Flexible piezoresistive pressure sensor, preparation method and application thereof

Abstract

The flexible piezoresistive pressure sensor comprises a lower substrate layer, an electrode layer, a three-dimensional conductive layer, an active layer and an upper substrate layer which are sequentially arranged from bottom to top, the three-dimensional conductive layer is of a three-dimensional structure printed on the surface of the active layer, the three-dimensional structure comprises a plurality of elastic conductors which are regularly or randomly arranged, each elastic conductor is of a conical or cylindrical three-dimensional structure, and the thicknesses of the elastic conductors are different; the cross section of each elastic conductor is in the shape of a dot, a circle, a triangle, a rectangle, a diamond, a polygon or other irregular shapes. The invention also discloses a preparation method of the flexible piezoresistive pressure sensor. The preparation method specifically comprises the following steps: printing the electrode layer; printing an active layer; printing a three-dimensional conductive layer; assembling: after the three-dimensional conductive layer is printed, assembling the three-dimensional conductive layer with the electrode layer; in conclusion, the flexible piezoresistive pressure sensor disclosed by the invention has the characteristics of large measurement range and high sensitivity.

Description

Technical Field

[0001] The present invention belongs to the field of methods for preparing flexible piezoresistive pressure sensors, and in particular relates to a flexible piezoresistive pressure sensor. The present invention also relates to methods for preparing and applying the flexible piezoresistive pressure sensor. Background Art

[0002] Flexible piezoresistive pressure sensors can be used for pressure signal detection on complex surfaces and in harsh environments, such as industrial manufacturing fields such as internal air pressure monitoring of battery packs, soft robots, and intelligent manipulators; smart medical fields such as electrocardiograms and electromyograms; sports detection fields such as bicycle power meters, smart cushions, and electronic skins; wearable devices such as smart insoles and flexible displays; and commercial equipment such as desktop pressure detection and shelf detection.

[0003] At present, the electrode layer and active layer of large-area flexible sensors based on printing technology are sandwiched with a pressure-sensitive material composed of a conductive agent and other adhesive materials, and the pressure-sensitive material is mostly printed and processed into a planar two-dimensional structure. When pressure is applied, the pressure-sensitive material undergoes compression deformation. When deformation occurs, the internal microstructure of the conductive material inside the pressure-sensitive material undergoes compression deformation, resulting in a change in the internal conductive connection state, thereby changing the resistance of the pressure-sensitive material of the planar two-dimensional structure, thereby realizing the pressure sensing function.

[0004] Traditional flexible piezoresistive pressure sensors mainly rely on the change in resistance of the pressure-sensitive layer caused by the compressive deformation of the planar two-dimensional pressure-sensitive layer to sense pressure. The amount of compressive deformation of the pressure-sensitive layer depends entirely on the elastic properties of the conductive agent and bonding material in the pressure-sensitive material. Once the material of the pressure-sensitive layer is determined, its elastic properties are also fixed. Therefore, the pressure-sensitive layer is limited in its compressive deformation due to its elastic properties such as elastic modulus and hardness, and its sensitivity is highly dependent on the hardness of the pressure-sensitive material. As a result, the sensitivity and sensing range of existing flexible pressure sensors are restricted. Summary of the invention

[0005] The purpose of the present invention is to provide a flexible piezoresistive pressure sensor, which solves the problems of low sensitivity and limited detection range of the existing flexible piezoresistive pressure sensors.

[0006] The technical solution adopted by the present invention is a flexible piezoresistive pressure sensor, comprising:

[0007] A lower substrate layer, an electrode layer, a three-dimensional conductive layer, an active layer, and an upper substrate layer are sequentially arranged from bottom to top;

[0008] The three-dimensional conductive layer is a three-dimensional structure printed on the active layer. The three-dimensional structure includes a plurality of regularly or randomly arranged elastic conductors. The elastic conductors are three-dimensional structures in the shape of cones or columns. The thicknesses of the plurality of elastic conductors are different.

[0009] Preferably, the cross-sectional shape of each elastic conductor is dot-shaped, circular, triangular, rectangular, rhombus-shaped, polygonal or other irregular shapes.

