Capacitive Sensor and Its Fabrication Method

Abstract

This application belongs to the field of sensor technology, specifically relating to a capacitive sensor and its fabrication method. The capacitive sensor includes an electrode layer and a dielectric layer bonded together. The electrode layer and the dielectric layer are composite materials made by mixing conductive fillers in the same polymer at different doping ratios. Because the electrode layer and the dielectric layer use the same polymer and both are doped with conductive fillers, the conductive layer and the dielectric layer have the same material system, similar elastic modulus, and matched mechanical and physical properties. This solves the problem of sensor failure caused by mechanical mismatch under complex mechanical conditions, improving the mechanical performance matching of the capacitive sensor and the stability and reliability of capacitive sensing.

Description

Technical Field

[0001] This application belongs to the field of sensor technology, specifically relating to a capacitive sensor and its fabrication method. Background Technology

[0002] In recent years, with the development of robotics research technology, how to enable robots to possess more human-like intelligent behavior and thus widely participate in the development of various industries has become a major research hotspot. Among them, flexible sensors, as an important functional device for providing tactile signals to robots, have significant advantages such as high sensitivity, high flexibility, high stability, and durability. They have been widely integrated into various curved surfaces, mechanical grippers, and soft robots to adapt to different degrees of bending deformation, thus making outstanding contributions to the fields of human-computer interaction systems, flexible electronic skin, and intelligent soft robots.

[0003] Most flexible sensors, especially capacitive sensors, have a multi-layer structure. Different conductive and dielectric materials are usually used for each electrode layer and dielectric layer to achieve different functions. This will lead to mechanical property mismatch between the layers, which can easily cause sensing failures such as signal distortion in practical applications. Summary of the Invention

[0004] The purpose of this application is to provide a capacitive sensor and its fabrication method, which at least to some extent overcomes the technical problem of performance mismatch in multilayer structures in related technologies.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] According to one aspect of the embodiments of this application, a capacitive sensor is provided, including an electrode layer and a dielectric layer bonded together, wherein the electrode layer and the dielectric layer are composite materials made by mixing conductive fillers in the same polymer at different doping ratios.

[0007] In some embodiments of this application, based on the above technical solutions, the electrode layer and the dielectric layer are doped with the same conductive filler, and the doping ratio of the conductive filler in the electrode layer is greater than the doping ratio of the conductive filler in the dielectric layer.

[0008] In some embodiments of this application, based on the above technical solutions, the polymer is any one of polydimethylsiloxane, polyurethane, polyimide, epoxy resin, polyethylene, polyvinylidene fluoride, polycarbonate, polyethylene naphthalate, nylon, polypropylene, rubber, and polyoxymethylene; the conductive filler is any one or a combination of metal nanowires, carbon nanotubes, graphite, graphene, carbon black, and metal conductive powder.

[0009] In some embodiments of this application, based on the above technical solutions, the polymer is polydimethylsiloxane and the conductive filler is carbon nanotubes.

[0010] In some embodiments of this application, based on the above technical solutions, the mass ratio of carbon nanotubes doped in the electrode layer is 6-90%, and the mass ratio of carbon nanotubes doped in the dielectric layer is 0.1-5%.

[0011] In some embodiments of this application, based on the above technical solutions, the mass ratio of carbon nanotubes doped in the electrode layer is 7%, and the mass ratio of carbon nanotubes doped in the dielectric layer is 2%.

[0012] In some embodiments of this application, based on the above technical solutions, the polymer is polydimethylsiloxane and the conductive filler is carbon black.

[0013] In some embodiments of this application, based on the above technical solutions, the mass ratio of carbon black doped in the electrode layer is 8-60%, and the mass ratio of carbon black doped in the dielectric layer is 0.1-3%.

[0014] In some embodiments of this application, based on the above technical solutions, the polymer is polyurethane and the conductive filler is metal nanowires.

[0015] In some embodiments of this application, based on the above technical solutions, the mass ratio of the metal nanowires doped in the electrode layer is 7-30%, and the mass ratio of the metal nanowires doped in the dielectric layer is 0.1-3%.

[0016] In some embodiments of this application, based on the above technical solutions, the conductive filler is a mixed filler composed of at least two conductive materials with different materials or different structures.

[0017] In some embodiments of this application, based on the above technical solutions, the electrode layer includes a first electrode layer attached to the first surface of the dielectric layer and a second electrode layer attached to the second surface of the dielectric layer, wherein at least one of the first electrode layer, the second electrode layer and the dielectric layer is a thin film layer with a micro-protrusion structure.

[0018] In some embodiments of this application, based on the above technical solutions, the micro-convex structure is the surface microstructure of a velvet calathea leaf.

[0019] According to one aspect of the embodiments of this application, a method for fabricating a capacitive sensor is provided. The method includes: mixing conductive fillers in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution; curing the conductive solution and the non-conductive solution respectively to obtain an electrode layer and a dielectric layer; and assembling the electrode layer and the dielectric layer into a capacitive sensor.

[0020] In some embodiments of this application, based on the above technical solutions, the conductive solution and the non-conductive solution are cured to obtain an electrode layer and a dielectric layer, including: curing the conductive solution on a microstructure template to obtain a first electrode layer with a micro-convex structure; curing the conductive solution on a smooth substrate to obtain a second electrode layer with a smooth surface; and curing the non-conductive solution on a smooth substrate to obtain a dielectric layer with a smooth surface.

[0021] In some embodiments of this application, based on the above technical solutions, the conductive solution is cured on a microstructure template to obtain a first electrode layer with a micro-convex structure, including: casting the conductive solution onto the microstructure template; heating the conductive solution carried on the microstructure template to obtain a conductive thin film layer cured on the microstructure template; and peeling the conductive thin film layer off the microstructure template to obtain the first electrode layer with a micro-convex structure.

[0022] In some embodiments of this application, based on the above technical solutions, the microstructure template is a polydimethylsiloxane template with a micro-convex inverse structure; before casting the conductive solution onto the microstructure template, the method further includes: mixing a prepolymer of polydimethylsiloxane with a curing agent solution in a preset ratio to obtain a mixed solution; casting the mixed solution onto the surface of a velvet calathea leaf; heating the mixed solution on the surface of the velvet calathea leaf to obtain a polydimethylsiloxane film cured on the surface of the velvet calathea leaf; and peeling the polydimethylsiloxane film off the surface of the velvet calathea leaf to obtain a polydimethylsiloxane template with a micro-convex inverse structure.

