Wide-range gradient microstructure ion capacitive pressure sensor and manufacturing method thereof

Abstract

The present application relates to a kind of wide-range gradient microstructure ion capacitive pressure sensor and its preparation method, sensor includes outer wrapping layer and sensor main part;Sensor main part is encapsulated in outer wrapping layer;Sensor main part is multilayer combination structure, including top polyimide film layer, top copper electrode layer, dielectric layer, bottom copper electrode layer and bottom polyimide film layer arranged in sequence;Dielectric layer material is ion gel, and ion gel is mixed by polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methyl imidazoline double trifluoromethylsulfonyl imidazoline salt;Top polyimide film and top copper electrode layer are fixedly connected, and bottom polyimide film and bottom copper electrode layer are fixedly connected, and dielectric layer is between top copper electrode and bottom copper electrode;Dielectric layer is provided with uniform gradient microstructure with high-low difference on the side close to top copper electrode.The present application realizes that sensor sensitivity keeps higher level in wide range.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pressure sensors, and particularly relates to a wide-range gradient microstructure ionic capacitive pressure sensor and a manufacturing method thereof. BACKGROUND

[0002] Capacitive pressure sensors are a common type of pressure sensor, which are mainly composed of a driving electrode plate, a sensing electrode plate and a dielectric layer. The sensing mechanism is to convert pressure into a change in capacitance. Unlike other pressure sensor structures, capacitive sensor structures are simple, low in power consumption, short in dynamic response time, small in temperature effect, and can realize continuous detection of pressure. The sensing sensitivity of the capacitive pressure sensor depends on the compressibility of the dielectric layer material. Therefore, the performance of the capacitive sensor can be improved by designing the structure of the dielectric material to improve its compressibility, such as a porous structure and a microstructure surface. The parallel plate capacitive sensor has a dielectric between two electrodes and exhibits a change in capacitance when pressure is applied according to the change in distance between the two electrodes. The formula for calculating its capacitance is: C=(ε0ε r r A) / d. Where C is the capacitance, ε0is the dielectric constant of space, ε r r is the relative dielectric constant, A is the overlapping area between the two electrodes, and d is the distance between the two electrodes. The parallel plate capacitive sensor is widely used due to its simple design and direct manufacturing technology. Ionic capacitive sensors are a class of sensors with a wide pressure detection range. Unlike traditional capacitive pressure sensors, ionic capacitive sensors use an ion film instead of a dielectric layer, and a double electric layer (EDL) is formed at the electrode / ion film interface, and the signal is enhanced by several orders of magnitude.

[0003] In 2011, Pan and his team proposed an ionic capacitive pressure sensor concept based on the supercapacitor characteristics of the EDL. The unique liquid-solid phase integrated capacitive pressure sensor combines an ionic conductor with an electrode material, and forms an EDL capacitor at the ion-electric interface, so that the capacitance density of the device can reach μF / cm 2 , which is 3-5 orders of magnitude higher than the pF / cm 2 of the traditional parallel plate capacitor, thereby significantly improving the resolution and sensitivity of the capacitive sensor to pressure. However, the development of this liquid electrolyte-based ion-electric interface capacitive sensor faces the dual challenges of low mechanical stability and poor material processability.

[0004] When an electrode comes into contact with an ionic conductor, to maintain charge neutrality, the surface charge of the electrode attracts an equal amount of counterions from the ionic conductor under the influence of electrostatic attraction and van der Waals forces, thus forming an electric double layer (EDL) at their interface. The classical EDL theory can be described using the Gouy-Chapman-Stern model: assuming that ions also have actual size, the inner layer of ions tightly bound to the electrode layer forms a Helmholtz layer. The thickness of this layer is related to the size of the adsorbed ions; therefore, in a fixed system, the capacitance C generated by the Helmholtz layer is... H This can be considered a constant value, unaffected by the potential difference. The outer ions, located farther from the electrode layer, form a diffusion layer, and the resulting capacitance is denoted as C. D ,like Figure 8 As shown. Both the Helmholtz layer and the diffusion layer can be simply viewed as a single capacitor element C. H and C D Therefore, the equivalent model of EDL can be represented as the series connection of two interface capacitors.

