CN116793546A - High-sensitivity array type touch sensor with needle-shaped structure - Google Patents
High-sensitivity array type touch sensor with needle-shaped structure Download PDFInfo
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- CN116793546A CN116793546A CN202310008683.4A CN202310008683A CN116793546A CN 116793546 A CN116793546 A CN 116793546A CN 202310008683 A CN202310008683 A CN 202310008683A CN 116793546 A CN116793546 A CN 116793546A
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2206—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/225—Measuring circuits therefor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/225—Measuring circuits therefor
- G01L1/2262—Measuring circuits therefor involving simple electrical bridges
Abstract
The invention discloses a high-sensitivity array type touch sensor with a needle-shaped structure. The invention comprises a metal electrode, a sensitive unit, a silicon beam, a piezoresistor and a chip frame; the invention adopts the mass block with the supporting structure to connect the top of the contactor with the micro-beam structure to achieve the effect of detecting and separating the vertical acting force and the transverse acting force. The micro-beam structure is adopted, original torsional deformation is changed, most of stress and strain are concentrated on the beam through the straight-pull straight-press mode, the detection of piezoresistors is contributed, and compared with the traditional piezoresistor type sensor, the sensitivity of the sensor is greatly improved. The piezoresistance principle is adopted to measure the touch force such as friction force, pressure and the like, the beam structure is adopted to measure the normal force and the shearing force, and under the same load, compared with a capacitive sensor, the chip is miniaturized on the premise of not losing sensitivity.
Description
Technical Field
The invention relates to the technical field of tactile sensors, in particular to a tactile sensing structure with high sensitivity in a 'straight-pull straight-press' mode.
Background
With the development of robot technology, the touch sensor with high precision is increasingly paid attention to, and can be widely applied to intelligent sensing technology and man-machine interaction systems. External environmental information acquired by the tactile sensor is critical to achieve a natural interactive experience, and the robot can make corresponding behavioral decisions including, but not limited to, pressure, temperature, humidity, slippage, etc., based on the complex and diverse tactile information obtained.
Haptic perception is defined in the robot art as continuous perception of variable contact force, and these information can be used to help the robot determine whether to contact with an object, grasp whether to be stable, recognize object information, feedback on control force, etc., and the object operation task is analyzed by the haptic information obtained by the haptic sensor, so that the versatility of the robot can be further improved, so that the haptic sensor is essential for the robot to have a smart operation. The sliding friction force is mainly detected and judged by a sensor through the change of pressure mapping, and is closely related to sliding detection, material identification and sliding roughness identification. In recent years, various novel piezoresistive, capacitive, piezoelectric, magnetically permeable sensor structures have been developed, and compared with capacitive sensors, piezoresistive sensors have simple design rules and small size, but have lower sensitivity, and meanwhile, the mechanical sensing direction of the sensing technology is mainly concentrated on the normal force, so that the measurement of three-dimensional force cannot be realized, thereby limiting the application in touch interaction.
In the prior art, MEMS-based tactile sensors are capable of detecting tactile information, such as sliding friction. A local slip sensor based on MEMS anti-fall was proposed by university of tokyo, japan in 2021. The sensor chip consists of a side wall doped silicon beam for shear stress sensing and a surface doped silicon beam for normal stress sensing, and meanwhile, the response of the silicon beam is not only in direct proportion to the applied stress, but also is not interfered by the rest stress, and the sensor chip has the characteristic of no need of decoupling. The chip is completely covered by an elastic material (such as PDMS), the two ends of the silicon beam are fixed, and an air cavity is not arranged below the beam, so that the sensitivity of the sensor is greatly reduced by the design.
In comparison with human fingertip touch, the sensor can help the robot to realize the perception of object touch information, but the sensor has a great progress in terms of sensitivity.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a sensor based on a detection principle with high sensitivity under the precondition that various tactile information can be measured, and the sensor does not use an elastomer (or polymer), so that the loss of the elastomer to force is reduced, and the sensor is realized only by a silicon micro-mechanical structure.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the invention comprises a metal electrode, a sensitive unit, a silicon beam, a piezoresistor and a chip frame;
the sensing unit adopts needle-shaped contactors, and a plurality of contactors in the chip frame are arranged at intervals and are used for simulating the cross section of human fingerprints;
the chip frame provides supporting function for the sensitive unit and the silicon beam, and is also used as a supporting platform of the piezoresistor detection circuit.