[0023] In some embodiments of this application, based on the above technical solutions, the conductive solution and the non-conductive solution are respectively cured to obtain an electrode layer and a dielectric layer, including: curing the conductive solution on a smooth substrate to obtain a smooth electrode layer; and curing the non-conductive solution on a microstructure template to obtain a dielectric layer with a micro-convex structure.

[0024] In some embodiments of this application, based on the above technical solutions, the conductive filler is carbon nanotubes, and the polymer is polydimethylsiloxane; mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution includes: mixing carbon nanotubes with polydimethylsiloxane at a mass ratio of 7-10% to obtain a first mixed raw material; dispersing the first mixed raw material in chloroform to obtain a conductive solution; the mass ratio of polydimethylsiloxane to chloroform in the conductive solution is 1:3; mixing carbon nanotubes with polydimethylsiloxane at a mass ratio of 1-3% to obtain a second mixed raw material; dispersing the second mixed raw material in chloroform to obtain a non-conductive solution.

[0025] In some embodiments of this application, based on the above technical solutions, the conductive filler is carbon black, and the polymer is polydimethylsiloxane; mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution includes: mixing carbon black with polydimethylsiloxane at a mass ratio of 8-60% to obtain a third mixed raw material; dispersing the third mixed raw material in chloroform to obtain a conductive solution; mixing carbon black with polydimethylsiloxane at a mass ratio of 0.1-3% to obtain a fourth mixed raw material; and dissolving the fourth mixed raw material in chloroform to obtain a non-conductive solution.

[0026] In some embodiments of this application, based on the above technical solutions, the conductive filler is a metal nanowire, and the polymer is polyurethane; mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution includes: mixing the metal nanowire with polyurethane at a mass ratio of 7-30% to obtain a fifth mixed raw material; dispersing the fifth mixed raw material in an aqueous solvent to obtain a conductive solution; mixing the metal nanowire with polyurethane at a mass ratio of 0.1-3% to obtain a sixth mixed raw material; and dispersing the sixth mixed raw material in an aqueous solvent to obtain a non-conductive solution.

[0027] In the technical solution provided in the embodiments of this application, since the electrode layer and the dielectric layer use the same polymer and both are doped with conductive fillers, the conductive layer and the dielectric layer have the same material system, similar elastic modulus, and matching mechanical and physical properties. This solves the problem of sensor failure caused by mechanical mismatch under complex mechanical conditions, and improves the mechanical performance matching of capacitive sensors as well as the stability and reliability of capacitive sensing.

[0028] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0030] Figure 1 A cross-sectional structural schematic diagram of a capacitive sensor according to one embodiment of this application is shown.

[0031] Figure 2 A flowchart illustrating the steps involved in fabricating a capacitive sensor according to one embodiment of this application is shown.

[0032] Figure 3 This application illustrates a method for fabricating a capacitive sensor by introducing microstructures into the electrode layer in one embodiment.

[0033] Figure 4 A flowchart illustrating the steps for preparing a microstructure template in one embodiment of this application is shown.

[0034] Figure 5 A flowchart illustrating the steps for testing the device performance of the capacitive sensor prepared in the embodiments of this application is shown.

[0035] Figure 6 A schematic diagram showing the performance comparison of the capacitive sensor prepared in the embodiments of this application with that of sensors in the prior art in terms of capacitive response is illustrated.

[0036] Figure 7 A schematic diagram comparing the elastic moduli of the electrode layer and the dielectric layer of the capacitive sensor in an embodiment of this application is shown.

[0037] Figure 8 A schematic diagram showing the change of dielectric constant of the dielectric layer of the capacitive sensor in an embodiment of this application with pressure is shown.

[0038] Figure 9 A schematic diagram of the tensile strain performance of the lower electrode layer in a capacitive sensor according to an embodiment of this application is shown.

[0039] Figure 10 A schematic diagram of the stretching cycle state of the lower electrode layer in the capacitive sensor according to an embodiment of this application is shown.

[0040] Figure 11 This diagram illustrates the capacitance value variation of a capacitive sensor according to an embodiment of this application under different pressures and tensile strains.

[0041] Figure 12The finite element analysis results of the pressure distribution at the microstructure tip and dielectric layer interface of the capacitive sensor in the embodiments of this application under different pressures are shown.

[0042] Figure 13 A schematic diagram is shown of the process of a soft robot grasping and releasing a doll using the capacitive sensor described in the embodiments of this application.

[0043] Figure 14 This diagram illustrates the changes in resistance and capacitance of a capacitive sensor during the operation of a soft robot. Detailed Implementation

[0044] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0045] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0046] Although relative terms such as "up" and "down" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as the orientation of the examples shown in the accompanying drawings. It is understood that if the icon's objects are flipped so that they are upside down, the component described as "up" will become the component described as "down." When a structure is "up" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" set on the other structure, or that the structure is "indirectly" set on the other structure through another structure.

[0047] The terms “a,” “one,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components besides those listed; the terms “first,” “second,” and “third” are used only as markers and are not a limitation on the number of objects.

[0048] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0049] In the related technologies of this application, capacitive sensors mostly employ rigid electrodes and elastomer dielectric layers or composite electrodes and composite dielectric layers. Both of these methods present the problem of matching the mechanical properties of different materials. Typically, the elastic moduli of polymeric materials and conductive materials differ significantly, easily leading to mechanical mismatch issues. This results in mechanical mismatches within the composite electrode itself and between the composite electrode and the dielectric layer, causing sensing failures such as signal distortion in practical applications. Furthermore, due to the significant difference in elastic moduli between the electrode layer and the dielectric layer, the mechanical properties are difficult to match, resulting in poor flexibility and tensile properties of the sensor, making it unable to adapt well to the bending and deformation movements of robots.

[0050] To address the problems of existing sensors, this application proposes a dual-modal flexible capacitive sensor with a single material system. The sensor includes an electrode layer and a dielectric layer bonded together. The electrode layer and dielectric layer are composite materials made by mixing conductive fillers in the same polymer at different doping ratios. Because the electrode layer and dielectric layer use the same polymer and both are doped with conductive fillers, they share the same material system, have similar elastic moduli, and exhibit matched mechanical and physical properties. This solves the problem of sensor failure caused by mechanical mismatch under complex mechanical conditions, improving the mechanical matching performance of the capacitive sensor and the stability and reliability of capacitive sensing. This dual-modal capacitive sensor can not only realize capacitive signal responses under tensile, compressive, and bending conditions but also identify the resistance signal responses of the electrodes. This dual-modal response mechanism can be applied to fields such as robot motion recognition.