[0005] As can be seen from the formula, the value of a capacitor decreases when connected in series, therefore C EDL Less than C H With C D The smaller value in the range. When the potential difference is low, C EDL Mainly affected by C D The effect of the value. When the potential difference is high, C D The value is very large; it is significant for C. EDL The value is negligible, C EDL Approaching C H value.

[0006] Therefore, double-layer capacitance (C EDL It can also be expressed as:

[0007] C EDL =UAC·A

[0008] In the formula, UAC represents the unit capacitance density (pF / cm²). 2 );

[0009] The formula clearly shows that once the electrode layer and the ion conductor material are determined, the EDL interface capacitance mainly depends on the size of the contact area between the electrode layer and the ion layer.

[0010] The construction of the ion layer with microstructure can improve the change amount of the contact area of the ion-electric interface, and effectively improve the elastic deformation ability of the sensing layer. In order to improve the sensing performance of the parallel plate type capacitive pressure sensor, a method of constructing surface microstructures such as columnar, pyramidal, spherical and the like in the existing soft material system is proposed to improve the mechanical deformation ability of the dielectric, thereby effectively improving the sensing performance of the capacitive pressure sensor. First, the construction of the microstructure will introduce compressible air in the structure, which reduces the stiffness of the overall structure, so compared with the solid block structure, the thickness change of the microstructured material is easier under the same pressure, and the capacitance increment is also increased. Second, due to the presence of air, the effective dielectric constant of the dielectric layer is reduced, which reduces the initial capacitance C0 of the device, thereby amplifying the relative change amount of the capacitance (ΔC / C0). Moreover, in the process of compression under stress, the air filled in the microstructure will be squeezed out, so that the air ratio in the actual air-dielectric composite material is reduced, and the effective dielectric constant of the dielectric layer is increased, thereby allowing ΔC / C0 to be further increased. When the air ratio is small and the dielectric constant of the elastic dielectric material such as PDMS is about 2-3, the change of the dielectric constant is small, and the greater thickness change and lower C0 are generally considered to be the main reason for the improvement of the sensitivity of the sensor.

[0011] Based on the characteristics of the capacitive pressure sensor with the microstructure type ion layer, in order to meet the requirements of the sensor in some use cases, such as being installed on a smart helmet for head collision monitoring, a capacitive pressure sensor with ultra-wide range and high sensitivity needs to be designed. SUMMARY

[0012] The present application is directed to the deficiencies of the prior art, and proposes a wide range of gradient microstructure ion capacitive pressure sensor and its manufacturing method.

[0013] One of the above-mentioned purposes of the present application is achieved by the following technical solutions:

[0014] The application discloses a wide-range gradient microstructure ionic capacitive pressure sensor, which comprises an outer wrapping layer and a sensor main body part; the sensor main body part is encapsulated in the outer wrapping layer; the sensor main body part is a multilayer combined structure, which comprises a top polyimide film layer, a top copper electrode layer, a dielectric layer, a bottom copper electrode layer and a bottom polyimide film layer arranged in sequence; the dielectric layer is made of ionic gel which is mixed by polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methyl imidazoline double trifluoromethyl sulfonimide salt; the top polyimide film is tightly attached to and fixedly connected with the top copper electrode layer, the bottom polyimide film is tightly attached to and fixedly connected with the bottom copper electrode layer, and the dielectric layer is located between the top copper electrode and the bottom copper electrode; and the dielectric layer is provided with a uniform gradient microstructure with high and low differences on one side close to the top copper electrode.

[0015] Moreover, the uniform gradient microstructure is composed of microspheres with different sizes and diameters which are staggered.

[0016] Moreover, the capacitive pressure sensor is a regular hexagon, the diameter of the top polyimide circumscribed circle is 52 mm, and the thickness is 25 mu m; the diameter of the top copper electrode layer circumscribed circle is 36 mm, and the thickness is 12 mu m; the diameter of the dielectric layer circumscribed circle is 42 mm, and the thickness is 350 mu m; the diameter of the bottom copper electrode layer circumscribed circle is 36 mm, and the thickness is 12 mu m; and the diameter of the bottom polyimide film layer circumscribed circle is 52 mm, and the thickness is 25 mu m.

