Flexible pressure sensor and preparation method thereof

Abstract

The invention discloses a flexible pressure sensor and a preparation method thereof, and belongs to the technical field of pressure sensors. Through the combination of the microstructure sensing layer with higher modulus and the elastic microstructure protective layer, the sensitivity of the sensor in a micro-force state is ensured, the measuring range of the sensor can be increased, and meanwhile, in the long-term recycling process, the microstructure sensing layer is not easy to damage and has better fatigue resistance; a proper conductive composite material formula and a proper laser marking process are adopted, the sectional area of the obtained microstructure layer is gradually increased from top to bottom, the precision is high, and therefore the consistency and precision of the sensing point array of the prepared pressure sensor are excellent.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor fabrication technology, specifically to a flexible pressure sensor and its fabrication method. Background Technology

[0002] Flexible pressure sensors, as electronic devices capable of sensing pressure changes, have broad application prospects. With the increasing demand for portability, comfort, and flexibility in electronic products, research on flexible pressure sensors with high sensitivity and wide measurement range is particularly important. Improving the sensitivity and measurement range of sensors to enable them to accurately and quickly respond to pressure changes in various complex environments is a current research focus and challenge. Microstructure-based flexible pressure sensors offer advantages such as high sensitivity and linearity. Under low force, the sensor primarily relies on changes in the contact area between the microstructure and the electrode to feedback the force magnitude. As pressure increases, the thickness of the microstructure layer gradually compresses, resulting in closer contact between the conductive particles within the microstructure, thus allowing for the feedback of larger force values. However, the conductive material of the microstructure rapidly reaches its deformation saturation threshold under pressure load, leading to a relatively small pressure detection range, typically reaching saturation at 200-300 kPa. Furthermore, after multiple pressure cycles, local defects easily develop in the microstructure layer, causing problems such as decreased product consistency and accuracy. Therefore, it is difficult to apply these sensors in medium-to-high pressure ranges, limiting their application scope. Summary of the Invention

[0003] Based on this, in order to solve one of the above-mentioned technical problems, the present invention provides a flexible pressure sensor and its manufacturing method, so as to solve the problems of small range and poor consistency of pressure sensors in the prior art. The specific technical solution is as follows: A flexible pressure sensor includes a substrate layer, a microstructure sensing layer, a microstructure protective layer, an adhesive isolation layer, an electrode layer, and an encapsulation layer, wherein the microstructure sensing layer is a conductive composite material coating; and the microstructure protective layer is an elastic polyurethane coating and / or a polydimethylsiloxane coating.

[0004] Furthermore, the thickness of the substrate layer is 0.08mm-0.25mm; the substrate layer is a flexible sheet material.

[0005] Furthermore, the raw materials for preparing the conductive composite material coating include epoxy resin and conductive filler, and the sheet resistance of the conductive composite material coating ranges from 0.3kΩ / □ to 200kΩ / □.

[0006] Furthermore, the hardness of the elastic polyurethane coating and / or polydimethylsiloxane coating is 20A-60A.

[0007] Furthermore, the adhesive release layer is a double-sided adhesive with a PET or PI substrate and a thickness of 0.1mm-0.15mm; The electrode layer is an interdigitated electrode array; The encapsulation layer is a flexible sheet material with a thickness of 0.08mm-0.25mm.

[0008] In addition, the present invention also provides a method for fabricating a flexible pressure sensor, the method comprising the following steps: Step 1: Prepare a conductive composite material, and coat the conductive composite material onto a substrate layer and dry it to obtain a conductive composite material coating; Step 2: On the conductive composite material coating obtained in Step 1, polyurethane material and / or polydimethylsiloxane material are screen-printed or sprayed using a screen printing machine or a spraying machine. After drying, a polyurethane coating and / or a polydimethylsiloxane coating are formed. Step 3: Establish a three-dimensional microstructure sensing array pattern. Use an infrared picosecond laser marking machine to etch polyurethane coating and / or polydimethylsiloxane coating and conductive composite material coating layer by layer. After etching, a microstructure protective layer and a microstructure sensing layer are formed. The cross-sectional area of ​​the microstructure protective layer and the microstructure sensing layer gradually increases from top to bottom, presenting a circular arc structure, a pyramid structure, and a trapezoidal structure. The etching depth is 15μm-30μm. Step 4: Silkscreen the interdigitated electrode array onto the encapsulation layer; Step 5: After bonding the microstructure protective layer and the encapsulation layer with the screen-printed electrode layer together with double-sided adhesive, the flexible pressure sensor is obtained.