[0010] Preferably, the thickness of the three-dimensional conductive layer is 0.1um-50um, the thickness of the electrode layer is 0.5um-50um, and the thickness of the active layer is 0.5um-50um.

[0011] Another technical solution adopted by the present invention is a method for preparing a flexible piezoresistive pressure sensor, which specifically comprises the following steps:

[0012] Printing electrode layer: printing the electrode layer on the lower substrate layer;

[0013] Printing active layer: printing the active layer on the upper substrate layer;

[0014] Printing three-dimensional conductive layer:

[0015] Placing a conductive nanomaterial and a solvent in a container and performing water bath ultrasound to form a conductive material dispersion;

[0016] Adding conductive nanomaterials and conductive material dispersion into the elastomer material, heating and stirring the mixed solution, and stopping stirring when the solution is completely volatilized, at which time the three-dimensional conductive layer ink is prepared;

[0017] Adding a curing agent to the three-dimensional conductive layer ink for curing, and after the curing is completed, printing the three-dimensional conductive layer ink on the active layer to obtain a three-dimensional conductive layer;

[0018] Assembly: After the three-dimensional conductive layer is printed, it is assembled with the electrode layer.

[0019] Preferably, the active layer is obtained by printing an active layer conductive ink on the upper substrate layer by screen printing, gravure printing, flexographic printing, or inkjet printing, wherein the active layer conductive ink is prepared by mixing conductive carbon black, carbon nanotubes, a binder, a solvent, and an additive;

[0020] Preferably, the electrode layer is obtained by printing an electrode layer conductive ink on the lower substrate layer by screen printing, gravure printing, flexographic printing, or inkjet printing, and the electrode layer conductive ink is prepared by mixing micro-nano gold wires, micro-nano metal particles, conductive polymers, binders, solvents, and additives;

[0021] Preferably, the three-dimensional conductive layer is a three-dimensional structure obtained by printing three-dimensional conductive layer ink on the active layer by screen printing, gravure printing, flexographic printing, and inkjet printing, and the three-dimensional structure is composed of a plurality of elastic conductors in a conical or cylindrical shape, and the plurality of elastic conductors are randomly or regularly arranged on the surface of the active layer;

[0022] Preferably, when printing the three-dimensional conductive layer, by changing the printing pattern of the silk screen printing plate, the gravure printing plate, or the flexographic printing plate, the cross-sectional shape of each elastic conductor constituting the three-dimensional conductive layer can be printed into a dot, circle, triangle, rectangle, rhombus, polygon, or other irregular shape;

[0023] Preferably, when printing the three-dimensional conductive layer, the thickness of the three-dimensional conductive layer can be controlled by setting the screen film thickness, the gravure cell depth, the flexographic dot structure, or by setting the inkjet resolution, and the thickness of the three-dimensional conductive layer obtained by printing is finally 0.1um-50um.

[0024] Preferably, the conductive nanomaterial is any one or more of carbon nanotubes, conductive carbon black, octane, graphene, graphite sheets, metal nanoparticles, nanosilver wires, transition metal carbides, silicon, germanium, gallium arsenide, and conductive polymers;

[0025] Preferably, the elastomeric material is any one or more of industrial rubber, thermoplastic rubber, styrene elastomeric polymer, thermoplastic polyolefin, thermoplastic vulcanized rubber, styrene thermoplastic elastomer, styrene-isoprene-styrene block copolymer, linear triblock copolymer, EPDM rubber, polyolefin elastomer, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, polyphenylene ether, and polydimethylsiloxane;

[0026] Preferably, the solvent is one or more of ethanol, pure water, toluene, chloroform, tetrahydrofuran, dimethylformamide, dimethylacetamide, propylene glycol, dimethyl silicone oil, n-hexane, isophorone, and dibasic acid esters.

[0027] Preferably, when preparing the conductive material dispersion, the mass ratio of the conductive nanomaterial to the solvent is 0.1%-1%.

[0028] Preferably, when preparing the three-dimensional conductive layer ink, the mass ratio of the elastomeric material, the conductive nanomaterial and the conductive material dispersion is 5:0.1:10 to 5:0.4:10.

