Composite Flexible Pressure Sensor with Microstructure Gradient and Preparation Method Thereof

Abstract

The present invention discloses a composite flexible pressure sensor with microstructural gradient and a preparation method thereof. The preparation method includes: pouring GPC ink on the conductive surface of a flexible conductive base film and pressing it with sandpaper, heating and curing to form a flexible conductive base film containing a GPC microstructure thin film layer; pouring GPC ink between two layers of sandpaper, heating and curing to form a double-sided GPC microstructure thin film layer; stacking two flexible conductive base films with single-sided GPC microstructure thin film layers and at least one double-sided GPC microstructure thin film layer in sequence to obtain the sensor. In the above sensor, sandpaper is used as a template to be pressed on the GPC thin film layer to form a GPC microstructure thin film layer. GPC microstructure thin film layers with gradients are formed by using sandpapers with different mesh numbers, enabling the rapid preparation of a sensor with multi-layer microstructure and gradient pore structure, reducing the manufacturing steps, and achieving the purpose of manufacturing a composite flexible pressure sensor at low cost and high efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and particularly relates to a composite flexible pressure sensor with microstructural gradient and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of flexible electronic devices, it has attracted great attention in the fields of electronic skin, robotics, intelligent prosthetics, and human physiological signal detection. Among them, when robots and prosthetics need to perform intelligent and precise operations in some complex environments, the perception of delicate touch similar to that of the skin is crucial. Therefore, to meet the intelligent sensing usage requirements in various application scenarios, pressure sensors should have characteristics such as high sensitivity, wide linear range, high pressure resolution, fast response time, and low detection limit.

[0003] Currently, the most commonly used technology to improve the performance of piezoresistive sensors is the design and optimization of microstructures and bionic structures. Although the performance of the sensors has been significantly improved, it mainly focuses on the improvement of a single performance, such as sensitivity or pressure response range. For example, cone structures, interlocking structures, cylindrical structures, and porous structures effectively improve the sensitivity of the sensors due to the reduction of the initial contact area and elastic modulus, but the pressure sensing range is usually narrow. The design of multi-layer microstructures and gradient pore structures greatly expands the pressure sensing range due to the pressure self-adaptive characteristics of the structures.

[0004] For example, in 2022, the academic journal Chemical Engineering Journal, Volume 457, published a paper titled "High sensitivity tactile sensors with ultrabroad linear range based on gradient hybrid structure for gesture recognition and precise grasping". The proposed flexible pressure sensor designed and prepared a gradient pore / pyramid hybrid structure conductive composite film with gradient compression characteristics and high structural compression performance by combining high-pressure steam treatment and repeated template replication, improving the sensitivity and expanding the linear range.

[0005] For example, the invention patent with publication number CN115235660A discloses a bionic flexible pressure sensor with a stiffness gradient microstructure distribution. In this method, raw materials are placed in a template and cured using the template method, and then the template is removed to obtain a conductive layer and a layer of convex microstructure. Alternatively, the conductive layer and the convex microstructure are printed layer by layer using 3D printing, and a layer of convex microstructure is pasted to another conductive layer, and a conductive layer is formed on another layer of convex microstructure to obtain a bionic flexible pressure sensor with a stiffness gradient microstructure distribution.

[0006] For example, the invention patent with publication number CN113008417A discloses a flexible pressure sensor, a preparation method and a measurement system based on a multi-level structure. An intaglio template with an array of microstructures including one or a mixture of convex hemispheres, concave hemispheres, triangular prisms, cylinders, frustums, cubes, cuboids or other polygonal shapes is prepared by photolithography or machining. According to the arrangement order of the multi-level structure design scheme, tape or other adhesive materials are used, and wires are introduced to connect with the leads of the flexible electrodes, and the flexible pressure sensor based on the multi-level structure is obtained by encapsulation.

[0007] However, after the applicant summarized the above technical solutions, it was found that the main disadvantages of the existing technical solutions include: (1) The production process of high-pressure steam treatment is cumbersome and time-consuming; (2) The equipment cost of 3D printing technology is high, and there are certain restrictions on the selection of materials; (3) Photolithography technology limits the shape and size of the template pattern and is costly. Therefore, the sensors with multi-layer microstructures and gradient pore structures in the existing technical methods have the problem of high production costs. Summary of the Invention

[0008] An embodiment of the present invention provides a composite flexible pressure sensor with microstructural gradient and a preparation method thereof, aiming to solve the problem of high production costs of sensors with multi-layer microstructures and gradient pore structures in existing technical methods.

[0009] In a first aspect, an embodiment of the present invention provides a preparation method of a composite flexible pressure sensor with microstructural gradient. The method includes:

[0010] Adding graphene powder to a siliconized organic prepolymer and stirring to obtain GPC ink; the mass fraction of graphene in the GPC ink is 15-45%;

[0011] Using tape to attach two parallel PET strips to the edge of the conductive surface of the flexible conductive base film, and pouring GPC ink into the gap between the PET strips;

[0012] Smoothing the GPC ink poured on the surface layer of the flexible conductive base film so that the thickness of the GPC ink is equal to the thickness of the PET strip and a GPC thin film layer is formed;

[0013] Sandpapers with different mesh numbers are respectively laminated on the surface layers of the GPC thin film layers of the two flexible conductive base films and are laminated through a laminating member, and each flexible conductive base film corresponds to a sandpaper of a specification;

[0014] The sandpaper and the flexible conductive base film to be laminated are placed at a preset temperature for heating and curing, and the sandpaper is peeled off to obtain a flexible conductive base film with a single-sided GPC microstructure thin film layer;

[0015] Two parallel PET strips are attached to the edge of the same side of the sandpaper with tape, and GPC ink is poured into the gap between the PET strips;