[0009] Furthermore, the thickness of the conductive composite material coating is 30μm-50μm; the thickness of the microstructure protective layer is 3μm-10μm.

[0010] Furthermore, the method for preparing the conductive composite material is as follows: Epoxy resin and solvent are added to a reaction vessel and heated to 50℃-80℃. The mixture is stirred at 1000-3000 r / min for 0.5-1 h. Then, conductive filler is added and stirred at 1000-3000 r / min for another 0.5-2 h. The temperature is then lowered to 30℃-40℃. Curing agent and anti-sticking agent are added, and the mixture is stirred for another 1-3 h. After cooling to room temperature, the mixture is ground. The roller spacing is adjusted to ensure that the fineness of the slurry after grinding is below 20 μm. The mixture is then filtered and the viscosity is adjusted to 5000 cps-12000 cps. After thorough mixing, the conductive composite material is obtained.

[0011] Furthermore, the conductive filler is obtained by mixing carbon black, copper powder and graphite in a mass ratio of (1~3):(1~2):(1~3), and the average particle size of the carbon black, copper powder and graphite is 0.5μm-100μm.

[0012] Furthermore, the process parameters of the infrared picosecond laser marking machine are as follows: wavelength of 1026nm-1064nm, pulse energy of 0.2mJ-2.0mJ, repetition frequency of 100kHz-500kHz, focused spot diameter controlled at 1μm-3μm, and interlayer Z-axis step size of 1μm-3μm.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention combines a high-modulus microstructure sensing layer with an elastic microstructure protective layer, ensuring both the sensor's sensitivity under low force conditions and increasing its measurement range. Furthermore, the microstructure sensing layer is resistant to damage and exhibits good fatigue resistance during long-term cyclic use. By employing a suitable conductive composite material formulation and a suitable laser marking process, the resulting microstructure layer gradually increases in cross-sectional area from top to bottom, resulting in high precision. Consequently, the pressure sensor exhibits excellent consistency and accuracy of its sensing point array. Attached Figure Description

[0014] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0015] Figure 1 This is a schematic diagram of the interdigitated electrode array used in Embodiment 1 of the present invention, with a 5*6 array containing a total of 30 counter electrodes; Figure 2 This is a schematic diagram of the microstructure sensing layer in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the microstructure sensing layer in Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the microstructure sensing layer in Embodiment 3 of the present invention; Figure 5 This is a SEM image of the microstructure sensing layer and the conductive composite material layer in Embodiment 3 of the present invention; Figure 6 This is a piezoresistive curve of the pressure sensor prepared in Embodiment 1 of the present invention.

[0016] Explanation of reference numerals in the attached figures 1-1. Microstructure protective layer; 1-2. Conductive composite material layer; 1-3. Base layer; 2-1. Microstructure protective layer; 2-2. Conductive composite material layer; 2-3. Base layer; 3-1. Microstructure protective layer; 3-2. Conductive composite material layer; 3-3. Base layer. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] A flexible pressure sensor according to one embodiment of the present invention includes a substrate layer, a microstructure sensing layer, a microstructure protective layer, an adhesive isolation layer, an electrode layer, and an encapsulation layer, wherein the microstructure sensing layer is a conductive composite material coating; and the microstructure protective layer is an elastic polyurethane coating and / or a polydimethylsiloxane coating.

[0020] In one embodiment, the thickness of the substrate layer is 0.08 mm to 0.25 mm; the substrate layer is a flexible sheet material.

[0021] In one embodiment, the flexible sheet material in the substrate layer is at least one of PET, PEI, PI, and PC.

