Microstructure electronic skin and preparation method and application thereof

Abstract

The invention belongs to the technical field of electronic skin, and provides microstructure electronic skin and a preparation method and application thereof. The micro-structure electronic skin comprises a flexible pressure sensor and a micro-structure layer which are arranged in a stacked mode. The flexible pressure sensor comprises a substrate layer and a circuit layer which are stacked. The other side of the circuit layer is in contact with the microstructure layer; a recessed circuit pattern is arranged on the surface of one side, which is in contact with the substrate layer, of the circuit layer; the circuit patterns are conductive units distributed in an array; the conductive unit is formed by a circuit channel, and the circuit channel is of a double-helix structure. The circuit channel is filled with a conductive material; the microstructure layer comprises a bearing layer and protrusions arranged on the bearing layer in an array mode, and the bearing layer makes contact with the circuit layer. The micro-structure electronic skin can sense information of a three-dimensional level, can recognize the micro-scale surface appearance, and has good application value. Meanwhile, the micro-structure electronic skin can be applied to various complex curved surface environments.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic skin, and in particular to a microstructured electronic skin and its preparation method and application. Background Art

[0002] In the field of flexible electronics, flexible electronic skin is a current research hotspot. The electronic skin can sense external stimuli to obtain environmental information and convert it into electrical signals, providing rich physical information during the interaction between machines and the environment, and between humans and machines. The electronic skin has the softness and stretchability similar to biological skin, and at the same time has high sensing performance and high mechanical stability. It has received extensive attention in the fields of human-computer interaction interfaces, wearable electronics, medical monitoring, etc., and is expected to become an important part of the new Internet of Things era.

[0003] The existing electronic skin has only a two-dimensional sensing dimension, which limits its further development. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a microstructured electronic skin and its preparation method and application. The microstructured electronic skin provided by the present invention can sense in three dimensions.

[0005] It can accurately detect the height of microscale surface topography. Further, the electronic skin can be applied to the field of braille detection. It shows good recognition and reading ability for current standard braille, can recognize a variety of complex braille letters, and has application value for human-computer interface interaction and braille reading for special blind groups with prosthetics.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a microstructured electronic skin, including a flexible pressure sensor and a microstructured layer arranged in a stacked manner;

[0008] The flexible pressure sensor includes a base layer and a circuit layer arranged in a stacked manner; the other side of the circuit layer is in contact with the microstructured layer;

[0009] On the surface of the side where the circuit layer is in contact with the base layer, there is an indented circuit pattern;

[0010] The circuit pattern is an array of conductive units; the conductive units are formed by circuit channels, and the circuit channels are in a double-helix structure; the conductive units are filled with a conductive material;

[0011] The microstructured layer includes a receiving layer and protrusions arranged in an array on the receiving layer, and the protrusions are centrally corresponding to the conductive units; the receiving layer is in contact with the circuit layer.

[0012] Preferably, the material of the base layer is polydimethylsiloxane; the material of the circuit layer is platinum-catalyzed silicone rubber, and the material of the micro-structure layer is platinum-catalyzed silicone rubber.

[0013] Preferably, the shape of the conductive unit is circular, triangular, square, pentagonal or hexagonal; the size of the conductive unit is 1-2 mm; the depth of the conductive unit is 0.08-0.3 mm.

[0014] Preferably, the distance between adjacent conductive units is greater than or equal to 5 mm.

[0015] Preferably, the cross-sectional shape of the circuit channel is square, and the side length of the square is 0.08-0.3 mm; the distance between adjacent circuit channels is 0.3-0.32 mm.

[0016] Preferably, the conductive material is an ionic liquid, and the ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate.

[0017] Preferably, the shape of the protrusion is a pyramid, the bottom size of the pyramid is 1-2 mm, and the height is 3-4.5 mm; the thickness of the receiving layer is 1 mm.

[0018] Preferably, the thickness of the circuit layer is 0.5-2 mm; the thickness of the base layer is 0.5 mm.

[0019] The present invention also provides a preparation method of the micro-structure electronic skin described in the above technical solution, including the following steps:

[0020] Prepare a base layer template, a circuit layer template and a micro-structure layer template respectively;

[0021] Using the micro-structure layer template, obtain a cured micro-structure layer;

[0022] Using the circuit layer template, obtain a semi-solid circuit layer;

[0023] Bond the cured micro-structure and the semi-solid circuit layer, and cure to obtain a circuit and micro-structure composite layer;

[0024] Using the base layer template, obtain a semi-solid base layer;

[0025] Bond the semi-solid base layer and the circuit and micro-structure composite layer, and cure to obtain a flexible sensor outer body;

[0026] Inject a conductive material into the circuit pattern of the flexible sensor outer body to obtain the micro-structure electronic skin.

[0027] The present invention also provides an application of the microstructured electronic skin described in the above technical solution or the microstructured electronic skin prepared by the preparation method described in the above technical solution in the field of sensing.

[0028] The present invention provides a microstructured electronic skin.

[0029] In the microstructured electronic skin of the present invention, the setting of the microstructured layer successfully extends the sensing dimension of the electronic skin from two-dimensional to three-dimensional, can sense different heights, and can identify microscale surface topographies, having good application value. At the same time, the microstructured electronic skin of the present invention can be applied to various complex curved surface environments.

[0030] Furthermore, using 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid as the conductive material improves the low-temperature performance of the microstructured electronic skin, enabling the microstructured electronic skin to still have three-dimensional sensing ability and sense different heights at low temperatures.

[0031] The data of the examples show that: The present invention uses [BMIM]BF4 ionic liquid with a melting point of -71°C as the conductive material to successfully prepare an electronic skin applicable to complex environments. The microstructured electronic skin is prepared by laminating two flexible materials, Ecoflex and PDMS, and the peel strength between the two is greater than 65 N / m, having sufficient mechanical strength. Then, by reducing the size of the circuit channels, the resistance drift phenomenon of the microstructured electronic skin is weakened, and the sensing ability is improved by changing the thickness of the circuit layer. Finally, the cross-section of the circuit channels in the obtained circuit layer is a square with a size of 0.08 mm × 0.08 mm, the thickness of the circuit layer is 1 mm, and the thickness of the base layer is 0.5 mm. The prepared microstructured electronic skin can accurately respond to pressure loads of 100 - 10,000 Pa, and its resistance response shows a good linear relationship with the load, and the magnitude of the external load can be directly calculated based on the change in resistance. This microstructured electronic skin can maintain stable sensing performance in different curved surface environments, and can maintain normal sensing ability to external loads in a low-temperature environment as low as -50°C, having strong environmental adaptability. At the same time, it maintains a stable resistance response during 500 cycles of cyclic stretching and can maintain sufficient reliability during long-term use. The 3×3 arrayed microstructured electronic skin shows the ability to independently identify pressures without crosstalk when the distance between adjacent conductive units is greater than 5 mm. It can accurately detect the static pressure loading conditions of different positions and different sizes of loads, and the resistance response shows a good linear relationship with the pressure loading. At the same time, it has good dynamic sliding trajectory recognition ability and can identify the trajectories of multi-point sliding simultaneously.

[0032] The setting of the microstructural layer broadens the application of the electronic skin in microscale three-dimensional recognition. First, the sensing performance of microstructures with various parameters was explored, and it was found that the micro-pyramid with a bottom diameter D = 2 mm and a length L = 3.5 mm has the best height recognition ability. Then, the relationship between the sliding height H, the deflection angle θ of the microstructure, and the resistance response ΔR of the electronic skin was explored. It was found that for a sliding height of 0.2 mm to 2.5 mm, the sliding height H can be intuitively obtained through the resistance response ΔR, and real-time dynamic detection of height can be accurately achieved in a low-temperature environment of -10°C, with a detection error of less than 2%. The microstructural electronic skin can accurately recognize the microscale three-dimensional surface topography in a low-temperature environment of -10°C. For microscale topographies such as square, semicircular, and triangular shapes, the electronic skin can roughly detect the shape through the resistance response curve. At the same time, its resistance response value conforms to the linear relationship between the resistance response ΔR and the sliding height H, so it can accurately detect the height of the microscale surface topography. Further, this microstructural electronic skin can be applied to the field of Braille detection. It shows good recognition and reading ability for current standard Braille, can recognize a variety of complex Braille letters, and has application value for special blind people with prosthetics to perform human-machine interface interaction and read Braille. Brief Description of the Drawings

[0033] Figure 1 is a schematic diagram of the circuit layer;

[0034] Figure 2 is the preparation flow chart of the microstructural electronic skin provided by the present invention;

[0035] Figure 3 is the peel strength test result of the flexible pressure sensor obtained in Example 1, where the inset is a diagram of the test device;

[0036] Figure 4 is the resistance change curve of the flexible pressure sensor with different cross-sectional dimensions (0.3 mm, 0.2 mm, 0.15 mm, 0.1 mm, and 0.08 mm) of the flexible pressure sensor obtained in Example 1 when energized for 60 s;

[0037] Figure 5 is the sensing result of the flexible pressure sensor obtained in Example 1 under different thickness conditions;

[0038] Figure 6 is the pressure load experiment of the flexible pressure sensor obtained in Example 1, where (a) is a schematic diagram of the applied external pressure load; (b) is the resistance response curve of the applied external pressure load; (c) is the fitting curve of different external load weights and resistance changes; (d) is the response time when the applied external pressure load is 100 Pa;

[0039] Figure 7For the pressure load experiment of the flexible pressure sensor obtained in Example 1 under different curved surface environments, where (a) is the load resistance response curve under different curved surface environments; (b) is the fitting result of the resistance change and the load under different curved surface environments;