[0051] In one embodiment of this application, the same conductive filler is doped in both the electrode layer and the dielectric layer, with the doping ratio of the conductive filler in the electrode layer being greater than that in the dielectric layer. Conductivity and dielectric properties are achieved by controlling the amount of conductive filler doped in the polymer. Doping the dielectric layer with conductive filler can effectively improve the sensor's response performance.

[0052] Conductive fillers and polymers can be blended into polymer blends by appropriate methods, such as solution blending, colloidal emulsion blending, or melt blending.

[0053] In one embodiment of this application, the conductive filler is a mixed filler composed of at least two conductive materials with different materials or different structures. For example, metal nanoparticles and carbon nanotubes can be mixed to form a mixed filler, or metal nanowires and carbon nanotubes can be mixed to form a mixed filler.

[0054] In one embodiment of this application, the conductive filler includes at least one of conductive particles, conductive linear materials, or conductive network materials. Conductive particles may include, for example, carbonaceous material particles or metal nanoparticles; conductive linear materials may include, for example, carbon nanowires, carbon nanotubes, or metal nanowires; and conductive network materials may include, for example, graphite or graphene.

[0055] In one embodiment of this application, both the electrode layer and the dielectric layer are made of polymer films containing conductive fillers and elastomers. The conductive fillers can be any one or a combination of two of the following: metal nanowires (silver nanowires, gold nanowires, and copper nanowires, etc.), carbon nanotubes, graphite, graphene, carbon black, and conductive metal powders (gold powder, silver powder, copper powder, etc.). The polymer can be any one of the following, but is not limited to: polydimethylsiloxane, polyurethane, polyimide, epoxy resin, polyethylene, polyvinylidene fluoride, polypropylene, rubber, and polyoxymethylene. The electrode layer has a higher content of conductive fillers, resulting in better conductivity; the dielectric layer has a lower content of conductive fillers, resulting in better dielectric properties.

[0056] In one embodiment of this application, the electrode layer includes a first electrode layer attached to a first surface of the dielectric layer and a second electrode layer attached to a second surface of the dielectric layer, wherein at least one of the first electrode layer, the second electrode layer and the dielectric layer is a thin film layer with a micro-protrusion structure.

[0057] Figure 1 A schematic cross-sectional view of a capacitive sensor according to one embodiment of this application is shown. Figure 1 As shown, the capacitive sensor is composed of three parallel thin film layers bonded together by physical or chemical adhesion. The structure of the capacitive sensor includes: a dielectric layer 101 located in the center, an upper electrode layer 102 bonded to the upper surface of the dielectric layer 101, and a lower electrode layer 103 bonded to the lower surface of the dielectric layer. The upper electrode layer 102 has a micro-protrusion structure on the surface where it is bonded to the dielectric layer 101, while both the dielectric layer 101 and the lower electrode layer 103 are thin film layers with smooth surfaces.

[0058] The capacitance formula for a capacitive sensor is C ~ εS / d, where ε is the relative permittivity of the dielectric layer, S is the contact area between the electrode layer and the dielectric layer, and d is the distance between the two electrode layers. Introducing microstructures into the electrode layer or dielectric layer can form multiple microcapacitors and a mesh-like air capacitor in the sensor. During the process of the sensor being compressed, the pressure is locally amplified through the interface between the microstructure tip and the dielectric layer, which can significantly increase the relative permittivity, thereby significantly increasing the capacitance change of the sensor and further improving the sensor's response performance.

[0059] The introduction of micro-convex structures can be achieved through etching, biomimetic replication, electroplating, or 3D printing. The micro-convex structures can be any of the following: pyramids, micro-columns, irregular shapes, hemispheres, waves, ellipsoids, or cones.

[0060] In one embodiment of this application, the micro-convex structure is the surface microstructure of a velvety calathea leaf. Introducing this velvety calathea leaf surface microstructure into a capacitive sensor based on biomimetic technology can significantly improve the sensor's sensitivity under various morphological changes such as stretching, compression, and bending.

[0061] In one embodiment of this application, the polymer used to prepare the electrode layer and the dielectric layer is polydimethylsiloxane, and the conductive filler is carbon nanotubes. The mass proportion of carbon nanotubes doped in the electrode layer can be 6%–90%, and the mass proportion of carbon nanotubes doped in the dielectric layer can be 0.1%–5%. The carbon nanotubes can be any one of single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes.

[0062] In one embodiment of this application, the mass ratio of carbon nanotubes doped in the electrode layer is 7-10%, and the mass ratio of carbon nanotubes doped in the dielectric layer is 0.1-3%.

[0063] In one embodiment of this application, the mass ratio of carbon nanotubes doped in the electrode layer is 7%, and the mass ratio of carbon nanotubes doped in the dielectric layer is 2%.

[0064] Since the doping ratios of the electrode layer and the dielectric layer are not significantly different, the electrode layer and dielectric layer prepared based on this doping ratio have a good matching relationship in terms of elastic modulus and sensing performance. By ensuring that the electrode layer has good conductivity and the dielectric layer has good dielectric properties, the electrode layer and dielectric layer have more similar elastic moduli, thus ensuring that each layer structure has similar mechanical properties and improving the operational stability and reliability of the sensor.

[0065] In one embodiment of this application, the polymer is polydimethylsiloxane, and the conductive filler is carbon black. The mass percentage of carbon black doped in the electrode layer is 8-60%, and the mass percentage of carbon black doped in the dielectric layer is 0.1-3%. Using carbon black as the conductive filler can reduce the fabrication cost of the capacitive sensor, and by increasing the difference in the doping ratio of the conductive filler between the electrode layer and the dielectric layer, it can improve the sensor's sensing performance.

[0066] In one embodiment of this application, the polymer is polyurethane, and the conductive filler is metal nanowires. Specifically, the mass proportion of metal nanowires doped in the electrode layer is 7–30%, and the mass proportion of metal nanowires doped in the dielectric layer is 0.1–3%. Polyurethane is a wear-resistant elastomer with good deformability, and it has a higher relative permittivity compared to many other polymers.

[0067] Figure 2 A flowchart illustrating the steps involved in fabricating a capacitive sensor according to one embodiment of this application is shown. Figure 2 As shown, the method for fabricating a capacitive sensor may include the following steps S210 to S230.

[0068] Step S210: The conductive filler is mixed in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution;

[0069] Step S220: The conductive solution and the non-conductive solution are cured separately to obtain the electrode layer and the dielectric layer;

[0070] Step S230: Assemble the electrode layer and dielectric layer into a capacitive sensor.