[0016] The GPC ink poured on the surface layer of the sandpaper is scraped flat so that the thickness of the GPC ink is equal to the thickness of the PET strip and a GPC thin film layer is formed;

[0017] Another sandpaper with a different mesh number is laminated on the surface layer of the GPC thin film layer of the sandpaper and is laminated through a laminating member;

[0018] The sandpaper and the GPC thin film layer to be laminated are placed at a preset temperature for heating and curing, and the sandpaper is peeled off to obtain a double-sided GPC microstructure thin film layer;

[0019] The two flexible conductive base films with single-sided GPC microstructure thin film layers and at least one double-sided GPC microstructure thin film layer are stacked in sequence to prepare a composite flexible pressure sensor with a microstructure gradient, wherein the flexible conductive base films with single-sided GPC microstructure thin film layers are respectively located on the upper and lower sides of the composite flexible pressure sensor, and the mesh numbers of the sandpapers corresponding to the GPC microstructure thin film layers included in the composite flexible pressure sensor increase or decrease in sequence.

[0020] The preparation method of the composite flexible pressure sensor with a microstructure gradient, wherein, placing the sandpaper and the flexible conductive base film to be laminated at a preset temperature for heating and curing includes:

[0021] The sandpaper and the flexible conductive base film to be laminated are placed at 80-100 °C for thermal annealing for 2-5 hours.

[0022] The preparation method of the composite flexible pressure sensor with a microstructure gradient, wherein, using sandpapers with different mesh numbers to be respectively laminated on the surface layers of the GPC thin film layers of the two flexible conductive base films and being laminated through a laminating member includes:

[0023] Sandpapers with different mesh numbers are respectively laminated on the surface layers of the GPC thin film layers of the two flexible conductive base films;

[0024] A roller is used to roll and press on the outer surface layer of the sandpaper to assist in lamination;

[0025] A pressing member composed of two groups of pressing plates is clamped on both sides of the sandpaper and the flexible conductive base film.

[0026] The preparation method of the composite flexible pressure sensor with microstructural gradient, wherein, pressing another sandpaper with different mesh numbers on the surface layer of the GPC thin film layer of the sandpaper and performing pressing through the pressing member includes:

[0027] Pressing another sandpaper with different mesh numbers on the surface layer of the GPC thin film layer of the sandpaper;

[0028] Using a roller to roll and press on the outer surface layer of the other sandpaper to assist in pressing;

[0029] A pressing member composed of two groups of pressing plates is clamped on both sides of the two sandpapers.

[0030] The preparation method of the composite flexible pressure sensor with microstructural gradient, wherein, the siliconized organic prepolymer is a polydimethylsiloxane prepolymer.

[0031] The preparation method of the composite flexible pressure sensor with microstructural gradient, wherein, before pressing different mesh number sandpapers on the surface layers of the GPC thin film layers of the two flexible conductive base films respectively and performing pressing through the pressing member, it further includes:

[0032] Cleaning the sandpaper with ethanol;

[0033] Blowing nitrogen to dry the cleaned sandpaper.

[0034] The preparation method of the composite flexible pressure sensor with microstructural gradient, wherein, the mesh number of the sandpaper corresponding to the GPC microstructure thin film layer included in the composite flexible pressure sensor is 100 - 600 meshes.

[0035] The preparation method of the composite flexible pressure sensor with microstructural gradient, wherein, the thickness of the PET strip is 200 - 600 um.

[0036] The preparation method of the composite flexible pressure sensor with microstructural gradient, wherein, the pressure for pressing through the pressing member is 50 - 200 kPa.

[0037] In a second aspect, an embodiment of the present invention further provides a composite flexible pressure sensor with microstructural gradient. The composite flexible pressure sensor is manufactured by using the preparation method described in the first aspect above. The composite flexible pressure sensor includes two flexible conductive base films with single-sided GPC microstructure thin film layers and at least one double-sided GPC microstructure thin film layer;

[0038] The double-sided GPC microstructure thin film layers are both clamped between the flexible conductive base films of the single-sided GPC microstructure thin film layers, and the flexible conductive base film in the flexible conductive base films of the single-sided GPC microstructure thin film layers is located in the outermost layer of the composite flexible pressure sensor.

[0039] An embodiment of the present invention provides a composite flexible pressure sensor with microstructural gradient and a preparation method thereof. The preparation method includes: adding graphene powder to a silicified organic prepolymer and stirring to obtain GPC ink, pouring the GPC ink on the conductive surface of the flexible conductive base film and pressing it with sandpaper, heating and curing to form a flexible conductive base film including a GPC microstructure thin film layer, pouring GPC ink between two layers of sandpaper, heating and curing to form a double-sided GPC microstructure thin film layer, and sequentially stacking the flexible conductive base films of two single-sided GPC microstructure thin film layers and at least one double-sided GPC microstructure thin film layer to obtain the sensor. For the above composite flexible pressure sensor, sandpaper is used as a template to press on the surface layer of the GPC thin film layer to form a GPC microstructure thin film layer. GPC microstructure thin film layers with gradient are formed by using sandpapers with different mesh numbers, which can conveniently and quickly prepare a sensor with a multi-layer microstructure and a gradient pore structure, reduce the manufacturing steps of the sensor and lower the complexity of the manufacturing process, and achieve the purpose of manufacturing a composite flexible pressure sensor with low cost and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 It is a flowchart of the method for preparing a composite flexible pressure sensor with microstructural gradient provided by an embodiment of the present invention;

[0042] Figure 2 It is a process flowchart of the flexible conductive base film of the single-sided GPC microstructure thin film layer provided by an embodiment of the present invention;