[0029] Another technical solution adopted by the present invention is that the flexible piezoresistive pressure sensor as described above is used in electronic skin or a pressure sensing detection device.

[0030] The beneficial effects of the present invention are:

[0031] The present invention discloses a flexible piezoresistive pressure sensor, which comprises a lower substrate layer, an electrode layer, a three-dimensional conductive layer, an active layer, and an upper substrate layer which are sequentially arranged from bottom to top, wherein the active layer mainly provides a relatively large resistance and serves as an electrode for the three-dimensional conductive layer distributed on the active layer, so as to form a path with the electrode layer, wherein the three-dimensional wire layer printed on the surface of the active layer has a three-dimensional structure, and the three-dimensional structure is composed of many printed dots (elastic conductors) of different sizes and heights. When pressure is applied, firstly, the conductive material is deformed, the internal conductive network is changed, and the resistance is also changed; secondly, due to the pressure, the height of the elastic conductor is reduced, and the area is increased at the same time, so that the contact area between the material and the electrode of the interdigitated structure is increased, which also changes the resistance of the circuit; in addition, due to the different heights of the elastic conductors, when the height of the higher conductive elastic body is reduced to the same height as the lower conductive elastic body, the lower conductive elastic body also starts to participate in the work, even if the higher conductive elastic body has reached the detection limit at this time, the resistance no longer changes, and the sensitivity is reduced, but the lower conductive elastic body still has a higher sensitivity, which increases the detection range and enables the sensor to have a higher sensitivity within a larger detection range. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is an exploded diagram of a flexible piezoresistive pressure sensor disclosed in the present invention.

[0033] In the figure, 1. upper substrate layer, 2. active layer, 3. three-dimensional conductive layer, 4. electrode layer, 5. lower substrate layer. DETAILED DESCRIPTION

[0034] The present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection solution of the present invention.

[0035] Flexible piezoresistive pressure sensors can be used for pressure signal detection on complex surfaces and in harsh environments, such as industrial manufacturing fields such as internal air pressure monitoring of battery packs, soft robots, and intelligent manipulators; smart medical fields such as electrocardiograms and electromyograms; sports detection fields such as bicycle power meters, smart cushions, and electronic skins; wearable devices such as smart insoles and flexible displays; and commercial equipment such as desktop pressure detection and shelf detection.

[0036] At present, the electrode layer and active layer of large-area flexible sensors based on printing technology are sandwiched with a pressure-sensitive material composed of a conductive agent and other adhesive materials, and the pressure-sensitive material is mostly printed and processed into a planar two-dimensional structure. When pressure is applied, the pressure-sensitive material undergoes compression deformation. When deformation occurs, the internal microstructure of the conductive material inside the pressure-sensitive material undergoes compression deformation, resulting in a change in the internal conductive connection state, thereby changing the resistance of the pressure-sensitive material of the planar two-dimensional structure, thereby realizing the pressure sensing function.

[0037] Traditional flexible piezoresistive pressure sensors mainly rely on the change in resistance of the pressure-sensitive layer caused by the compressive deformation of the planar two-dimensional pressure-sensitive layer to sense pressure. The amount of compressive deformation of the pressure-sensitive layer depends entirely on the elastic properties of the conductive agent and bonding material in the pressure-sensitive material. Once the material of the pressure-sensitive layer is determined, its elastic properties are also fixed. Therefore, the pressure-sensitive layer is limited in its compressive deformation due to its elastic properties such as elastic modulus and hardness, and its sensitivity is highly dependent on the hardness of the pressure-sensitive material. As a result, the sensitivity and sensing range of existing flexible pressure sensors are restricted.

[0038] A flexible piezoresistive pressure sensor disclosed in the present invention comprises: a lower substrate layer 5, an electrode layer 4, a three-dimensional conductive layer 3, an active layer 2, and an upper substrate layer 1 which are arranged in sequence from bottom to top; the three-dimensional conductive layer 3 is a three-dimensional structure printed on the surface of the active layer 2, and the three-dimensional structure comprises a plurality of elastic conductors arranged regularly or randomly, the elastic conductors are three-dimensional structures in the shape of cones or columns, the thicknesses of the plurality of elastic conductors are different, and the cross-sectional shape of each elastic conductor is a dot, circle, triangle, rectangle, rhombus, polygon or other irregular shape; the thickness of the three-dimensional conductive layer 3 is 0.1um-50um; the thickness of the electrode layer 4 is 0.5-50um; the thickness of the active layer 2 is 0.5um-50um.