[0071] In the method for preparing a capacitive sensor provided in this application embodiment, by doping different proportions of conductive fillers into the same polymer, an electrode layer with good conductivity and a dielectric layer with good dielectric properties can be prepared. The electrode layer and the dielectric layer are then assembled into a capacitive sensor of a single material system. The electrode layer and the dielectric layer in this sensor have similar elastic moduli, and their mechanical and physical properties are matched, which solves the problem of sensor failure caused by mechanical mismatch under complex mechanical conditions.

[0072] Figure 3 This application illustrates a method for fabricating a capacitive sensor by introducing microstructures into the electrode layer, as shown in one embodiment. Figure 3 As shown, the capacitive sensor fabrication method in this application embodiment may include the following steps S310 to S350.

[0073] Step S310: The conductive filler is mixed in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution.

[0074] By controlling the doping ratio of conductive filler in the polymer, the conductivity of the mixed solution can be adjusted, thereby preparing a conductive solution with good conductivity and a non-conductive solution with good dielectric properties. In some optional embodiments, the conductive solution and the non-conductive solution have the same conductive filler, the same polymer, and the same solvent.

[0075] Step S320: The conductive solution is cured on the microstructure template to obtain the first electrode layer with a micro-convex structure.

[0076] By using a pre-prepared microstructure template to solidify and mold a conductive solution, a first electrode layer with a micro-convex structure can be obtained.

[0077] In some alternative embodiments, the method of curing the first electrode layer may include: casting a conductive solution onto a microstructure template; heating the conductive solution carried on the microstructure template to obtain a conductive thin film layer cured on the microstructure template; and peeling the conductive thin film layer off the microstructure template to obtain a first electrode layer with a micro-convex structure.

[0078] The microstructure template can be an inverse structure template prepared based on the surface structure of a velvet calathea leaf. Based on this template, a conductive solution can be solidified to obtain a first electrode layer with the micro-convex structure of a velvet calathea leaf. Introducing the microstructure of a velvet calathea leaf surface into a capacitive sensor using biomimetic technology can significantly improve the sensor's sensitivity under various morphological changes such as stretching, compression, and bending.

[0079] In some alternative embodiments, the surface micro-protrusion structure of the first electrode layer can also be any one or a combination of structures such as pyramids, micro-pillars, irregular shapes, hemispheres, waves, ellipsoids, or cones.

[0080] In some alternative implementations, a micro-convex structure template can be prepared by means of etching, biomimetic replication, electroplating or 3D printing, and then the conductive solution can be solidified and molded using the micro-convex structure template to obtain a first electrode layer with a micro-convex structure.

[0081] Step S330: The conductive solution is cured on a smooth substrate to obtain a smooth second electrode layer.

[0082] In some alternative embodiments, the method for curing the second electrode layer may include: casting a conductive solution onto a smooth substrate; heating the conductive solution supported on the smooth substrate to obtain a conductive thin film layer cured on the smooth substrate; and peeling the conductive thin film layer off the smooth substrate to obtain a second electrode layer with a smooth surface. The smooth substrate in the embodiments of this application may be, for example, a glass substrate.

[0083] Step S340: The non-conductive solution is cured on a smooth substrate to obtain a smooth dielectric layer.

[0084] In some alternative embodiments, the method for curing the dielectric layer may include: casting a non-conductive solution onto a smooth substrate; heating the non-conductive solution supported on the smooth substrate to obtain a non-conductive thin film layer cured on the smooth substrate; and peeling the non-conductive thin film layer off the smooth substrate to obtain a dielectric layer with a smooth surface. The smooth substrate in the embodiments of this application may be, for example, a glass substrate.

[0085] Step S350: Assemble the first electrode layer, the second electrode layer and the dielectric layer into a capacitive sensor.

[0086] In some alternative implementations, a first electrode layer with a micro-convex structure can be attached to the upper surface of the dielectric layer, and a second electrode layer with a smooth surface can be attached to the lower surface of the dielectric layer. After self-assembly stacking, a capacitive sensor with a microstructured electrode layer can be formed.

[0087] In one embodiment of this application, a conductive solution can be cured on a smooth substrate to obtain a smooth electrode layer; simultaneously, a non-conductive solution can be cured on a microstructure template to obtain a dielectric layer with a micro-convex structure. Based on this, two smooth electrode layers can be respectively attached to the two surfaces of the dielectric layer with the micro-convex structure, and after self-assembly stacking, a capacitive sensor with a microstructure dielectric layer is formed.

[0088] This application embodiment introduces microstructures into the electrode layer or dielectric layer to form multiple microcapacitors and mesh-like air capacitors in the sensor. During the process of the sensor being compressed, the pressure is locally amplified through the tip of the electrical microstructure, which can significantly improve the relative permittivity, thereby significantly increasing the capacitance change of the sensor and further improving the response performance of the sensor.

[0089] Figure 4 A flowchart illustrating the steps of preparing a microstructure template in one embodiment of this application is shown. This microstructure template is a biomimetic structural template with a velvety Maranta leaf surface structure, prepared based on polydimethylsiloxane (PDMS). Figure 4 As shown, the method for preparing a microstructure template may include the following steps S410 to S440.

[0090] Step S410: Mix the prepolymer of polydimethylsiloxane with the curing agent solution according to a preset ratio to obtain a mixed solution.

[0091] In some alternative embodiments, the prepolymer of polydimethylsiloxane and the curing agent solution (e.g., Sylgard 184 can be used) are mechanically mixed at a ratio of 5:1, and then placed in a vacuum oven at room temperature to remove excess air bubbles, resulting in a uniformly dispersed mixed solution.

[0092] Step S420: Pour the mixed solution onto the surface of the velvet calathea leaves.

[0093] Pour the well-mixed polydimethylsiloxane solution onto the surface of the velvet calathea leaves, which have been washed and dried with nitrogen multiple times, and let it stand at room temperature for 30 minutes to allow the polydimethylsiloxane to level out.

[0094] Step S430: Heat the mixed solution carried on the surface of the velvet calathea leaf to obtain a polydimethylsiloxane film solidified on the surface of the velvet calathea leaf.

[0095] The mixed solution can be cured at 60°C for 2 hours, or at 70°C for 1 hour.

[0096] Step S440: Peel off the polydimethylsiloxane film from the surface of the velvet calathea leaf to obtain a polydimethylsiloxane template with a micro-convex reverse structure.

