A pressure-sensitive resistive flexible array sensor and method of manufacture

Abstract

The application discloses a pressure-sensitive resistive flexible array sensor and a preparation method thereof. The sensor comprises a first flexible circuit board, a second flexible circuit board and a pressure-sensitive resistive layer between the first and second flexible circuit boards, and a first conductive electrode and a second conductive electrode intersect to form a cross electrode array. The pressure-sensitive resistive layer is prepared by film formation of a polymer and an aqueous solution of conductive filler, and the first and second substrates are both air-permeable substrates. The preparation process comprises the following steps: preparing a polymer aqueous solution A and an aqueous solution of conductive filler B respectively, mixing, stirring and centrifuging to obtain a mixed solution C; coating C on the first flexible circuit board by scraping and drying to form a pressure-sensitive resistive film; and finally covering the second flexible circuit board, extruding and further drying to obtain the finished product. The application solves the problems of poor air permeability of the existing sensor, environmental pollution in the preparation process, serious array signal crosstalk, complex process, high cost and being not conducive to large-scale production.

Description

Technical Field

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

[0002] Flexible piezoresistive materials play an important role in the field of flexible technology applications due to their stable electrical properties, excellent pressure sensitivity, and fast response characteristics. This technology is widely used in health monitoring (such as foot health monitoring and heartbeat monitoring), smart wearable devices (such as smart clothing physiological parameter monitoring), and tactile feedback systems (such as motion trajectory analysis). Compared with traditional sensing devices, flexible sensing technology effectively overcomes problems such as complex wiring, difficulty in achieving real-time monitoring, and poor user experience, and significantly improves the overall performance of pressure sensors in terms of user experience and structural form.

[0003] Currently, common flexible array sensors typically consist of an electrode layer and a pressure-sensitive layer. The electrode layer often uses flexible printed circuit boards (FPCs) or PET films coated with metal electrodes, while the pressure-sensitive layer often uses elastomers such as PDMS, Ecoflex, and polyurethane as the matrix material and is constructed by incorporating conductive fillers such as carbon nanotubes, graphene, or carbon powder. Although existing flexible array sensors possess certain functional capabilities, they still suffer from the following technical shortcomings: First, the preparation process of the pressure-sensitive layer requires the conductive filler to be dispersed in volatile or toxic organic solvents for mixing and film formation. These organic solvents pollute the environment and do not conform to the concept of green environmental protection. Second, the preparation process of the pressure-sensitive layer is complex and cumbersome, and the cost is high, which is not conducive to large-scale mass production. Third, the materials used in the preparation of pressure-sensitive layers are mostly dense structures, which can easily cause skin discomfort in application scenarios where they are in long-term contact with the skin, lack breathability, and affect the comfort of use. Fourth, most existing flexible array sensors use external electronic devices, external electrical signal output circuits and shared loops. Under pressure, they are susceptible to interference between substrate layers, resulting in unstable electrical signal output and signal crosstalk problems, which limit the accuracy and reliability of the detection results. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a piezoresistive flexible array sensor and its fabrication method, which solves the problems of poor air permeability, environmental pollution during fabrication, severe crosstalk in array signals, low sensitivity, complex processes, high costs, and unfavorable conditions for large-scale production in existing sensors. The present invention provides a piezoresistive flexible array sensor, comprising: A first flexible circuit board includes a first substrate and a first conductive electrode. The first conductive electrode is arranged on the side of the first substrate facing the varistor layer. The first conductive electrode includes a plurality of conductive lines extending along a first direction. The second flexible circuit board includes a second substrate and a second conductive electrode. The second conductive electrode is arranged on the side of the second substrate facing the varistor layer. The second conductive electrode includes a plurality of conductive lines extending along a second direction. A varistor layer is disposed between the first flexible circuit board and the second flexible circuit board; The first conductive electrode and the second conductive electrode intersect to form a cross electrode array; The varistor layer is prepared by forming a film from an aqueous solution of polymer and conductive filler; Both the first substrate and the second substrate are made of breathable substrate.

[0005] Furthermore, the materials of the first substrate and the second substrate are respectively selected from at least one of polyisoprene, polybutadiene, polyphenylene sulfide, polyimide, polyether ether imide, polycarbonate, polyethylene naphthalate, polyester, silicone, thermoplastic polyurethane, polyether ether ketone, polytetrafluoroethylene, SBS, and SEBS.