[0043] Figure 3 It is a process flowchart of the double-sided GPC microstructure thin film layer provided by an embodiment of the present invention;

[0044] Figure 4 It is a structural diagram of a composite flexible pressure sensor with microstructural gradient provided by an embodiment of the present invention;

[0045] Figure 5 It is an application effect diagram of a composite flexible pressure sensor with microstructural gradient provided by an embodiment of the present invention;

[0046] Figure 6 This is the micrograph of the composite flexible pressure sensor with microstructure gradient provided by the embodiments of the present invention. Detailed implementation manners

[0047] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0048] Introduction to each raw material and equipment in the embodiment:

[0049] Sandpaper, purchased from Foshan Zhejiang Hardware Tools Co., Ltd., with models of 120 mesh, 240 mesh, and 400 mesh;

[0050] Graphene powder, purchased from Shenzhen Suiheng Technology Co., Ltd., with a model of 99% multi-layer graphene;

[0051] Indium tin oxide-coated poly(ethylene terephthalate) (ITO-PET), purchased from Shenzhen Tianmidun Electronics Co., Ltd., with a model of 150 ohms and 0.05 mm thickness;

[0052] Ethanol, purchased from Taifu Biotechnology (Shanghai) Co., Ltd., with a model of 64-17-5;

[0053] Polydimethylsiloxane, purchased from Huishan Xizhang Guangxiangsheng Chemical Products Business Department, with a model of SYLGARD184;

[0054] Curing agent, purchased from Huishan Xizhang Guangxiangsheng Chemical Products Business Department, with a model of DC184;

[0055] Heating table, purchased from Louis Enterprise Co., Ltd., with a model of Super-Nuova;

[0056] Pressure gauge, purchased from Beijing Jipin Times Technology Co., Ltd., with a model of MARK-10;

[0057] Source meter, purchased from Shenzhen Haochen Electronic Technology, with a model of Keithley 2614B.

[0058] It should be understood that when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0059] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0060] It should be further understood that the term "and / or" used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0061] In this embodiment, please refer to Figure 1 , as shown in the figure, the embodiment of the present invention provides a preparation method of a composite flexible pressure sensor with microstructure gradient, wherein the method includes steps S110 to S200.

[0062] S110. Add graphene powder to the silicified organic prepolymer and stir to obtain GPC ink; the mass fraction of graphene in the GPC ink is 15-45%.

[0063] Add graphene powder to the silicified organic prepolymer, which is made by mixing a silicon-based organic monomer and a curing agent. The mass ratio of the silicon-based organic monomer to the curing agent is (3.5-6):1. In the optimal embodiment, the mass ratio of the silicon-based organic monomer to the curing agent is 5:1. For example, the silicified organic prepolymer can be a PDMS (Polydimethylsiloxane) prepolymer, then the silicon-based organic monomer is a PDMS polymer monomer. Mechanically stir the graphene powder and the silicified organic prepolymer to mix them evenly to obtain GPC ink, which is also graphene-PDMS composite (graphite / PMDS composite, GPC). Among them, the stirring duration is 20-50 minutes, and the stirring speed is 300-1000 r / min. The mass fraction of graphene in the GPC ink is 15-45%. In the optimal embodiment, the mass fraction of graphene in the GPC ink is 30%.

[0064] S120. Use tape to attach two parallel PET strips to the edge of the conductive surface of the flexible conductive base film, and pour GPC ink into the gap between the PET strips.

[0065] Attach two parallel PET (polyethylene glycol terephthalate) strips to the edge of the conductive surface of the flexible conductive base film using tape. The tape can be PI (Polyimide) tape, such as Figure 2 , and the two PET strips are respectively attached to the edges on both sides of one side of the flexible conductive base film. At this time, a gap is formed between the two PET strips. Among them, the flexible electrode is laid on the flexible substrate to obtain the flexible conductive base film. The thickness of the flexible conductive base film is 10 - 80um, the thickness of the flexible electrode is at the nanometer level, and the thickness of the flexible substrate can be 8 - 60um. Then, conductive surfaces and non-conductive surfaces are respectively formed on both sides of the flexible conductive base film. In the embodiment of the present application, the PET strip is attached to the conductive surface of the flexible conductive base film, and at the same time, the GPC ink is also poured onto the conductive surface of the flexible conductive base film. Preferably, the material of the flexible substrate includes any one or a combination of two or more of polyimide, polyethylene glycol terephthalate, polytetrafluoroethylene, polycarbonate, and polyethylene naphthalate glycol ester, but is not limited thereto. The material of the flexible electrode in the flexible conductive base film includes any one or a combination of two or more of indium oxide, metal nanowires made of silver, copper, or gold, and carbon-based nanomaterials, but is not limited thereto. Preferably, the flexible electrode is also electrically connected to the lead wire. Preferably, the lead wire includes any one or a combination of two or more of copper wire, copper tape, and conductive non-woven fabric, but is not limited thereto. The thickness of the flexible conductive base film is 10um - 80um, and the polymer in the flexible conductive base film includes any one or a combination of two or more of polydimethylsiloxane, polyurethane, thermoplastic polyurethane, and polyethylene, but is not limited thereto. For example, in a specific embodiment, an ITO-PET base film can be selected as the flexible conductive base film. The ITO-PET base film is a flexible conductive thin film formed by containing ITO (Indium tin oxide) and PET material. Pour the above-mentioned GPC ink into the gap between the two PET strips on the surface layer of the flexible conductive base film.

[0066] S130. Level the GPC ink poured on the surface layer of the flexible conductive base film so that the thickness of the GPC ink is equal to the thickness of the PET strip and form a GPC thin film layer.

