WO2024031842A1

WO2024031842A1 - Microstructure elastomer film and preparation method therefor, and flexible pressure sensor and preparation method therefor

Info

Publication number: WO2024031842A1
Application number: PCT/CN2022/128150
Authority: WO
Inventors: 杨小牛; 李宗林; 张通
Original assignee: 中国科学院长春应用化学研究所
Priority date: 2022-08-09
Filing date: 2022-10-28
Publication date: 2024-02-15
Also published as: CN115290231A

Abstract

A microstructure elastic film, comprising a substrate and a microstructure layer attached to the surface of the substrate. The microstructure layer has a granular microstructure connected to the substrate and having a small lower end, an expanded upper end, a rough surface and a fluffy interior, or a mountain-like microstructure connected to the substrate and having a large lower end, a small upper end, a rough surface and a fluffy interior, or a fabric-like microstructure formed by vertically and horizontally staggering fibers. Also provided are a spraying process-based preparation method for the microstructure elastomer film, and a flexible pressure sensor and a preparation method therefor. The current signal and the pressure of the flexible pressure sensor prepared by using the film are in a good linear relationship within the range of 20 MPa, and the flexible pressure sensor can be used for radial pulse monitoring.

Description

A microstructured elastomer film, its preparation method and a flexible pressure sensor, and its preparation method

This application requires priority for the Chinese patent application submitted to the China Patent Office on August 9, 2022, with the application number 202210951117.2 and the invention title "A microstructured elastomer film, its preparation method and a flexible pressure sensor, and its preparation method" rights, the entire contents of which are incorporated herein by reference.

Technical field

The invention belongs to the technical field of pressure sensors, and in particular relates to a microstructured elastomer film, its preparation method, and a flexible pressure sensor and its preparation method.

Background technique

Flexible pressure sensors are light, thin, and flexible, can be attached to complex-shaped surfaces, and are easy to carry. Therefore, they have broad application prospects in the fields of electronic skin, health monitoring, human-computer interaction, and motion recognition. Piezoresistive flexible pressure sensors have attracted widespread attention due to their simple structure, easy signal reading, and convenient production. The sensing mechanism of piezoresistive flexible pressure sensors can be divided into two types: bulk conductivity and surface conductivity. Bulk conductivity means that the conductive filler is evenly dispersed in the elastomer. However, the sensor with this mechanism is greatly affected by the viscoelasticity and temperature changes of the material itself, so the output signal is unstable. Surface microstructure conductivity is a device structure developed to address the lack of bulk conductivity. When this type of sensor is pressed, the surface microstructure of the elastomer film deforms, and the contact area between the conductive film and the interdigital electrode becomes larger. The resistance is reduced, thereby achieving force-to-electricity conversion.

In recent years, with the efforts of scientific researchers, the performance of microstructured flexible pressure sensors has been greatly improved. At present, most of the microstructures used by researchers use transfer printing methods to obtain them from the microstructure surface. For example, the application number is 202111156003.0, and the invention patent titled "Preparation method and application of a flexible pressure sensor" uses sandpaper as the template, multi-walled carbon nanotubes (MWCNTs) as the conductive material, and polydimethylsiloxane (PDMS). ) obtains a microstructured flexible sensing layer for a flexible substrate, but there is a problem of small linear interval. In order to expand the linear range of the sensor, the invention patent with application number 201910240874.7, titled "An elastomer film and its preparation method and a flexible pressure sensor containing the elastomer film" uses selective laser sintering 3D printing technology to prepare a microstructure template , the obtained microstructure sensing film has a good linear response within the pressure range of 200kPa, which improves the performance of the sensor.

However, the transfer method also has shortcomings that hinder the commercialization of flexible pressure sensors. First of all, the transfer printing method is limited by the template size, elastomer leveling requirements, separation of the film and template and other operational aspects, and cannot be used in large areas; secondly, the microstructure of the template will wear out during multiple uses, resulting in The production quality is unstable; finally, the processing of the template and the commonly used elastomer material (PDMS) make the cost of the template method high, and the complexity of the transfer operation makes the production efficiency low. There are also related reports on the preparation of microstructured elastomer films by non-transfer printing methods, such as the application number 202110855000. Electrospinning technology can achieve the preparation of microstructured films of a certain area, but it has the problems of low production efficiency and small linear range. In summary, the development of a non-transferable, large-area, efficient, and low-cost method for preparing high-performance microstructured elastomer films is of great significance to promote the commercial application of flexible pressure sensors.