[0097] The cured polydimethylsiloxane film was peeled off the leaf to obtain a polydimethylsiloxane template with an inverse structure that has the micro-convex structure of a velvety calathea leaf. The thickness of the polydimethylsiloxane template was 400 μm.

[0098] In one embodiment of this application, after the polydimethylsiloxane template is prepared, it can be further subjected to air plasma treatment. The plasma is used to clean the surface of the polydimethylsiloxane template and generate polar groups, thereby improving the surface adhesion of the polydimethylsiloxane template.

[0099] In one embodiment of this application, the conductive filler used to prepare the capacitive sensor is carbon nanotube, the polymer is polydimethylsiloxane, and the solvent is chloroform. Based on the above embodiments, step S310, which involves mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution, may include steps S3111 to S3114.

[0100] Step S3111: Mix carbon nanotubes with polydimethylsiloxane at a mass ratio of 7-10% to obtain the first mixed raw material.

[0101] In some optional embodiments, a first mixed raw material can be obtained by mixing 7 wt% of multi-walled carbon nanotubes with polydimethylsiloxane. The multi-walled carbon nanotubes have a length of 10–30 μm, a diameter of 10–20 nm, and a purity of 95%.

[0102] Step S3112: Disperse the first mixed raw material in chloroform to obtain a conductive solution; the mass ratio of polydimethylsiloxane to chloroform in the conductive solution is 1:3.

[0103] The first mixed raw material is dispersed in chloroform, and a uniformly dispersed conductive solution is obtained by sonication at 70% power for 2 hours using a cell disruptor.

[0104] Step S3113: Mix carbon nanotubes with polydimethylsiloxane at a mass ratio of 1-3% to obtain a second mixed raw material.

[0105] In some alternative embodiments, a second mixed raw material can be obtained by mixing 2 wt% of multi-walled carbon nanotubes with polydimethylsiloxane. When preparing the second mixed raw material, the same multi-walled carbon nanotubes and polydimethylsiloxane are used as in the first mixed raw material.

[0106] Step S3114: Disperse the second mixed raw material in chloroform to obtain a non-conductive solution.

[0107] The second mixture is dispersed in chloroform and sonicated at 70% power for 2 hours using a cell disruptor to obtain a uniformly dispersed, non-conductive solution. The second mixture can be produced using the same solvent mass ratio as the first mixture.

[0108] The prepared conductive solution was poured onto a clean glass substrate and a pre-prepared inverse template with a micro-convex structure of velvet calathea leaves, respectively. The substrate was left to stand for 20 minutes to allow the chloroform to evaporate completely. After curing at 80°C for 4 hours, the solution was peeled off from the glass substrate and the inverse template with the micro-convex structure of velvet calathea leaves to obtain an electrode without microstructure and an electrode with micro-convex structure of velvet calathea leaves with a thickness of 60–120 μm. The resistance of the electrodes was 100–1000 Ω / cm and the elastic modulus was 2–10 MPa.

[0109] A non-conductive solution was spin-coated onto a glass substrate at a speed of 600–1000 rpm for 30–60 s, and then heated at 80 °C for 4 h to obtain a dielectric film with a thickness of 80–120 μm, a dielectric constant of 10–20, and an elastic modulus of 2–10 MPa.

[0110] The microstructured upper electrode layer, the unstructured dielectric layer, and the unstructured lower electrode layer prepared above are self-assembled and stacked together. Metal conductive leads are then connected to the surfaces of the upper and lower electrode layers to obtain a flexible capacitive sensor composed of a single multi-walled carbon nanotube / polydimethylsiloxane system.

[0111] The capacitive sensor prepared in this application embodiment has dual-mode sensing capability of capacitance and resistance. Based on this, this application embodiment also provides a method for detecting the device performance of the dual-mode sensing of the capacitive sensor. This method can realize functions such as acquiring the resistance and capacitance signals of the sensor, signal conditioning, and front-end and back-end data communication.

[0112] This paper designs universal device performance testing circuits for the capacitance and resistance signal responses of dual-mode capacitive sensors under conditions of tension, compression, and bending. For capacitance detection, this includes, but is not limited to, using capacitance-to-digital converters or capacitance detection circuits to read the sensor's capacitance value. For resistance detection, this includes, but is not limited to, using series voltage divider, parallel current divider, and bridge methods combined with ADC sampling of analog signals to detect the resistance signal. An MCU (ARM, DSP, etc., but not limited to this) is used to cyclically read the resistance and capacitance data and then synchronize it in real time to a PC or other devices. Data transmission in the link is not limited to wired or wireless connections; data communication methods include, but are not limited to, USB, IIC, SPI, and UART.

[0113] Figure 5 A flowchart illustrating the steps for testing the device performance of the capacitive sensor prepared in the embodiments of this application is shown. Figure 5 As shown, the method for simultaneously detecting the resistance and capacitance sensing performance of a capacitive sensor includes the following steps S510 to S560.

[0114] Step S510: After the program starts running, initialize the parameters of various external devices.

[0115] External device parameters are used to control data transmission between the detection circuit and external devices such as the host computer and user terminals. The core processor of the detection circuit is used to perform data acquisition, data processing, and data transmission to the host computer and user terminals.

[0116] Step S520: Determine whether the communication between the detection circuit and the external device is normal.

[0117] If communication between the detection circuit and the external device fails, return to step S510 to reinitialize all external device parameters. If communication between the detection circuit and the external device is normal, continue to step S530.

[0118] Step S530: Update the raw data of the capacitive sensor.

[0119] The raw data from the capacitive sensor includes real-time detected capacitance and resistance data. After communication is established, the MCU reads the sensor's capacitance data via a capacitance-to-digital converter chip and its resistance data via an ADC.

[0120] Step S540: Filter and transform the original data.

[0121] After filtering and data conversion of the acquired raw data in the MCU, stable and denoised resistance and capacitance values ​​are obtained.

[0122] Step S550: Send the data to an external device.

[0123] The data is fed back to the host computer for display or to the user terminal for further processing via USB interface or other communication links, thus completing one acquisition cycle of sensor resistance and capacitance data.

[0124] Step S560: Determine whether the data acquisition loop condition is met.

[0125] When the loop condition is met, return to step S530 to continue collecting and updating the original data in a loop. The user terminal can continuously receive real-time updated sensor resistance and capacitance data at different times.

[0126] The device performance testing process of the capacitive sensor can be terminated when the loop condition is no longer met.

