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

Abstract

The invention relates to a wide-range gradient microstructure ion capacitive pressure sensor and a preparation method thereof. The sensor comprises an outer wrapping layer and a sensor main body part, the sensor main body part is packaged in the outer wrapping layer; the sensor main body part is of a multi-layer combined structure and 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 which are arranged in sequence; the dielectric layer is made of ionic gel, and the ionic gel is formed by mixing polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methylimidazoline bis (trifluoromethylsulfonyl) imide salt; the top polyimide film and the top copper electrode layer are tightly attached and fixed, the bottom polyimide film and the bottom copper electrode layer are tightly attached and fixed, and the dielectric layer is located between the top copper electrode and the bottom copper electrode. And one side, close to the top copper electrode, of the dielectric layer is provided with a uniformly-distributed gradient microstructure with height difference. According to the invention, the sensitivity of the sensor is kept at a high level in a wide range.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure sensors, and in particular relates to a wide range gradient microstructure ion capacitance pressure sensor and a manufacturing method thereof. Background Art

[0002] Capacitive pressure sensor is a common type of pressure sensor, which is mainly composed of a driving plate, a sensing plate and a dielectric layer. Its sensing mechanism is to convert pressure into a change in capacitance. Unlike other pressure sensor structures, capacitive sensors have a simple structure, low power consumption, short dynamic response time, and small temperature effect, which can achieve continuous pressure detection. 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 porous structures and microstructured surfaces. The parallel plate capacitive sensor has a dielectric between the two electrodes and exhibits a change in capacitance when pressure is applied according to the change in the distance between the two electrodes. The calculation formula for its capacitance is: C = (ε0ε r A) / d. Where C is the capacitance, ε0 is the dielectric constant of the space, ε r is the relative dielectric constant, A is the overlap area between the two electrodes, and d is the distance between the two electrodes. Parallel plate capacitive sensors are commonly used due to their simple design and straightforward manufacturing technology. Ion capacitive sensors are a type of sensor with a wide pressure detection range. Unlike traditional capacitive pressure sensors, ion capacitive sensors use ion membranes instead of dielectric layers. The electric double layer (EDL) formed at the electrode / ion membrane interface enhances the signal by several orders of magnitude.

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

[0004] When the electrode is in contact with an ionic conductor, in order to maintain electrical neutrality, the surface charge of the electrode will attract an equal amount of counterions in the ionic conductor under the action of electrostatic attraction and van der Waals force, thereby forming an electrical double layer effect (EDL) at their contact interface. The classic EDL theory can be described by the Gouy-Chapman-Stern model: assuming that the ions actually have a size, the inner ions that are tightly bound to the electrode layer form a Helmholtz layer, the thickness of which is related to the size of the adsorbed ions. Therefore, in a fixed system, the capacitance C generated by the Helmholtz layer is H It can be regarded as a constant value, which is not affected by the potential difference. The outer ions far away from the electrode layer form a diffusion layer, and the capacitance generated is expressed as C D ,like Figure 8 As shown. The Helmholtz layer and the diffusion layer can be simply regarded as a single capacitor element C H and C D Therefore, the equivalent model of EDL can be expressed as a series connection of two interface capacitors.

[0005] From the formula, we can see that the capacitance in series becomes smaller, so C EDL Less than C H With C D When the potential difference is low, C EDL Mainly affected by C D When the potential difference is high, C D The value is very large, it has an effect on C EDL The value can be ignored, C EDL Approaching C H value.

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

[0007] C EDL =UAC·A

[0008] Where UAC is the unit capacitance density (pF / cm 2 );

[0009] It can be clearly seen from the formula that when 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] Constructing an ion layer with a microstructure can increase the change in the contact area of ​​the ion-electrode interface and effectively improve the elastic deformation capacity of the sensing layer. In order to improve the sensing performance of the parallel plate capacitive pressure sensor, it is currently proposed to directly construct surface microstructures such as columns, pyramids, and spheres in the existing soft material system to improve the ability of the dielectric to undergo mechanical deformation, thereby effectively improving the sensing performance of the capacitive pressure sensor. First, the construction of the microstructure will introduce compressible air into the structure, reducing the stiffness of the overall structure. Therefore, compared with the solid block structure, the thickness of the microstructured material is easier to change under the same pressure, and the capacitance increment also increases accordingly. Secondly, due to the presence of air, the effective dielectric constant of the dielectric layer is reduced, resulting in a decrease in the initial capacitance C0 of the device, thereby amplifying the relative capacitance change (ΔC / C0). Moreover, during the process of force compression, 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 increases accordingly, thereby allowing ΔC / C0 to increase further. When the proportion of air is small and the dielectric constant of the elastic dielectric material used, such as PDMS, is about 2-3, the change in dielectric constant is small, and the larger thickness change and lower C0 are generally considered to be the main reasons for the improvement in sensor sensitivity.

[0011] Based on the characteristics of the above-mentioned capacitive pressure sensor with a microstructured ion layer, in order to meet the sensor in some usage scenarios, for example, installation on a smart helmet for head collision monitoring, it is necessary to design an ultra-wide range, high-sensitivity capacitive pressure sensor. Summary of the invention

[0012] In view of the deficiencies in the prior art, the present invention provides an ion capacitive pressure sensor with a gradient microstructure in a wide range and a manufacturing method thereof.

[0013] One of the above objects of the present invention is achieved by the following technical solution:

[0014] A wide range gradient microstructure ion capacitive pressure sensor, comprising an outer wrapping layer and a sensor main body; the sensor main body is encapsulated in the outer wrapping layer; the sensor main body is a multilayer composite 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 ion gel, and the ion gel is a mixture of polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methylimidazoline bistrifluoromethylsulfonyl imide 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; a uniformly distributed gradient microstructure with a height difference is arranged on one side of the dielectric layer close to the top copper electrode.