[0067] Use a scraper to level the GPC ink poured on the surface layer of the flexible conductive base film, so that the thickness of the GPC ink is equal to the thickness of the PET strip, and form a GPC thin film layer. The implementation process of this step is as shown in Figure 2 Figure (a). Among them, the thickness of the PET strip is 200 - 600um, and correspondingly, the thickness of the formed GPC thin film layer is also 200 - 600um.

[0068] S140. Sandpapers with different mesh numbers are respectively pressed onto the surface layers of the GPC thin film layers of the two flexible conductive base films and pressed through a pressing member. Each flexible conductive base film corresponds to a sandpaper of a specific specification.

[0069] The mesh number of the sandpaper determines the roughness of the GPC microstructure thin film layer. The smaller the mesh number of the sandpaper, the rougher the GPC microstructure thin film layer prepared correspondingly. Therefore, sandpapers with different mesh numbers can be respectively pressed onto the surface layers of the GPC thin film layers of the two flexible conductive base films. The implementation process of this step is as Figure 2 shown in Figure (b). GPC microstructure thin film layers with different roughnesses can be prepared using sandpapers with different mesh numbers. After pressing the sandpaper onto the surface layer of the GPC thin film layer of the flexible conductive base film, further pressing can be carried out through the pressing member to improve the pressing effect between the sandpaper and the GPC thin film layer. Among them, the mesh number of the sandpaper used is 100 - 600 meshes; the pressure for pressing through the pressing member is 50 kPa - 200 kPa.

[0070] Step S140 specifically includes: pressing sandpapers with different mesh numbers onto the surface layers of the GPC thin film layers of the two flexible conductive base films respectively; using a roller to roll and press on the outer surface layer of the sandpaper to assist in pressing; clamping the pressing member composed of two groups of pressing plates on both sides of the sandpaper and the flexible conductive base film.

[0071] How to respectively use two sandpapers with 120 meshes and 400 meshes and press them onto the surface layers of the GPC thin film layers of the two flexible conductive base films. Then, use a roller to assist in pressing on the outer surface layer of the sandpaper. The roller rolls back and forth on the sandpaper, so that the sandpaper is pressed more evenly onto the surface layer of the GPC thin film layer, making the formed GPC microstructure thin film layer more uniform. The implementation process of this step is as Figure 2 shown in Figure (c). The pressing member is composed of two groups of pressing plates, and the two groups of pressing plates can be clamped on both sides of the sandpaper and the flexible conductive base film for pressing. Among them, the pressing plate can be a flat steel plate.

[0072] Before step S140, it also includes: cleaning the sandpaper with ethanol; blowing nitrogen to dry the cleaned sandpaper.

[0073] Before pressing the sandpaper onto the GPC thin film layer, the sandpaper can also be cleaned. In the specific application process, the sandpaper can be cleaned with ethanol (95%). The sandpaper is soaked in the ethanol solution to remove the residual impurities on the sandpaper. Then, nitrogen is blown to dry the cleaned sandpaper until there is no ethanol solution residue on the surface layer of the sandpaper.

[0074] S150. Place the pressed sandpaper and the flexible conductive base film under a preset temperature for heating and curing, and peel off the sandpaper to obtain a flexible conductive base film with a single-sided GPC microstructure thin film layer.

[0075] The sandpaper and the flexible conductive base film that can be pressed against the workpiece to be pressed are heated, so that the GPC thin film layer on the flexible conductive base film is cured. After that, the sandpaper covering the surface layer of the cured GPC thin film layer is peeled off, and a flexible conductive base film with a single-sided GPC microstructure thin film layer can be obtained. The implementation process of heating and curing to obtain a flexible conductive base film with a single-sided GPC microstructure thin film layer is as follows Figure 2 shown in Figure (d). For example, the microstructure of the upper surface layer of a flexible conductive base film with a single-sided GPC microstructure thin film layer formed by pressing with 120-mesh sandpaper is as follows Figure 6 shown in Figure (a); the microstructure of the upper surface layer of a flexible conductive base film with a single-sided GPC microstructure thin film layer formed by pressing with 400-mesh sandpaper is as follows Figure 6 shown in Figure (b).

[0076] Specifically, heating and curing the sandpaper and the flexible conductive base film to be pressed at a preset temperature includes: placing the sandpaper and the flexible conductive base film to be pressed at 80 - 100 °C for thermal annealing for 2 - 5 hours.

[0077] S160. Stick two parallel PET strips on the edge of the same side of the sandpaper with tape, and pour GPC ink into the gap between the PET strips; S170. Level the GPC ink poured on the surface layer of the sandpaper so that the thickness of the GPC ink is equal to the thickness of the PET strip and form a GPC thin film layer; S180. Press another sandpaper with a different mesh number on the surface layer of the GPC thin film layer of the sandpaper and press it through a pressing member.

[0078] Steps S120 to S150 can prepare a flexible conductive base film with a single-sided GPC microstructure thin film layer, and steps S160 to S190 are used to prepare a double-sided GPC microstructure thin film layer. The difference between steps S160 to S190 and the previous steps is only that in step S160, sandpaper is used instead of the flexible conductive base film, two parallel PET strips are stuck on the edge of the same side of the sandpaper with tape, and GPC ink is poured into the gap between the two PET strips on the sandpaper surface. Use a scraper to level the GPC ink poured on the surface layer of the sandpaper, so that the thickness of the GPC ink is equal to the thickness of the PET strip and form a GPC thin film layer. The implementation process of this step is as follows Figure 3 shown in Figure (a). After that, press another sandpaper with a different mesh number on the surface layer of the GPC thin film layer of the sandpaper.