Contents of the invention

The object of the present invention is to provide a method for preparing a microstructured elastomer film and a method for preparing a flexible pressure sensor. The method for preparing the microstructured elastomer film of the present invention is easy to industrialize, and the flexible pressure sensor prepared based on the microstructured film Its current signal has a good linear relationship with pressure within a wide range of 20MPa, and can be used for radial artery pulse monitoring.

The invention provides a microstructured elastomer film, which includes a substrate and a microstructured layer attached to the surface of the substrate;

The microstructure layer has a granular microstructure with a small lower end connected to the base, an enlarged upper end, a rough surface, and a fluffy interior; or a mountain-like microstructure with a large lower end connected to the base, a small upper end, a rough surface, and a fluffy interior. structure; or a fabric-like microstructure with interlaced fibers.

Preferably, the substrate is polyethylene terephthalate film, thermoplastic polyurethane elastomer film, polyethylene film, polypropylene film or polyimide film;

The thickness of the substrate is 50-100 μm.

The present invention provides a method for preparing the microstructured elastomer film as described above, which includes the following steps:

A) Dissolve the thermoplastic elastomer material in the solvent and prepare an elastomer solution with a concentration of 10 to 120 mg/mL;

The thermoplastic elastomer material is one or more of hydrogenated styrene-butadiene block copolymer and thermoplastic polyurethane; the solvent is tetrahydrofuran, butyl acetate, 1,4-dioxane, cyclohexane One or more of ketone and N,N-dimethylformamide;

B) Spray the elastomer solution evenly onto the substrate surface, and obtain a microstructured elastomer film after removing the solvent.

Preferably, an air-assisted spray gun is used to spray the elastomer solution onto the substrate surface; the carrier gas pressure of the spraying is 0.1~0.8MPa; the diameter of the nozzle is 0.8~2.5mm; the spraying distance is 20 ~50cm.

Preferably, the thickness of the microstructured elastomer film is 50-300 μm.

Preferably, the solvent is removed by heating or evaporation at room temperature.

The present invention provides a flexible pressure sensor including the microstructured elastomer film described above.

The invention provides a method for preparing a flexible pressure sensor, which includes the following steps:

1) Obtain a microstructured elastomer film according to the preparation method above;

2) Form a conductive layer on the surface of the microstructured elastomer film to obtain a sensing film;

3) Combine and package the conductive layer side of the sensing film with the interdigital electrode to obtain a flexible pressure sensor.

Preferably, conductive ink is sprayed on the surface of the microstructured elastomer film to form a conductive layer;

Alternatively, a metal conductive layer is formed on the surface of the microstructured elastomer film by magnetron sputtering or vacuum evaporation.

Preferably, the conductive ink is an organic dispersion of conductive carbon material; the thickness of the conductive layer is 1 to 2 μm.

The invention provides a microstructure elastomer film, which includes a substrate and a microstructure layer attached to the surface of the substrate; the microstructure layer has a small lower end connected to the substrate, an enlarged upper end, a rough surface, and a fluffy granular microstructure inside. structure; or it has a mountain-like microstructure with a large lower end connected to the base, a small upper end, a rough surface, and a fluffy interior; or it has a fabric-like microstructure with interlaced fibers.

The invention provides a method for preparing a microstructured elastomer film, which includes the following steps: A) dissolving a thermoplastic elastomer material in a solvent to prepare an elastomer solution with a concentration of 10 to 120 mg/mL; the elastomer material It is one or more of hydrogenated styrene-butadiene block copolymer and thermoplastic polyurethane; the solvent is tetrahydrofuran, butyl acetate, 1,4-dioxane, cyclohexanone, N,N- One or more of dimethylformamide; B) Spray the elastomer solution evenly onto the surface of the substrate, and obtain a microstructured elastomer film after removing the solvent. The preparation method of the elastomer film of the present invention is mainly based on the spraying process. First, select a suitable soluble elastomer polymer material and prepare it into a solution of a certain concentration. Then use an air-assisted spray gun to spray the solution on the temperature-controlled substrate to form a film. After the solution evaporates, a multi-layered surface can be obtained. Microstructured elastomeric films. The flexible pressure sensor prepared with this film has a good linear relationship between the current signal and the pressure within the range of 20MPa, and can be used for radial artery pulse monitoring.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without exerting creative efforts.