[0039] The three-dimensional conductive layer 3 is a three-dimensional structure obtained by printing the three-dimensional conductive layer ink on the surface of the active layer. The three-dimensional structure ( Figure 1 On the lower surface of the active layer), the three-dimensional structure is composed of many printed dots (elastic conductors) of different sizes and heights; the printing method of the three-dimensional conductive layer 3 is any one of screen printing, gravure printing, flexographic printing, and inkjet printing, and the thickness of the printed three-dimensional conductive layer 3 is 0.1um-50um, and there is no fixed requirement for the length and width; when printing the three-dimensional conductive layer, different screen patterns are designed through screen printing, gravure printing, and flexographic printing. Different screens can print on the three-dimensional conductive layer to obtain regularly arranged or randomly arranged patterns in the shape of dots, circles, triangles, rectangles, diamonds, polygons, or other irregular shapes; after printing, a vacuum oven is used for heating and curing.

[0040] When printing the three-dimensional conductive layer, it is produced by a single sheet or roll-to-roll transfer method. During the printing process, the printing quality of a single print is improved by changing the viscosity and tension of the conductive ink, the surface tension of the substrate, the printing speed, the strength, etc. At the same time, the thickness of the three-dimensional conductive layer is increased by increasing the thickness of the printing plate, multiple printings, and multi-layer printing, so that the printed three-dimensional conductive layer has a more obvious three-dimensional structure. By increasing the viscosity of the ink, the surface of the printed three-dimensional conductive layer can have regular textures. Compared with a smooth surface, a printed object with regular textures has an additional layer of three-dimensional textures on the basis of the three-dimensional structure, which can improve the sensitivity of the sensor. However, since the high viscosity of the ink will affect the normal printing effect, it needs to be used selectively.

[0041] The shape of the three-dimensional conductive layer is diverse. The shape of the printed object can be changed by changing the pattern of the printing plate. The printing thickness of the three-dimensional conductive layer can be adjusted by changing the rheological properties of the ink (such as viscosity, surface tension, adhesion, etc.), screen film thickness, screen pattern size, scraper angle, printing speed, printing force, screen and table spacing and other parameters. At the same time, through multi-layer printing or adjusting the viscosity of the ink, the printed pattern surface can have a regular screen shape, and a layer of miniature three-dimensional structure can be added to the surface of the three-dimensional structure; the three-dimensional conductive layer can be designed as dots, lines, and large-area planes, mainly depending on the shape design of the electrode layer. The interdigitated electrode can be in the form of dots and lines, and by increasing the pressure, the three-dimensional conductive layer is deformed to increase the contact area with the interdigitated structure, thereby changing the resistance; the large-area plane can be used in fields such as electronic skin that require large-area sensors.

[0042] The elastomeric material used in preparing the three-dimensional conductive layer ink is any one or more of industrial rubber, thermoplastic rubber, styrene elastomeric polymer, thermoplastic polyolefin, thermoplastic vulcanized rubber, styrene thermoplastic elastomer, styrene-isoprene-styrene (SIS) block copolymer, linear triblock copolymer, EPDM rubber, polyolefin elastomer, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, polyphenylene ether, and polydimethylsiloxane. The conductive nanomaterial is any one or more of carbon nanotubes (CNT), conductive carbon black (CB), soccer ene (C60), graphene GE), graphite flakes (GNS), metal nanoparticles, nano silver wires (AgNW), transition metal carbides (MXene), silicon, germanium, gallium arsenide, and conductive polymers.

[0043] The solvent is one or more of ethanol, pure water, toluene, chloroform, tetrahydrofuran, dimethylformamide, dimethylacetamide, propylene glycol, dimethyl silicone oil, n-hexane, isophorone, and dibasic acid ester.