[0040] Figure 8 For the pressure load test of the flexible pressure sensor obtained in Example 1 at different temperatures, where (a) is the load resistance response curve at different temperatures; (b) is the fitting result of the resistance change and the load at different temperatures;

[0041] Figure 9 For the response time of the flexible pressure sensor obtained in Example 1 at different temperatures, where (a) is the fitting result of the response time and the load at different temperatures; (b) is the response time under a load of 100 Pa in an environment of -50°C;

[0042] Figure 10 For the relative resistance change image of the flexible pressure sensor obtained in Example 1 under 50% strain condition with 500 repeated cyclic tensile tests;

[0043] Figure 11 For the exploration experiment of the minimum spacing of the sensing array, where (a) is the schematic diagram of the spacing d of the conductive unit, (b) is the resistance response of the left conductive unit when the spacing of the conductive unit is 4.5 mm, and (c) is the resistance response of the left conductive unit when the spacing of the conductive unit is 5 mm;

[0044] Figure 12 For the multi-point load experiment of the flexible pressure sensor obtained in an environment of -10°C, where (a) is the schematic diagram of three-point load; (b) is the schematic diagram of five-point load; (c) is the schematic diagram of nine-point load; (d) is the detection result of three-point load; (e) is the detection result of five-point load; (f) is the detection result of nine-point load;

[0045] Figure 13 For the single-track sliding experiment of the flexible pressure sensor obtained in Example 1 in an environment of -10°C, where (a) is the schematic diagram of spiral track sliding; (b)-(d) are the resistance response results of spiral track sliding, (e) is the schematic diagram of butterfly track sliding; (f)-(h) are the resistance response results of butterfly track sliding;

[0046] Figure 14 For the sliding sensing experiment of the flexible pressure sensor obtained in Example 1 in an environment of -10°C, where (a)-(c) are the schematic diagrams of sliding; (d)-(f) are the resistance response results of sliding sensing;

[0047] Figure 15 For the schematic diagram of the pyramid structure, where (a) is the pyramid structure; (b) is the light microscope image of the pyramid with D = 2 mm and L = 3.5 mm; (c) is the schematic diagram of bending;

[0048] Figure 16 Resistance response results of the pyramid structures with various parameters at different sliding heights H; (a) shows the resistance response results of pyramids with length L = 4.5 mm and different base diameters D; (b) shows the resistance response results of pyramids with length L = 4 mm and different base diameters D; (c) shows the resistance response results of pyramids with length L = 3.5 mm and different base diameters D; (d) shows the resistance response results of pyramids with length L = 3 mm and different base diameters D;

[0049] Figure 17 3D map of the resistance response of the microstructured e - skin modified with pyramids with various parameters at different sliding heights H;

[0050] Figure 18 Schematic diagram of pyramid deflection; (a) shows the sliding schematic diagram and the definition of the deflection angle θ; (b) shows the images of the pyramid deflection mirror at sliding heights H = 0, 0.4 mm, 0.8 mm, 1.2 mm, 1.6 mm, and 2 mm;

[0051] Figure 19 Fitting results of the deflection angle θ and the sliding height H;

[0052] Figure 20 Sliding test of the microstructured e - skin; (a) shows the resistance response results of the sliding test; (b) shows the fitting results of the resistance response of the sliding test and the sine value of the deflection angle;

[0053] Figure 21 Continuous sliding experiment of the microstructured e - skin; (a) shows the experimental schematic diagram; (b) shows the resistance response results of continuous sliding; (c) shows the fitting graph of the resistance response and the sine value of the deflection angle;

[0054] Figure 22 Sliding test of the microstructured e - skin at - 10°C; (a) shows the resistance response results of the sliding test; (b) shows the fitting results of the resistance response of the sliding test and the sine value of the deflection angle;

[0055] Figure 23 Continuous sliding experiment of the microstructured e - skin at - 10°C; (a) shows the resistance response results of continuous sliding; (b) shows the fitting graph of the resistance response and the sine value of the deflection angle;

[0056] Figure 24 Multi - touch ability of the microstructured e - skin; (a) shows the schematic diagram of the position and size of the pressing and folding application; (b) shows the resistance response results of the nine - unit;

[0057] Figure 25 Multi - point continuous response ability of the microstructured e - skin to height, where (a) shows the sliding schematic diagram; (b) shows the resistance response of the sliding test;

[0058] Figure 26 For micro-scale surface topography recognition tests; among them, (a)-(c) are schematic diagrams of surface topographies with different shapes and corresponding parameters; (d) is the resistance response curve corresponding to different surface topographies;

[0059] Figure 27 For electronic skin braille recognition tests, among them, (a) is a schematic diagram of a braille board; (b) is the braille recognition response result. Detailed implementation manners

[0060] The present invention provides a microstructured electronic skin, which includes a flexible pressure sensor and a microstructured layer arranged in a stacked manner;

[0061] The flexible pressure sensor includes a base layer and a circuit layer arranged in a stacked manner;

[0062] On the surface of one side where the circuit layer is in contact with the base layer, an indented circuit pattern is provided, and the other side is in contact with the microstructured layer;

[0063] The circuit pattern is an array of conductive units; the conductive units are formed by circuit channels, and the circuit channels are in a double-helix structure; the conductive units are filled with a conductive material;

[0064] The microstructured layer includes a receiving layer and protrusions arranged in an array on the receiving layer, and the protrusions are arranged in central correspondence with the conductive units; the receiving layer is in contact with the circuit layer.

[0065] Unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0066] The microstructured electronic skin provided by the present invention includes a flexible pressure sensor. In the present invention, the flexible pressure sensor includes a base layer and a circuit layer arranged in a stacked manner.

[0067] In the present invention, the material of the base layer is preferably polydimethylsiloxane. In the present invention, the thickness of the base layer is preferably 0.5 mm.

[0068] In the present invention, the schematic diagram of the circuit layer is as Figure 1 shown. Below, in combination with Figure 1 the circuit layer will be introduced. In the present invention, the material of the circuit layer is preferably platinum-catalyzed silicone rubber, and more preferably Ecoflex platinum-catalyzed silicone rubber. In the present invention, the thickness of the circuit layer is preferably 0.5-2 mm, specifically preferably 0.5 mm, 1 mm, 1.5 mm or 2 mm. In the present invention, the thickness of the circuit layer refers to the thickness of the part without the circuit pattern.

[0069] In the present invention, a recessed circuit pattern is provided on the surface of the side where the circuit layer is in contact with the base layer. In the present invention, the circuit pattern is an array of conductive units, and more preferably, a 3×3 array of conductive units. In the present invention, the shape of the conductive unit is preferably circular, triangular, square, pentagonal or hexagonal, and more preferably circular. In the present invention, the size of the conductive unit is preferably 1 to 2 mm, specifically preferably 2 mm; specifically: when the shape of the conductive unit is circular, the size of the conductive unit refers to the diameter of the circle; when the shape of the conductive unit is triangular, the size of the conductive unit refers to the diameter of the circumcircle of the triangle; when the shape of the conductive unit is square, the size of the conductive unit refers to the diameter of the circumcircle of the square; when the shape of the conductive unit is pentagonal, the size of the conductive unit refers to the diameter of the circumcircle of the pentagon; when the shape of the conductive unit is hexagonal, the size of the conductive unit refers to the diameter of the circumcircle of the hexagon. In the present invention, the depth of the conductive unit is preferably 0.08 to 0.3 mm, specifically preferably 0.08 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm or 0.3 mm. In the present invention, the spacing between the conductive units is preferably greater than or equal to 5 mm, specifically preferably 5 mm. In the present invention, when the shape of the conductive unit is circular, the spacing between adjacent conductive units refers to the distance between the centers of adjacent circles; when the shape of the conductive unit is triangular, the spacing between adjacent conductive units refers to the distance between the centers of the circumcircles of adjacent triangles; when the shape of the conductive unit is square, the spacing between adjacent conductive units refers to the distance between the centers of the circumcircles of adjacent squares; when the shape of the conductive unit is pentagonal, the spacing between adjacent conductive units refers to the distance between the centers of the circumcircles of adjacent pentagons; when the shape of the conductive unit is hexagonal, the spacing between adjacent conductive units refers to the distance between the centers of the circumcircles of adjacent hexagons.

[0070] In the present invention, the conductive unit is formed by a circuit channel, the circuit channel is a double helix structure, and the circuit channel is filled with a conductive material; the conductive material is preferably an ionic liquid, and the ionic liquid is preferably 1-butyl-3-methylimidazolium tetrafluoroborate. In the present invention, in the double helix structure, the distance between adjacent circuit channels is preferably 0.3 to 0.32 mm, specifically preferably 0.3 mm, 0.31 mm or 0.32 mm. In the present invention, the conductive unit and the circuit channel are as Figure 1 shown.

[0071] In the present invention, the cross-sectional shape of the circuit channel is preferably square, and the side length of the square is preferably 0.08 - 0.3 mm, specifically preferably 0.08 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm or 0.3 mm.

[0072] The microstructured electronic skin provided by the present invention includes a microstructured layer, and the material of the microstructured layer is preferably platinum-catalyzed silicone rubber, more preferably Ecoflex platinum-catalyzed silicone rubber. In the present invention, the microstructured layer is in contact with the other side of the circuit layer. In the present invention, the microstructured layer includes a receiving layer and protrusions arranged in an array on the receiving layer, the receiving layer is in contact with the circuit layer; the protrusions are arranged in central correspondence with the conductive units. In the present invention, the shape of the protrusions is preferably a pyramid, and the bottom shape of the pyramid is preferably the same as the shape of the conductive unit, which will not be elaborated here. In the present invention, the bottom size of the pyramid is preferably 1 - 2 mm, specifically preferably 1 mm, 1.5 mm or 2 mm, and the height is preferably 3 - 4.5 mm, specifically preferably 3 mm, 3.5 mm, 4 mm or 4.5 mm. In the present invention, the distance between adjacent protrusions is the same as the distance between adjacent conductive units described in the above technical solution, which will not be elaborated here. In the present invention, the thickness of the receiving layer is preferably 1 mm.