[0017] The second purpose of the application is achieved by the following technical scheme.

[0018] A manufacturing method of the above-mentioned gradient microstructure ionic capacitive pressure sensor, characterized by comprising the following steps.

[0019] Step 1: firstly, a proper amount of polyvinylidene fluoride-hexafluoropropylene is taken in a beaker with tweezers, then dimethyl sulfoxide solution is added into the beaker, the mass ratio of polyvinylidene fluoride-hexafluoropropylene to dimethyl sulfoxide is 1:10, then the beaker is completely sealed with tin paper, and finally the beaker is placed in an oil bath pot and stirred at a speed of 1000 r / min and a heating temperature of 120 DEG C for 2 hours;

[0020] Step 2: after the polyvinylidene fluoride-hexafluoropropylene is completely dissolved in the dimethyl sulfoxide solution, ionic liquid 1-ethyl-3-methyl imidazoline double trifluoromethyl sulfonimide salt is quickly added into the beaker, the mass ratio of the ionic liquid 1-ethyl-3-methyl imidazoline double trifluoromethyl sulfonimide salt to the polyvinylidene fluoride-hexafluoropropylene is 1:2, then the oil bath pot is stirred for 2 hours, and ionic gel liquid is obtained after completion, and the glass bottle with good sealing performance is stored.

[0021] Step 3: design the required pattern by using computer-aided modeling software, print the gradient microstructure resin mold by using a 3D printer, customize the top polyimide film layer, the top copper electrode layer, the bottom copper electrode layer and the bottom polyimide film layer;

[0022] Step 4: drop the prepared polydimethylsiloxane solution on the printed resin mold, and cure at 80 DEG C for 1h, and after peeling, a polydimethylsiloxane mold with a gradient microstructure array is obtained;

[0023] Step 5: coat the ion gel solution obtained in step 2 on the polydimethylsiloxane mold, and then place the polydimethylsiloxane mold in a drying oven and dry at a temperature of 80 DEG C for 1h, so that the ion gel is fully cured inside and an ion gel film is formed on the surface of the polydimethylsiloxane mold;

[0024] Step 6: finally, tear off the cured ion gel film with tweezers to obtain an ion gel dielectric layer with a gradient microstructure; then place the polydimethylsiloxane mold in an ultrasonic cleaning instrument and ultrasonically clean for 1 minute, and dry for 15 minutes after standing;

[0025] Step 7: stack the customized bottom polyimide film layer, bottom copper electrode layer, dielectric layer, top copper electrode and top polyimide film from bottom to top, and package with 3M double-sided tape, and then use conductive tape to lead out as wires from the top and bottom electrodes, respectively, to complete the production of the ion capacitor pressure sensor based on the gradient microstructure.

[0026] Moreover, in step 4, the mass ratio of elastomer to curing agent in the polydimethylsiloxane solution is 10:1.

[0027] The application has the advantages and positive effects that:

[0028] 1. The ion capacitor pressure sensor of the application adopts a five-layer structure, wherein the dielectric layer adopts ion gel, and the ion gel is mixed by polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methyl imidazoline bis-trifluoromethylsulfonyl imidazoline salt. The ion gel sensor has the advantages of high sensitivity, rapid response and best comprehensive performance.

[0029] 2. The dielectric layer of the application adopts a gradient microstructure on the side close to the top copper electrode layer. When the pressure gradually increases, the gradient structure is gradually compressed from high to low, the compression stroke is large, the contact area change rate is large, and especially the microspherical structure is adopted, so that the sensor sensitivity can be kept at a high level in a wide range.