[0044] The lower substrate layer and the upper substrate layer are any one of polyethylene terephthalate, polyethylene naphthalate, polydimethylsiloxane, polyparaxylene, polyimide, aliphatic aromatic copolyester, styrene-ethylene-butylene-styrene block copolymer, thermoplastic polyurethane elastomer, and polyvinyl alcohol fiber. These materials are flexible polymer films suitable for use as printing substrates.

[0045] The electrode layer is a metal or non-metal electrode obtained by printing the electrode layer conductive ink on the surface of the lower substrate layer by one of the printing methods such as screen printing, gravure printing, flexographic printing, and inkjet printing. The printed electrode layer is also a three-dimensional structure with thickness. The specific thickness of the electrode layer is 0.5-50um. The electrode layer conductive ink is prepared by mixing micro-nano gold wires, micro-nano metal particles, conductive polymers, binders, solvents and additives.

[0046] The active layer is printed on the surface of the upper substrate layer by active layer conductive ink through one of screen printing, gravure printing, flexographic printing, and inkjet printing. The thickness of the active layer is 0.5-50um. The active layer conductive ink is prepared by mixing conductive carbon black, carbon nanotubes, binders, solvents and additives.

[0047] Example 1

[0048] Step 1, printing the electrode layer: pouring the electrode layer conductive ink prepared by mixing micro-nano gold wires, micro-nano metal particles, conductive polymers, binders, solvents and additives onto the electrode layer screen printing screen, starting the screen printer, and placing the printed electrode layer in an oven at 130° C. and baking for 40 minutes;

[0049] Step 2, printing the active layer: pouring the active layer conductive ink prepared by mixing conductive carbon black, carbon nanotubes, binder, solvent and additives onto the active layer screen printing screen, starting the screen printing machine, and baking the printed active layer in an oven at 130° C. for 10 minutes;

[0050] Step 3: Printing a three-dimensional conductive layer:

[0051] Step 3.1, conductive material dispersion: Add carbon nanotubes and isopropyl alcohol into a clean sealed glass container, put the container into a water bath ultrasonic machine for water bath ultrasonication, and evenly disperse the conductive nanomaterial in the solution to obtain a conductive material dispersion;

[0052] Step 3.2, conductive material dispersion: add 5 g of polydimethylsiloxane into a beaker, then add 150 mg of acetylene black and 15 ml (containing 20 mg of carbon nanotubes) of the conductive material dispersion obtained in step 3.1, heat and stir the mixture until the solution is completely volatilized, then stop stirring, and the three-dimensional conductive layer ink is ready;

[0053] Step 3.3, add 0.5 g of curing agent to the three-dimensional conductive layer ink for curing. After curing, use the three-dimensional conductive layer ink to print on the surface of the active layer to obtain a three-dimensional conductive layer. Use a printing speed of 150 mm / s and a 20-micron thick screen for printing. The three-dimensional conductive layer is printed with a thickness of 5-10 microns. The specific amount of curing agent is normally added at 1 / 10 of the weight of the three-dimensional conductive layer ink. Changing the ratio can adjust the hardness of the elastomer.

[0054] Step 4, assembly: Align the solidified three-dimensional conductive layer and the electrode layer by visual recognition or manually according to the accuracy requirements, and package the aligned devices with adhesives or tapes to complete the assembly of the sensor.

[0055] Example 2

[0056] Step 1, printing the electrode layer: pouring the conductive ink of the electrode layer prepared by mixing micro-nano gold wires, micro-nano metal particles, conductive polymers, binders, solvents and additives onto the electrode layer gravure printing plate, scraping off the ink in the blank part with a scraper, starting the gravure printing machine, and baking the printed electrode layer in an oven at 130°C for 40 minutes;

[0057] Step 2, printing the active layer: pour the conductive ink for the active layer prepared by mixing conductive carbon black, carbon nanotubes, binder, solvent and additives on the gravure printing plate of the active layer, scrape off the ink in the blank part with a scraper, start the gravure printing machine, and bake the printed active layer in an oven at 130°C for 10 minutes;