[0079] Among them, step S180 specifically includes: pressing another sandpaper with a different mesh number on the surface layer of the GPC thin film layer of the sandpaper; rolling and pressing on the outer surface layer of the other sandpaper with a roller to assist pressing; clamping a pressing member composed of two groups of pressing plates on both sides of the two sandpapers.

[0080] Another sandpaper with a different mesh number is pressed onto the surface layer of the GPC film layer of the said sandpaper. The implementation process of this step is as shown in Figure 3 Figure (b) of Figure 3 ; After that, rollers are also used to roll and press on the outer surface layers of the two sides of the sandpaper respectively. The implementation process of this step is as shown in Figure (c) of

[0081] ; Then, it is clamped on both sides of the two sandpapers through a pressing member.

[0082] S190. Place the sandpaper to be pressed and the GPC film layer under a preset temperature for heating and curing, and peel off the sandpaper to obtain a double-sided GPC micro-structure film layer.

[0082] Similarly, place the sandpaper to be pressed and the GPC film layer under a preset temperature for heating and curing, and then peel off the sandpapers on both sides respectively to obtain a double-sided GPC micro-structure film layer. The specific process of heating and curing is: place the sandpaper to be pressed and the GPC film layer under 80 - 100 °C for thermal annealing for 2 - 5 hours. The implementation process of heating and curing to obtain a double-sided GPC micro-structure film layer is as shown in Figure 3 Figure (d) of

[0083] For example, use a 240-mesh sandpaper as the base, attach two PET strips to the surface layer of the sandpaper, scrape the GPC ink flat after pouring to form a GPC film layer, press another 300-mesh sandpaper onto the surface layer of the GPC film layer, and prepare a double-sided GPC micro-structure film layer with different roughness on both sides after heating and curing.

[0084] S200. Stack the flexible conductive base films of two single-sided GPC micro-structure film layers and at least one double-sided GPC micro-structure film layer in sequence to prepare a composite flexible pressure sensor with micro-structure gradient. Among them, the flexible conductive base films of the single-sided GPC micro-structure film layers are respectively located on the upper and lower sides of the said composite flexible pressure sensor, and the mesh numbers of the sandpapers corresponding to the GPC micro-structure film layers included in the composite flexible pressure sensor increase or decrease in sequence.

[0085] After that, stack the flexible conductive base films of the two prepared single-sided GPC micro-structure film layers and at least one double-sided GPC micro-structure film layer in combination in sequence, so as to prepare a composite flexible pressure sensor with micro-structure gradient; the mesh numbers of the sandpapers corresponding to the GPC micro-structure film layers included in the composite flexible pressure sensor increase or decrease in sequence. That is to say, the micro-structure gradient is realized by the GPC micro-structure film layers with different roughness formed after pressing sandpapers with different mesh numbers. Among them, the flexible conductive base films with single-sided micro-structure film layers are respectively located on the upper and lower sides of the composite flexible pressure sensor, and the double-sided GPC micro-structure film layer is clamped between the two flexible conductive base films with single-sided micro-structure film layers.

[0086] The embodiments of the present application also disclose a composite flexible pressure sensor with a gradient microstructure. Among them, the composite flexible pressure sensor is manufactured by using the manufacturing method in the above embodiments. The composite flexible pressure sensor includes a flexible conductive base film with two single-sided GPC microstructure film layers and at least one double-sided GPC microstructure film layer; the double-sided GPC microstructure film layers are all sandwiched between the flexible conductive base films of the single-sided GPC microstructure film layers, and the flexible conductive base film in the flexible conductive base film of the single-sided GPC microstructure film layer is located on the outermost layer of the composite flexible pressure sensor.

[0087] Specifically, as Figure 4 shown, in the technical method of the present application, the flexible conductive base films of the two single-sided GPC microstructure film layers are stacked and combined with the two double-sided GPC microstructure film layers to obtain a composite flexible pressure sensor with a four-layer structure; among them, film layer 1 is the flexible conductive base film with a single-sided GPC microstructure film layer on the outermost layer, and film layer 4 is the flexible conductive base film with a single-sided GPC microstructure film layer on the lowermost layer; film layers 2 and 3 are the double-sided GPC microstructure film layers sandwiched in the middle. In order to make the composite flexible pressure sensor form a gradient microstructure, in the embodiments of the present application, the sandpaper corresponding to the GPC microstructure film layer on the lower surface of film layer 1 is 120 mesh, the sandpaper corresponding to the GPC microstructure film layer on the upper surface of film layer 4 is 400 mesh, the sandpaper corresponding to the GPC microstructure film layer on the upper surface of film layer 2 is 120 mesh, the sandpaper corresponding to the GPC microstructure film layer on the lower surface of film layer 2 is 240 mesh, the sandpaper corresponding to the GPC microstructure film layer on the upper surface of film layer 3 is 240 mesh, and the sandpaper corresponding to the GPC microstructure film layer on the lower surface of film layer 2 is 400 mesh. In other embodiments, a composite flexible pressure sensor with other layer structures can also be stacked, and the sandpaper mesh number used can also be adjusted accordingly. Among them, the flexible electrode is laid on the flexible substrate to obtain a flexible conductive base film, and the thickness of the flexible conductive base film is 10-80um.

[0088] Compared with the prior art, the advantages of the present invention include: (1) The present invention uses sandpaper as a template. Due to the characteristics that the larger the sandpaper mesh number and the denser and smaller the sandpaper particles, it can be directly used to manufacture a sensor with a gradient pore structure, which has the advantages of low cost and simple manufacturing method; (2) The composite flexible pressure sensor with a gradient microstructure of the present invention has the characteristics of being thin, light, and flexible, can be processed into various shapes, and has the advantages of being wearable and attachable; (3) The design of the multi-layer microstructure and the gradient pore structure, due to the pressure self-adaptive characteristics of the structure, greatly expands the pressure sensing range, and at the same time also has the advantages of high precision, high reliability, and long life.