[0030] 3. The structure design of the application is scientific and reasonable, low in cost, convenient to use, good in effect, and capable of reasonably realizing pressure monitoring, and good applicability is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is the structural schematic diagram of the ion type pressure sensor of the present application;

[0032] Figure 2 is the schematic diagram of the gradient microstructure ion capacitor type pressure sensing mechanism of the present application, 2a is a cross-sectional schematic diagram, and 2b is a circuit schematic diagram;

[0033] Figure 3 is the finite element analysis diagram, 3a is the finite element analysis schematic diagram of the existing isometric microsphere structure, and 3b is the finite element analysis schematic diagram of the gradient microstructure of the present application;

[0034] Figure 4 is the schematic diagram of the relative contact area change rate of the existing structure and the structure of the present application;

[0035] Figure 5 is the schematic diagram of the sensitivity comparison of the existing structure and the structure of the present application; 5a is the relative capacitance of the ion capacitor type pressure sensor of the existing isometric microsphere and the gradient microstructure changes with pressure; and 5b is the linear curve of the relative capacitance of the gradient microstructure changes with pressure in the low pressure (0-100 kPa) and high pressure (100-1500 kPa) range;

[0036] Figure 6 is the diagram of the sensor of the present application placed inside the helmet to monitor head collision data;

[0037] Figure 7 is the diagram of the pressure recorded by the sensor of the present application under different motion states;

[0038] Figure 8 is the Gouy-Chapman-Stern model diagram. DETAILED DESCRIPTION

[0039] The structure of the present application will be further described below in combination with the drawings and through examples. It should be noted that the present examples are narrative and not limiting.

[0040] A gradient microstructure ion capacitor type pressure sensor, please see Figures 1-8The application point is: including an outer wrapping layer and a sensor main body part. The sensor main body part is encapsulated in the outer wrapping layer. The sensor main body part is a multilayer combined structure, including a top polyimide film layer 1, a top copper electrode layer 2, a dielectric layer 3, a bottom copper electrode layer 4 and a bottom polyimide film layer 5 arranged in sequence. The dielectric layer is an ionic gel mixed by polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and 1-ethyl-3-methyl imidazolium bis-trifluoromethylsulfonylimide salt ([EMIM][TFSI]), the top polyimide film is tightly attached to and fixedly connected with the top copper electrode layer, the bottom polyimide film is tightly attached to and fixedly connected with the bottom copper electrode layer, and the dielectric layer is located between the top copper electrode and the bottom copper electrode.

[0041] The dielectric layer is provided with a uniform gradient microstructure with high-low difference on the side close to the top copper electrode. In the application, the uniform gradient microstructure is composed of microspheres with different sizes and diameters distributed in an interlaced manner.

[0042] In the application, the capacitive pressure sensor preferably has a regular hexagonal shape, the top polyimide circumscribed circle has a diameter of 52 mm and a thickness of 25 microns, the top copper electrode layer has a circumscribed circle diameter of 36 mm and a thickness of 12 microns, the dielectric layer has a circumscribed circle diameter of 42 mm and a thickness of 350 microns, the bottom copper electrode layer has a circumscribed circle diameter of 36 mm and a thickness of 12 microns, and the bottom polyimide film layer has a circumscribed circle diameter of 52 mm and a thickness of 25 microns.

[0043] When various shapes of flexible electronic devices are attached to complex curved surfaces, mismatched strain may occur in the devices, which may cause non-conformal contact in the interface or have an important influence on the performance of the electronic devices. When analyzing the conformal contact state, the energy minimization method is often used, and the total energy of the system includes the bending energy of the film (ignoring the thin film-substrate shear stress, the film energy can be ignored), the elastic energy stored in the deformed substrate and the adhesion energy of the thin film-substrate interface. For any type of thin film, when the length of the thin film is relatively small, the curvature of the substrate is relatively large, and the length-curvature product of the thin film and the substrate is large, more energy is required for conformal. Hexagonal thin film is more easily to reach the conformal state than other thin films with the same area. Compared with rectangular, elliptical and hexagonal thin films with the same area, the hexagonal thin film requires the least energy to contact the hard substrate, has the smallest dimensionless strain energy, and better maintains stable conformal.