[0073] Figure 2 is the preparation flow chart of the microstructured electronic skin provided by the present invention. The preparation method of the microstructured electronic skin of the present invention will be described below in conjunction with Figure 2 Describe the preparation method of the microstructured electronic skin of the present invention.

[0074] The present invention provides a preparation method of the microstructured electronic skin described in the above technical solution, including the following steps:

[0075] Prepare a base layer template, a circuit layer template and a microstructured layer template respectively;

[0076] Using the microstructured layer template, obtain a cured microstructured layer;

[0077] Using the circuit layer template, obtain a semi-solid circuit layer;

[0078] Bond the cured microstructures and the semi-solid circuit layer, and cure them to obtain a circuit and microstructured composite layer;

[0079] Using the base layer template, obtain a semi-solid base layer;

[0080] Bond the semi-solid base layer and the circuit and microstructured composite layer, and cure them to obtain a flexible sensor outer body;

[0081] Inject a conductive material into the circuit pattern of the flexible sensor outer body to obtain the microstructured electronic skin.

[0082] The present invention separately prepares a base layer template, a circuit layer template, and a micro-structure layer template.

[0083] In the present invention, the preparation methods of the base layer template, the circuit layer template, and the micro-structure layer template are preferably 3D printing, and the 3D printing is preferably carried out on a MoFang P150 precision 3D printer. In the present invention, when preparing the micro-structure layer template, after 3D printing, the present invention preferably further includes curing (denoted as the first curing), the first curing is preferably ultraviolet curing, and the time of the first curing is preferably 24 h. In the present invention, performing the first curing in the preparation of the micro-structure layer template is beneficial to completely removing the micro-structure layer.

[0084] The present invention uses the micro-structure layer template to obtain a cured micro-structure layer.

[0085] In the present invention, the preparation parameters of the cured micro-structure layer include: the raw materials are preferably component A and component B of Ecoflex, and the mass ratio of component A to component B is preferably 1:1; the temperature of curing (denoted as the second curing) is preferably 60 °C, and the time is preferably 2 h; the second curing is preferably carried out in an oven.

[0086] The present invention uses the circuit layer template to obtain a semi-solid circuit layer. In the present invention, the preparation parameters of the semi-solid circuit layer include: the raw materials are preferably component A and component B of platinum-catalyzed silicone rubber, and the mass ratio of component A to component B is preferably 1:1; the temperature of curing (denoted as the third curing) is preferably 60 °C, and the time is preferably from 3 to 10 min; the third curing is preferably carried out in an oven.

[0087] After obtaining the cured micro-structure layer and the semi-solid circuit layer, the present invention laminates the cured micro-structure layer and the semi-solid circuit layer and performs curing (denoted as the fourth curing) to obtain a circuit and micro-structure composite layer. In the present invention, the temperature of the fourth curing is preferably 60 °C, and the time is preferably 10 min; the fourth curing is preferably carried out in an oven.

[0088] The present invention uses the base layer template to obtain a semi-solid base layer. In the present invention, the preparation parameters of the semi-solid base layer include: the raw materials preferably include monomers and curing agents for forming PDMS, and the mass ratio of the monomers to the curing agents is preferably 10:1; the temperature of curing (denoted as the fifth curing) is preferably 60 °C, and the time is preferably 20 min; the fifth curing is preferably carried out in an oven.

[0089] After obtaining the composite layer of the circuit and the microstructure and the semi-solid base layer, the present invention bonds the semi-solid base layer and the composite layer of the circuit and the microstructure, and cures them (denoted as the sixth curing) to obtain the flexible sensor outer body. In the present invention, the temperature of the sixth curing is preferably 60 °C, and the time is preferably 30 min; the sixth curing is preferably carried out in an oven.

[0090] After obtaining the flexible sensor outer body, the present invention injects a conductive material into the circuit pattern of the flexible sensor outer body to obtain the microstructure electronic skin. In the present invention, when injecting the conductive material, it is preferably ensured that the conductive material enters from one end of the circuit channel and then escapes from the other end of the circuit channel, and it can be considered that the injection of the conductive material is completed.

[0091] After the injection of the conductive material is completed, the present invention preferably further includes: leading out wires in the circuit channel and performing encapsulation to obtain the microstructure electronic skin. The material of the wire is preferably copper; the encapsulation method is preferably glue encapsulation, and the glue for the glue encapsulation is preferably AB glue.

[0092] The present invention also provides the application of the microstructure electronic skin described in the above technical solution or the microstructure electronic skin prepared by the preparation method described in the above technical solution in the sensing field.

[0093] The present invention does not specifically limit the application method of the microstructure electronic skin, and those skilled in the art can set it according to actual needs.

[0094] The following describes in detail the microstructure electronic skin provided by the present invention, its preparation method and application in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0095] Example 1

[0096] Preparation of Flexible Pressure Sensor

[0097] (1) First, use Solidworks 3D modeling software to design the base layer template and the circuit layer template. The base layer is designed as a cuboid with dimensions of 22 mm × 30 mm × 0.5 mm, and the circuit layer is designed as a cuboid with dimensions of 20 mm × 26 mm × 1 mm; the circuit pattern on the circuit layer is designed as conductive units uniformly distributed in a 3×3 array on the circuit layer. The conductive units are designed as circles with a diameter of 2 mm and a depth of 0.08 mm; the conductive units are formed by conductive channels, and the conductive channels are in a double helix structure. The distance between adjacent circuit channels in the double helix structure is 0.32 mm; the cross-section of the circuit channel is a square with a size of 0.08×0.08 mm, and the distance between adjacent conductive units is 5 mm. Then, use a MoFang P150 precision 3D printer to print out the mold.

[0098] (2) Mix components A and B of Ecoflex evenly at a mass ratio of 1:1. After defoaming, coat it evenly in the circuit layer template, cure it in an oven at 60 °C for 10 min, and then peel it off to obtain a circuit layer with a circuit pattern. Mix PDMS evenly according to the mass ratio of 10:1 of the monomer to the curing agent of commercially available PDMS. After defoaming, coat it evenly in the base layer template, take it out after curing in an oven at 60 °C for 20 min to obtain a semi-solid base layer. The surface of the semi-solid base layer has a relatively high viscosity and its shape is basically fixed, and no bubbles will appear in subsequent operations.

[0099] (3) Bond the circuit layer and the semi-solid base layer. The side of the circuit layer with the circuit pattern is in contact with the semi-solid base layer, and place it in an oven at 60 °C for further curing for 30 min to completely bond the circuit layer and the base layer to obtain the outer body of the flexible sensor. Then, slowly inject 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid into the circuit channel with a micro syringe. When injecting, it is necessary to ensure that the ionic liquid fills the entire conductive unit until it overflows from the other end of the circuit channel, and there should be no tiny bubbles in the conductive unit to ensure stable performance. Finally, lead out copper (Cu) wires from both ends of the circuit channel and encapsulate them with epoxy resin AB glue to obtain the flexible pressure sensor.

[0100] 1. Mechanical strength characterization experiment of flexible pressure sensor

[0101] To prove that the obtained flexible pressure sensor has sufficient mechanical strength, the peel strength of the flexible pressure sensor was tested. After the prepared flexible pressure sensor was preliminarily peeled off, it was placed on a universal tensile testing machine for peeling, and the results are as Figure 3 shown. As can be seen from Figure 3 , the peel strength between the circuit layer and the base layer of the flexible pressure sensor can reach 89 N / m at the beginning of peeling; as the peeling distance increases, its peel strength decreases to a certain extent and drops to about 65 N / m after 30 mm, and then maintains this strength until complete peeling. According to existing research, an interfacial peel strength greater than 50 N / m can provide sufficient mechanical strength for flexible sensors, and the peel strength of the obtained flexible pressure sensor is far higher than this value even at the lowest stage. Therefore, the flexible pressure sensor prepared by the circuit layer and the base layer has sufficient mechanical properties to ensure that it will not be damaged during the sensing process and has sufficient reliability.

[0102] 2. Optimization of the resistance drift phenomenon of the flexible pressure sensor

[0103] The phenomenon of resistance drift refers to the change in the resistance value of a sensor under the action of an electric field and time under the same conditions; this phenomenon will cause the sensor to fail to respond accurately to external stimuli in a timely manner, seriously affecting the credibility of the sensor. Therefore, reducing the level of resistance drift of the sensor is one of the key points in the preparation of the sensor.

[0104] Flexible pressure sensors with five different sizes of cross-sectional areas of the circuit channels, namely 0.3 mm × 0.3 mm, 0.2 mm × 0.2 mm, 0.15 mm × 0.15 mm, 0.1 mm × 0.1 mm, and 0.08 mm × 0.08 mm, were respectively prepared. Each flexible pressure sensor was powered on for 60 s and the real-time resistance change was detected. The results are as Figure 4 shown. From Figure 4 it can be seen that as the cross-sectional size of the circuit channel decreases, the initial resistance drift value of the flexible pressure sensor decreases significantly, from a drift close to 10% at 0.3 mm × 0.3 mm to a drift less than 0.5% at 0.08 mm × 0.08 mm. At the same time, as the cross-sectional size of the circuit channel decreases, the time for it to reach a stable resistance also shortens. When the cross-sectional size of the circuit channel is reduced to 0.15 mm × 0.15 mm, the flexible pressure sensor can reach a stable resistance at 55 s; while when the cross-sectional size of the circuit channel is further reduced to 0.08 mm × 0.08 mm, the flexible pressure sensor can already reach a stable state in less than 1 s. This proves that reducing the cross-sectional size of the circuit channel can effectively inhibit the phenomenon of resistance drift.