[0089] The following is an illustration of the specific implementation process and beneficial effects of the solution through a comparison of embodiments.

[0090] Example 1

[0091] Graphene powder was added to the silicone organic prepolymer and stirred to obtain GPC ink; the mass fraction of graphene in the GPC ink was 30%. Among them, the mass ratio of the silicone-based organic monomer to the curing agent was 5:1. If the silicone organic prepolymer was a PDMS (Polydimethylsiloxane) prepolymer, the silicone-based organic monomer was a PDMS polymer monomer. The graphene powder and the silicone organic prepolymer were mechanically stirred to be uniformly mixed to obtain the GPC ink, and the GPC ink was also a graphene-PDMS composite material. Among them, the stirring duration was 30 minutes and the stirring speed was 500 r / min.

[0092] Two parallel PET strips were adhered to the edge of the conductive surface of the flexible conductive base film using tape, and the GPC ink was poured into the gap between the PET strips. The tape was a polyimide (PI) tape, the flexible conductive base film was an ITO-PET base film, and the thickness of the flexible conductive base film was 50 μm.

[0093] The GPC ink poured on the surface layer of the flexible conductive base film was leveled so that the thickness of the GPC ink was equal to the thickness of the PET strip and a GPC thin film layer was formed.

[0094] The GPC ink poured on the surface layer of the flexible conductive base film was leveled using a scraper, so that the thickness of the GPC ink was equal to the thickness of the PET strip, and a GPC thin film layer was formed. Among them, the thickness of the PET strip was 250 μm.

[0095] The sandpaper was cleaned with ethanol; nitrogen was blown in to dry the cleaned sandpaper. Two pieces of sandpaper with 120 meshes and 400 meshes were respectively pressed on the surface layer of the GPC thin film layer of two flexible conductive base films. Then, a roller was used to assist in pressing on the outer surface layer of the sandpaper, and the roller rolled back and forth on the sandpaper. The pressing part consisted of two groups of pressing plates, and the pressing plates were flat steel plates. The sandpaper and the flexible conductive base film to be pressed were placed at 90 °C for heat annealing for 3 hours for heating and curing to obtain two flexible conductive base films with a single-sided GPC microstructure thin film layer. The pressure for pressing by the pressing part was 120 kPa.

[0096] Use tape to attach two parallel PET strips to the edge of the same side of the sandpaper, and pour GPC ink into the gap between the PET strips; scrape the poured GPC ink on the surface of the sandpaper so that the thickness of the GPC ink is equal to the thickness of the PET strip and form a GPC thin film layer. Use another grit sandpaper to press on the surface layer of the GPC thin film layer and press through a pressing piece. Among them, in the first group, use 120-mesh and 240-mesh sandpapers to press the GPC thin film layer from both sides and press through a pressing piece; in the second group, use 240-mesh and 400-mesh sandpapers to press the GPC thin film layer from both sides and press through a pressing piece; place the pressed sandpaper and GPC thin film layer at 90 °C for heat annealing for 3 hours for heating and curing to obtain two double-sided GPC microstructural thin film layers.

[0097] The flexible conductive base films of two single-sided GPC microstructural thin film layers and two double-sided GPC microstructural thin film layers are stacked in sequence to prepare a composite flexible pressure sensor with a gradient micro-structure. The obtained composite flexible pressure sensor is as Figure 4 shown, where film layer 1 is the flexible conductive base film with a single-sided GPC microstructural thin film layer on the uppermost layer, and film layer 4 is the flexible conductive base film with a single-sided GPC microstructural thin film layer on the lowermost layer; film layers 2 and 3 are double-sided GPC microstructural thin film layers sandwiched in the middle. In order to make the composite flexible pressure sensor form a gradient micro-structure, in the embodiment of the present application, the sandpaper corresponding to the GPC microstructural thin film layer on the lower surface of film layer 1 is 120 mesh, the sandpaper corresponding to the GPC microstructural thin film layer on the upper surface of film layer 4 is 400 mesh, the sandpaper corresponding to the GPC microstructural thin film layer on the upper surface of film layer 2 is 120 mesh, the sandpaper corresponding to the GPC microstructural thin film layer on the lower surface of film layer 2 is 240 mesh, the sandpaper corresponding to the GPC microstructural thin film layer on the upper surface of film layer 3 is 240 mesh, and the sandpaper corresponding to the GPC microstructural thin film layer on the lower surface of film layer 2 is 400 mesh.

[0098] Comparative Example 1

[0099] Add graphene powder to the siliconized organic prepolymer and stir to obtain GPC ink; the mass fraction of graphene in the GPC ink is 30%. Among them, the mass ratio of the silicon-based organic monomer to the curing agent is 5:1. If the siliconized organic prepolymer is a PDMS (polydimethylsiloxane) prepolymer, then the silicon-based organic monomer is a PDMS polymer monomer. Mechanically stir the graphene powder and the siliconized organic prepolymer to mix evenly to obtain GPC ink, and GPC ink is also a graphene-PDMS composite material. Among them, the stirring duration is 30 minutes and the stirring speed is 500 r / min.

[0100] Attach two parallel PET strips to the edge of the conductive surface of the flexible conductive base film using tape, and pour GPC ink into the gap between the PET strips. The tape is a polyimide (PI) tape, the flexible conductive base film is an ITO-PET base film, and the thickness of the flexible conductive base film is 50um.

[0101] Level the GPC ink poured on the surface layer of the flexible conductive base film so that the thickness of the GPC ink is equal to the thickness of the PET strip and form a GPC thin film layer.