The metal electrode is positioned on the surface of the silicon chip frame and is used for being connected with the piezoresistor to form a Wheatstone bridge;
the piezoresistor is positioned on the silicon beam, and the longitudinal and transverse movements of each sensitive unit are respectively detected by connecting the independent piezoresistor into a Wheatstone bridge circuit;
the silicon beams are divided into two groups, one group is composed of two transverse side beams which are distributed on two sides of the top end of the sensitive unit in a horizontal arrangement mode, the other group is composed of four micro beams, each micro beam is arranged at the upper end and the lower end of the same side of the mass block in a pair, one end of each micro beam is connected with the chip frame, the other end of each micro beam is connected with the mass block, and the mass blocks are positioned at the top of the sensitive unit;
the micro beam is deformed into axial stretching or compression in the stress process and is used for normal stress sensing;
the side beam is deformed into torsion in the stress process and is used for shear stress sensing.
Preferably, the distance between the contactors is 500 μm, which is close to the average fingerprint gap of human skin.
Preferably, the top end of the contactor is designed into a needle shape, so that the contact area between the sensitive unit and the object is reduced, the detectable object range is enlarged, and the resolution of the sensor is increased.
Preferably, the piezoresistor is obtained by doping the upper surface of the silicon beam.
Preferably, the micro beams have a width of 3 μm and a length of 60 μm, each micro beam is provided with a piezoresistor, the length of the piezoresistor is 40 μm, and the thickness is 100nm.
Preferably, the side beams have a width of 10 μm and a length of 180 μm, each side beam also has a varistor, and the varistor has a length of 150 μm and a thickness of 100nm.
Preferably, the two groups of micro beams on the mass are spaced 30 μm apart.
The invention has the beneficial effects that: the top of the contactor is connected with the micro-beam structure by adopting the mass block with the supporting structure, so that the effect of detecting and separating the vertical acting force and the transverse acting force is achieved. The micro-beam structure is adopted, original torsional deformation is changed, most of stress and strain are concentrated on the beam through the straight-pull straight-press mode, the detection of piezoresistors is contributed, and compared with the traditional piezoresistor type sensor, the sensitivity of the sensor is greatly improved. The piezoresistance principle is adopted to measure the touch force such as friction force, pressure and the like, the beam structure is adopted to measure the normal force and the shearing force, and under the same load, compared with a capacitive sensor, the chip is miniaturized on the premise of not losing sensitivity.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention.
FIG. 2 is a schematic diagram of a single array element of the sensor.
Fig. 3 is an enlarged schematic view of the micro-beam structure of the sensor.
Fig. 4 is an enlarged schematic view of a side beam construction detail of the sensor.
Fig. 5 is a schematic diagram illustrating the operation of a tactile sensor array unit having a needle-like structure when subjected to a normal force.
Fig. 6 is an enlarged schematic view of the stress details of the micro beam structure.
FIG. 7 is a schematic diagram of the operation of the tactile sensor array unit when subjected to tangential forces.
Fig. 8 is a flow chart of a process for fabricating a microbeam in a tactile sensor.
Detailed Description
The sensor mainly comprises 6 needle-like sharp contactors with the same length and orderly arrangement, a silicon beam structure and a chip frame. The contact ends are made into needle-like shapes and are arranged at the same interval to form a sensing array so as to obtain a touch signal with larger resolution. The beam structure comprises a micro beam and a side beam, and the small-size beam structure can be changed from torsional deformation into straight-pull straight-press deformation, so that stress is concentrated, and the sensitivity of the sensor is improved.
The invention adopts the piezoresistance sensing principle, and the chip consists of 6 needle-shaped contactors with the same length, 12 pairs of micro beams (total 24), 6 pairs of side beams (total 12) which are horizontally arranged and a chip frame. The adopted micro-beam structure is deformed into axial stretching/compression in the stress process, and most of stress is uniformly distributed in the beam structure, so that most of strain can be considered to contribute to the detection of the piezoresistor. The side beam is positioned at the top end of the contactor and used for shear stress sensing, and the micro beam is connected with the contactor through the mass block and used for normal stress sensing. The beam structure is etched by a deep ion reaction technology, the piezoresistor forms a piezoresistor strip doped on the surface on the upper silicon of the SOI by adopting an ion implantation process, and the movement of the contactor is detected by a Wheatstone bridge circuit integrated on the chip frame.