[0127] Figure 6 A schematic diagram comparing the performance of the capacitive sensor prepared in this embodiment with that of a prior art sensor in terms of capacitive response is shown. In the capacitive sensor prepared in this embodiment, the dielectric layer is carbon nanotubes doped with 2 wt% of PDMS; while in the prior art sensor, the dielectric layer is pure PDMS material.

[0128] As a key parameter for pressure sensing, the sensitivity of a capacitive sensor is defined as:

[0129] S=(ΔC / C0) / ΔP

[0130] Where C0 is the initial capacitance before loading, ΔC is the change in capacitance with pressure, and ΔP is the change in pressure. Figure 6 As can be seen, the sensor in this embodiment has a sensitivity of 0.15 kPa when the pressure is below 47 kPa. -1 When the pressure is between 47 kPa and 214 kPa, the sensitivity drops to 0.08 kPa. -1When the pressure is between 214 kPa and 450 kPa, the sensitivity drops to 0.04 kPa. -1 At a pressure of 450 kPa, the normalized change in capacitance (ΔC / C0) is approximately 30, which is 33 times that of a sensor with a pure PDMS dielectric layer.

[0131] Therefore, it can be seen that the capacitive sensor prepared in the embodiments of this application has a much higher sensitivity than the sensors of the prior art.

[0132] Figure 7 A schematic diagram comparing the elastic moduli of the electrode layer and the dielectric layer of the capacitive sensor in an embodiment of this application is shown. Figure 7 As shown, in this embodiment, the electrode layer of the capacitive sensor is doped with 7 wt% carbon nanotubes (CNTs) in PDMS, while the dielectric layer is doped with 2 wt% carbon nanotubes (CNTs) in PDMS, with corresponding elastic moduli of 3.4 MPa and 1.4 MPa, respectively. The elastic modulus of pure PDMS material is 1.2 MPa. This unified material system, doped with a small amount of carbon nanotubes or other conductive fillers on a PDMS substrate, can maintain similar mechanical properties across the sensor layers. This mechanical matching is difficult to achieve in other sensors, including those with soft dielectric layers, metal or plastic electrodes.

[0133] Figure 8 This diagram illustrates the variation of the dielectric constant of the dielectric layer of the capacitive sensor in this embodiment with pressure. In this embodiment, the dielectric layer of the capacitive sensor is composed of 2 wt% carbon nanotubes (CNTs) doped in PDMS. As the pressure increases from 0 to 700 kPa, the relative dielectric constant of the dielectric layer gradually increases from 2.74 to 93.2. In contrast, pure PDMS material does not exhibit a significant change in relative dielectric constant under the same pressure variation conditions.

[0134] Figure 9 A schematic diagram illustrating the tensile strain properties of the lower electrode layer in a capacitive sensor according to an embodiment of this application is shown. Figure 9 As shown, the lower electrode layer of the capacitive sensor in this embodiment is a smooth planar PMDS-CNTs electrode (7wt% CNTs). It exhibits a constant strain coefficient GF1 of 2.5 within the strain range of 0-60%, and a relatively constant strain coefficient GF2 of 3.4 within the strain range exceeding 60%. Therefore, the capacitive sensor in this embodiment can also be used as a strain sensor. The strain coefficient GF is defined as ΔR / (R0·e), where ΔR is the change in resistance with loading, R0 is the initial resistance before loading, and e is the engineering strain.

[0135] Figure 10 A schematic diagram illustrating the stretching cycle state of the lower electrode layer in a capacitive sensor according to an embodiment of this application is shown. Figure 10As shown, the lower electrode layer maintains a relatively constant strain coefficient after 10,000 cycles at a strain level of 30%, indicating high repeatability of the response over a long period. Therefore, the pressure sensor of this embodiment can be used as a dual-peak sensor—providing a capacitive signal for pressure sensing and a resistive signal for strain sensing. These two signals are decoupled from each other because they are measured from different channels. Furthermore, the capacitive sensor can be stretched to ~100%, which is sufficient for most applications in conventional robotic systems and soft robots.

[0136] Figure 11 This diagram illustrates the capacitance variation of a capacitive sensor according to an embodiment of this application under different pressures and tensile strain levels. Figure 11 As shown, under continuously increasing pressure, the normalized change in capacitance (ΔC / C0) also shows a continuously increasing trend; under continuously increasing tensile strain, the normalized change in capacitance (ΔC / C0) remains almost constant at 0. This demonstrates that the capacitance sensor of this embodiment has good tensile stability in terms of capacitance response.

[0137] Figure 12 The finite element analysis results of the pressure distribution at the microstructure tip and dielectric layer interface of the capacitive sensor in this embodiment under different pressures are shown. Figure 12 As shown, when the capacitive sensor is subjected to a large external force, the pressure at the interface between the microstructure tip and the dielectric layer is locally amplified, and the normalized change in capacitance value shows a continuous increasing trend.

[0138] Figure 13 A schematic diagram is shown of the process of a soft robot grasping and releasing a doll using the capacitive sensor described in the embodiments of this application. Figure 14 This diagram illustrates the changes in resistance and capacitance of a capacitive sensor during the operation of a soft robot.

[0139] In this embodiment, the capacitive sensor, which measures pressure and strain sensitively from both capacitance and resistance signals, acts as a bimodal sensor, by comparing... Figure 13 and Figure 14 As can be seen, by integrating the capacitive sensor into the gripper of a soft robot, the capacitive and resistive responses are demonstrated during the dynamic processes of grasping, lifting, holding, and releasing the doll.

[0140] In its initial state, the gripper is fully open to grasp large objects and applies tensile strain to the sensors. When the doll is touched and grasped, the capacitance increases sharply, and the resistance decreases due to the reduced strain on the gripper surface. The doll is then lifted and held for approximately 2 seconds before being released. Correspondingly, the capacitance signal remains constant during the holding period and drops sharply to its initial value after release; the resistance signal also exhibits a relatively stable value when the doll is held, returning to its original value after release.

[0141] Therefore, the capacitive sensor in this embodiment can not only identify the pressure situation during the grasping process through capacitance changes, but also reflect the bending and stretching of the gripper through resistance changes.

[0142] In one embodiment of this application, the conductive filler used to prepare the capacitive sensor is carbon black, the polymer is polydimethylsiloxane, and the solvent is chloroform. Based on the above embodiments, step S310, which involves mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution, may include steps S3121 to S3124 as follows.

[0143] Step S3121: Mix carbon black with polydimethylsiloxane at a mass ratio of 8-60% to obtain a third mixed raw material.

[0144] Step S3122: Disperse the third mixed raw material in chloroform to obtain a conductive solution.