[0105] It should be noted that when the height of the cross-section of the circuit channel is less than 0.08 mm, the channel may collapse (the substrate layer and the conductive layer adhere) when subjected to an external pressure, resulting in the circuit channel of the flexible pressure sensor being unable to return to its original state in time when the external pressure is removed, further causing the resistance to not return to the initial state, and instead leading to a decrease in sensing reliability. Therefore, considering the two factors of reducing resistance drift and the stability of the circuit channel, 0.08 mm × 0.08 mm was finally selected as the cross-sectional size of the circuit channel of the flexible pressure sensor.

[0106] 3. Optimization experiment on the thickness of the circuit layer of the flexible pressure sensor

[0107] Generally speaking, the thickness of the sensing layer is directly related to the sensitivity, flexibility, and mechanical strength of the sensor. A thin sensing layer is easy to respond to external signals, with higher sensitivity and flexibility; however, the thinner the sensing layer, the greater the difficulty of the manufacturing process, and it is easily damaged under large load or deformation conditions. A thicker sensing layer usually has better mechanical stability, but usually has a lower detection limit. At the same time, for flexible electronic devices worn on the human body, a larger thickness will also affect the wearing experience.

[0108] To achieve a balance between sensitivity and mechanical stability, and considering the actual process difficulty of the demolding method, the thickness of the base layer of the flexible pressure sensor was fixed at 0.5 mm, while four parameters of 0.5 mm, 1 mm, 1.5 mm, and 2 mm were selected for the circuit layer for further research. The preparation of circuit layers with different thicknesses was achieved by designing mold circuit layer boards with different thicknesses, and the quality of Ecoflex used was controlled during coating to ensure the accuracy of preparation. The relationship between the specific thickness and the quality of Ecoflex is shown in Table 1.

[0109] Table 1 Ecoflex mass parameter table for different circuit layer thicknesses

[0110]

[0111]

[0112] The study of the sensing performance was achieved by conducting the same pressure load experiment on four sensors with different parameters. An external load of 5000 Pa, 1000 Pa, 500 Pa, and 100 Pa was applied to the sensing unit every 60 s, and the final resistance response curve is as Figure 5 shown. As can be seen from Figure 5 the flexible pressure sensor with a circuit layer thickness of 0.5 mm only had slight fluctuations when the load was applied, could not produce a recognizable resistance response, and could not change corresponding to the applied external load. In contrast, the flexible pressure sensors with circuit layer thicknesses of 1 mm and 1.5 mm exhibited the most sensitive sensing performance.

[0113] Among them, the flexible pressure sensor with a 1.5 mm thick circuit layer had a slightly higher sensitivity than the flexible pressure sensor with a 1 mm thick circuit layer, but it took nearly 50 s to reach a stable state for a pressure load of 5000 Pa, and the response to a pressure load of 100 Pa was too small, which limited its detection range for external pressure loads. In contrast, the flexible pressure sensor with a 1 mm thick circuit layer could quickly detect large loads, could produce a recognizable resistance response to a small load of 100 Pa, and had the ability to resist signal interference such as micro-vibrations. Therefore, the circuit layer thickness was finally selected to be 0.1 mm.

[0114] 4. Performance Characterization of Flexible Pressure Sensors

[0115] 4.1 Pressure Sensing Performance Characterization

[0116] The prepared flexible sensor can be considered as a conductive unit embedded in an elastomer and then injected with conductive material. When an external load is applied above the conductive unit, the cross-sectional area of the conductive unit decreases, resulting in an increase in resistance. The resistance change value ΔR can be calculated by formula 1:

[0117]

[0118] In Equation 1, ρ represents the resistivity of the conductive filler (Ω·m), L, ω, and h represent the length (m), width (m), and height (m) of the circuit path, respectively. v is the Poisson's ratio of Ecoflex, E is the elastic modulus of Ecoflex (Pa), p is the pressure applied to the sensor (Pa), and χ is the calibration constant. Equation 1 is primarily used for qualitative analysis. The responsiveness of the flexible pressure sensor to pressure loads is specifically studied through detailed pressure load experiments.

[0119] In order to ensure accurate pressure application, an inverted frustum is placed directly above the sensing unit to ensure that the force area of the circuit is the same each time the weight is placed. Figure 6 During the pressure load experiment, pressures of 10000Pa, 5000Pa, 2000Pa, 1000Pa, 500Pa, 200Pa and 100Pa were applied every 60s. The resistance response results are shown in Figure 2. Figure 6 As shown in (b) in the figure. Figure 6 As can be seen from (b) in the figure, the flexible pressure sensor can respond quickly and accurately to pressure loads of 100 to 10,000 Pa. Under an external load of 10,000 Pa, the resistance change of the flexible pressure sensor reaches about 47%, indicating that the flexible pressure sensor has excellent detection capabilities for large loads. Even under a low load of 100 Pa, the flexible pressure sensor still shows a recognizable resistance change of 0.8%, demonstrating sensitive detection capabilities for tiny loads. Further extraction of the load and the corresponding resistance change for fitting shows that the selected 7 groups of data points show a good linear fit relationship, and the fitting equation is: ΔR = 1.98 × 10 -4 P + 0.129; In the fitting equation, ΔR represents the resistance change value (MΩ), P represents the equivalent pressure of the external load (Pa), and the corresponding fitting correlation coefficient R 2 is 0.9937, as shown in the following example: Figure 6 This shows that the flexible pressure sensor can not only accurately identify the size of the pressure load, but also intuitively calculate the specific value of the external load through the resistance change, providing a theoretical basis for its practical pressure identification application.

[0120] In addition, the pressure response time of the flexible pressure sensor is extracted, as shown in Figure 6As shown in (d). The results show that the flexible pressure sensor can complete the response to pressure changes in an extremely short time. Under a pressure load of 100 Pa, the response time of the sensor is only 150 ms, demonstrating excellent dynamic response performance. In summary, the obtained flexible pressure sensor has a wide detection range and a low response time, showing good real-time response ability to pressure load changes. These characteristics lay the foundation for subsequent practical applications such as pressure touch and trajectory recognition of flexible pressure sensors.

[0121] 4.2 Characterization of Curved Surface Sensing Performance

[0122] One advantage of flexible sensors is that they can be applied to various complex surface environments. Therefore, it is very important to determine the influence of the curved surface environment on the sensing performance of flexible sensors.

[0123] The performance of the flexible pressure sensor was tested in four different environments: flat, 30°, 60°, and 90°. Pressures of 5000 Pa, 2000 Pa, 1000 Pa, 500 Pa, and 200 Pa were applied every 60 s, and the results are as Figure 7 shown in (a). As can be seen from Figure 7 (a), the curve shapes and resistance changes in the four curved surface environments are basically the same, only the initial resistance is different. This is because the curved surface environment exerts an initial deformation on the circuit, increasing its initial resistance. When the flexible pressure sensor senses pressure in a 90° curved surface environment, it is equivalent to sensing under an initial pressure load of 5000 Pa. Figure 7 (b) shows the fitting results of the resistance response to the load in the four curved surface environments, and the corresponding fitting correlation coefficient R 2 is greater than 0.9840. It can be seen that the resistance responses in different curved surface environments are basically the same, and can meet the same fitting results, and the obtained fitting equation is also basically the same as the previous fitting equation. Therefore, the flexible pressure sensor can maintain the same response to pressure load in different curved surface environments and has the potential to be applied in complex environments.

[0124] 4.3 Characterization of Low-Temperature Sensing Performance

[0125] The detection ability of the flexible pressure sensor to pressure load in different temperature environments was tested. The detection environments at different temperatures were set up by a cryogenic refrigerator. The flexible pressure sensor was repeatedly tested for pressure load in 6 different temperature environments (-50 °C, -30 °C, -10 °C, 10 °C, 30 °C, 50 °C). Pressures of 10000 Pa, 5000 Pa, 2000 Pa, 1000 Pa, 500 Pa, 200 Pa, and 100 Pa were applied every 60 s for resistance response, and the results are as Figure 8 shown, Figure 8For the pressure load test of the obtained flexible pressure sensor at different temperatures, where (a) is the load resistance response curve at different temperatures; (b) is the fitting result of the resistance change and the load at different temperatures. From Figure 8 It can be seen that the trends of the resistance response curves of the flexible pressure sensor at different temperatures are basically the same. For the same pressure load, the resistance response of the flexible pressure sensor does not change significantly above 30 °C, increases with the decrease of temperature below 30 °C, and the resistance change is more drastic below 0 °C. For a pressure load of 10,000 Pa, the resistance response increases from 1.16 MΩ at 30 °C to 39.26 MΩ at -50 °C. Further extract the resistance changes under different pressure loads at each temperature and perform linear fitting with the applied load. The results are as shown in Figure 8 (b). At each temperature, the change in the resistance of the flexible pressure sensor and the applied load show a good linear relationship. At the same time, as the temperature decreases, the slope of the fitting curve gradually increases, from 1.10×10 -4 at 50 °C to 3.77×10 -3 at -50 °C. This proves that the flexible pressure sensor can normally identify the applied load in a low-temperature environment and exhibits more sensitive electrical response characteristics.