In the invention, as a microstructure which is directly contacted with an object, contactors are orderly arranged at intervals of 500 μm and are close to the average fingerprint gap of human skin, and the top end is designed to be in a needle shape, so that finer tactile information is acquired. The contactor tips are designed as a set of lateral side beams. In the sweeping process, the tip of the contactor is twisted to drive the transverse side beam to deform, and the deformation is obtained through the change of the piezoresistor doped on the surface. Two pairs of micro beams are connected above the contactor, the micro beams are designed to be smaller than transverse side beams in size, the tail ends of the micro beams are axially deformed in the stress process, and stress strain can be concentrated on the micro beam parts. Different from the torsion deformation generated by the side beams, the micro beams generate a 'straight-pull straight-press' effect, and under the action of the vertical movement of the contactor, the micro beams axially stretch/compress to form stress difference, and the variable quantity of the piezoresistor is obtained through the variable quantity of the output voltage of the Wheatstone bridge.
According to the invention, the size of the micro-beam structure is greatly reduced, the deformation mode is changed, under the action of force, the deformation is converted into the axial deformation of the straight-pull straight-press generated by the micro-beam, the dispersed stress is concentrated on the micro-beam, one micro-beam is axially stretched, and one micro-beam is axially compressed to form a stress difference, and the resistance change stress of the piezoresistor reaches the maximum.
The invention adopts a Wheatstone bridge as a measuring circuit, and the Wheatstone bridge is a detection mode for detecting the change of the piezoresistor in the MEMS piezoresistive pressure sensor. The piezoresistor is connected into a Wheatstone bridge to realize the purpose of detecting the resistance change of the piezoresistor, and the full bridge has the advantages of providing full-scale output, reducing zero temperature drift and the like. Under the action of force, the other micro Liang Zhiya of the contactor is pulled directly by one micro beam, the resistance value of the piezoresistor generates the same delta R, and the delta R is converted into a voltage signal through a bridge circuit to be output.
Embodiments of the present invention are described below with reference to the accompanying drawings:
the embodiment comprises five parts, namely a metal electrode, a sensitive unit, a silicon beam, a piezoresistor and a chip frame. The silicon beams are divided into two groups, one group consists of 2 transverse side beams with the width of 10 mu m, the two groups are distributed on two sides of the top end of the contactor in a horizontal arrangement mode, the other group consists of 4 micro beams with the length of 60 mu m, the two groups are orderly arranged on the same side of the mass block at intervals of 30 mu m, one end of each micro beam is connected with the chip frame, and the other end of each micro beam is connected with the top of the needle-shaped structure through the mass block. The sensing unit comprises 6 needle-shaped contactors with the same length, the contactors are orderly arranged at intervals of 500 mu m and are close to the average fingerprint gap of human skin, the purpose is to simulate the cross section of human fingerprint, and meanwhile, the top end is designed to be in a needle shape, so that the contact area between the sensing unit and an object is reduced, the detectable object range is enlarged, and the resolution of the sensor is increased. The chip frame provides supporting function for the contactor and the silicon beam, and is also used as a supporting platform of the piezoresistor detection circuit. The metal electrode is positioned on the surface of the silicon chip frame and is used for being connected with the piezoresistor to form a Wheatstone bridge. The piezoresistor is positioned on the silicon beam, the surface doping can be obtained through an ion diffusion process, and the longitudinal and transverse movements of each contactor are respectively detected by connecting the independent piezoresistor into a Wheatstone bridge circuit.