[0006] Furthermore, the materials of the first conductive electrode and the second conductive electrode are respectively selected from at least one of gold, silver, copper foil, liquid metal alloy, water-soluble silver nanowires, conductive silver paste, graphene, carbon nanotube paste, gallium indium alloy, copper ink, and conductive carbon paste.

[0007] Furthermore, the first conductive electrode and the second conductive electrode are prepared by a flexible printed circuit manufacturing process, wherein the flexible printed circuit manufacturing process is selected from any one of screen printing, circuit printing, inkjet printing, aerosol printing, gravure printing, flexographic printing, and nano-jet printing, so as to print the first conductive electrode and the second conductive electrode on the first substrate and the second substrate respectively.

[0008] Furthermore, the conductive filler material is selected from at least one of carbon nanotubes, graphene, fullerene, liquid metal, carbon black, conductive silver paste, silver nanowires, gold nanowires, and conductive silicone grease.

[0009] Furthermore, the polymer material is selected from at least one of polyurethane, thermoplastic elastomer, polyacrylic acid, natural rubber, synthetic rubber, fluorocarbon elastomer, acrylic gel, sodium alginate hydrogel, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, sodium polyacrylate, cellulose derivatives, SBS, and SEBS.

[0010] Furthermore, the mass fraction of the aqueous solution of the polymer is 10% to 90%, and the mass fraction of the aqueous solution of the conductive filler is 1% to 40%. In the varistor layer, the conductive filler is uniformly dispersed in the matrix formed by the polymer and constructs a conductive network for generating electrical signals.

[0011] Further, the width of the first conductive electrode and the second conductive electrode in the corresponding arrangement direction is 0.1mm~5mm, the thickness is 0.01mm~0.1mm, and the spacing between adjacent conductive lines is 0.01mm~3mm; the thickness of the first flexible circuit board and the second flexible circuit board is 0.01mm~1mm; the thickness of the varistor layer is 0.01mm~1mm; the surface resistance of the varistor layer is 0.1kΩ~100MΩ; the volume resistivity of the varistor layer is 0.1kΩ·cm~100MΩ·cm; and the overall thickness of the varistor flexible array sensor is 0.05mm~0.5mm.

[0012] The present invention also provides a method for fabricating the above-mentioned piezoresistive flexible array sensor, comprising the following steps: (1) Disperse the polymer in water and mix thoroughly by stirring to obtain aqueous solution A; (2) Disperse the conductive filler in water and mix thoroughly by stirring to obtain aqueous solution B; (3) Mix aqueous solution A and aqueous solution B, stir, and centrifuge at high speed to obtain mixed solution C; (4) The mixture C is scraped onto the first flexible circuit board and dried to form a varistor film; (5) Cover the surface of the varistor film with the second flexible circuit board, squeeze it, and dry it to obtain the varistor flexible array sensor.

[0013] The solid content of the aqueous solution A is 1wt%~60wt%; The solid content of the aqueous solution B is 5wt%~20wt%; The stirring time in steps (1), (2), and (3) is 30 min to 12 h; The thickness of the varistor film is 20μm~200μm; The drying time for step (4) is 10 min to 6 h; The drying time for step (5) is 6h~12h; The drying temperature in steps (4) and (5) is 25℃~100℃.

[0014] The beneficial effects of this invention are: (1) The varistor layer of the present invention is prepared by a film-forming process using an aqueous solution of polymer and conductive filler. The entire process uses an aqueous solution system, which avoids the use of organic solvents, thus reducing the preparation cost and avoiding the pollution of the environment by organic solvents from the source. The preparation process is more green and environmentally friendly and has better safety. (2) The preparation process of the varistor layer is simple. It can be completed by simple processes such as mixing, stirring, centrifugation, coating, drying and extrusion. It does not require expensive equipment, which simplifies the preparation process, reduces the preparation difficulty, and is more suitable for high-efficiency large-scale industrial production. (3) Using a breathable substrate as the base material of the flexible circuit board can enhance the breathability of the flexible circuit board, reduce the discomfort caused by long-term contact with the skin, and improve the comfort when wearing it. (4) By combining the cross electrode array and the uniformly distributed conductive network, the signal crosstalk between sensing units can be effectively reduced under pressure, thereby improving the accuracy and reliability of the detection results. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure and cross-electrode signal principle of the present invention; Figure 2 This is a schematic diagram of the preparation process of the present invention; Figure 3 This is a schematic diagram of the state of sample A formed after the mixture is coated and dried on the lower flexible circuit board during the preparation process of this invention; Figure 4 This is a schematic diagram showing the state of the varistor film formed by peeling off the coating after drying according to the present invention. Figure 5 This is a schematic diagram of the thickness distribution at different array points of the present invention; Figure 6 This is a schematic diagram of the resistance distribution at different array points of the present invention; Figure 7 This is a schematic diagram illustrating the change in the rate of resistance under multiple cycles of pressure according to the present invention. Figure 8 This is a planar schematic diagram of different pressing areas of the present invention; Figure 9 This is a graph showing the resistance change data of an existing conventional array sensor when pressing area 1 and acquiring signals from area 1. Figure 10 This is a graph showing the resistance change data of an existing conventional array sensor when pressing region 2 and acquiring signals from region 1. Figure 11 This is a graph showing the resistance change data when pressing area 1 and collecting signals from area 1 according to the present invention; Figure 12This is a graph showing the resistance change data when pressing area 2 and collecting signals from area 1 according to the present invention. Detailed Implementation