Figure 1 is an optical microscope side view of the microstructured elastomer film prepared in Example 1 of the present invention;

Figure 2 is an SEM image of the microstructured elastomer film prepared in Example 1 of the present invention;

Figure 3 is an optical microscope top view of the microstructured elastomer film prepared in Example 2 of the present invention;

Figure 4 is an optical microscope top view of the microstructured elastomer film prepared in Example 3 of the present invention;

Figure 5 is an SEM image of the microstructured elastomer film prepared in Example 3 of the present invention;

Figure 6 is an SEM image of the microstructured elastomer film prepared in Example 4 of the present invention;

Figure 7 is a electromechanical test diagram of the flexible pressure sensor in Embodiment 6 of the present invention under a pressure of 0 to 20MPa;

Figure 8 is a pulse test chart of the flexible pressure sensor in Embodiment 6 of the present invention.

Detailed ways

In the present invention, the microstructure layer has three morphologies, namely:

1) It is granular, with a small bottom part connected to the base, an enlarged upper end, a rough surface and a fluffy interior, showing a "broccoli"-like appearance;

The distribution of this kind of granular microstructure on the surface of the substrate is random in space, and the particle height distribution is relatively even. This microstructure with the characteristics of "small at the bottom and large at the top" cannot be obtained by transfer printing (difficult to demould), and it has not yet been There are reports of similar structures processed by other processes and further used in flexible pressure sensors.

2) In the shape of a mountain range, large at the bottom and small at the top, continuous, rough on the surface and fluffy on the inside;

3) The fibrous filaments are crisscrossed vertically and horizontally, and the overall surface height is not very undulating.

The invention provides a method for preparing a microstructured elastomer film, which includes the following steps:

The elastomer material is one or more of hydrogenated styrene-butadiene block copolymer and thermoplastic polyurethane; the solvent is tetrahydrofuran, butyl acetate, 1,4-dioxane, and cyclohexanone , one or more of N,N-dimethylformamide;

In the present invention, the use of spraying method to prepare microstructured elastomer films requires the selection of appropriate elastomer materials. The elastomer materials are preferably hydrogenated styrene-butadiene block copolymer (SEBS) or thermoplastic polyurethane (TPU). One or more of them; the solvent is preferably one or more of tetrahydrofuran, butyl acetate, 1,4-dioxane, cyclohexanone, N,N-dimethylformamide, more preferably It is a low boiling point solvent, such as tetrahydrofuran (THF).

The applicant's research has found that the concentration of the elastomer material directly affects the microstructure morphology of the surface of the microstructured elastomer film. In the present invention, the concentration of the elastomer material is preferably 10 to 120 mg/mL, such as 10 mg/mL, 15 mg/mL. mL, 20mg/mL, 25mg/mL, 30mg/mL, 35mg/mL, 40mg/mL, 45mg/mL, 50mg/mL, 55mg/mL, 60mg/mL, 65mg/mL, 70mg/mL, 75mg/mL, 80 mg/mL, 85 mg/mL, 90 mg/mL, 95 mg/mL, 100 mg/mL, 105 mg/mL, 110 mg/mL, 115 mg/mL, 120 mg/mL, preferably a range value with any of the above values as the upper limit or lower limit.

In the present invention, the droplets sprayed with a low-concentration (10-30 mg/mL) solution can be dispersed well to obtain a broccoli-like microstructure; the viscosity of the medium-concentration (30-70 mg/mL) solution increases during spraying. It cannot be dispersed well, and some stringing appears. At this time, the microstructure is like a mountain range, with large bottom and small top, continuous; continue to increase the solution concentration (70~120mg/mL), and the main thing sprayed out at this time is filaments, and we get It has a fabric-like surface with fibrous filaments criss-crossing in a criss-cross pattern, and the overall height of the surface does not fluctuate much.