[0126] In addition, the response times of each pressure load at different temperatures are selected and fitted with the applied pressure load. The results are as shown in Figure 9 shown in Figure 9 For the response time of the obtained flexible pressure sensor at different temperatures, where (a) is the fitting result of the response time and the load at different temperatures; (b) is the response time of the load of 100 Pa at -50 °C. From Figure 9 It can be seen that for the same pressure load, the response time of the flexible pressure sensor does not change significantly above 30 °C and increases with the decrease of temperature below 30 °C. For the same temperature, the response time of the flexible pressure sensor increases with the increase of the applied pressure load. Among them, the response time of the flexible pressure sensor to a pressure load of 100 Pa at 30 °C is 150 ms, and the change in resistance is approximately 6.21×10 -4 MΩ. When the temperature drops to -50 °C, the response time corresponding to a pressure load of 100 Pa increases to 910 ms, and the change in resistance increases to 5.36×10 -1 MΩ.

[0127] The main reason for the above experimental results can be attributed to the influence of temperature on the ionic liquid and the circuit layer (Ecoflex). The conductivity of the ionic liquid is caused by the migration of anions and cations. As the external temperature decreases, the thermal motion of anions and cations in the ionic liquid also becomes slower, so the response time increases. At the same time, the increase in the resistance of ions in the conductive unit also leads to an increase in the overall resistance and an increase in the resistance response.

[0128] Temperature also has a great influence on the circuit layer. Ecoflex will harden in a low-temperature environment. Its relaxation stress at -45°C can even reach four times the initial stress, and the elastic modulus decreases. This phenomenon may be due to the glass transition temperature of Ecoflex being approximately -30°C. The hardening of Ecoflex will result in a decrease in the deformation of the circuit channel for the same pressure load, and at the same time, a more significant deformation hysteresis is exhibited, thus leading to an increase in the resistance response time. The reason for the final increase in the resistance response may be that the resistance increase effect of the ionic liquid dominates.

[0129] Nevertheless, Ecoflex does not fail in a low-temperature environment, and the flexible pressure sensor also maintains excellent sensing performance in a low-temperature environment. Secondly, the low-temperature environment applied in the present invention is mainly at -10°C. Since this temperature is higher than the glass transition temperature of Ecoflex, its hardening phenomenon is not obvious, and the response time does not increase too much. At the same time, the greater resistance response enables it to have a more sensitive detection ability for the same pressure load. Therefore, the obtained flexible pressure sensor has good low-temperature application performance.

[0130] 4.4 Stability Characterization

[0131] Flexible pressure sensors are often in an environment where mechanical deformation needs to be carried out frequently. For this reason, a repeated stretching test was designed to characterize the performance of the flexible pressure sensor. During the experiment, the flexible pressure sensor was stretched cyclically 500 times in total. The final resistance change results are as Figure 10 shown, Figure 10 is the relative resistance change image of the obtained flexible pressure sensor under 50% strain and repeated stretching cyclically 500 times. From Figure 10It can be seen that the flexible pressure sensor maintained good stability during the 500 - cycle tensile test. Its resistance baseline did not show obvious drift or hysteresis phenomena. The peak value of ΔR / R0 always remained within the range of 0.040 - 0.042, and the overall change was less than 5%. By magnifying and observing the images of the first 50 stretches and the last 50 stretches, the resistance change remained consistent. Moreover, no cracks or plastic deformation phenomena were observed in the flexible pressure sensor after stretching, and the ionic liquid in the conductive channel did not leak, maintaining reliable sensing performance. The above results indicate that the obtained flexible pressure sensor has excellent durability in a frequently mechanically deformed environment and can meet the usage requirements of long - term wearable devices.

[0132] 4.5 Multi - touch Performance Characterization

[0133] 4.5.1 Exploration Experiment on the Minimum Spacing of the Sensing Array

[0134] The flexible sensors were combined into an e - skin with a 3×3 array of effective touch points to further explore its touch performance.

[0135] First, it was necessary to determine the minimum spacing d between adjacent conductive units without mutual crosstalk. Conductive unit templates with two distances of 4.5 mm and 5 mm for the spacing d were prepared. During the experiment, a pressure load of 1000 Pa was applied to the conductive unit on the right, and the resistance response of the conductive unit on the left was detected. The results are as Figure 11 shown. Figure 11 This is the exploration experiment on the minimum spacing of the sensing array. (a) is a schematic diagram of the spacing d between conductive units. (b) is the resistance response of the left - hand conductive unit when the spacing between conductive units is 4.5 mm. (c) is the resistance response of the left - hand conductive unit when the spacing between conductive units is 5 mm. It can be Figure 11 seen that when the spacing is 4.5 mm, it can be observed that the pressure loading on the right - hand conductive unit causes a slight resistance response in the left - hand conductive unit. When the spacing increases to 5 mm, the resistance response of the left - hand conductive unit completely disappears, indicating that the pressure loading on the right - hand conductive unit no longer has any effect on the left - hand conductive unit at this time. Therefore, a 5 - mm spacing was adopted as the standard for the conductive unit spacing in the subsequent circuit pattern preparation.

[0136] 4.5.2 Exploration of Static Pressure Touching Ability

[0137] The static pressure touch ability of the flexible pressure sensor was explored. To confirm that the flexible pressure sensor can be applied to touch in a low-temperature environment, subsequent touch experiments were all carried out in an environment of -10°C. During the experiment, 3-point pressure loading, 5-point pressure loading, and 9-point pressure loading were respectively performed on the effective touch points of the flexible pressure sensor (the applied pressures were 100 Pa, 200 Pa, 500 Pa, 1000 Pa, 2000 Pa, 3000 Pa, 4000 Pa, 5000 Pa, and 6000 Pa), and the specific pressure application positions and magnitudes are as shown in Figure 12 (a)-(c). At the same time, the real-time resistance responses of the nine units were monitored, and the data were plotted as a bar chart, and the results are as shown in Figure 12 (d)-(f). It can be seen from Figure 12 that the obtained flexible pressure sensor can accurately identify the loading positions of different pressure loads, and for the same magnitude of pressure load, its resistance response shows a high degree of consistency. This indicates that the flexible pressure sensor can accurately detect the loading conditions of loads of different positions and magnitudes, and there is no crosstalk between adjacent units.

[0138] In addition, by analyzing the relationship between the resistance response of each point and the applied pressure load, it is found that the results basically conform to the fitting formula, indicating that even in the case of multi-point pressure load, the resistance responses of each touch point still show a linear change with the pressure load and do not affect each other, and the magnitude of the load can be deduced from the value of the resistance response.

[0139] 4.5.3 Single-trajectory sliding experiment in low-temperature environment

[0140] The above results show that the flexible pressure sensor exhibits excellent touch performance in a low-temperature environment, can accurately identify pressure loads of different positions and magnitudes, and has good static multi-point touch response ability. On the basis of the static touch experiment, a dynamic touch detection experiment in a low-temperature environment was further carried out.

[0141] First, a low-temperature environment of -10°C was constructed with a ultra-low temperature refrigerator, and a single iron rod was slid on the e-skin according to two preset trajectories. The specific preset trajectories are as shown in Figure 13 (a) and (e). The mass of the iron rod used in the experiment is about 10 g, and its contact area with the flexible pressure sensor is approximately 0.2 cm 2 . Figure 13 For the single-trajectory sliding experiment of the flexible pressure sensor obtained in a -10°C environment, where (a) is the schematic diagram of the spiral trajectory sliding; (b)-(d) are the resistance response results of the spiral trajectory sliding; (e) is the schematic diagram of the butterfly trajectory sliding; (f)-(h) are the resistance response results of the butterfly trajectory sliding; from Figure 13It can be seen that the flexible pressure sensor accurately responds to both preset sliding trajectories. The difference is that for the spiral sliding trajectory, the flexible pressure sensor does not show resistance responses outside the trajectory during the sliding process and can accurately detect the resistance change along the trajectory; while for the butterfly-shaped sliding trajectory, the flexible pressure sensor shows weak responses outside the trajectory during the sliding process. This is because in the butterfly-shaped trajectory, there is an inclined sliding along the diagonal direction. When the iron rod slides obliquely to the center points of the four sensing units, its distances from these four sensing units are all less than the minimum non-interfering distance of 5 mm mentioned above. Therefore, weak resistance responses also occur in the two sensing units that are not on the sliding trajectory.

[0142] Nevertheless, from the overall data, the peak value of the resistance response of the sensing units on the sliding trajectory is approximately 0.8 MΩ, and the resistance response generated by the sensing units not on the sliding trajectory is approximately 0.05 MΩ, which is only 6% of the normal response. This significant difference enables the resistance response of the sensing units not on the trajectory to be easily distinguished from the response of the actual sensing units. Therefore, despite a little interference response, the flexible pressure sensor can still accurately identify complex sliding trajectories, demonstrating excellent sliding trajectory response capabilities and reliable trajectory recognition performance.

[0143] 4.5.4 Multi-trajectory Sliding Experiment in Low-temperature Environment

[0144] The recognition ability of the flexible pressure sensor for multi-sliding trajectories in a low-temperature environment was further tested. A low-temperature environment of -10 °C was built with an ultra-low temperature refrigerator. Then, pressure loads were applied to the flexible pressure sensor with three iron rods of the same size and they were slid along the same direction. The specific sliding methods are as Figure 14 shown in (a)–(c). For distinction, the pressure applied when the iron rod sliding on the far right was set to be slightly less than that of the two iron rods on the left. At the same time, the real-time resistance responses of the nine units were monitored and the data were plotted as a bar chart. The results are as Figure 14 shown in (d)–(f). Figure 14 Flexible pressure sensor sliding sensing experiment at -10 °C. Among them, (a)–(c) are sliding schematic diagrams; (d)–(f) are the results of sliding sensing resistance responses.