[0016] This invention discloses a piezoresistive flexible array sensor, specifically comprising: The first flexible circuit board (i.e.) Figure 1 The lower FPC in the middle includes a first substrate and a first conductive electrode. The first conductive electrode is arranged on the side of the first substrate facing the varistor layer. The first conductive electrode includes a plurality of conductive lines extending along a first direction. The second flexible circuit board (i.e.) Figure 1 The upper FPC in the middle includes a second substrate and a second conductive electrode. The second conductive electrode is arranged on the side of the second substrate facing the varistor layer. The second conductive electrode includes a plurality of conductive lines extending along a second direction. Varistor layer (i.e.) Figure 1 The sensitive layer in the middle is disposed between the first flexible circuit board and the second flexible circuit board and is used to bond the first flexible circuit board and the second flexible circuit board together. The first flexible circuit board, the varistor layer, and the second flexible circuit board form a "sandwich composite structure".

[0017] The first conductive electrode and the second conductive electrode intersect to form a cross electrode array, and the first direction and the second direction are preferably perpendicular to each other.

[0018] The varistor layer is prepared by forming a film from an aqueous solution of polymer and conductive filler; Both the first substrate and the second substrate are made of breathable substrate, and the materials of the first substrate and the second substrate are respectively selected from at least one of polyisoprene, polybutadiene, polyphenylene sulfide, polyimide, polyether etherimide, polycarbonate, polyethylene naphthalate, polyester, silicone, thermoplastic polyurethane, polyether ether ketone, polytetrafluoroethylene, SBS, and SEBS.

[0019] The materials of the first conductive electrode and the second conductive electrode are respectively selected from at least one of gold, silver, copper foil, liquid metal alloy, water-soluble silver nanowires, conductive silver paste, graphene, carbon nanotube paste, gallium indium alloy, copper ink, and conductive carbon paste.

[0020] Both the first flexible circuit board and the second flexible circuit board are FPC (Flexible Printed Circuit) boards, i.e., flexible printed circuit boards. The conductive patterns of the first conductive electrode and the second conductive electrode are prepared by flexible printed circuit manufacturing process. The flexible printed circuit manufacturing process is selected from any one of screen printing, circuit printing, inkjet printing, aerosol printing, gravure printing, flexographic printing, and nano-jet printing.

[0021] The conductive filler material is selected from at least one of carbon nanotubes, graphene, fullerene, liquid metal, carbon black, conductive silver paste, silver nanowires, gold nanowires, and conductive silicone grease.

[0022] The polymer is selected from at least one of polyurethane, thermoplastic elastomer, polyacrylic acid, natural rubber, synthetic rubber, fluorocarbon elastomer, acrylic gel, sodium alginate hydrogel, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, sodium polyacrylate, cellulose derivatives, SBS, and SEBS.

[0023] The mass fraction of the aqueous solution of the polymer is 10% to 90%, and the mass fraction of the aqueous solution of the conductive filler is 1% to 40%. In the varistor layer, the conductive filler is uniformly dispersed in the matrix formed by the polymer and forms a conductive network for generating electrical signals.

[0024] The width of the first and second conductive electrodes in their corresponding arrangement directions is 0.1mm~5mm, and the thickness is 0.01mm~0.1mm, with a spacing of 0.01mm~3mm between adjacent conductive lines; the thickness of the first and second flexible circuit boards is 0.01mm~1mm; the thickness of the varistor layer is 0.01mm~1mm; the surface resistance of the varistor layer is 0.1kΩ~100MΩ; the volume resistivity of the varistor layer is 0.1kΩ·cm~100MΩ·cm; and the overall thickness of the varistor-type flexible array sensor is 0.05mm~0.5mm.