Fig. 1 is a schematic structural view of an array type touch sensor with a needle structure, wherein a region a is an enlarged schematic structural detail of a micro beam, a region B is an enlarged schematic structural detail of a side beam, and fig. 2 is a schematic structural view of a single array unit of the sensor. 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l, 1m, 1n, 1o, 1p are fixed metal electrodes and are connected with piezoresistors to form a wheatstone bridge circuit. 2a, 2b, 2c, 2d, 2e, 2f are sensitive units (contactors) of the sensor, 6 contactors are arranged at a pitch of 500 μm, which aims to simulate human fingerprint gaps, and the contactors are made into needle-point shapes, which aims to increase the contactable range of the sensor and the object. 3a, 3b, 3C, 3d, 3e, 3f, 3g, 3h, 3i, 3j, 3k and 3l are micro-beam structures, the detailed enlarged schematic diagram of the micro-beam structures is shown in fig. 3, the micro-beam structures are 3 μm wide and 60 μm long, the mass block and the chip frame are connected, the right side is an enlarged view of the micro-beams, C is a piezoresistor on the micro-beams, each micro-beam corresponds to one piezoresistor, and the piezoresistor is 40 μm long and 100nm thick and is positioned in the center of the beam structure. 4a, 4b, 4C, 4d, 4e and 4f are side beams, the detailed enlarged schematic diagram of the side beam structure is shown in fig. 4, the side beams are 10 μm wide and 180 μm long, and C is a piezoresistor on the side beam, each side beam corresponds to a piezoresistor, the piezoresistor is 150 μm long and 100nm thick, and the piezoresistor is also positioned in the center of the beam structure. 5a, 5b, 5c, 5d, 5e, 5f are mass blocks. And 6 is a chip frame. The side beam generates torsion deformation along with the transverse movement of the contactor, the friction force applied to the sensitive part of the sensor is detected through the change of the piezoresistor, the micro beam generates 'straight-pull straight-press' deformation along with the vertical movement of the contactor, and the positive pressure applied to the sensitive part of the sensor is detected through the change of the piezoresistor. One array unit comprises 2 pairs of micro beams, 1 pair of side beams, 3 pairs of piezoresistors (2 pairs of the micro beams are positioned on the surfaces of the side beams, 1 pair of the piezoresistors are positioned on the surfaces of the side beams), the sensor comprises 6 array units, 18 pairs of the piezoresistors are combined, wherein 12 pairs of piezoresistors (positioned on the surfaces of the micro beams) form a Wheatstone bridge for detecting positive pressure, and 6 pairs of piezoresistors (positioned on the surfaces of the side beams) are combined into a pair of piezoresistors for detecting transverse acting force.
Fig. 5 is a schematic diagram illustrating the operation of a tactile sensor array unit having a needle-like structure when subjected to a normal force.
FIG. 6 is an enlarged schematic view of the micro-beam structure force on the tactile sensor.
The principle of normal force operation in this example is shown in fig. 5: when the contactor receives normal force, the mass block at the top is driven to move to generate certain displacement, and finally axial deformation is generated at the micro beam. The enlarged schematic diagram of the region D is shown in fig. 6, and is the working principle of the micro-beam structure. The left end of the micro beam is a fixed end, and the right end is a movable end. The length of the micro beam is designed to be far larger than the width and the thickness of the micro beam, and under the action of the characteristic, the micro beam generates axial deformation under the drive of the mass block, and most of the generated strain is concentrated on the micro beam. One beam is axially stretched, the other beam is axially compressed, the length change is delta l, stress difference is formed on the two beams, and finally the doped piezoresistor resistance value is changed.
Fig. 7 is a schematic diagram of the operation of a tactile sensor array unit having a needle-like structure when subjected to tangential force.
The principle of operation in this example under tangential force: the needle-like structure of the contactor is in contact with the surface of the object, the object is in contact with the contact point and generates a reaction force, and the force signal is amplified through the beam structure on the contactor. When tangential acting force is applied, the contactor deflects at a certain angle to drive the side beam above to deform to form stress difference, the piezoresistor is positioned at the center of the side beam, and the generated deformation and stress difference are output through the bridge circuit to obtain the linear relation between voltage and resistance.
Fig. 8 is a process flow chart of a micro silicon beam in an array type tactile sensor with needle-like structure, which is specifically described as follows:
(a) An SOI wafer having an upper silicon layer thickness of 20um, a lower silicon layer thickness of 20um, an intermediate oxide layer thickness of 10um and a back oxide layer thickness of 10um was prepared and cleaned. Thinning the upper silicon layer to a proper thickness by using KOH corrosive liquid;
(b) And (5) oxidizing at high temperature, and photoetching to form a beam structure region. Manufacturing a piezoresistor by adopting a light boron ion diffusion process, and then performing a thermal annealing process;
(c) Forming silicon oxide as a mask to cover the piezoresistive strips during light boron ion diffusion redistribution, and performing a concentrated boron ion diffusion process in the other areas;
(d) Sputtering a film on the front surface of the wafer to form a mask pattern, and manufacturing a movable structure by adopting an RIE etching process technology;
(e) Polyimide is adopted to protect the front structure, photoresist is coated on the back of the wafer to form a pattern, a DRIE etching technology is adopted to etch the movable sensor structure, hydrofluoric acid solution is adopted to etch the silicon dioxide layer, and the movable structure is released.