[0044] In the application, the dielectric layer close to the top copper electrode layer is interlaced with microspheres with different sizes and diameters, forming a uniform gradient microstructure with high-low difference. Figure 2The gradient microstructure shown is equivalent to an alternating distribution of microspheres of different diameters, resulting in a high effective utilization of the dielectric layer area. Under no external pressure, the contact points between the dielectric layer and the top copper electrode layer are few, resulting in a small contact area. Only a minimal EDL capacitance is formed at the top copper electrode layer. In this case, the sensor's capacitance value is mainly determined by the non-contact C... EDL1 The capacitance is determined by the large distance between the dielectric layer and the top copper electrode layer, therefore C EDL2 The initial capacitance of the sensor is low due to its small initial capacitance, thus limiting the rate of change of capacitance. As pressure increases, the microspheres are compressed, increasing the contact area between the microspheres and the top copper electrode layer. More ions within the dielectric layer accumulate at the interface between the dielectric layer and the top copper electrode layer due to the electric field, forming a larger and more abundant EDL capacitance. At this point, the sensor's capacitance value essentially increases from C... EDL2 The capacitance determines the value of C. EDL1 The capacitance value is negligible; therefore, the sensor's capacitance value is positively correlated with the contact area between the dielectric layer and the electrode. Based on the above analysis, it can be concluded that the ion-capacitive sensor based on this gradient microstructure has extremely high sensitivity.

[0045] The geometry of the dielectric layer is designed to enhance its compressibility and improve the performance of capacitive pressure sensors. Microstructures can be designed as micropillars, pyramids, microspheres, etc. Micropillars exhibit buckling instability; under small applied forces, the contact area increases significantly. With further deformation, the sensitivity of the pressure sensor drops sharply, leading to nonlinearity and rapid saturation. Pyramid structures are characterized by uneven stress distribution. When a pyramid deforms, stress concentrates at the apex. Initially, this large local stress concentration leads to significant changes in the contact area, but it gradually saturates with increasing pressure. Microsphere structures, on the other hand, have even greater stress concentration at the tip, resulting in greater compressibility. Under a given applied pressure, compared to a pyramid with the same base length and diameter, the microsphere shape withstands less stress but exhibits a larger change in contact area. Therefore, the microsphere structure will have higher sensitivity than a pyramid of the same size and is a preferred structural form.

[0046] The deformation of the microstructure under pressure loading was studied using two-dimensional finite element analysis (FEA). The pressure-sensing capacitance change of the EDL-based capacitive sensor mainly comes from the change in the contact area (ΔA / A0) at the electrode / dielectric interface. For a uniform microsphere (500 μm in diameter) with the same height, the contact area gradually approaches saturation as the pressure increases, as shown in Figure 3. Unlike the uniform microsphere microstructure with the same height, in the present invention, initially at lower pressures, only the taller microspheres contact the top copper electrode layer, thus generating a certain EDL capacitance. As the pressure gradually increases, the gradient structure gradually compresses from high to low, and the degree of deformation increases, leading to a gradual increase in the contact area between the top copper electrode layer and the dielectric layer. As pressure increases, it becomes increasingly difficult for the taller microspheres (750 μm in diameter) to deform, resulting in a decrease in the area change rate of the interfacial capacitance. Meanwhile, due to the movement of the top copper electrode layer, the smaller microspheres (500 μm in diameter) will gradually come into contact with the upper electrode, forming an EDL capacitor. Since these microspheres are just beginning to contact the upper electrode, they are easier to deform than the taller microspheres, making it easier to obtain new interfacial capacitance increments. Therefore, these new interfacial capacitance increments will compensate for the lack of decrease in the area change rate of the interfacial capacitance of the taller microspheres, allowing the sensor sensitivity to remain at a high level.