After obtaining the elastomer solution, the present invention sprays the elastomer solution evenly onto the surface of the substrate by spraying. The spraying path is a serpentine curve, and the path parameters are adjusted according to the base area and spray width to ensure uniform coverage.

The spraying method used in the present invention can quickly and uniformly prepare a variety of elastomer films with different microstructures and morphologies over a large area. During the spraying process with a pneumatic spray gun, the material liquid is affected by gravity or pressure in the storage tank and flows out from the nozzle to form a liquid film. The surface of the liquid film produces unstable fluctuations under the action of the surrounding high-speed gas jets. As the fluctuations develop, the liquid film breaks into liquid lines, liquid rings or larger particles, and at the same time leaves the nozzle and moves forward. The droplets formed by the initial rupture will continue to be affected by the rear airflow in the air. When the gas force is greater than the surface tension and internal viscosity of the liquid, the droplets formed by the initial rupture will undergo secondary rupture, resulting in a finer spray liquid. drop. As these small droplets continue to fly forward, they will also partially collide and merge, and finally hit the substrate and attach to its surface. By changing spraying parameters such as carrier gas flow rate, feed liquid composition, base material, and spraying speed, different atomization and drying effects can be achieved, and surface microstructure films with different morphologies can be obtained.

In the present invention, an air-assisted spray gun is preferably used to spray the elastomer solution. The nozzle diameter of the air-assisted spray gun is preferably 0.8 to 2.5 mm, more preferably 1 to 2 mm, and the carrier gas pressure is preferably 0.1 to 0.8 MPa, more preferably 0.3 ~0.5MPa, such as 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, preferably a range value with any of the above values as the upper limit or lower limit; the spraying distance is preferably 20-50cm, more preferably 30-40cm.

After each spraying is completed, after the solvent has evaporated and the surface has dried, the spraying process can be repeated and sprayed multiple times until the required thickness is reached to ensure the elasticity of the film.

The present invention preferably uses a heating method to remove the solvent in the sprayed layer. Specifically, a temperature-controllable heating device can be provided below the substrate, or an infrared radiation lamp can be used to heat from the top. The purpose of heating in the present invention is to volatilize and remove the solvent. Therefore, the heating temperature needs to be adjusted according to the type of solvent. At the same time, the selection of the heating temperature must also take into account the resistance temperature of the base material and the resistance temperature of the elastomer. In the present invention, The heating temperature is preferably 70 to 150°C, more preferably 90°C.

In the present invention, the thickness of the elastomer microstructure layer prepared by the spraying method is preferably 50 to 300 μm, and more preferably 100 to 200 μm.

In the present invention, the substrate is preferably polyethylene terephthalate (PET) film, TPU film, polyethylene (PE) film, polypropylene (PP) film or polyimide (PI) film, The thickness of the substrate is preferably 50-100 μm, more preferably 60-80 μm.

The present invention also provides a flexible pressure sensor, which includes the microstructured elastomer film described above.

Based on the preparation method of the above-mentioned microstructured elastomer film, the present invention also provides a preparation method of a flexible pressure sensor, which includes the following steps:

In the present invention, the conductive ink can be sprayed on the surface of the microstructured elastomer by air-assisted spraying or ultrasonic spraying to form a conductive layer, or the conductive layer can be formed on the surface of the microstructure by magnetron sputtering or vacuum evaporation. Build a metal conductive layer.

In the present invention, the conductive ink preferably includes a conductive carbon material and an organic solvent. Specifically, an N,N-dimethylformamide (DMF) dispersion of multi-walled carbon nanotubes can be used, and the concentration is preferably 1 to 10 mg. /mL, more preferably 3 to 8 mg/mL, most preferably 5 to 6 mg/mL; the metal in the metal conductive layer may be gold or silver.

After obtaining the sensing film, the conductive layer side of the sensing film is combined with the interdigital electrode and packaged to obtain a flexible pressure sensor. In the present invention, the interdigital electrode is preferably a PI base and a silver conductive layer.