[0025] The method for fabricating the piezoresistive flexible array sensor of the present invention, as follows: Figure 2 As shown, it includes the following steps: (1) Disperse the polymer in water and mix thoroughly by stirring to obtain aqueous solution A; (2) Disperse the conductive filler in water and mix thoroughly by stirring to obtain aqueous solution B; (3) Mix aqueous solution A and aqueous solution B, stir, and centrifuge at high speed to obtain mixed solution C; (4) The mixture C is scraped onto the first flexible circuit board and dried to form a varistor film; (5) Cover the surface of the varistor film with the second flexible circuit board, squeeze it, and dry it to obtain the varistor flexible array sensor.

[0026] Furthermore, in the fabrication method of the aforementioned piezoresistive flexible array sensor: The solid content of the aqueous solution A is 1wt%~60wt%; The solid content of the aqueous solution B is 5wt%~20wt%; The stirring time in steps (1), (2), and (3) is 30 min to 12 h; The thickness of the varistor film is 20μm~200μm; The drying time for step (4) is 10 min to 6 h; The drying time for step (5) is 6h~12h; The drying temperature in steps (4) and (5) is 25℃~100℃.

[0027] In the piezoresistive layer, the selection and ratio of the elastic matrix and conductive filler have a significant impact on the sensitivity and stability of the sensor. In some preferred embodiments, the specific limitations of each component are as follows: Polymer matrix selection and solid content limitation The polymer raw materials used in this invention are preferably commercially available water-based materials to ensure the green and environmentally friendly nature of the process. Waterborne polyurethane (WPU): The preferred solid content range is 20wt%-50wt%; Polyacrylate emulsion: The preferred solid content range is 30wt%-60wt%; Acrylic gel: The preferred solid content range is 30wt%-60wt%; Polyvinyl alcohol (PVA): The preferred solid content range is 20wt%-50wt%; Sodium alginate, natural rubber and cellulose derivatives: The preferred solid content range is 1wt%-10wt%.

[0028] Selection of conductive fillers and limits on solid content The conductive filler is used to construct a conductive network within the matrix. In some preferred embodiments: Carbon nanotube slurry: Commercially available single-walled carbon nanotube slurry is preferred, with a solid content ranging from 5wt% to 30wt%. Other fillers: The conductive filler may be further selected from at least one of graphene, fullerene, liquid metal, gold nanowires, and conductive silicone grease.

[0029] Mass fraction limit of varistor layer material To balance the flexibility and electrical response of the sensor, the preferred mass fraction ratio of each component in the varistor layer material is as follows: The polymer components (including waterborne polyurethane, polyacrylate emulsion, sodium alginate, natural rubber, acrylic gel, polyvinyl alcohol, cellulose derivatives, etc.) are preferably 3%-50% by mass in the flexible piezoresistive array sensor material; The mass fraction of conductive filler components (including carbon nanotube slurry, graphene, liquid metal, gold nanowires, conductive silicone grease, etc.) in the flexible piezoresistive array sensor material is preferably 1%-40%.

[0030] This invention proposes a flexible array sensor based on a sandwich composite structure of a flexible printed circuit board (FPC)-varistor layer-flexible printed circuit board (FPC) and a green and environmentally friendly fabrication process suitable for large-scale mass production. This solves several technical challenges faced by traditional flexible varistors in production and application. The process significantly simplifies the sensor fabrication process, reduces production costs, and improves production efficiency. At the material level, the sensitive layer uses an aqueous solution system, avoiding environmental pollution from organic solvents at the source. This design, while ensuring electrical signal stability, improves the sensor's breathability and wearing comfort, reducing discomfort caused by prolonged skin contact.

[0031] The flexible piezoresistive array sensor of the present invention has broad application prospects in many fields such as health monitoring (e.g., foot health monitoring, heartbeat monitoring), smart wearable devices (e.g., smart clothing physiological parameter monitoring) and tactile feedback systems (e.g., motion trajectory analysis).

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of the invention.