[0102] Use a scraper to level the GPC ink poured on the surface layer of the flexible conductive base film, so that the thickness of the GPC ink is equal to the thickness of the PET strip, and form a GPC thin film layer. Among them, the thickness of the PET strip is 250um.

[0103] Clean the sandpaper with ethanol; blow nitrogen to dry the cleaned sandpaper; use two 120-mesh sandpapers and press them on the surface layers of the GPC thin film layers of two flexible conductive base films respectively. Then, use a roller to assist in pressing on the outer surface of the sandpaper, and the roller rolls back and forth on the sandpaper. The pressing part consists of two groups of pressing plates, and the pressing plates are flat steel plates. Place the sandpaper and the flexible conductive base film to be pressed at 90°C for 3 hours of thermal annealing for heating and curing to obtain two flexible conductive base films with single-sided GPC microstructure thin film layers. The pressure for pressing by the pressing part is 120 kPa.

[0104] Overlap and combine two flexible conductive base films with single-sided GPC microstructure thin film layers to obtain a composite flexible pressure sensor with a double-layer structure, and the GPC microstructure thin film layers in the two flexible conductive base films are arranged oppositely and adhered to each other.

[0105] Comparative Example 2

[0106] Add graphene powder to the silicone organic prepolymer and stir to prepare GPC ink; the mass fraction of graphene in the GPC ink is 30%. Among them, the mass ratio of the silicon-based organic monomer to the curing agent is 5:1. The silicone organic prepolymer is a PDMS (Polydimethylsiloxane) prepolymer, and the silicon-based organic monomer is a PDMS polymer monomer. Mechanically stir the graphene powder and the silicone organic prepolymer to mix evenly to prepare GPC ink, and the GPC ink is also a graphene-PDMS composite material. Among them, the stirring time is 30 minutes and the stirring speed is 500 r / min.

[0107] Attach two parallel PET strips to the edge of the conductive surface of the flexible conductive base film using tape, and pour GPC ink into the gap between the PET strips. The tape is a polyimide (PI) tape, the flexible conductive base film is an ITO-PET base film, and the thickness of the flexible conductive base film is 50um.

[0108] Smoothing the GPC ink cast on the surface layer of the flexible conductive base film so that the thickness of the GPC ink is equal to the thickness of the PET strip and forming a GPC thin film layer.

[0109] Use a scraper to smooth the GPC ink cast on the surface layer of the flexible conductive base film, so that the thickness of the GPC ink is equal to the thickness of the PET strip, forming a GPC thin film layer. Among them, the thickness of the PET strip is 250um.

[0110] Clean the sandpaper with ethanol; blow nitrogen to dry the cleaned sandpaper; use two pieces of 400-mesh sandpaper and press them on the surface layers of the GPC thin film layers of two flexible conductive base films respectively. Then, use a roller to assist in pressing on the outer surface of the sandpaper, and the roller rolls back and forth on the sandpaper. The pressing part consists of two groups of pressing plates, and the pressing plates are flat steel plates. Place the sandpaper and the flexible conductive base film to be pressed at 90 °C for 3 hours of thermal annealing for heating and curing to obtain two flexible conductive base films with single-sided GPC microstructure thin film layers. The pressure for pressing by the pressing part is 120 kPa.

[0111] Overlap and combine two flexible conductive base films with single-sided GPC microstructure thin film layers to obtain a composite flexible pressure sensor with a double-layer structure. The GPC microstructure thin film layers in the two flexible conductive base films are arranged opposite to each other and are in contact.

[0112] Test Example 1

[0113] Use a Keithley 2614B source meter (Tektronix, inc., USA) to measure the resistance of the sensors obtained in Example 1, Comparative Example 1, and Comparative Example 2. By applying a DC voltage of 1V, according to I = U / R, the resistance can be converted into current. The response of the current to pressure is recorded by a computer-controlled test system, and this pressure test system is composed of a pressure gauge (Mark-10) and an electric test bench (Mark-10).

[0114] Test the sensitivity of the three sensors to record the output current of each downward pressure and calculate its sensitivity. The obtained measurement results are as Figure 5 shown. Among them, the pressure response curve of the double-layer device obtained in Comparative Example 1 is as Figure 5 shown in Figure (a), the pressure response curve of the double-layer device obtained in Comparative Example 2 is as Figure 5 shown in Figure (b), and the pressure response curve of the four-layer gradient hole device obtained in Example 1 is as Figure 5 shown in Figure (c). Among them, for the double-layer 120-mesh device, its sensitivity in the range of 0 - 20 kPa is S1 = 3.57×10 3 kPa -1, the sensitivity at 20 - 100 kPa is S2 = 0.14×10 3 kPa -1 ; for the double - layer device with 400 mesh, its sensitivity at 0 - 20 kPa is S1 = 2.57×10 3 kPa -1 , and the sensitivity at 20 - 100 kPa is S1 = 3.57×10 3 kPa -1 ; for the four - layer device with 120 mesh - (120 / 240) mesh - (240 / 400) mesh - 400 mesh from top to bottom, its sensitivity at 0 - 100 kPa is S1 = 6.02×10 3 kPa -1 , and the sensitivity at 100 - 200 kPa is S2 = 1.1×10 3 kPa -1 , it can be clearly seen that the sensitivity of the device with non - gradient pore structure at 0 - 100 kPa is less than that of the device with gradient pore structure, and the device with gradient pore structure still maintains a high sensitivity at 100 - 200 kPa. Therefore, the device with gradient pore structure has been improved in both sensitivity and pressure response range.