[0058] Step 3: Printing a three-dimensional conductive layer:

[0059] Step 3.1, conductive material dispersion: Add carbon nanotubes and isopropyl alcohol into a clean sealed glass container, put the container into a water bath ultrasonic machine for water bath ultrasonication, and evenly disperse the conductive nanomaterial in the solution to obtain a conductive material dispersion;

[0060] Step 3.2, conductive material dispersion: add 5 g of polydimethylsiloxane, 200 mg of acetylene black and 15 ml (50 mg of carbon nanotubes) of the conductive material dispersion obtained in step 3.1 into a beaker, heat and stir the mixture until the solution is completely volatilized, then stop stirring, and the three-dimensional conductive layer ink is ready;

[0061] Step 3.3, add 0.5 g of curing agent to the three-dimensional conductive layer ink for curing. After curing, use the three-dimensional conductive layer ink to print on the surface of the active layer to obtain a three-dimensional conductive layer. Use a printing speed of 130 mm / s and a 40-micron film thickness screen for printing. The three-dimensional conductive layer is printed with a thickness of 15-20 microns. The specific amount of curing agent is normally added at 1 / 10 of the weight of the three-dimensional conductive layer ink. Changing the ratio can adjust the hardness of the elastomer.

[0062] Step 4, assembly: Align the solidified three-dimensional conductive layer and the electrode layer by visual recognition or manually according to the accuracy requirements, and package the aligned devices with adhesives or tapes to complete the assembly of the sensor.

[0063] Example 3

[0064] Step 1, printing the electrode layer: pouring the conductive ink of the electrode layer prepared by mixing micro-nano gold wires, micro-nano metal particles, conductive polymers, binders, solvents and additives on the ink substrate, starting the flexographic printing machine, and putting the printed electrode layer into an oven at 130°C for 40 minutes;

[0065] Step 2, printing the active layer: pouring the active layer conductive ink prepared by mixing conductive carbon black, carbon nanotubes, binder, solvent and additives onto the ink substrate, starting the flexographic printing machine, and baking the printed active layer in an oven at 130° C. for 10 minutes;

[0066] Step 3: Printing a three-dimensional conductive layer:

[0067] Step 3.1, conductive material dispersion: Add carbon nanotubes and isopropyl alcohol into a clean sealed glass container, put the container into a water bath ultrasonic machine for water bath ultrasonication, and evenly disperse the conductive nanomaterial in the solution to obtain a conductive material dispersion;

[0068] Step 3.2, conductive material dispersion: add 5 g of polydimethylsiloxane, 300 mg of acetylene black and 18 ml (containing 50 mg of carbon nanotubes) of the conductive material dispersion obtained in step 3.1 into a beaker, heat and stir the mixture until the solution is completely volatilized, then stop stirring, and the three-dimensional conductive layer ink is ready;

[0069] Step 3.3, add 0.5 g of curing agent to the three-dimensional conductive layer ink for curing. After curing, use the three-dimensional conductive layer ink to print on the surface of the active layer to obtain a three-dimensional conductive layer. Use a printing speed of 150 mm / s and a 20-micron thick screen for printing. The three-dimensional conductive layer is printed with a thickness of 5-10 microns. The specific amount of curing agent is normally added at 1 / 10 of the weight of the three-dimensional conductive layer ink. Changing the ratio can adjust the hardness of the elastomer.

[0070] Step 4, assembly: Align the solidified three-dimensional conductive layer and the electrode layer by visual recognition or manually according to the accuracy requirements, and package the aligned devices with adhesives or tapes to complete the assembly of the sensor.

[0071] The flexible piezoresistive pressure sensor disclosed in the present invention and the flexible piezoresistive pressure sensor prepared by the above-mentioned flexible piezoresistive pressure sensor preparation method can be used in electronic skin or pressure detection devices.