[0022] In one embodiment, the raw materials for preparing the conductive composite material coating include epoxy resin and conductive filler, and the sheet resistance of the conductive composite material coating is in the range of 0.3kΩ / □-200kΩ / □.

[0023] In one embodiment, the hardness of the elastic polyurethane coating and / or polydimethylsiloxane coating is 20A-60A. The elastic polyurethane coating and / or polydimethylsiloxane coating in this invention are conventional techniques and will not be described in detail here.

[0024] In one embodiment, the adhesive release layer is a double-sided adhesive with a PET or PI substrate and a thickness of 0.1mm-0.15mm; The electrode layer is an interdigitated electrode array; The encapsulation layer is a flexible sheet material with a thickness of 0.08mm-0.25mm.

[0025] In one embodiment, the flexible sheet material in the encapsulation layer is PET, PEI, PI, or PC.

[0026] In addition, the present invention also provides a method for fabricating a flexible pressure sensor, the method comprising the following steps: Step 1: Prepare a conductive composite material, and coat the conductive composite material onto a substrate layer and dry it to obtain a conductive composite material coating; Step 2: On the conductive composite material coating obtained in Step 1, polyurethane material and / or polydimethylsiloxane material are screen-printed or sprayed using a screen printing machine or a spraying machine. After drying, a polyurethane coating and / or a polydimethylsiloxane coating are formed. Step 3: Establish a three-dimensional microstructure sensing array pattern. Use an infrared picosecond laser marking machine to etch polyurethane coating and / or polydimethylsiloxane coating and conductive composite material coating layer by layer. After etching, a microstructure protective layer and a microstructure sensing layer are formed. The cross-sectional area of ​​the microstructure protective layer and the microstructure sensing layer gradually increases from top to bottom, presenting a circular arc structure, a pyramid structure, and a trapezoidal structure. The etching depth is 15μm-30μm. Step 4: Silkscreen the interdigitated electrode array onto the encapsulation layer; Step 5: After bonding the microstructure protective layer and the encapsulation layer with the screen-printed electrode layer together with double-sided adhesive, the flexible pressure sensor is obtained.

[0027] In one embodiment, the thickness of the conductive composite material coating is 30μm-50μm; the thickness of the microstructure protective layer is 3μm-10μm.

[0028] In one embodiment, the conductive composite material is prepared by: Epoxy resin and solvent are added to a reaction vessel and heated to 50℃-80℃. The mixture is stirred at 1000-3000 r / min for 0.5-1 h. Then, conductive filler is added and stirred at 1000-3000 r / min for another 0.5-2 h. The temperature is then lowered to 30℃-40℃. Curing agent and anti-sticking agent are added, and the mixture is stirred for another 1-3 h. After cooling to room temperature, the mixture is ground. The roller spacing is adjusted to ensure that the fineness of the slurry after grinding is below 20 μm. The mixture is then filtered and the viscosity is adjusted to 5000 cps-12000 cps. After thorough mixing, the conductive composite material is obtained.

[0029] In one embodiment, the epoxy resin, solvent, conductive filler, curing agent and anti-sticking agent are in the following weight ratios: 100:(10-40):(5-30):(0.1-1):(1-5).

[0030] In one embodiment, the epoxy resin is at least one of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin.

[0031] In one embodiment, the solvent is at least one of 1-methyl-2-pyrrolidone, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, terpineol, diester, and dibutyl phthalate.

[0032] In one embodiment, the curing agent is at least one of ethylenediamine, diethylenetriamine, triethanolamine, dicyandiamide, and low molecular weight polyamide.

[0033] In one embodiment, the anti-sticking agent is at least one of wax emulsion, calcium carbonate, and kaolin.

[0034] In one embodiment, the conductive filler is obtained by mixing carbon black, copper powder and graphite in a mass ratio of (1~3):(1~2):(1~3), and the average particle size of the carbon black, copper powder and graphite is 0.5μm-100μm.