[0145] From Figure 14It can be seen that as the iron rod slides, the flexible pressure sensor responds successively in units 1, 2, and 3, units 4, 5, and 6, and units 7, 8, and 9, successfully reflecting the number of iron rods and the sliding trajectory. At the same time, when the iron rod slides to the center of units 4, 5, and 6, the resistance response of units 1, 2, and 3 has completely disappeared; when the iron rod slides to the center of units 7, 8, and 9, the resistance response of units 4, 5, and 6 has completely disappeared. At the same time, the resistance responses of units 3, 6, and 9 are also significantly smaller than those of the other units. This indicates that the sensing units of this flexible pressure sensor have a high regional response ability, which can avoid signal interference between adjacent units, thus ensuring the accurate detection of the sliding trajectory.

[0146] In summary, this flexible pressure sensor demonstrates excellent sliding touch performance and can achieve precise recognition of multi-point simultaneous sliding. By real-time recording and analyzing the responses of different units, not only can the sliding direction and trajectory be detected, but also the signal change characteristics during the sliding process can be captured. This characteristic highlights its application potential in the field of human-machine interface interaction and lays a foundation for realizing efficient human-machine interface interaction.

[0147] Example 2

[0148] Preparation of Micro-Pyramid Structure Electronic Skin

[0149] (1) First, use Solidworks 3D modeling software to design the base layer template, circuit layer template, and micro-structure layer template. The base layer is designed as a cuboid with dimensions of 22mm×30mm×0.5mm, and the circuit layer is designed as a cuboid with dimensions of 20mm×26mm×1mm; the circuit pattern on the circuit layer is designed as a 3×3 array of conductive units distributed on the circuit layer. The conductive units are circular with a diameter of 2mm and a depth of 0.08mm. The conductive units are formed by conductive channels, and the conductive channels are in a double-helix structure. The distance between adjacent circuit channels in the double-helix structure is 0.32mm; the cross-section of the circuit channel is a square with dimensions of 0.08mm×0.08mm, and the distance between adjacent conductive units is 5mm. The micro-structure layer template is also designed as a cuboid with dimensions of 20mm×26mm×1mm. The protrusions are pyramid-shaped, with a circular bottom radius of 1mm and a height of 3.5mm. They are designed to be evenly distributed in a 3×3 array on the micro-structure layer template, and the center of the pyramid bottom coincides exactly with the center of the conductive unit.

[0150] (2) Use a MoFang P150 precision 3D printer to print the templates. The micro-structure layer template needs to be further cured in an ultraviolet curing box for 24h to ensure complete formation of the structure side and ensure that the micro-pyramids can be completely removed in subsequent steps.

[0151] (3) Mix components A and B of Ecoflex evenly at a mass ratio of 1:1. After defoaming, coat it evenly in the microstructure layer template, and then place it in a vacuum environment for 30 min to ensure that the Ecoflex completely fills the template. After that, cure it in an oven at 60 °C for 2 h and then peel it off to obtain the cured microstructure layer.

[0152] (4) Coat the defoamed Ecoflex evenly in the circuit layer template and cure it in an oven at 60 °C for 3 min to make it in a semi-cured state, obtaining a semi-solid circuit layer; then attach the cured microstructure layer to the back of the semi-solid circuit layer (ensuring that the microstructures and conductive units are aligned), and continue to cure it in an oven at 60 °C for 10 min to obtain a circuit and microstructure composite layer. Mix PDMS evenly according to the mass ratio of 10:1 of the monomer to the curing agent of commercially available PDMS. After defoaming, coat it evenly in the base layer template, take it out after curing in an oven at 60 °C for 20 min to obtain semi-solid PDMS. Attach the side with the conductive pattern of the peeled circuit and microstructure composite layer to the semi-solid PDMS, and place it in an oven at 60 °C for further curing for 30 min to obtain the outer body of the flexible sensor.

[0153] (5) Use a micro syringe to inject the [BMIM][BF4] ionic liquid into the circuit channels. When injecting, it is necessary to ensure that the ionic liquid fills the entire conductive unit until it overflows from the other end of the circuit channel, and there should be no tiny bubbles in the conductive unit to ensure the stability of the performance. Finally, lead out the Cu wires from both ends of the circuit channel and encapsulate them with epoxy resin AB glue to obtain the microstructure electronic skin.

[0154] 1. Pyramid parameter regulation

[0155] Pyramids with different structural parameters were set up to explore the influence on the performance of the microstructure electronic skin. 12 kinds of pyramids with different parameters were prepared by the demoulding method, and their parameters are marked as shown in Figure 15 (a). The bottom diameter D of the pyramid was selected with three parameters of 1 mm, 1.5 mm, and 2 mm, and the length (also referring to the height of the pyramid structure) L was selected with four parameters of 3 mm, 3.5 mm, 4 mm, and 4.5 mm. The micrographs of the prepared microstructures are shown in Figure 15 (b) (in the figure is a pyramid with D = 2 mm and L = 3.5 mm). After successfully preparing pyramids with different parameters, bond them with the flexible pressure sensor to obtain the microstructure electronic skin with different microstructures. When the pyramid structure slides over surfaces at different heights, its tip will deflect, causing deformation of the bottom microchannels, and then leading to changes in the resistance response, as specifically shown in (c) of 14. Figure 15It is a schematic diagram of a pyramid structure. (a) is the pyramid structure; (b) is the optical microscope image of the pyramid with D = 2 mm and L = 3.5 mm; (c) is the bending schematic diagram. When the length L is reduced to 3.5 mm, the pyramid with D = 2 mm can make a resistance response to the sliding height of H = 0.2 mm. The pyramids with D = 2 mm and 1.5 mm can both make a resistance response to the sliding height of H = 0.5 mm, while the microstructure with D = 1 mm cannot produce an identifiable resistance response in the height test with H ≤ 0.5 mm. When the length L is further reduced to 3 mm, at the height of H = 2.5 mm, the pyramids with D = 2 mm and 1.5 mm are difficult to produce obvious and stable bending. At this height, there is a significant and irregular increase in resistance and they cannot sense the height normally. Although the pyramid with D = 1 mm can still bend normally at the height of H = 2.5 mm, the too small bottom diameter D is difficult to cause obvious deformation of the bottom circuit channel, so the change of its resistance response is always very weak and it is not conducive to the sensor to distinguish different sliding heights H.

[0156] In order to obtain the relationship between the resistance response and the sliding height corresponding to pyramids with different parameters, four sliding heights of H = 0.2 mm, 0.5 mm, 1.5 mm and 2.5 mm were selected for exploration respectively, and the changes of resistance response under each parameter were recorded. The results are as Figure 16 shown. Figure 16 are the resistance response results of pyramids with different parameters at different sliding heights H. Among them, (a) is the resistance response results of pyramids with different bottom diameters D when the length L = 4.5 mm; (b) is the resistance response results of pyramids with different bottom diameters D when the length L = 4 mm; (c) is the resistance response results of pyramids with different bottom diameters D when the length L = 3.5 mm; (d) is the resistance response results of pyramids with different bottom diameters D when the length L = 3 mm. It can be seen from Figure 16 that for pyramids with the same length L, their resistance response increases with the increase of the bottom diameter D and the sliding height H. At the same time, with the increase of the sliding height H, the degree of change of the resistance response also becomes larger and larger, which is reflected in the gradually increasing slope of the broken line in the figure. However, when the length L of the pyramid exceeds 4 mm, all pyramids do not produce a resistance response in the height test with H ≤ 0.5 mm. This is because when the length is too long, the tiny deformation at the tip of the pyramid is not enough to cause the deformation of the bottom circuit channel. For the pyramid with L = 4.5 mm, even when H = 2.5 mm, the pyramid with D = 2 mm, which has the largest resistance response, only has a resistance response of about 0.2 MΩ. Such a weak resistance response is not conducive to the sensor to distinguish different sliding heights H.

[0157] All the resistance response data are plotted as a 3D bar chart, specifically as Figure 17 shown. Figure 173D resistance response graph of the microstructured e-skin modified by pyramids with various parameters at different sliding heights H. From the previous analysis, it can be obtained that the pyramids with D = 1 mm have relatively weak resistance responses at all lengths L and sliding heights H, and are not suitable for height detection. For the pyramids with D = 2 mm and 1.5 mm, their height detection ability is mainly related to the difference between the length and the sliding height (L - H), that is, the distance from the sliding position to the bottom. By sorting out the data, it can be obtained that the pyramids with these two bottom diameters D all produce recognizable and stable resistance responses in the range of 1 - 3.5 mm from the bottom of the pyramid for the sliding position. This range is the effective height detection range of the microstructured e-skin modified by pyramids. When (L - H) exceeds 3.5 mm, the tiny deformation at the tip of the pyramid is not sufficient to cause deformation of the bottom circuit channel, and no recognizable resistance response will be generated; when (L - H) is less than 1 mm, the pyramid cannot be bent normally, resulting in unstable resistance response data and inability to accurately identify the height. Therefore, the microstructured e-skin modified by the pyramid structure with a height L of 3.5 mm has the best sensing range.

[0158] For pyramid structures with the same length L, a larger bottom diameter D can make the microstructured e-skin produce a larger resistance response to the same sliding height. This is because a larger bottom area can magnify the bending of the upper part of the pyramid, causing deformation of a larger area of the circuit channel. However, pyramids with too large a volume will make the e-skin appear bulky, and at the same time, a smaller aspect ratio will also reduce the effective bending distance and the effective height detection range. Therefore, the final bottom diameter of the pyramid is determined to be D = 2 mm. It can also be seen from Figure 17 that the pyramids with L = 3.5 mm and D = 2 mm are the only group of microstructures that can produce good responses at four sliding heights. Therefore, these parameters are finally selected for subsequent preparation.