[0033] Example 1: (1) Take an appropriate amount of 30g of commercial waterborne polyurethane (the solid content of waterborne polyurethane is 40wt%), 10g of commercial polyacrylate emulsion (the solid content of polyacrylate emulsion is 50wt%), and 20g of sodium alginate aqueous solution as polymer (the solid content of sodium alginate aqueous solution is 8wt%), and mix them thoroughly for 12h by mechanical stirring, magnetic stirring, etc. to obtain polymer aqueous solution A for preparing the varistor layer; (2) Disperse 10g of commercial carbon nanotube slurry (the solid content of carbon nanotube slurry is 30wt%) in water and mix thoroughly for 2h by mechanical stirring, magnetic stirring, etc. to obtain the conductive filler aqueous solution B for preparing the varistor layer; (3) The polymer aqueous solution A for preparing the varistor layer and the conductive filler aqueous solution B for preparing the varistor layer are thoroughly mixed for 3 hours by mechanical stirring, magnetic stirring, etc., and pretreated by high-speed centrifugation to obtain a uniform varistor layer resistor solution mixture, which is the mixture C for preparing the varistor layer. (4) The mixture C was coated onto the lower FPC plate and dried at room temperature (25°C) for 6 hours to obtain sample A with a varistor layer covering the surface of the lower FPC plate; a varistor layer with a thickness of about 200 μm was obtained. (5) Cover the sample surface with the upper FPC plate, then squeeze it, and further dry it at room temperature for 12 hours to obtain the piezoresistive flexible array sensor.

[0034] Example 2: A pressure-sensitive resistor type flexible array sensor material differs from Example 1 only in that the elastomer polyurethane in the elastic matrix is ​​replaced with styrene-butadiene rubber. The other raw material ratios, preparation parameters and preparation methods are the same as in Example 1. The difference is that the amount of styrene-butadiene rubber used is adjusted according to the solid content of the aqueous emulsion of styrene-butadiene rubber, so that the mass fraction of styrene-butadiene rubber in the stretchable conductive material is consistent with the mass fraction of polyurethane in Example 1.

[0035] Example 3: A pressure-sensitive resistor type flexible array sensor material differs from Example 1 only in that the elastomeric polyurethane in the elastic matrix is ​​replaced with ethylene-vinyl acetate copolymer. The other raw material ratios, preparation parameters, and preparation methods are the same as in Example 1. The difference is that the amount of ethylene-vinyl acetate copolymer used is adjusted according to its solid content to ensure that the mass fraction of styrene-butadiene rubber in the stretchable conductive material is consistent with the mass fraction of polyurethane in Example 1.

[0036] Example 4: A pressure-sensitive resistor type flexible array sensor material differs from Example 1 only in that the mass of aqueous polyurethane in the elastic matrix in polymer aqueous solution A is changed to 40g, while the other raw material ratios, preparation parameters and preparation methods are the same as in Example 1.

[0037] Example 5: A piezoresistive flexible array sensor material differs from Example 1 only in that the solid content of sodium alginate aqueous solution in the elastic matrix is ​​changed to 10wt%, while the other raw material ratios, preparation parameters and preparation methods are the same as in Example 1.

[0038] Example 6: A piezoresistive flexible array sensor material differs from Example 1 only in that the single-walled carbon nanotubes in the conductive filler are replaced with double-walled carbon nanotubes. The other raw material ratios, preparation parameters, and preparation methods are the same as in Example 1.

[0039] Example 7: A piezoresistive flexible array sensor material differs from Example 1 only in that the single-walled carbon nanotubes in the conductive filler are replaced with multi-walled carbon nanotubes. The other raw material ratios, preparation parameters, and preparation methods are the same as in Example 1.

[0040] Example 8: A piezoresistive flexible array sensor material differs from Example 1 only in that the mass of carbon nanotube slurry in the conductive filler is changed to 15g, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 1.

[0041] Example 9: A piezoresistive flexible array sensor material differs from Example 1 only in that the mass of carbon nanotube slurry in the conductive filler is changed to 20g, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 1.

[0042] Example 10: (1) Take an appropriate amount of 20g natural rubber, 10g polyvinyl alcohol (polyvinyl alcohol solid content is 20wt%), 10g acrylic gel (acrylic gel solid content is 40wt%), and 20g cellulose derivative as polymers, and mix them thoroughly for 12h by mechanical stirring, magnetic stirring, etc. to obtain polymer aqueous solution A for preparing varistor layer; (2) Disperse 8g of graphene slurry (the solid content of graphene slurry is 30wt%) and 2g of conductive silicone grease (the solid content of conductive silicone grease is 40wt%) in water, and mix thoroughly for 2h by mechanical stirring, magnetic stirring, etc., to obtain the conductive filler aqueous solution B for preparing the varistor layer; (3) The polymer aqueous solution A for preparing the varistor layer and the conductive filler aqueous solution B for preparing the varistor layer are thoroughly mixed for 3 hours by mechanical stirring, magnetic stirring, etc., and pretreated by high-speed centrifugation to obtain a uniform varistor layer resistor solution mixture to obtain the varistor layer mixture C. (4) The mixture C was coated onto the lower FPC plate and dried at room temperature (25°C) for 6 hours to obtain sample A with a varistor layer covering the surface of the lower FPC plate; a varistor layer with a thickness of about 200 μm was obtained. (5) Cover the sample surface with the upper FPC plate, then squeeze it, and further dry it at room temperature for 12 hours to obtain the piezoresistive flexible array sensor.