[0035] In one embodiment, the process parameters of the infrared picosecond laser marking machine are: wavelength of 1026nm-1064nm, pulse energy of 0.2mJ-2.0mJ, repetition frequency of 100kHz-500kHz, focused spot diameter controlled at 1μm-3μm, and interlayer Z-axis step size of 1μm-3μm.

[0036] The flexible pressure sensor obtained by the above scheme has excellent consistency and accuracy of the sensing point array.

[0037] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0038] Example 1: A flexible pressure sensor includes a substrate layer, a microstructure sensing layer, a microstructure protective layer, an adhesive isolation layer, an electrode layer, and an encapsulation layer; The substrate layer is a flexible sheet material made of PET with a thickness of 0.15mm; The microstructure sensing layer is obtained by etching a conductive composite material coating, and the sheet resistance of the conductive composite material coating is 0.3 kΩ / □. The microstructure protective layer is obtained by etching an elastic polyurethane coating with a hardness of 30A. The double-sided adhesive of the PET substrate used for the bonding and isolation layer has a thickness of 0.1 mm. The electrode layer is an interdigitated electrode array; The encapsulation layer is a flexible sheet material made of PET with a thickness of 0.15mm.

[0039] A method for fabricating a flexible pressure sensor includes the following steps: Step 1: Apply conductive composite material to the substrate using a scraper. After drying, a conductive composite material coating with a thickness of 30 μm is obtained. The preparation method of the conductive composite material is as follows: 100 parts of epoxy resin and 40 parts of 1-methyl-2-pyrrolidone are added to a reaction vessel, heated to 80°C, stirred at 1000 r / min for 0.5 h, 30 parts of conductive filler are added, and stirring is continued at 3000 r / min for 2 h. The temperature is then lowered to 35°C, followed by the addition of 0.5 parts of ethylenediamine and 3 parts of wax emulsion. The reaction is continued for 3 h, and after cooling to room temperature, the material is ground. The roller spacing is adjusted to ensure that the fineness of the slurry after grinding is below 20 μm. The material is filtered out, and the viscosity is adjusted to 12000 cps. After thorough mixing, the heat-resistant conductive composite material is obtained. The conductive filler is obtained by mixing carbon black, copper powder and graphite in a mass ratio of 1:1:1, and the average particle size of carbon black, copper powder and graphite is 0.5μm-100μm. Step 2: A layer of polyurethane material is screen-printed onto the conductive composite material layer obtained in Step 1 using a screen printing machine. After drying, a polyurethane coating with a thickness of 10 μm is formed. Step 3: Establish a three-dimensional microstructure sensing array pattern. Use an infrared picosecond laser marking machine to etch the polyurethane coating and conductive composite material layer layer by layer. After etching, a microstructure protective layer and a microstructure sensing layer are formed. The cross-sectional area of ​​the microstructure protective layer and the microstructure sensing layer gradually increases from top to bottom, presenting an arc-shaped structure. The etching depth is 30um. The process parameters of the infrared picosecond laser marking machine are: wavelength of 1026-1064nm, pulse energy of 2.0mJ, repetition frequency of 500kHz, focused spot diameter controlled at 3μm, and interlayer Z-axis step size of 1μm. Step 4: Silkscreen the interdigitated electrode array layer onto the encapsulation layer; Step 5: After bonding the microstructure protective layer and the encapsulation layer with the screen-printed electrode layer together with double-sided adhesive, the flexible pressure sensor is obtained.

[0040] Example 2: A flexible pressure sensor includes a substrate layer, a microstructure sensing layer, a microstructure protective layer, an adhesive isolation layer, an electrode layer, and an encapsulation layer; The substrate layer is a flexible sheet material, made of PI, with a thickness of 0.25 mm; The microstructure sensing layer is obtained by etching a conductive composite material coating, and the sheet resistance of the conductive composite material coating is 10kΩ / □. The microstructure protective layer is obtained by etching an elastic polydimethylsiloxane coating with a hardness of 20A. The adhesive isolation layer is a double-sided adhesive with a PI substrate and a thickness of 0.15 mm; The electrode layer is an interdigitated electrode array; The encapsulation layer is a flexible sheet material made of PI material with a thickness of 0.2 mm.