[0072] In summary, the flexible piezoresistive pressure sensor disclosed in the present invention includes a lower substrate layer, an electrode layer, a three-dimensional conductive layer, an active layer, and an upper substrate layer arranged in sequence from bottom to top, wherein the active layer mainly provides a larger resistance and serves as an electrode for the three-dimensional conductive layer distributed on the active layer, so as to form a path with the electrode layer, wherein the three-dimensional wire layer printed on the surface of the active layer has a three-dimensional structure, and the three-dimensional structure is composed of many printed dots (elastic conductors) of different sizes and heights. When pressure is applied, first the conductive material is deformed, the internal conductive network is changed, and the resistance is also changed; secondly, due to the pressure, the height of the elastic conductor is reduced, and the area is increased, so that the material and the finger structure are electrically connected. The contact area of ​​the pole increases, which also changes the resistance of the circuit; in addition, due to the different heights of the elastic conductors, when the height of the higher conductive elastomer is reduced to the same height as the lower conductive elastomer, the lower conductive elastomer also begins to participate in the work, even if the higher conductive elastomer has reached the detection limit at this time, the resistance no longer changes, and the sensitivity decreases, but the lower conductive elastomer still has a higher sensitivity, while increasing the detection range, it also enables the sensor to have a higher sensitivity within a larger detection range; in summary, the three-dimensional conductive layer of the pressure sensor sensing part of the present invention combines the high conductivity of the conductive filler and the advantages of the strong flexibility of the elastomer, which can improve the sensitivity of the sensor. In addition, the flexible piezoresistive pressure sensor disclosed in the present invention has excellent dynamic force and static force test performance at the same time, and has a faster response time and recovery time.

[0073] In addition, the elastomers in the existing flexible piezoresistive pressure sensor structure are mainly manufactured by model curing, and cannot be mass-produced. We can use printing to solve this problem. Using roll-to-roll technology based on printing can further speed up the manufacturing speed and reduce manufacturing costs. The existing roll-to-roll printing equipment can print 30,000 flexible sensors per hour. This speed far exceeds the traditional flexible sensor manufacturing speed. In addition, the packaging substrate of the current flexible piezoresistive pressure sensor is mainly special materials such as hydrogel film. Most of these materials need to be customized according to the sensor parameters. Even the cost of those sold on the market is very high. The measurement area is calculated in square centimeters. Our sensors use low-cost materials such as PET as substrates. The price of one square meter is about 6 yuan, which can greatly reduce costs.

[0074] Compared with the prior art, the present invention combines printing technology with conductive elastic materials and applies them to the field of pressure detection, providing a new method for making pressure sensors. The present invention has a simple preparation process, low cost, does not require additional complex signal processing circuits, and can accurately identify pressure changes.

[0075] The embodiments described above are only preferred specific implementation methods of the present invention, and the protection scope of the present invention is not limited thereto. Any simple changes or equivalent replacements of the technical solutions that can be obviously obtained by any technician familiar with the field within the technical scope disclosed in the present invention belong to the protection scope of the present invention.

Claims

1. A flexible piezoresistive pressure sensor, characterized in that: include: A lower substrate layer (5), an electrode layer (4), a three-dimensional conductive layer (3), an active layer (2), and an upper substrate layer (1) are sequentially arranged from bottom to top; The three-dimensional conductive layer (3) is a three-dimensional structure printed on the active layer (2), and the three-dimensional structure includes a plurality of regularly or randomly arranged elastic conductors, each of the elastic conductors is a three-dimensional structure in the shape of a cone or a column, and the thicknesses of the plurality of elastic conductors are different.

2. A flexible piezoresistive pressure sensor according to claim 1, characterized in that: The cross-sectional shape of each elastic conductor is dot-shaped, circular, triangular, rectangular, rhombus-shaped, polygonal or other irregular shapes.

3. The flexible piezoresistive pressure sensor according to claim 1, characterized in that: The thickness of the three-dimensional conductive layer (3) is 0.1um-50um, the thickness of the electrode layer (4) is 0.5um-50um, and the thickness of the active layer (2) is 0.5um-50um.