[0145] The third mixed raw material was dispersed in chloroform, mechanically stirred, and then placed in a vacuum oven to remove excess air bubbles at room temperature, resulting in a uniformly dispersed carbon black / polydimethylsiloxane conductive solution.

[0146] Step S3123: Mix carbon black with polydimethylsiloxane at a mass ratio of 0.1-3% to obtain the fourth mixed raw material.

[0147] When preparing the fourth mixture, the same multi-walled carbon black and polydimethylsiloxane as the third mixture are used.

[0148] Step S3124: Disperse the fourth mixed raw material in chloroform to obtain a non-conductive solution.

[0149] The fourth mixed raw material was dispersed in chloroform, mechanically stirred, and then placed in a vacuum oven to remove excess air bubbles at room temperature, yielding a uniformly dispersed carbon black / polydimethylsiloxane non-conductive solution. The fourth mixed raw material can be produced using the same solvent mass ratio as the third mixed raw material.

[0150] The aforementioned carbon black / polydimethylsiloxane conductive solution was spin-coated onto a glass substrate at 600–1000 rpm for 30–60 s, and then heated at 80°C for 2 h to obtain a structureless electrode layer film with a thickness of 80–120 μm, a resistivity of 1–300 Ω / cm, and an elastic modulus of 2–10 MPa. The carbon black / polydimethylsiloxane conductive solution was then cast onto a microstructure template prepared by photolithography. After removing excess air bubbles by standing in a vacuum oven at room temperature, the template was heated at 80°C for 2 h to cure. The carbon black / polydimethylsiloxane dielectric layer was then peeled off the template to obtain a microstructured carbon black / polydimethylsiloxane electrode layer film with a thickness of 80–120 μm, a resistivity of 1–300 Ω / cm, and an elastic modulus of 2–10 MPa.

[0151] By controlling the carbon black doping ratio to 0.1wt%–3wt%, a uniformly dispersed carbon black / polydimethylsiloxane non-conductive solution can be obtained. This solution is then spin-coated onto a glass substrate at a speed of 600–1000 rpm for 30–60 s and heated at 80°C for 2 h to obtain a microstructure-free dielectric film with a thickness of 80–120 μm, a dielectric constant of 5–100, and an elastic modulus of 2–10 MPa.

[0152] The microstructured upper electrode layer, the unstructured dielectric layer, and the unstructured lower electrode layer prepared above are self-assembled and stacked together. Metal conductive leads are then connected to the surfaces of the upper and lower electrode layers to obtain a flexible capacitive sensor composed of a single carbon black / polydimethylsiloxane system.

[0153] In one embodiment of this application, the conductive filler used to prepare the capacitive sensor is silver nanowire, and the polymer is polyurethane. Polyurethane is a wear-resistant elastomer with good deformability. Compared with many other polymers, polyurethane has a higher relative permittivity, making it an ideal choice for the dielectric layer of capacitive sensors. Based on the above embodiments, step S310, which involves mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution, may include steps S3131 to S3134 as follows.

[0154] Step S3131: Mix silver nanowires with polyurethane at a mass ratio of 7-30% to obtain the fifth mixed raw material.

[0155] Step S3132: Disperse the fifth mixed raw material in an aqueous solvent to obtain a conductive solution.

[0156] The fifth mixed raw material was dispersed in an aqueous solvent, mechanically stirred, and then placed in a vacuum oven to remove excess air bubbles at room temperature, resulting in a uniformly dispersed silver nanowire / polyurethane conductive solution.

[0157] Step S3133: Mix silver nanowires with polyurethane at a mass ratio of 0.1-3% to obtain the sixth mixed raw material.

[0158] When preparing the sixth mixture, the same multi-walled silver nanowires and polyurethane as the fifth mixture are used.

[0159] Step S3134: Disperse the sixth mixed raw material in an aqueous solvent to obtain a non-conductive solution.

[0160] The sixth mixed raw material was dispersed in chloroform, mechanically stirred, and then placed in a vacuum oven to remove excess air bubbles at room temperature, yielding a uniformly dispersed silver nanowire / polyurethane non-conductive solution. The sixth mixed raw material can be used in the same solvent mass ratio as the fifth mixed raw material.

[0161] The above-mentioned silver nanowire / polyurethane conductive solution was spin-coated on a glass substrate at a speed of 600-1000 rpm for 30-60 s, and then heated at 80°C for 2 h to obtain a microstructure-free electrode layer film with a thickness of 80-120 μm, a resistance of 1-300 Ω / cm, and an elastic modulus of 2-10 MPa.

[0162] By controlling the doping ratio of silver nanowires to 0.1 wt%–3 wt%, a uniformly dispersed silver nanowire / polyurethane non-conductive solution can be obtained. This non-conductive solution is cast onto a microstructure template prepared by photolithography, and allowed to stand at room temperature in a vacuum oven to remove excess air bubbles. Then, it is heated at 80°C for 2 hours to solidify. After curing, the silver nanowire / polyurethane dielectric layer is peeled off from the template to obtain a microstructured silver nanowire / polyurethane dielectric layer with a thickness of 80–120 μm, a dielectric constant of 5–100, and an elastic modulus of 2–10 MPa.

[0163] The microstructure-free upper electrode layer, microstructure-free dielectric layer, and microstructure-free lower electrode layer prepared above are self-assembled and stacked together. Metal conductive leads are then connected to the surfaces of the upper and lower electrode layers to obtain a flexible capacitive sensor composed of a single silver nanowire / polyurethane system.

[0164] The dual-modal flexible capacitive sensor with a single material system provided in this application uses the same material system for both the electrode layer and dielectric layer, resulting in high modulus matching and similar mechanical properties among the layers. Since both the electrode layer and dielectric layer are composite materials of polymers and conductive fillers, both conductivity and dielectric properties can be achieved by adjusting the doping amount of the conductive filler. In this application embodiment, both the electrode layer and dielectric layer are flexible materials, capable of bending, twisting, and folding, and also possess excellent tensile strength. The capacitive sensor in this application embodiment can not only achieve capacitive signal response under tensile, compressive, and bending conditions, but also identify the resistance signal response of the electrodes. This dual-modal response mechanism can be applied to fields such as robot motion recognition. Furthermore, this capacitive sensor is simple and easy to fabricate, can be mass-produced, has high integration, and can be integrated into any wearable electronic product.

[0165] It should be noted that the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0166] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0167] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A capacitive sensor, characterized by The electrode layer and the dielectric layer are composite materials made by mixing the same conductive filler in the same polymer at different doping ratios, and the doping ratio of the conductive filler in the electrode layer is greater than that in the dielectric layer.