[0159] 2. Characterization of the height recognition performance of the microstructured e-skin

[0160] 2.1 Exploration of the relationship between the deflection angle θ and the sliding height H

[0161] After determining the parameters of the pyramid, pyramids with a bottom diameter D = 2 mm and a height L = 3.5 mm were prepared. As mentioned before, when the e-skin with microstructures slides over the surfaces of objects at different heights, the tip of the pyramid will be restricted and flattened. The bent pyramid structure can be approximately regarded as a combination of a flat body and a deflected body. Define the angle between the line connecting the tangent point of the pyramid deflection to the center of the bottom and the vertical direction as the deflection angle θ, as shown in Figure 18as shown in (a). Immediately afterwards, a flat and smooth glass plate was slid uniformly over the pyramid under six conditions of sliding height H = 0, 0.4 mm, 0.8 mm, 1.2 mm, 1.6 mm, and 2 mm, and the deflection angle θ corresponding to each sliding height was photographed with an optical microscope. Specifically, as shown in Figure 18 (b). Figure 18 is a schematic diagram of the pyramid deflection. Among them, (a) is a schematic diagram of the sliding and the definition of the deflection angle θ; (b) is the pyramid deflection light microscope images when the sliding height H = 0, 0.4 mm, 0.8 mm, 1.2 mm, 1.6 mm, and 2 mm. According to the obtained light microscope photos, the deflection angle θ under each sliding height H was measured respectively, and the measured angle values were plotted against the sliding height H and linearly fitted. The results are as shown in Figure 19 . Figure 19 is the fitting result of the deflection angle θ and the sliding height H. As can be seen from Figure 19 , there is a good linear relationship between the deflection angle θ and the sliding height H. The linear fitting equation 1 is: θ = 25.80978H - 0.11829; where H is the sliding height (mm) and θ is the deflection angle (°), and its fitting coefficient R 2 is 0.9944. This shows that as long as the deflection angle θ is measured, the sliding height H can be accurately calculated, which provides a theoretical support for the height recognition of the pyramid-modified electronic skin.

[0162] 2.2 Relationship between the resistance response of the microstructured electronic skin and the deflection angle θ

[0163] In further research, the relationship between the resistance response of the pyramid-modified electronic skin and the deflection angle θ was explored through sliding tests. Four sliding heights of H = 0.2 mm, 0.5 mm, 1.5 mm, and 2.5 mm were selected for the sliding test, and two sliding modes were adopted: one was to remove the glass plate immediately after the pyramid was bent, and the other was to remove the glass plate 5 s after bending. The resistance response results of the sliding test are as shown in Figure 20 (a). Since there is also a certain resistance fluctuation when the sensor is completely unbent in the pyramid, when the sliding height is too small, the resistance change may be confused with the resistance fluctuation, and the sliding height cannot be accurately identified. After testing, the electronic skin can initially produce an identifiable resistance response (0.0189 MΩ) to a sliding height of 0.2 mm. Therefore, the test sliding height starts from 0.2 mm. From the test results, it can be seen that for sliding heights from 0.2 mm to 2.5 mm, the electronic skin can respond. In addition, the response peak of immediately removing the glass plate is the same as the response platform height of keeping the glass plate, which indicates that the electronic skin has a stable detection ability for the same height and can make different and accurate responses to different heights.

[0164] The numerical values of the resistance responses at different heights are further extracted and fitted with the sine value of the deflection angle θ. The results are as follows: Figure 20 As shown in (b). Figure 20 As can be seen in (b), the resistance response of the electronic skin shows a good linear relationship with the sine value of the deflection angle, and the fitting equation 2 is: ΔR = 0.263tanθ-0.00257; where ΔR is the sliding height (mm), θ is the deflection angle (°), and the fitting coefficient R 2 The good linear relationship shows that the flexible electronic skin can infer the deflection angle from the resistance response.

[0165] Furthermore, by simultaneously fitting equation 1 and equation 2, the relationship between the resistance response and the sliding height H can be obtained:

[0166]

[0167] Therefore, the sliding height H can be directly calculated from the resistance response of the sensor.

[0168] In summary, the microstructured electronic skin can intuitively and accurately respond to different sliding heights and has excellent height resolution.

[0169] 2.3 Research on the recognition ability of microstructured electronic skin for continuously changing heights

[0170] Next, we further tested the microstructured electronic skin's ability to recognize continuously changing heights. In order to verify the resistance response effect of the microstructured electronic skin, a step with continuously changing heights was set up. The resistance response results are shown in Figure 2. Figure 21 , Figure 21 The continuous sliding experiment of the microstructured electronic skin, where (a) is the experimental schematic diagram; (b) is the continuous sliding resistance response result; (c) is the fitting diagram of the resistance response and the sine value of the deflection angle. Figure 21 It can be seen that the microstructured electronic skin successfully responded to each step, and for steps of the same height, the resistance response of the microstructured electronic skin remained stable and consistent. At the same time, for the same height difference (0.2mm), the resistance response of the microstructured electronic skin continued to increase with the increase of the sliding height H. This is because the resistance response of the microstructured electronic skin is proportional to the sine of the deflection angle tanθ, and the sliding height H is proportional to the deflection angle θ. Therefore, as the sliding height H increases, the rate of change of the resistance response also increases.

[0171] The resistance change corresponding to each sliding height H is further extracted and plotted against the sine value of the deflection angle tanθ to obtain Figure 21(c) shows that for continuous height changes, the resistance response of the microstructured electronic skin shows a good linear relationship with the sine value of the deflection angle. The linear fitting equation 4 is: ΔR = 0.266tanθ-0.011; its fitting coefficient R 2 It can be seen that the fitting equation is almost the same as the fitting equation 2 above, which shows that the resistance response change of the microstructured electronic skin is not affected by the initial height before the change and can continuously respond to different heights.

[0172] 3. Characterization of low-temperature sensing performance of microstructured electronic skin

[0173] After completing the preliminary characterization of the height sensing performance, the height recognition ability of the microstructured electronic skin in a low-temperature environment was explored. In order to prove the feasibility of height detection in a low-temperature environment, the sliding test experiment mentioned above was repeated in a -10℃ environment. The specific results are as follows: Figure 22 As shown in (a). Figure 22 The sliding test of the microstructured electronic skin at -10℃, where (a) is the resistance response of the sliding test and (b) is the fitting result of the resistance response of the sliding test and the sine value of the deflection angle. Figure 22 As can be seen in (a), the microstructured electronic skin still maintains an accurate response to various sliding heights in a low-temperature environment, and is significantly better than the response at 30°C. However, when the detection height is greater than 1.5mm, there is a slight difference between the response of immediately removing the glass plate and the response of keeping the glass plate. When the detection height is 2.5mm, the response value of immediately removing the glass plate is 1.75MΩ, while the response value of keeping the glass plate is 1.81MΩ. This is because at -10°C, although the pressure sensing performance of the microstructured electronic skin has increased to a certain extent, its response time has also increased to a certain extent. For a height of 2.5mm, the accurate response value cannot be reached immediately, so the response value of immediately removing the glass plate will be slightly smaller than the response value of keeping the glass plate.

[0174] The numerical values of the resistance response at different heights are extracted and fitted with the sine value of the deflection angle θ. The results are as follows: Figure 22 As shown in (b). Figure 22 As can be seen in (b), the resistance response of the electronic skin shows a good linear relationship with the sine value of the deflection angle, and the fitting equation is 5: ΔR = 0.908tanθ-0.062; its fitting coefficient R 2 is 0.9998. Similarly, by simultaneously fitting equation 1 and equation 5, the relationship between the resistance response and the sliding height H can be obtained:

[0175]

[0176] Therefore, the microstructured e-skin can also perform high-precision recognition normally at low temperatures. At the same time, by substituting the two response values during a 2.5-mm sliding into the equation, the recognized height can be obtained as 2.46 mm when the glass plate is immediately removed, and 2.50 mm when the glass plate is kept in place. The height recognition error is less than 2%. Therefore, the low-temperature environment does not affect the accuracy of its sensing height recognition.

[0177] Similarly, the continuous sliding test experiment described above was further repeated in a low-temperature environment of -10 °C. The results are as shown in Figure 23 (a) in Figure 23 The continuous sliding experiment of the microstructured e-skin in a -10 °C environment. Among them, (a) shows the results of the continuous sliding resistance response; (b) is the fitting graph of the resistance response and the sine value of the deflection angle. As can be seen from Figure 23 (a) in, even under low-temperature conditions, the microstructured e-skin still makes accurate responses to the steps with continuously changing heights. Although the response time increases slightly compared with the 30 °C environment, overall it does not significantly affect the accuracy of height recognition.

[0178] Furthermore, the resistance change corresponding to each sliding height H was extracted and plotted against the sine value of the deflection angle tanθ, resulting in Figure 23 (b) in Figure 23 As can be seen from (b) in, the resistance response of the microstructured e-skin and the sine value of the deflection angle still show a good linear relationship. The linear fitting equation 7 is: ΔR = 0.873tanθ - 0.051; its fitting coefficient R 2 is 0.9998. This fitting equation has a slight deviation from the previous fitting equation 5. However, by substituting the sliding height of 2.5 mm into fitting equations 1 and 7, the calculated resistance change is 1.77 MΩ, and the result only differs by 2.2% from the resistance change of 1.81 MΩ obtained from the single-height recognition of 2.5 mm in Figure 23 . Therefore, in a low-temperature environment, the microstructured e-skin can still accurately recognize continuously changing heights and is not affected by the initial height. This indicates its excellent adaptability and reliability in a low-temperature environment.

