array (304), thirteenth fixed comb tooth array (305) and fourteenth fixed comb tooth array (306) located on the seventh comb tooth cantilever frame (56), ninth comb tooth cantilever frame (58), tenth comb tooth cantilever frame (59) and eighth comb tooth cantilever frame (57) to form the ninth comb tooth array (311 / 301), tenth comb tooth array (312 / 302), eleventh comb tooth array (313 / 303), twelfth comb tooth array (314 / 304), thirteenth comb tooth array (315 / 305) and fourteenth comb tooth array (316 / 306).

5. The planar micro-force sensor according to any one of claims 1-4, characterized in that: When the probe structure (31) is loaded, the internal support beam (22) and the external support beam (21) deform, the movable structure and the moving comb teeth on it are displaced, while the fixed comb teeth fixed on the comb tooth cantilever frame do not move, so that the relative positions of the moving and fixed comb teeth in the overall capacitance comb tooth array of the sensor change, the relative spacing or relative area of ​​the moving and fixed comb teeth changes, and thus the capacitance changes.

6. The planar micro-force sensor according to claim 5, characterized in that: When the relative spacing between the moving and fixed comb teeth changes, the capacitive comb teeth in the differential capacitive comb array (Ⅰ) at the front of the sensor have the same comb tooth width, the same comb tooth length, and the same overlap area. The spacing d between each moving comb tooth and its adjacent fixed comb tooth on the first comb array (111 / 101) is... 11 and spacing d 12 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the second comb tooth array (112 / 102) is not equal. 13 and spacing d 14 The spacing d between each moving comb tooth and its adjacent fixed comb tooth in the third comb tooth array (113 / 103) is not equal. 15 and spacing d 16 The distance d between each moving comb tooth and its adjacent fixed comb tooth in the fourth comb tooth array (114 / 104) is not equal. 17 and spacing d 18 They are not equal; in the initial state, the distance d between the moving and stationary comb plates in the comb array is... 11 =d 13 =d 15 =d 17 The distance d between the moving and fixed comb teeth plates 12 =d 14 =d 16 =d 18 .

7. The planar micro-force sensor according to claim 5, characterized in that: When the relative spacing between the moving and fixed comb teeth changes, the capacitive comb teeth in the differential capacitor comb array (II) in the middle of the sensor have equal comb tooth widths. The fifth comb array (211 / 201), the sixth comb array (212 / 202), the seventh comb array (213 / 203), and the eighth comb array (214 / 204) have the same moving and fixed comb tooth spacing. In the initial state, the moving and fixed comb teeth in the comb array are aligned with a length l. o1 =l o2 =l o3 =l o4 The length of the moving and fixed comb teeth is l g1 =l g2 =l g3 =l g4 .

8. The planar micro-force sensor according to claim 5, characterized in that: When the relative spacing between the moving and fixed comb teeth changes, the ninth comb array (311 / 301), the twelfth comb array (314 / 304), and the thirteenth comb array (315 / 305) in the differential capacitor comb array (Ⅲ) at the rear of the sensor have the same comb tooth arrangement, wherein the spacing d between each moving comb tooth and its adjacent fixed comb tooth is... 21 and spacing d 22 They are not equal; the comb teeth of the tenth comb tooth array (312 / 302), the eleventh comb tooth array (313 / 303), and the fourteenth comb tooth array (316 / 306) have the same comb tooth arrangement, wherein the spacing d between each moving comb tooth and its adjacent fixed comb tooth is equal. 23 and spacing d 24 They are not equal; in the initial state, the distance d between the moving and stationary comb plates in the capacitor comb array is... 21 =d 23 The distance d between the moving and fixed comb teeth plates 22 =d 24 .

9. The planar micro-force sensor according to claim 5, characterized in that: When the relative areas of the moving and fixed comb teeth change, the comb teeth of the twelfth comb tooth array (314 / 304) and the thirteenth comb tooth array (315 / 305) in the differential capacitance comb tooth array (Ⅲ) at the rear of the sensor are arranged in the same way, wherein the distance d between each moving comb tooth cantilever and its adjacent fixed comb tooth cantilever is... a1 and spacing d a2 They are not equal; the comb teeth of the tenth comb tooth array (312 / 302), the eleventh comb tooth array (313 / 303), and the fourteenth comb tooth array (316 / 306) have the same comb tooth arrangement, wherein the distance d between each moving comb tooth cantilever and its adjacent fixed comb tooth cantilever is... a3 and spacing d a4 They are not equal; the comb teeth in the differential capacitor comb array (Ⅲ) at the rear of the sensor have equal widths, and in the initial state, the distance d between the moving and fixed comb teeth cantilever arms is equal. a1 =d a3 The distance d between the movable and fixed comb teeth small cantilever is... a2 =d a4 The ninth comb array (311 / 301), tenth comb array (312 / 302), eleventh comb array (313 / 303), twelfth comb array (314 / 304), thirteenth comb array (315 / 305), and fourteenth comb array (316 / 306) have the same moving and fixed comb tooth spacing and comb tooth width; in the initial state, they have the same moving and fixed comb tooth facing length l. oa1 =l oa2 and the same comb tooth length l ga1 =l ga2 .

10. The planar micro-force sensor according to claim 5, characterized in that: By setting different spacing between moving and fixed plates, overlap length of comb plates, total length of comb array, length of inner and outer flexible support beams, and thickness of structural layer, planar micro-force linear sensing, precise sensing of decoupled axial components of planar micro-force, and decoupling and precise measurement of sub-nN planar micro-force can be achieved within different measurement ranges.

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