[0043] Example 11: A pressure-sensitive resistor-type flexible array sensor material differs from Example 10 only in that the acrylic gel in the elastic matrix is ​​replaced with sodium polyacrylate. All other raw material ratios, preparation parameters, and preparation methods are the same as in Example 10. The difference lies in adjusting the amount of sodium polyacrylate used based on its solid content, ensuring that the mass fraction of sodium polyacrylate in the stretchable conductive material remains consistent with the mass fraction of the acrylic gel in Example 10.

[0044] Example 12: A piezoresistive flexible array sensor material differs from Example 10 only in that the graphene slurry in the conductive filler is replaced with liquid metal. All other raw material ratios, preparation parameters, and preparation methods are the same as in Example 10. The difference lies in adjusting the amount of liquid metal used based on its solid content, ensuring that the mass fraction of liquid metal in the stretchable conductive material remains consistent with the mass fraction of graphene in Example 10.

[0045] Example 13: A piezoresistive flexible array sensor material differs from Example 10 only in that the graphene slurry in the conductive filler is replaced with gold nanowires. All other raw material ratios, preparation parameters, and preparation methods are the same as in Example 10. The difference lies in adjusting the amount of gold nanowires used based on their solid content, ensuring that the mass fraction of gold nanowires in the stretchable conductive material remains consistent with the mass fraction of graphene in Example 10.

[0046] Example 14: A pressure-sensitive resistor type flexible array sensor material differs from Example 10 only in that the mass of the cellulose derivative in the elastic matrix is ​​changed to 30g, while the other raw material ratios, preparation parameters and preparation methods are the same as in Example 10.

[0047] Example 15: A pressure-sensitive resistor type flexible array sensor material differs from Example 10 only in that the solid content of polyvinyl alcohol in the elastic matrix is ​​changed to 30wt%, while the other raw material ratios, preparation parameters and preparation methods are the same as in Example 10.

[0048] Example 16: A piezoresistive flexible array sensor material differs from Example 10 only in that the solid content of the graphene slurry in the conductive filler is changed to 40wt%, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 10.

[0049] Example 17: A piezoresistive flexible array sensor material differs from Example 10 only in that the solid content of conductive silicone grease in the conductive filler is changed to 50wt%, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 10.

[0050] Example 18: (1) 60g of commercial waterborne polyurethane (waterborne polyurethane solid content of 40wt%) was used as polymer aqueous solution A for preparing the varistor layer; (2) Disperse 8g of conductive silver paste (conductive silver paste solid content is 60wt%) and 2g of conductive silicone grease (conductive silicone grease solid content is 40wt%) in water, and mix thoroughly for 2h by mechanical stirring, magnetic stirring, etc. to obtain conductive filler aqueous solution B for preparing varistor layer; (3) The polymer aqueous solution A for preparing the varistor layer and the conductive filler aqueous solution B for preparing the varistor layer are thoroughly mixed for 3 hours by mechanical stirring, magnetic stirring, etc., and pretreated by high-speed centrifugation to obtain a uniform varistor layer resistor solution mixture to obtain the varistor layer mixture C. (4) The mixture C was coated onto the lower FPC plate and dried at room temperature (25°C) for 6 hours to obtain sample A with a varistor layer covering the surface of the lower FPC plate; a varistor layer with a thickness of about 200 μm was obtained. (5) Cover the sample surface with the upper FPC plate, then squeeze it, and further dry it at room temperature for 12 hours to obtain the piezoresistive flexible array sensor.

[0051] Example 19: A piezoresistive flexible array sensor material differs from Example 18 only in that the conductive silver paste in the conductive filler is replaced with multi-walled carbon nanotubes. All other raw material ratios, preparation parameters, and preparation methods are the same as in Example 18. The difference lies in adjusting the amount of multi-walled carbon nanotubes used based on their solid content, ensuring that the mass fraction of multi-walled carbon nanotubes in the stretchable conductive material remains consistent with the mass fraction of conductive silver paste in Example 18.