4. A method for preparing a flexible piezoresistive pressure sensor, characterized in that: The specific steps include: Printing an electrode layer (4): printing an electrode layer (4) on the lower substrate layer (5); Printing an active layer (2): printing the active layer (2) on the upper substrate layer (1); Printing three-dimensional conductive layer (3): Placing a conductive nanomaterial and a solvent in a container and performing water bath ultrasound to form a conductive material dispersion; Adding the conductive nanomaterial and the conductive material dispersion into the elastomer material, heating and stirring the mixed solution, and stopping stirring when the solution is completely volatilized, at which time the three-dimensional conductive layer ink is prepared; Adding a curing agent to the three-dimensional conductive layer ink for curing, and after curing, printing on the active layer (2) to obtain a three-dimensional conductive layer (3); Assembly: After the three-dimensional conductive layer (3) is printed, it is assembled with the electrode layer (4).

5. The method for preparing a flexible piezoresistive pressure sensor according to claim 4, characterized in that: The active layer (2) is obtained by printing active layer conductive ink on the upper substrate (1) by screen printing, gravure printing, flexographic printing, or inkjet printing, wherein the active layer conductive ink is prepared by mixing conductive carbon black, carbon nanotubes, a binder, a solvent, and an additive; The electrode layer (4) is obtained by printing an electrode layer conductive ink on the lower substrate layer (5) by screen printing, gravure printing, flexographic printing, or inkjet printing, wherein the electrode layer conductive ink is prepared by mixing micro-nano gold wires, micro-nano metal particles, a conductive polymer, a binder, a solvent, and an additive; The three-dimensional conductive layer (3) is a three-dimensional structure obtained by printing a three-dimensional conductive layer ink on the active layer (2) by screen printing, gravure printing, flexographic printing, or inkjet printing, and the three-dimensional structure is composed of a plurality of elastic conductors in a conical or cylindrical shape, and the plurality of elastic conductors are randomly or regularly arranged on the active layer (2).

6. The method for preparing a flexible piezoresistive pressure sensor according to claim 5, characterized in that: When printing the three-dimensional conductive layer (3), by changing the printing plate pattern of the silk screen printing plate, the gravure printing plate, or the flexographic printing plate, the cross-sectional shape of each elastic conductor constituting the three-dimensional conductive layer (3) can be printed into a dot, circle, triangle, rectangle, rhombus, polygon, or other irregular shape; When printing the three-dimensional conductive layer (3), the thickness of the three-dimensional conductive layer (3) can be controlled by setting the screen film thickness, the gravure cell depth, the flexographic dot structure, or by setting the inkjet resolution. Finally, the thickness of the three-dimensional conductive layer (3) obtained by printing is 0.1um-50um.

7. The method for preparing a flexible piezoresistive pressure sensor according to claim 4, characterized in that: The conductive nanomaterial is any one or more of carbon nanotubes, conductive carbon black, octylene, graphene, graphite sheets, metal nanoparticles, nanosilver wires, transition metal carbides, silicon, germanium, gallium arsenide, and conductive polymers; The elastomeric material is any one or more of industrial rubber, thermoplastic rubber, styrene elastomeric polymer, thermoplastic polyolefin, thermoplastic vulcanized rubber, styrene thermoplastic elastomer, styrene-isoprene-styrene block copolymer, linear triblock copolymer, EPDM rubber, polyolefin elastomer, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, polyphenylene ether, and polydimethylsiloxane; The solvent is one or more of ethanol, pure water, toluene, chloroform, tetrahydrofuran, dimethylformamide, dimethylacetamide, propylene glycol, dimethyl silicone oil, n-hexane, isophorone, and dibasic acid ester.

8. The method for preparing a flexible piezoresistive pressure sensor according to claim 4, characterized in that: When preparing the conductive material dispersion, the mass ratio of the conductive nano material to the solvent is 0.1%-1%.

9. The method for preparing a flexible piezoresistive pressure sensor according to claim 4, characterized in that: When preparing the three-dimensional conductive layer ink, the mass ratio of the elastomer material, the conductive nanomaterial and the conductive material dispersion is 5:0.1:10 to 5:0.4:

10.

10. The flexible piezoresistive pressure sensor according to any one of claims 1 to 3 or the flexible piezoresistive pressure sensor prepared by the method for preparing the flexible piezoresistive pressure sensor according to any one of claims 4 to 9 is used for electronic skin or a pressure sensing detection device.

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