[0041] A method for fabricating a flexible pressure sensor includes the following steps: Step 1: Apply conductive composite material to the substrate layer using a scraper. After drying, a conductive composite material coating with a thickness of 40 μm is obtained. The preparation method of the conductive composite material is as follows: 100 parts of epoxy resin and 20 parts of 1-methyl-2-pyrrolidone are added to a reaction vessel, heated to 60°C, stirred at 3000 r / min for 0.5 h, 20 parts of conductive filler are added, and stirred at 2000 r / min for 1 h, cooled to 40°C, then 0.5 parts of ethylenediamine and 5 parts of wax emulsion are added, and the reaction is stirred for 1 h. After cooling to room temperature, the mixture is ground, the roller spacing is adjusted to ensure that the fineness of the slurry after grinding is below 20 μm, the mixture is filtered out, and the viscosity is adjusted to 5000 cps. After thorough mixing, the conductive composite material is obtained. The conductive filler is obtained by mixing carbon black, copper powder and graphite in a mass ratio of 1:1:1, and the average particle size of carbon black, copper powder and graphite is 0.5μm-100μm. Step 2: Apply a layer of polydimethylsiloxane material to the conductive composite material coating obtained in step 1 by screen printing or spraying using a spraying machine. After drying, the thickness of the polydimethylsiloxane coating is 5 μm. Step 3: Establish a three-dimensional microstructure sensing array pattern. Use an infrared picosecond laser marking machine to etch the polydimethylsiloxane coating and the conductive composite material coating layer by layer. After etching, a microstructure protective layer and a microstructure sensing layer are formed. The cross-sectional area of ​​the microstructure protective layer and the microstructure sensing layer gradually increases from top to bottom, presenting a pyramid-shaped structure. The etching depth is 20μm. The infrared picosecond laser marking machine has the following process: wavelength of 1026-1064nm, pulse energy of 1.0mJ, repetition frequency of 300kHz, focused spot diameter controlled at 1μm, and interlayer Z-axis step size of 2μm.

[0042] Step 4: Silkscreen the interdigitated electrode array layer on the encapsulation layer; Step 5: After bonding the microstructure protective layer and the encapsulation layer with the screen-printed electrode layer together with double-sided adhesive, the flexible pressure sensor is obtained.

[0043] Example 3: A flexible pressure sensor includes a substrate layer, a microstructure sensing layer, a microstructure protective layer, an adhesive isolation layer, an electrode layer, and an encapsulation layer; The substrate layer is a flexible sheet material, made of PEI, with a thickness of 0.08 mm; The microstructure sensing layer is a conductive composite material coating with a sheet resistance of 200kΩ / □. The microstructure protective layer is an elastic polyurethane coating with a hardness of 60A. The double-sided adhesive of the PET substrate used for the bonding and isolation layer has a thickness of 0.12 mm. The electrode layer is an interdigitated electrode array; The encapsulation layer is a flexible sheet material made of PEI with a thickness of 0.25mm.

[0044] A method for fabricating a flexible pressure sensor includes the following steps: Step 1: Apply conductive composite material to the substrate layer using a scraper, and after drying, obtain a conductive composite material coating with a thickness of 50 μm. The preparation method of the conductive composite material is as follows: 100 parts of epoxy resin and 10 parts of 1-methyl-2-pyrrolidone are added to a reaction vessel, heated to 50°C, stirred at 3000 r / min for 1 h, 5 parts of conductive filler are added, and stirred at 1000 r / min for 2 h, cooled to 40°C, then 0.1 parts of ethylenediamine and 1 part of wax emulsion are added, and the reaction is stirred for 2 h. After cooling to room temperature, the slurry is ground, the roller spacing is adjusted to ensure that the fineness of the ground slurry is below 20 μm, filtered, and then the viscosity is adjusted to 8000 cps. After thorough mixing, the conductive composite material is obtained. The conductive filler is obtained by mixing carbon black, copper powder and graphite in a mass ratio of 1:1:1, and the average particle size of carbon black, copper powder and graphite is 0.5μm-100μm. Step 2: A layer of polyurethane is screen-printed onto the conductive composite material layer obtained in Step 1 using a screen printing machine. After drying, a polyurethane coating with a thickness of 3 μm is formed. Step 3: Establish a three-dimensional microstructure sensing array pattern. Use an infrared picosecond laser marking machine to etch the polyurethane coating and conductive composite material coating layer by layer. After etching, a microstructure protective layer and a microstructure sensing layer are formed. The cross-sectional area of ​​the microstructure protective layer and the microstructure sensing layer gradually increases from top to bottom, presenting a trapezoidal structure. The etching depth is 15μm. The process parameters of the infrared picosecond laser marking machine are as follows: wavelength of 1026-1064nm, pulse energy of 0.2mJ, repetition frequency of 100kHz, focused spot diameter controlled at 3μm, and interlayer Z-axis step size of 3μm.