[0052] Example 20: A piezoresistive flexible array sensor material differs from Example 18 only in that the conductive silver paste in the conductive filler is replaced with liquid metal. All other raw material ratios, preparation parameters, and preparation methods are the same as in Example 18. The difference lies in adjusting the amount of liquid metal used based on its solid content, ensuring that the mass fraction of liquid metal in the stretchable conductive material remains consistent with the mass fraction of conductive silver paste in Example 18.

[0053] Example 21: A pressure-sensitive resistor type flexible array sensor material differs from Example 18 only in that the mass of waterborne polyurethane in the elastic matrix is ​​changed to 70g, while the other raw material ratios, preparation parameters and preparation methods are the same as in Example 18.

[0054] Example 22: A piezoresistive flexible array sensor material differs from Example 18 only in that the solid content of conductive silver paste in the conductive filler is changed to 70wt%, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 18.

[0055] Example 23: A piezoresistive flexible array sensor material differs from Example 18 only in that the mass of conductive silver paste in the conductive filler is changed to 10g, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 18.

[0056] Example 24: A piezoresistive flexible array sensor material differs from Example 18 only in that the mass of conductive silicone grease in the conductive filler is changed to 4g, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 18.

[0057] Example 25: A piezoresistive flexible array sensor material differs from Example 18 only in that the solid content of conductive silicone grease in the conductive filler is changed to 60wt%, while the other raw material ratios, preparation parameters, and preparation methods are the same as in Example 18.

[0058] Performance testing and effect verification: To further demonstrate the beneficial effects of the present invention, the piezoresistive flexible array sensor prepared in Example 1 was used as an example to test and analyze its physical structure, electrical stability and anti-crosstalk performance.

[0059] Basic structure and electrical performance analysis Combination Figure 5 and Figure 6 As shown, the thickness distribution and resistance distribution of the piezoresistive flexible array sensor of the present invention were measured: Figure 5 This indicates that the thickness distribution of the sensor is very uniform at different array points, proving that the scraping and aqueous phase film formation process used in this invention has excellent film formation consistency. Figure 6 This indicates that the initial resistance values ​​of different sensing units are concentrated and have small differences, and the electrical performance of the sensing array is highly consistent. Combination Figure 7 As shown, the sensor of the present invention was subjected to multiple cyclic pressure tests. During continuous cyclic pressing, the resistance change rate of the sensor showed high regularity and repeatability, which proved that the aqueous conductive network formed by the polymer and conductive filler has excellent structural stability and fast response / recovery characteristics under repeated deformation. 2. Comparative Analysis of Crosstalk Immunity Performance of Array Signals To verify the effect of the sandwich structure and film formation process of this invention on suppressing signal crosstalk, a design was made as follows: Figure 8 The diagram shows different pressing areas. During testing, only the data signal of area 1 was connected and collected. The same force was used to press area 1 and the adjacent area 2, and the crosstalk between existing conventional array sensors and the sensor of this invention was compared.

[0060] Crosstalk testing of existing conventional array sensors Combination Figure 9 and Figure 10 As shown, when the test area 1 is pressed, the resistance of area 1 changes by up to -90%. However, when the adjacent area 2 is pressed with the same force, due to stress transmission and lateral diffusion of internal charges, the resistance of area 1, which is not directly pressed, still changes by as much as -30%. This indicates that there is a large amount of signal crosstalk between adjacent units, which leads to extremely inaccurate array detection.

[0061] Low crosstalk test of the array sensor of the present invention Combination Figure 11 and Figure 12 As shown, the same test was performed using the sensor prepared in Embodiment 1 of the present invention. When the test area 1 was pressed, the resistance change exceeded -90%, maintaining extremely high sensitivity; while when the adjacent area 2 was pressed with the same force, the resistance change rate of area 1 was only about -4%.

[0062] Test Conclusion Experimental data show that the present invention, through a specific sandwich structure design and a film-forming system of uniformly dispersed polymer and conductive filler in an aqueous solution, can control the signal crosstalk of the array sensor to a low level (below -40dB), effectively reducing the signal crosstalk problem between sensing units and improving the accuracy and reliability of the detection results.

[0063] The above embodiments are merely one preferred embodiment of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention are all included within the protection scope of the present invention.