In this example, the silicon-on-insulator (SOI) used for the sensor may obtain a uniform structure that is difficult to obtain by other processes, and high-precision material parameters, such as film thickness, elastic coefficient, doping characteristics, etc., for example, the self-stopping corrosion of the DRIE etching may be realized by using the intermediate silicon oxide layer of the SOI silicon wafer, and the sizes of each part of the structure may be precisely determined.
In summary, the sensor has the characteristics of high sensitivity, miniaturization and small crosstalk, and can separate vertical acting force and tangential acting force, the crosstalk problem and the stress concentration problem between the forces can be effectively reduced by adjusting the position and the size of the micro-beam of the sensor, and the micro-beam structure adopted concentrates most of stress strain to be contributed to the detection of the piezoresistor, so that the sensor has higher sensitivity. And finally, the needle-shaped contactor is adopted to amplify the force signal while reducing the contact area, so that the resolution of the sensor is increased, and the detectable object range is enlarged.
Claims (7)
1. A high sensitivity array type tactile sensor having a needle-like structure, characterized in that: the sensor comprises a metal electrode, a sensitive unit, a silicon beam, piezoresistors and a chip frame;
the sensing unit adopts needle-shaped contactors, and a plurality of contactors in the chip frame are arranged at intervals and are used for simulating the cross section of human fingerprints;
the chip frame provides a supporting function for the sensitive unit and the silicon beam and is also used as a supporting platform of the piezoresistor detection circuit;
the metal electrode is positioned on the surface of the silicon chip frame and is used for being connected with the piezoresistor to form a Wheatstone bridge;
the piezoresistor is positioned on the silicon beam, and the longitudinal and transverse movements of each sensitive unit are respectively detected by connecting the independent piezoresistor into a Wheatstone bridge circuit;
the silicon beams are divided into two groups, one group is composed of two transverse side beams which are distributed on two sides of the top end of the sensitive unit in a horizontal arrangement mode, the other group is composed of four micro beams, each micro beam is arranged at the upper end and the lower end of the same side of the mass block in a pair, one end of each micro beam is connected with the chip frame, the other end of each micro beam is connected with the mass block, and the mass blocks are positioned at the top of the sensitive unit;
the micro beam is deformed into axial stretching or compression in the stress process and is used for normal stress sensing;
the side beam is deformed into torsion in the stress process and is used for shear stress sensing.
2. A high sensitivity array type tactile sensor having a needle-like structure according to claim 1, wherein: the distance between the contactors is 500 mu m, and the distance is close to the average fingerprint gap of human skin.
3. A high sensitivity array type tactile sensor having a needle-like structure according to claim 1, wherein: the contactor top is designed into a needle shape and is used for reducing the contact area of the sensitive unit and an object, expanding the detectable object range and increasing the resolution of the sensor.
4. A high sensitivity array type tactile sensor having a needle-like structure according to claim 1, wherein: the piezoresistor is obtained by doping the upper surface of the silicon beam.
5. The high sensitivity array type tactile sensor having a needle structure according to any one of claims 1 to 4, wherein: the micro-beam width is 3 mu m, the length is 60 mu m, each micro-beam is provided with a piezoresistor, the piezoresistor is 40 mu m long, and the thickness is 100nm.
6. The high sensitivity array type tactile sensor having a needle-like structure according to claim 5, wherein: the side beam width be 10 mu m, long be 180 mu m, every curb girder also has a piezo-resistor, piezo-resistor length is 150 mu m, thick 100nm.
7. The high sensitivity array type tactile sensor having a needle-like structure according to claim 6, wherein: and a gap of 30 mu m is formed between the two groups of micro beams on the mass block.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310008683.4A CN116793546A (en) | 2023-01-04 | 2023-01-04 | High-sensitivity array type touch sensor with needle-shaped structure |
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| CN202310008683.4A CN116793546A (en) | 2023-01-04 | 2023-01-04 | High-sensitivity array type touch sensor with needle-shaped structure |
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| CN116793546A true CN116793546A (en) | 2023-09-22 |
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| CN202310008683.4A Pending CN116793546A (en) | 2023-01-04 | 2023-01-04 | High-sensitivity array type touch sensor with needle-shaped structure |
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2023
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