The invention provides a method for preparing a microstructured elastomer film, which includes the following steps: A) Mix the elastomer material with a solvent to prepare an elastomer solution with a concentration of 10 to 120 mg/mL; the elastomer material is hydrogenated One or more of styrene-butadiene block copolymer and thermoplastic polyurethane; the solvent is tetrahydrofuran, butyl acetate, 1,4-dioxane, cyclohexanone, N,N-dimethyl One or more of the base formamides; B) Spray the elastomer solution evenly onto the surface of the substrate, and obtain a microstructured elastomer film after removing the solvent. The preparation method of the elastomer film of the present invention is mainly based on the spraying process. First, select a suitable soluble polymer material and prepare it into a solution with a certain concentration. Then use an air-assisted spray gun to spray the solution on the temperature-controlled substrate to form a film. After the solution evaporates, you can obtain a multi-layered surface microstructure. Structural elastomeric film. The flexible pressure sensor prepared with this film has a good linear relationship between the current signal and the pressure within the range of 20MPa, and can be used for radial artery pulse monitoring.

In order to further illustrate the present invention, the preparation method of a microstructured elastomer film and the preparation method of a flexible pressure sensor provided by the present invention are described in detail below in conjunction with the examples, but they should not be understood as limiting the scope of the present invention.

Example 1

The selected material is SEBS, brand name is Karton G1650, and is dissolved in tetrahydrofuran (THF) to prepare a 20mg/mL solution. The spray gun is Iwata Wider2-25W1G, the carrier gas pressure is 0.25MPa, and the elastomer film with a thickness of about 200 μm and a granular surface microstructure is sprayed on a 100 μm thick polyimide (PI) film. This granular structure has the following characteristics: The morphological characteristics of small on large. Figures 1 to 2 are the optical microscope images and scanning electron microscope images respectively.

Example 2

The selected material is TPU, the brand name is Estane AlR MC 93A-V, and it is dissolved in tetrahydrofuran (THF) to prepare a 20mg/mL solution. The spray gun is Iwata Wider2-25W1G, the carrier gas pressure is 0.25MPa, and an elastomer film with a thickness of about 100 μm and a granular surface microstructure is sprayed on a 100 μm thick polyimide (PI) film. Its morphology and examples The appearance is similar to that in 1. Figure 3 is its optical microscope image.

Example 3

The selected material is SEBS, brand name is Karton G1650, and is dissolved in tetrahydrofuran (THF) to prepare a 50mg/mL solution. The spray gun is Iwata Wider2-25W1G, the carrier gas pressure is 0.25MPa, and an elastomer film with a thickness of about 200 μm and a "mountain"-like surface microstructure is sprayed on an 80 μm thick ethylene terephthalate (PET) film. Figures 4 to 5 show the optical microscope images and scanning electron microscope images respectively.

Example 4

The selected material is SEBS, brand name is Karton G1652, and is dissolved in tetrahydrofuran (THF) to prepare a 120mg/mL solution. The spray gun is Iwata Wider2-25W1G, the carrier gas pressure is 0.7MPa, and an elastomer film with a thickness of about 200 μm and a brushed surface microstructure is obtained by spraying on an 80 μm thick PET film. Figure 6 is its scanning electron microscope image.

Example 5

Conductive ink was sprayed on the surface of the elastomer film prepared in Example 1 using a pneumatic spray gun. The conductive ink is an N,N-dimethylformamide (DMF) dispersion of multi-walled carbon nanotubes (MWCNTs) with a concentration of 2mg/mL; the spraying carrier gas pressure is 0.25MPa, and the thickness of the conductive layer obtained by spraying is 1 ~2um. A flexible pressure sensor is obtained by combining a microstructured film with a conductive layer and an interdigital electrode (the interdigital electrode is a PI base, a silver conductive layer, a working area of 2cm*2cm, a total of 20 fingers, and a finger gap width of 150μm).

Example 6

Conductive ink was ultrasonically sprayed on the surface of the elastomer film prepared in Example 3. The conductive ink is an N,N-dimethylformamide (DMF) solution of multi-walled carbon nanotubes (MWCNTs) with a concentration of 5mg/mL; the ultrasonic spraying carrier gas pressure is 0.4MPa, the ultrasonic power is 3.5W, and the ink flow rate is 0.2mL/min, the thickness of the conductive layer obtained by spraying is 1~2μm. A flexible pressure sensor is obtained by combining a microstructured film with a conductive layer and an interdigital electrode (the interdigital electrode is a PI base, a silver conductive layer, a working area of 2cm*2cm, a total of 20 fingers, and a finger gap width of 150μm).