Claims

1. A piezoresistive flexible array sensor, characterized in that, include: A first flexible circuit board includes a first substrate and a first conductive electrode. The first conductive electrode is arranged on the side of the first substrate facing the varistor layer. The first conductive electrode includes a plurality of conductive lines extending along a first direction. The second flexible circuit board includes a second substrate and a second conductive electrode. The second conductive electrode is arranged on the side of the second substrate facing the varistor layer. The second conductive electrode includes a plurality of conductive lines extending along a second direction. A varistor layer is disposed between the first flexible circuit board and the second flexible circuit board; The first conductive electrode and the second conductive electrode intersect to form a cross electrode array; The varistor layer is prepared by forming a film from an aqueous solution of polymer and conductive filler; Both the first substrate and the second substrate are made of breathable substrate.

2. The piezoresistive flexible array sensor according to claim 1, characterized in that: The materials of the first substrate and the second substrate are respectively selected from at least one of polyisoprene, polybutadiene, polyphenylene sulfide, polyimide, polyether ether imide, polycarbonate, polyethylene naphthalate, polyester, silicone, thermoplastic polyurethane, polyether ether ketone, polytetrafluoroethylene, SBS, and SEBS.

3. The piezoresistive flexible array sensor according to claim 1, characterized in that: The materials of the first conductive electrode and the second conductive electrode are respectively selected from at least one of gold, silver, copper foil, liquid metal alloy, water-soluble silver nanowires, conductive silver paste, graphene, carbon nanotube paste, gallium indium alloy, copper ink, and conductive carbon paste.

4. The piezoresistive flexible array sensor according to claim 1, characterized in that: The first conductive electrode and the second conductive electrode are fabricated using a flexible printed circuit manufacturing process, which is selected from any one of screen printing, circuit printing, inkjet printing, aerosol printing, gravure printing, flexographic printing, and nano-jet printing, to print the first conductive electrode and the second conductive electrode on the first substrate and the second substrate, respectively.

5. A piezoresistive flexible array sensor according to claim 1, characterized in that: The conductive filler material is selected from at least one of carbon nanotubes, graphene, fullerene, liquid metal, carbon black, conductive silver paste, silver nanowires, gold nanowires, and conductive silicone grease.

6. A piezoresistive flexible array sensor according to claim 1, characterized in that: The polymer is selected from at least one of polyurethane, thermoplastic elastomer, polyacrylic acid, natural rubber, synthetic rubber, fluorocarbon elastomer, acrylic gel, sodium alginate hydrogel, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, sodium polyacrylate, cellulose derivatives, SBS, and SEBS.

7. A piezoresistive flexible array sensor according to claim 1, characterized in that: The mass fraction of the aqueous solution of the polymer is 10% to 90%, and the mass fraction of the aqueous solution of the conductive filler is 1% to 40%. In the varistor layer, the conductive filler is uniformly dispersed in the matrix formed by the polymer and forms a conductive network for generating electrical signals.

8. A piezoresistive flexible array sensor according to claim 1, characterized in that: The width of the first and second conductive electrodes in their corresponding arrangement directions is 0.1mm~5mm, and the thickness is 0.01mm~0.1mm, with a spacing of 0.01mm~3mm between adjacent conductive lines; the thickness of the first and second flexible circuit boards is 0.01mm~1mm; the thickness of the varistor layer is 0.01mm~1mm; the surface resistance of the varistor layer is 0.1kΩ~100MΩ; the volume resistivity of the varistor layer is 0.1kΩ·cm~100MΩ·cm; and the overall thickness of the varistor-type flexible array sensor is 0.05mm~0.5mm.

9. A method for fabricating a piezoresistive flexible array sensor as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Disperse the polymer in water and mix thoroughly by stirring to obtain aqueous solution A; (2) Disperse the conductive filler in water and mix thoroughly by stirring to obtain aqueous solution B; (3) Mix aqueous solution A and aqueous solution B, stir, and centrifuge at high speed to obtain mixed solution C; (4) The mixture C is scraped onto the first flexible circuit board and dried to form a varistor film; (5) Cover the surface of the varistor film with the second flexible circuit board, squeeze it, and dry it to obtain the varistor flexible array sensor.

10. The method for fabricating a piezoresistive flexible array sensor according to claim 9, characterized in that: The solid content of the aqueous solution A is 1wt%~60wt%; The solid content of the aqueous solution B is 5wt%~20wt%; The stirring time in steps (1), (2), and (3) is 30 min to 12 h; The thickness of the varistor film is 20μm~200μm; The drying time for step (4) is 10 min to 6 h; The drying time for step (5) is 6h~12h; The drying temperature in steps (4) and (5) is 25℃~100℃.

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