[0045] Step 4: Silkscreen the interdigitated electrode array layer on the encapsulation layer; Step 5: After bonding the microstructure protective layer and the encapsulation layer with the screen-printed electrode layer together with double-sided adhesive, the flexible pressure sensor is obtained.

[0046] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that no microstructure protective layer was provided in Comparative Example 1, but otherwise it is the same as Example 1.

[0047] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the microstructure protective layer in Comparative Example 2 uses an epoxy resin coating, while the rest is the same as in Example 1.

[0048] Comparative Example 3: Compared with Example 3, Comparative Example 3 differs in that the process parameters of the infrared picosecond laser marking machine in Comparative Example 3 are different. The interlayer Z-axis step size in Comparative Example 3 is 5 μm. After laser marking, it was found that the microstructure sensing layer did not form a regular microstructure.

[0049] The consistency, range, and other performance characteristics of the flexible pressure sensors prepared in Examples 1-3 and Comparative Examples 1-2 were evaluated, and the results are shown in Table 1 below.

[0050] Table 1: Performance Evaluation Results

[0051] As can be seen from the data in Table 1, by combining a high-modulus microstructure sensing layer with an elastic microstructure protective layer, the sensors prepared in Examples 1-3 have lower trigger pressure and better consistency compared to Comparative Examples 1 and 2, and can adapt to different application scenarios with a higher measurement range.

[0052] in addition, Figure 1 for Figure 1 This is a schematic diagram of the interdigitated electrode array used in Embodiment 1 of the present invention, which is selected as a 5*6 array with a total of 30 counter electrodes; Figure 2 This is a schematic diagram of the microstructure sensing layer in Embodiment 1 of the present invention. Figure 2 As can be seen from the figure, the flexible pressure sensor obtained in Embodiment 1 of the present invention is etched to obtain an arc-shaped microstructure, wherein 1-1 is a microstructure protective layer; 1-2 is a conductive composite material layer; and 1-3 is a base layer. Figure 3 This is a schematic diagram of the microstructure sensing layer in Embodiment 2 of the present invention; from Figure 3 As can be seen from the image, Example 3 etched a pyramid-shaped microstructure, where 2-1 is the microstructure protective layer; 2-2 is the conductive composite material layer; and 2-3 is the base layer. Figure 4 This is a schematic diagram of the microstructure sensing layer in Embodiment 3 of the present invention; from Figure 4 As can be seen from the figure, the trapezoidal microstructure obtained by etching in Example 3 is shown in the figure. 3-1 is the microstructure protective layer; 3-2 is the conductive composite material layer; and 3-3 is the base layer. Figure 5 This is a SEM image of the microstructure sensing layer and conductive composite material layer in Embodiment 3 of the present invention. From... Figure 5 As can be seen, the etched flexible pressure sensor can form a number of microstructures. Figure 6 This is a piezoresistive curve of the pressure sensor prepared in Embodiment 1 of the present invention. Figure 6 As can be seen from the above, the flexible pressure sensor obtained in Embodiment 1 of the present invention has excellent piezoresistive sensitivity and high accuracy.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A flexible pressure sensor, characterized in that, The flexible pressure sensor includes a base layer, a microstructure sensing layer, a microstructure protective layer, an adhesive isolation layer, an electrode layer, and an encapsulation layer. The microstructure sensing layer is obtained by etching a conductive composite material coating. The microstructure protective layer is obtained by etching an elastic polyurethane coating and / or a polydimethylsiloxane coating.