[0115] In the embodiments of the present invention, a composite flexible pressure sensor with micro - structure gradient and its preparation method are provided. The preparation method includes: pouring GPC ink on the conductive surface of the flexible conductive base film and pressing it with sandpaper, heating and curing to form a flexible conductive base film containing a GPC micro - structure thin film layer; pouring GPC ink between two layers of sandpaper, heating and curing to form a double - sided GPC micro - structure thin film layer; stacking two flexible conductive base films with single - sided GPC micro - structure thin film layers and at least one double - sided GPC micro - structure thin film layer in sequence to obtain the sensor. For the above - mentioned composite flexible pressure sensor, sandpaper is used as a template to press on the surface layer of the GPC thin film layer to form a GPC micro - structure thin film layer. GPC micro - structure thin film layers with gradient are formed by using sandpapers with different mesh numbers, which can conveniently and quickly prepare a sensor with multi - layer micro - structure and gradient pore structure, reduce the manufacturing steps of the sensor and lower the complexity of the manufacturing process, and achieve the purpose of manufacturing a composite flexible pressure sensor with low cost and high efficiency.

[0116] As mentioned above, the above is only the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of a composite flexible pressure sensor with microstructural gradient, characterized in that, The method includes: Adding graphene powder to a silicone organic prepolymer and stirring to obtain GPC ink; the mass fraction of graphene in the GPC ink is 15 - 45%; Using tape to attach two parallel PET strips to the edge of the conductive surface of the flexible conductive base film, and pouring GPC ink into the gap between the PET strips; Smoothing the poured GPC ink on the surface layer of the flexible conductive base film so that the thickness of the GPC ink is equal to the thickness of the PET strips and forming a GPC thin film layer; Using sandpapers with different mesh numbers to press on the surface layers of the GPC thin film layers of two flexible conductive base films respectively and performing pressing through a pressing member, each flexible conductive base film corresponding to a sandpaper of a specific specification; Placing the pressed sandpaper and flexible conductive base film at a preset temperature for heating and curing, and peeling off the sandpaper to obtain a flexible conductive base film with a single-sided GPC microstructure thin film layer; Using tape to attach two parallel PET strips to the edge of the same side of the sandpaper, and pouring GPC ink into the gap between the PET strips; Smoothing the poured GPC ink on the surface layer of the sandpaper so that the thickness of the GPC ink is equal to the thickness of the PET strips and forming a GPC thin film layer; Using another sandpaper with different mesh numbers to press on the surface layer of the GPC thin film layer of the sandpaper and performing pressing through a pressing member; Placing the pressed sandpaper and GPC thin film layer at a preset temperature for heating and curing, and peeling off the sandpaper to obtain a double-sided GPC microstructure thin film layer; Stacking two flexible conductive base films with single-sided GPC microstructure thin film layers and at least one double-sided GPC microstructure thin film layer in sequence to prepare a composite flexible pressure sensor with microstructure gradient, wherein the flexible conductive base films with single-sided GPC microstructure thin film layers are respectively located on the upper and lower sides of the composite flexible pressure sensor, and the mesh numbers of the sandpapers corresponding to the GPC microstructure thin film layers included in the composite flexible pressure sensor increase or decrease in sequence.

2. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 1, characterized in that, The placing the pressed sandpaper and flexible conductive base film at a preset temperature for heating and curing includes: Placing the pressed sandpaper and flexible conductive base film at 80 - 100 °C for thermal annealing for 2 - 5 hours.

3. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 1 or 2, characterized in that, The using sandpapers with different mesh numbers to press on the surface layers of the GPC thin film layers of two flexible conductive base films respectively and performing pressing through a pressing member includes: Using sandpapers with different mesh numbers to press on the surface layers of the GPC thin film layers of two flexible conductive base films respectively; Using a roller to roll and press on the outer surface layer of the sandpaper to assist in pressing; Clamping a pressing member composed of two groups of pressing plates on both sides of the sandpaper and the flexible conductive base film.

4. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 1 or 2, characterized in that, The using another sandpaper with different mesh numbers to press on the surface layer of the GPC thin film layer of the sandpaper and performing pressing through a pressing member includes: Using another sandpaper with different mesh numbers to press on the surface layer of the GPC thin film layer of the sandpaper; Using a roller to roll and press on the outer surface layer of the other sandpaper to assist in pressing; Clamping a pressing member composed of two groups of pressing plates on both sides of the two sandpapers.

5. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 1, characterized in that, The silicone organic prepolymer is a polydimethylsiloxane prepolymer.

6. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 1 or 2, characterized in that, Before pressing sandpapers with different mesh numbers onto the surface layer of the GPC thin film layer of the two flexible conductive base films respectively and performing pressing through a pressing member, it further includes: Cleaning the sandpapers with ethanol; Blowing nitrogen to dry the cleaned sandpapers.

7. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 6, characterized in that, The mesh number of the sandpaper corresponding to the GPC microstructure thin film layer included in the composite flexible pressure sensor is 100 - 600 meshes.

8. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 1 or 2, characterized in that, The thickness of the PET strip is 200 - 600 um.

9. The preparation method of the composite flexible pressure sensor with microstructural gradient according to claim 1 or 2, characterized in that, The pressure for pressing through the pressing member is 50 - 200 kPa.

10. A composite flexible pressure sensor with microstructural gradient, characterized in that, The composite flexible pressure sensor is manufactured by using the manufacturing method described in any one of claims 1 - 9. The composite flexible pressure sensor includes two flexible conductive base films with single-sided GPC microstructure thin film layers and at least one double-sided GPC microstructure thin film layer; Both of the double-sided GPC microstructure thin film layers are clamped between the flexible conductive base films of the single-sided GPC microstructure thin film layers, and the flexible conductive base film in the flexible conductive base film of the single-sided GPC microstructure thin film layer is located in the outermost layer of the composite flexible pressure sensor.

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