[0047] Experimental results validated the FEA prediction. Compared to existing uniform microsphere structures of the same height, the gradient microstructure of this invention exhibits the largest change in the relative contact area of ​​the sensor under pressure loading, such as... Figure 4 As shown. Furthermore, the gradient microstructure of this invention exhibits higher sensitivity than existing uniform-height microsphere structures, such as... Figure 5 As shown in b, 3.39 kPa can be obtained within the range of 0-100 kPa. -1 (R 2 It boasts a high sensitivity of 0.997 kPa, with a sensitivity of 1.69 kPa over an ultra-wide range of 100-1500 kPa. -1 (R 2 =0.999), the experiment verified that the present invention can achieve ultra-wide range detection.

[0048] The fabrication method of this gradient microstructure ion capacitive pressure sensor includes the following steps:

[0049] Step 1: First, use tweezers to take an appropriate amount of polyvinylidene fluoride-hexafluoropropylene into a beaker, then add dimethyl sulfoxide solution to the beaker, using a mass ratio of 1:10 between polyvinylidene fluoride-hexafluoropropylene and dimethyl sulfoxide. Then, completely seal the beaker with aluminum foil. Finally, place the beaker in an oil bath and stir at 1000 r / min and 120°C for 2 hours.

[0050] Step 2: After polyvinylidene fluoride-hexafluoropropylene is completely dissolved in dimethyl sulfoxide (DMSO) solution, quickly add ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide salt to a beaker. The mass ratio of ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide salt to polyvinylidene fluoride-hexafluoropropylene is 1:2. Then stir in an oil bath for 2 hours. After completion, an ionic gel liquid is obtained. Store it in a well-sealed glass bottle.

[0051] Step 3: Design the required pattern using computer-aided modeling software, print the gradient microstructure resin mold using a 3D printer, and customize the top polyimide film layer, top copper electrode layer, bottom copper electrode layer, and bottom polyimide film layer.

[0052] Step 4: Drop the prepared polydimethylsiloxane (PDMS) solution onto the printed resin mold and cure it at 80°C for 1 hour. After peeling, a polydimethylsiloxane mold with a gradient microstructure array is obtained. The preferred mass ratio of elastomer to curing agent in the polydimethylsiloxane solution is 10:1.

[0053] Step 5: Coat the polydimethylsiloxane mold with the ion gel solution obtained in step 2, then place the polydimethylsiloxane mold in a drying oven and dry it at 80°C for 1 hour to fully solidify the ion gel and form an ion gel film on the surface of the polydimethylsiloxane mold.

[0054] Step 6: Finally, use tweezers to peel off the cured ionogel film to obtain an ionogel dielectric layer with a gradient microstructure; then place the polydimethylsiloxane mold in an ultrasonic cleaner for ultrasonic cleaning for 1 minute, let it stand for 15 minutes to dry, and it can be reused.

[0055] Step 7: Stack the customized bottom polyimide film layer, bottom copper electrode layer, dielectric layer, top copper electrode, and top polyimide film from bottom to top, and encapsulate them with 3M double-sided tape. Then, use conductive tape to lead out from the top and bottom electrodes as wires to complete the fabrication of the gradient microstructure-based ion capacitive pressure sensor.

[0056] The ion-capacitive pressure sensor of this invention is placed inside a helmet to monitor head impacts. When an external pressure of approximately 300 kPa is applied to the helmet, the sensor responds rapidly, with its relative capacitance changing by a maximum of 647. Figure 6 As shown.

[0057] The sensor was placed on the sole of the foot during movement, including standing, walking, and running. Rapid changes in plantar pressure and acceleration revealed three states of capacitance changes on the sensor, each with different amplitudes and frequencies, to distinguish three distinct states. Figure 7shown.

[0058] While the embodiments of the application and the figures disclose the application for illustrative purposes, those skilled in the art can understand that various substitutions, changes and modifications are possible without departing from the spirit of the application and the appended claims, and therefore the scope of the application is not limited to the content disclosed in the embodiments and the figures.