2. The flexible pressure sensor according to claim 1, characterized in that, The thickness of the substrate layer is 0.08mm-0.25mm; the substrate layer is a flexible sheet material.

3. The flexible pressure sensor according to claim 1, characterized in that, The raw materials for preparing the conductive composite material coating include epoxy resin and conductive filler, and the sheet resistance of the conductive composite material coating ranges from 0.3kΩ / □ to 200kΩ / □.

4. The flexible pressure sensor according to claim 1, characterized in that, The hardness of the elastic polyurethane coating and / or polydimethylsiloxane coating is 20A-60A.

5. The flexible pressure sensor according to claim 1, characterized in that, The adhesive release layer is a double-sided adhesive with a PET or PI substrate and a thickness of 0.1mm-0.15mm. The electrode layer is an interdigitated electrode array; The encapsulation layer is a flexible sheet material with a thickness of 0.08mm-0.25mm.

6. A method for fabricating a flexible pressure sensor, characterized in that, The preparation method is used to prepare the flexible pressure sensor according to any one of claims 1 to 5, and the preparation method includes the following steps: Step 1: Prepare a conductive composite material, and coat the conductive composite material onto a substrate layer and dry it to obtain a conductive composite material coating; Step 2: On the conductive composite material coating obtained in Step 1, polyurethane material and / or polydimethylsiloxane material are screen-printed or sprayed using a screen printing machine or a spraying machine. After drying, a polyurethane coating and / or a polydimethylsiloxane coating are formed. Step 3: Establish a three-dimensional microstructure sensing array pattern. Use an infrared picosecond laser marking machine to etch polyurethane coating and / or polydimethylsiloxane coating and conductive composite material coating layer by layer. After etching, a microstructure protective layer and a microstructure sensing layer are formed. The cross-sectional area of ​​the microstructure protective layer and the microstructure sensing layer gradually increases from top to bottom, presenting a circular arc structure, a pyramid structure, and a trapezoidal structure. The etching depth is 15μm-30μm. Step 4: Silkscreen the interdigitated electrode array onto the encapsulation layer; Step 5: After bonding the microstructure protective layer and the encapsulation layer with the screen-printed electrode layer together with double-sided adhesive, the flexible pressure sensor is obtained.

7. The preparation method according to claim 6, characterized in that, The thickness of the conductive composite material coating is 30μm-50μm; the thickness of the microstructure protective layer is 3μm-10μm.

8. The preparation method according to claim 6, characterized in that, The method for preparing the conductive composite material is as follows: Epoxy resin and solvent are added to a reaction vessel and heated to 50℃-80℃. The mixture is stirred at 1000-3000 r / min for 0.5-1 h. Then, conductive filler is added and stirred at 1000-3000 r / min for another 0.5-2 h. The temperature is then lowered to 30℃-40℃. Curing agent and anti-sticking agent are added, and the mixture is stirred for another 1-3 h. After cooling to room temperature, the mixture is ground. The roller spacing is adjusted to ensure that the fineness of the slurry after grinding is below 20 μm. The mixture is then filtered and the viscosity is adjusted to 5000 cps-12000 cps. After thorough mixing, the conductive composite material is obtained.

9. The preparation method according to claim 8, characterized in that, The conductive filler is obtained by mixing carbon black, copper powder and graphite in a mass ratio of (1~3):(1~2):(1~3), and the average particle size of the carbon black, copper powder and graphite is 0.5μm-100μm.

10. The preparation method according to claim 8, characterized in that, The process parameters of the infrared picosecond laser marking machine are: wavelength of 1026nm-1064nm, pulse energy of 0.2mJ-2.0mJ, repetition frequency of 100kHz-500kHz, focused spot diameter controlled at 1μm-3μm, and interlayer Z-axis step size of 1μm-3μm.

Images