2. The capacitive sensor of claim 1, wherein, The polymer is any one of polydimethylsiloxane, polyurethane, polyimide, epoxy resin, polyethylene, polyvinylidene fluoride, polycarbonate, polyethylene naphthalate, nylon, polypropylene, rubber and polyformaldehyde; and the conductive filler is any one or a combination of multiple of metal nanowires, carbon nanotubes, graphite, graphene, carbon black and metal conductive powder.

3. The capacitive sensor of claim 2, wherein, The polymer is polydimethylsiloxane, and the conductive filler is carbon nanotube.

4. The capacitive sensor of claim 3, wherein, The mass ratio of the doped carbon nanotube in the electrode layer is 6-90%, and the mass ratio of the doped carbon nanotube in the dielectric layer is 0.1-5%.

5. The capacitive sensor of claim 4, wherein, The mass ratio of the doped carbon nanotube in the electrode layer is 7%, and the mass ratio of the doped carbon nanotube in the dielectric layer is 2%.

6. The capacitive sensor of claim 2, wherein, The polymer is polydimethylsiloxane, and the conductive filler is carbon black.

7. The capacitive sensor of claim 6, wherein, The mass ratio of the doped carbon black in the electrode layer is 8-60%, and the mass ratio of the doped carbon black in the dielectric layer is 0.1-3%.

8. The capacitive sensor of claim 2, wherein, The polymer is polyurethane, and the conductive filler is metal nanowire.

9. The capacitive sensor of claim 8, wherein, The mass ratio of the doped metal nanowire in the electrode layer is 7-30%, and the mass ratio of the doped metal nanowire in the dielectric layer is 0.1-3%.

10. The capacitive sensor of claim 1, wherein, The conductive filler is a mixed filler composed of at least two conductive materials with different materials or different structures.

11. The capacitive sensor according to any one of claims 1 to 10, characterized in that The electrode layer includes a first electrode layer attached to a first surface of the dielectric layer and a second electrode layer attached to a second surface of the dielectric layer, and at least one of the first electrode layer, the second electrode layer and the dielectric layer is a thin film layer with micro-convex structures.

12. The capacitive sensor of claim 11, wherein, The micro-convex structure is the surface microstructure of a velvet calathea leaf.

13. A method of fabricating a capacitive sensor, characterized by, The method comprises: mixing the same conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution; respectively, the conductive solution and the non-conductive solution are subjected to curing treatment to obtain an electrode layer and a dielectric layer; the doping ratio of the conductive filler in the electrode layer is greater than that in the dielectric layer; the electrode layer and the dielectric layer are assembled into a capacitive sensor.

14. The method of claim 13, wherein the method further comprises: respectively, the conductive solution and the non-conductive solution are subjected to curing treatment to obtain an electrode layer and a dielectric layer, comprising: the conductive solution is subjected to curing treatment on a microstructure template to obtain a first electrode layer with micro-convex structures; the conductive solution is subjected to curing treatment on a smooth substrate to obtain a second electrode layer with a smooth surface; the non-conductive solution is subjected to curing treatment on a smooth substrate to obtain a dielectric layer with a smooth surface.

15. The method of claim 14, wherein the method further comprises: the conductive solution is subjected to curing treatment on a microstructure template to obtain a first electrode layer with micro-convex structures, comprising: the conductive solution is cast on the microstructure template; the conductive solution carried on the microstructure template is subjected to heating treatment to obtain a conductive thin film layer cured on the microstructure template; Peeling the conductive thin film layer from the microstructure template to obtain a first electrode layer with micro-convex structure.

16. The method of claim 15, wherein The microstructure template is a polydimethylsiloxane template with micro-convex structure inverse structure; Before pouring the conductive solution on the microstructure template, the method further comprises: Mixing the prepolymer of polydimethylsiloxane and the curing agent solution according to a preset ratio to obtain a mixed solution; Pouring the mixed solution on the surface of the velvet calathea leaf; Heating the mixed solution carried on the surface of the velvet calathea leaf to obtain a polydimethylsiloxane film solidified on the surface of the velvet calathea leaf; Peeling the polydimethylsiloxane film from the surface of the velvet calathea leaf to obtain a polydimethylsiloxane template with micro-convex structure inverse structure.

17. The method of claim 13, wherein the method further comprises: Respectively, the conductive solution and the non-conductive solution are subjected to curing treatment to obtain an electrode layer and a dielectric layer, comprising: Curing treatment of the conductive solution on a smooth substrate to obtain a smooth-surface electrode layer; Curing treatment of the non-conductive solution on a microstructure template to obtain a micro-convex dielectric layer.

18. The method of claim 13 to 17, wherein The conductive filler is carbon nanotube, and the polymer is polydimethylsiloxane; Mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution, comprising: Mixing carbon nanotubes with polydimethylsiloxane at a mass ratio of 6-90% to obtain a first mixed raw material; Dispersing the first mixed raw material in chloroform to obtain a conductive solution; the mass ratio of polydimethylsiloxane to chloroform in the conductive solution is 1:3; Mixing carbon nanotubes with polydimethylsiloxane at a mass ratio of 0.1-5% to obtain a second mixed raw material; Dispersing the second mixed raw material in chloroform to obtain a non-conductive solution.

19. The method of claim 13 to 17, wherein The conductive filler is carbon black, and the polymer is polydimethylsiloxane; Mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution, comprising: Mixing carbon black with polydimethylsiloxane at a mass ratio of 8-60% to obtain a third mixed raw material; Dispersing the third mixed raw material in chloroform to obtain a conductive solution; Mixing carbon black with polydimethylsiloxane at a mass ratio of 0.1-3% to obtain a fourth mixed raw material; Dispersing the fourth mixed raw material in chloroform to obtain a non-conductive solution.

20. The method of claim 13 to 17, wherein The conductive filler is metal nanowire, and the polymer is polyurethane; mixing the conductive filler in the same polymer at different doping ratios to obtain a conductive solution and a non-conductive solution, comprising: Mixing metal nanowires with polyurethane at a mass ratio of 7-30% to obtain a fifth mixed raw material; Dispersing the fifth mixed raw material in a water-based solvent to obtain a conductive solution; Mixing metal nanowires with polyurethane at a mass ratio of 0.1-3% to obtain a sixth mixed raw material; Dispersing the sixth mixed raw material in a water-based solvent to obtain a non-conductive solution.

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