Claims

1. A wide-range gradient microstructured ion capacitive pressure sensor, characterized by: The sensor comprises an outer wrapping layer and a sensor body part; the sensor body part is encapsulated in the outer wrapping layer; the sensor body part is a multilayer combined structure, comprising a top polyimide film layer, a top copper electrode layer, a dielectric layer, a bottom copper electrode layer and a bottom polyimide film layer arranged in sequence; the dielectric layer is made of ionic gel, which is mixed by polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methyl imidazoline bis-trifluoromethylsulfonylimide salt; the top polyimide film is tightly attached to and fixedly connected with the top copper electrode layer, and the bottom polyimide film is tightly attached to and fixedly connected with the bottom copper electrode layer; the dielectric layer is located between the top copper electrode and the bottom copper electrode; a uniform gradient microstructure with high-low difference is arranged on the side of the dielectric layer close to the top copper electrode; the uniform gradient microstructure is composed of microspheres with different sizes and diameters distributed in a staggered manner; in a pressure range of 0-100 kPa, a high linearity of R 2 =0.997 is obtained; and in a super-wide pressure range of 100-1500 kPa, a high linearity of R 2 =0.999 is obtained.

2. The gradient microstructure ion capacitive pressure sensor of claim 1, wherein: The capacitive pressure sensor is a regular hexagon, the top polyimide outer circle diameter is 52mm, the thickness is 25um; the top copper electrode layer outer circle diameter is 36mm, the thickness is 12um; the dielectric layer outer circle diameter is 42mm, the thickness is 350um; the bottom copper electrode layer outer circle diameter is 36mm, the thickness is 12um; the bottom polyimide film layer outer circle diameter is 52mm, the thickness is 25um.

3. A method for fabricating a wide-range gradient micro-structured ion capacitive pressure sensor according to any one of claims 1-2, characterized in that: It comprises the following steps: Step 1: First, take a proper amount of polyvinylidene fluoride-hexafluoropropylene in a beaker with tweezers, then add dimethyl sulfoxide solution to the beaker, adopt the mass ratio of polyvinylidene fluoride-hexafluoropropylene to dimethyl sulfoxide of 1:10, then completely seal the beaker with tin paper, and finally place the beaker in an oil bath, stir at a speed of 1000r / min and a heating temperature of 120℃ for 2 hours; Step 2: After the polyvinylidene fluoride-hexafluoropropylene is completely dissolved in the dimethyl sulfoxide solution, quickly add the ionic liquid 1-ethyl-3-methyl imidazoline bis-trifluoromethylsulfonylimide salt to the beaker, the mass ratio of the ionic liquid 1-ethyl-3-methyl imidazoline bis-trifluoromethylsulfonylimide salt to polyvinylidene fluoride-hexafluoropropylene is 1:2, then stir in the oil bath for 2 hours, and after completion, obtain the ionic gel liquid, and store it in a glass bottle with good sealing performance; Step 3: Use computer-aided modeling software to design the required pattern, use a 3D printer to print a gradient microstructure resin mold, and customize the top polyimide film layer, top copper electrode layer, bottom copper electrode layer and bottom polyimide film layer; Step 4: Drop the prepared polydimethylsiloxane solution on the printed resin mold, and cure at 80℃ for 1h, then peel off to obtain a polydimethylsiloxane mold with a gradient microstructure array; Step 5: Apply the ionic gel solution obtained in step 2 to the polydimethylsiloxane mold, then place the polydimethylsiloxane mold in a drying oven and dry at a temperature of 80℃ for 1 hour to fully solidify the ionic gel inside and form an ionic gel film on the surface of the polydimethylsiloxane mold; Step 6: Finally, tear off the solidified ionic gel film with tweezers to obtain an ionic gel dielectric layer with a gradient microstructure; then place the polydimethylsiloxane mold in an ultrasonic cleaner and ultrasonically clean it for 1 minute, and let it stand for 15 minutes to dry; Step 7: Stack the customized bottom polyimide film layer, bottom copper electrode layer, dielectric layer, top copper electrode and top polyimide film from bottom to top, and package them with 3M double-sided tape, then use conductive tape to lead out as wires from the top and bottom electrodes respectively, and complete the production of the ionic capacitive pressure sensor based on the gradient microstructure.

4. The method of claim 3, wherein the method is based on any one of claims 1-2. In step 4, the mass ratio of elastomer to curing agent in the polydimethylsiloxane solution is 10:1.

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