[0179] 4. Characterization of the multi-point sensing performance of the microstructured e-skin

[0180] The multi-point sensing performance of a 3×3 arrayed microstructured e-skin was studied. The adjacent unit spacing of this sensing array was still selected as 5 mm. To prove that this spacing is still effective for the e-skin modified with pyramid structures, three microstructures on the diagonal were simultaneously subjected to pressing and folding with heights of 0.2 mm, 1.5 mm, and 2.5 mm, and the resistance responses of 9 units were monitored in real time. The results are as shown in Figure 24 shown in Figure 24For the multi-touch ability of the microstructured e-skin, where (a) is a schematic diagram of the application position and magnitude of the press-fold; (b) is the resistance response result of nine units. From Figure 24 it can be seen that the three units all have different resistance responses, and they conform to the relationship between the resistance response and the press-fold height obtained in the previous text. And the units without press-fold hardly produce recognizable resistance responses, which proves that they are not affected by the bending of adjacent microstructures. Therefore, the 5-mm adjacent unit spacing used in the previous text is also applicable here.

[0181] Immediately afterwards, the dynamic detection ability of the multi-unit microstructure for height was verified through a sliding experiment set on a uniformly varying height step. The step and the sliding method are specifically as Figure 25 shown in (a) of it. Figure 25 For the multi-point continuous response ability of the microstructured e-skin to height, where (a) is a schematic diagram of the slide; (b) is the resistance response of the slide test. For the convenience of distinction, the pyramids are numbered as columns 1, 2, and 3 in the order in which the steps are slid over. Figure 25 The height difference between adjacent steps in (a) of it is 0.5 mm, and the lowest step is 0.5 mm. During the sliding process, always ensure that the tip of the pyramid is aligned with the bottom of the step. The finally obtained resistance response is as Figure 25 shown in (b) of it. From Figure 25 it can be seen from (b) of it that as the sliding progresses, the units corresponding to the three columns of pyramids respond accurately to the steps in turn, and the obtained resistance response curves are generally the same and are not affected by the bending of adjacent pyramids. At the same time, its resistance change also conforms to the relationship between the sliding height and the resistance response obtained in the previous text. This shows that there is no mutual influence between multiple microstructures of this microstructured e-skin, and it can realize the non-crosstalk independent recognition of each unit for different heights, with sufficient practical application value.

[0182] 5. Microscale surface topography recognition

[0183] Based on the excellent recognition ability of this microstructured e-skin for height, an experiment on the recognition of microscale surface topography by the microstructured e-skin was further carried out.

[0184] To evaluate the recognition ability of the microstructured e-skin for different surface topographies in a low-temperature environment, a low-temperature environment of -10 °C was set up using an ultra-low temperature refrigerator, and three different surface topographies were set, namely square, semi-circular, and triangular. The square topography was composed of alternately arranged cube protrusions with side lengths of 0.5 mm and 1 mm, and the distance between adjacent protrusions was 2 mm; the semi-circular topography was composed of alternately arranged hemispherical protrusions with radii of 0.5 mm and 1 mm, and the distance between adjacent protrusions was 1.5 mm; the triangular topography was composed of alternately arranged quadrangular pyramid protrusions with heights of 0.5 mm and 1 mm, and the distance between adjacent protrusions was 2 mm. The specific surface topographies are shown in (a)–(c) of Figure 25.

[0185] The magnitude of the resistance response of the microstructured e-skin is linearly related to the sine value of the deflection angle (tanθ), and as the sliding height H increases, the degree of change in the resistance response also becomes larger. At the same time, the change in the resistance response of this microstructured e-skin is not affected by the initial height before the change. Therefore, in the case of having an initial bending height, the microstructured e-skin can exhibit better detection ability for protrusions of the same height. In the topography recognition experiment, first, a 0.5-mm initial bending height was given to the pyramid, and then the pyramid was slid uniformly over three different surface topographies to make full contact with the entire surface, and the real-time resistance response was recorded. The final resistance response obtained is as shown in Figure 26 (d) of Figure. From Figure 26 (d) of Figure, it can be seen that when the microstructured e-skin slides over different surface topographies, it can generate different resistance response waveforms. The characteristics of these waveforms correspond to the geometric features of different topographies. For example, the protrusions of the semi-circle and the square are more continuous and smooth, while the resistance response curve of the triangular protrusion is more sharp. At the same time, for surface topographies of the same height, their peak values ΔR are basically the same and are not affected by the shape of the surface topography. The peak value ΔR corresponding to the 0.5-mm surface topography is approximately 0.14 MΩ, while the peak value ΔR corresponding to the 1-mm surface topography is approximately 0.38 MΩ. By using the formula for conversion, the corresponding heights are 0.49 mm and 1.01 mm respectively, which are consistent with the actual heights. This shows that this microstructured e-skin can respond to surface topographies of different shapes and sizes. The type of surface topography can be analyzed from the shape of the curve, and the height of the surface topography can be reflected by the magnitude of the resistance response. This experimental result further verifies the potential of this microstructured e-skin in a variety of application scenarios, especially in the fields of tactile recognition and surface topography detection.

[0186] 6. Standard Braille recognition

[0187] On the basis of completing surface morphology recognition, since each unit of the microstructured electronic skin can independently recognize the surface morphology, we further attempted to test the microstructured electronic skin's ability to recognize Braille in a low-temperature environment.

[0188] First, use a 3D printer to accurately print out Braille characters, as shown below: Figure 27 As shown in (a), Figure 27 This is a Braille recognition test using electronic skin. (a) shows a schematic diagram of the Braille board; (b) shows the Braille recognition response. The four Braille characters correspond to the letters "l," "o," "v," and "e." The Braille dots are arranged according to international standards; each dot is a hemispherical protrusion with a base diameter of 1000μm and a height of 500μm.

[0189] Next, an ultra-low temperature freezer was used to create a -10°C low-temperature environment. The three microstructures of the microstructured electronic skin were placed in contact with the Braille board. The initial pressing height was set to 0.5 mm. The microstructured electronic skin was moved horizontally at a constant speed, so that the three microstructures of the microstructured electronic skin passed over the hemispherical bumps of the Braille board. The real-time resistance changes of the sensor units were recorded. The results are as follows: Figure 27 By comparing the signal responses of the three channels and comparing the resulting resistance change graph with a Braille comparison table, the corresponding Braille letters can be identified. The experimental results show that the resistance response signal of the microstructured electronic skin fully matches the arrangement of the Braille plate, demonstrating excellent Braille recognition capabilities. This result indicates that the microstructured electronic skin has great potential in practical Braille recognition applications and can effectively recognize and interpret complex tactile information.

[0190] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A microstructured electronic skin, characterized in that, Comprising a flexural pressure sensor and a microstructure layer which are stacked; The flexural pressure sensor comprises a base layer and a circuit layer which are stacked; the other side of the circuit layer is in contact with the microstructure layer; On the surface of the side where the circuit layer is in contact with the base layer, there is an indented circuit pattern provided; The circuit pattern is a conductive unit distributed in an array; the conductive unit is formed by a circuit channel, the circuit channel is a double helix structure; the circuit channel is filled with a conductive material; The microstructure layer comprises a bearing layer, and protrusions arranged in an array on the bearing layer, the protrusions and the conductive units are arranged in central correspondence; the bearing layer is in contact with the circuit layer.

2. The microstructured electronic skin according to claim 1, characterized in that, The material of the base layer is polydimethylsiloxane; the material of the circuit layer is platinum-catalyzed silicone rubber, and the material of the microstructure layer is platinum-catalyzed silicone rubber.

3. The microstructured electronic skin according to claim 1, wherein The shape of the conductive unit is circular, triangular, square, pentagonal or hexagonal; the size of the conductive unit is 1-2 mm; the depth of the conductive unit is 0.08-0.3 mm.

4. The microstructured electronic skin according to claim 1 or 3, characterized in that, The distance between adjacent conductive units is greater than or equal to 5 mm.

5. The microstructured electronic skin according to claim 1, characterized in that, The cross-sectional shape of the circuit channel is square, the side length of the square is 0.08-0.3 mm; the distance between adjacent circuit channels is 0.3-0.32 mm.

6. The microstructured electronic skin according to claim 1, characterized in that, The conductive material is an ionic liquid, and the ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate.

7. The microstructured electronic skin according to claim 1, characterized in that, The shape of the protrusion is a pyramid, the bottom surface size of the pyramid is 1-2 mm, and the height is 3-4.5 mm; the thickness of the bearing layer is 1 mm.

8. The microstructured electronic skin according to claim 1, characterized in that, The thickness of the circuit layer is 0.5-2 mm; the thickness of the base layer is 0.5 mm.

9. The preparation method of the microstructured electronic skin according to any one of claims 1 to 8, characterized in that, Comprising the following steps: Preparing a base layer template, a circuit layer template and a microstructure layer template respectively; Using the microstructure layer template to obtain a cured microstructure layer; Using the circuit layer template to obtain a semi-solid circuit layer; Bonding the cured microstructure and the semi-solid circuit layer and curing them to obtain a circuit and microstructure composite layer; Using the base layer template to obtain a semi-solid base layer; Bonding the semi-solid base layer and the circuit and microstructure composite layer and curing them to obtain a flexible sensor outer body; Injecting a conductive material into the circuit pattern of the flexible sensor outer body to obtain the microstructure electronic skin.

10. Application of the microstructure electronic skin according to any one of claims 1-8 or the microstructure electronic skin prepared by the preparation method according to claim 9 in the sensing field.

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