Example 7

The selected material is SEBS, brand name is Karton G1650, and is dissolved in tetrahydrofuran (THF) to prepare a solution of 80mg/mL. The spray gun is Iwata Wider2-25W1G, the carrier gas pressure is 0.25MPa, and an elastomer film with a thickness of about 200 μm and a brushed surface microstructure is obtained by spraying on a 100 μm thick PI film. Conductive ink is then sprayed on the surface of the film. The conductive ink is a DMF dispersion of MWCNTs with a concentration of 2 mg/mL; a pneumatic-assisted spray gun is used with a carrier gas pressure of 0.25 MPa and a conductive layer thickness of 1 to 2 μm. A flexible pressure sensor is obtained by combining a microstructured film with a conductive layer and an interdigital electrode (the interdigital electrode is a PI base, a silver conductive layer, a working area of 2cm*2cm, a total of 20 fingers, and a finger gap width of 150μm).

The films of three morphological microstructure films were made into sensors according to the method of Example 5 and tested. The results are shown in Figure 7. From Figure 7, it can be seen that the broccoli-like microstructure obtained by spraying with a low concentration solution has the widest Linear range, close to 20MPa.

The pressure sensor prepared in Example 5 is used to test human pulse. The test process is as follows: attach one side of the encapsulated sensor microstructure film to the radial artery of the wrist and fix it with tape. Then the sensor is powered through the source meter and the test data is recorded. The results are shown in Figure 8. It can be seen from Figure 8 that the sensor of the present invention can clearly distinguish the human radial artery pulse and has application potential.

The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims

A microstructured elastomer film includes a substrate and a microstructured layer attached to the surface of the substrate;

The microstructure layer has a granular microstructure with a small lower end connected to the base, an enlarged upper end, a rough surface, and a fluffy interior; or a mountain-like microstructure with a large lower end connected to the base, a small upper end, a rough surface, and a fluffy interior. structure; or a fabric-like microstructure with interlaced fibers.
The preparation method according to claim 1, wherein the substrate is a polyethylene terephthalate film, a thermoplastic polyurethane elastomer film, a polyethylene film, a polypropylene film or a polyimide film;

The thickness of the substrate is 50-100 μm.
The preparation method of microstructured elastomer film as claimed in claim 1, comprising the following steps:

A) Dissolve the thermoplastic elastomer material in the solvent and prepare an elastomer solution with a concentration of 10 to 120 mg/mL;

The thermoplastic elastomer material is one or more of hydrogenated styrene-butadiene block copolymer and thermoplastic polyurethane; the solvent is tetrahydrofuran, butyl acetate, 1,4-dioxane, cyclohexane One or more of ketone and N,N-dimethylformamide;

B) Spray the elastomer solution evenly onto the substrate surface, and obtain a microstructured elastomer film after removing the solvent.
The preparation method according to claim 3, characterized in that an air-assisted spray gun is used to spray the elastomer solution onto the substrate surface; the carrier gas pressure of the spraying is 0.1-0.8MPa; the diameter of the nozzle is 0.8 ~2.5mm; the spraying distance is 20~50cm.
The preparation method according to claim 3, characterized in that the thickness of the microstructured elastomer film is 50-300 μm.
The preparation method according to claim 3, characterized in that the solvent is removed by heating or evaporation at room temperature.
A flexible pressure sensor, characterized by comprising the microstructured elastomer film according to claim 1.
A method for preparing a flexible pressure sensor, including the following steps:

1) Obtain a microstructured elastomer film according to the preparation method in claim 1;

2) Form a conductive layer on the surface of the microstructured elastomer film to obtain a sensing film;

3) Combine and package the conductive layer side of the sensing film with the interdigital electrode to obtain a flexible pressure sensor.
The preparation method according to claim 8, characterized in that conductive ink is sprayed on the surface of the microstructured elastomer film to form a conductive layer;

Alternatively, a metal conductive layer is formed on the surface of the microstructured elastomer film by magnetron sputtering or vacuum evaporation.
The preparation method according to claim 9, characterized in that the conductive ink is an organic dispersion of conductive carbon material; the thickness of the conductive layer is 1 to 2 μm.