[0015] Moreover, the uniformly distributed gradient microstructure is composed of staggeredly distributed microspheres of different diameters.

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

[0017] The second objective of the present invention is achieved by the following technical solutions:

[0018] A method for manufacturing the above-mentioned gradient microstructure ion capacitive pressure sensor is characterized by comprising the following steps:

[0019] Step 1: First, use tweezers to take an appropriate amount of polyvinylidene fluoride-hexafluoropropylene into a beaker, then add dimethyl sulfoxide solution into the beaker, using a mass ratio of 1:10 between polyvinylidene fluoride-hexafluoropropylene and dimethyl sulfoxide, then completely seal the beaker with tin foil, and finally place the beaker in an oil bath, and stir at a speed of 1000 r / min and heating at 120°C for 2 hours;

[0020] Step 2: After the polyvinylidene fluoride-hexafluoropropylene is completely dissolved in the dimethyl sulfoxide solution, the ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl imide) salt is quickly added to the beaker, and the mass ratio of the ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl imide) salt to the polyvinylidene fluoride-hexafluoropropylene is 1:2, and then stirred in an oil bath for 2 hours. After completion, an ion gel liquid is obtained, and a glass bottle with intact sealing performance is taken to store it;

[0021] Step 3: Design the required pattern using computer-aided modeling software, use a 3D printer to print a gradient microstructure resin mold, and 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 it at 80°C for 1h, and then peel off to obtain a polydimethylsiloxane mold with a gradient microstructure array;

[0023] Step 5: The ion gel solution obtained in step 2 is applied to the polydimethylsiloxane mold, and then the polydimethylsiloxane mold is placed in a drying oven and dried at 80° C. for 1 hour to fully solidify the ion gel inside and form an ion gel film 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 cleaner for ultrasonic cleaning for 1 minute, and let it stand for 15 minutes to dry;

[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 encapsulate them with 3M double-sided tape, and then use conductive tape to lead out from the top and bottom electrodes as wires to complete the production of the gradient microstructure-based ionic capacitive pressure sensor.

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

[0027] The advantages and positive effects of the present invention are:

[0028] 1. The ion capacitive pressure sensor of the present invention adopts a five-layer structure, wherein the dielectric layer adopts ion gel, which is a mixture of polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methylimidazoline bistrifluoromethylsulfonyl imide salt. The sensor prepared by ion gel has the advantages of high sensitivity, fast response and best comprehensive performance.

[0029] 2. The dielectric layer of the present invention adopts a gradient microstructure on one side close to the top copper electrode layer. As the pressure gradually increases, the gradient structure is gradually compressed from high to low, with a large compression stroke and a large contact area change rate. In particular, the micro-spherical structure is adopted, so that the sensor sensitivity can be maintained at a high level within a wide range.

[0030] 3. The structural design of the present invention is scientific and reasonable, low in cost, easy to use, and effective. It can reasonably realize pressure monitoring and achieve good applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of the ion pressure sensor of the present invention;

[0032] Figure 2 2a is a schematic diagram of the mechanism of the gradient microstructure ion capacitive pressure sensor of the present invention, 2a is a cross-sectional schematic diagram, and 2b is a circuit schematic diagram;

[0033] Figure 3 3a is a finite element analysis diagram of the prior art iso-microsphere structure, and 3b is a finite element analysis diagram of the gradient microstructure of the present invention;

[0034] Figure 4 It is a schematic diagram of the change rate of the relative contact area between the prior art structure and the structure of the present invention;

[0035] Figure 5 5a is a schematic diagram comparing the sensitivity of the existing structure and the structure of the present invention; 5b is a linear curve of the relative capacitance of the gradient microstructure with pressure in the low pressure (0-100kPa) and high pressure (100-1500kPa) range of the existing ion capacitive pressure sensor with equal height microspheres and gradient microstructures; 5b is a linear curve of the relative capacitance of the gradient microstructure with pressure in the low pressure (0-100kPa) and high pressure (100-1500kPa) range of the gradient microstructure;

[0036] Figure 6 This is a diagram of head collision data monitored by placing the sensor inside the helmet;

[0037] Figure 7 The sensor of the present invention is used to record the pressure diagram under different motion states;

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

[0039] The structure of the present invention is further described below with reference to the accompanying drawings and by way of examples. It should be noted that the present examples are descriptive rather than restrictive.

[0040] A gradient microstructure ion capacitive pressure sensor, see Figure 1-Figure 8, the invention point is: it includes an outer wrapping layer and a sensor body. The sensor body is encapsulated in the outer wrapping layer. The sensor body is a multilayer composite 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 ion gel mixed with polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and 1-ethyl-3-methylimidazoline bistrifluoromethylsulfonyl imide 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] A uniformly distributed gradient microstructure with a height difference is arranged on one side of the dielectric layer close to the top copper electrode. In the present invention, the uniformly distributed gradient microstructure is composed of microspheres of different diameters distributed in an alternating manner.

[0042] In the present invention, the capacitive pressure sensor is preferably in the shape of a regular hexagon, and the top polyimide circumscribed circle has a diameter of 52 mm and a thickness of 25 μm. The top copper electrode layer has a circumscribed circle diameter of 36 mm and a thickness of 12 μm. The dielectric layer has a circumscribed circle diameter of 42 mm and a thickness of 350 μm. The bottom copper electrode layer has a circumscribed circle diameter of 36 mm and a thickness of 12 μm. The bottom polyimide film layer has a circumscribed circle diameter of 52 mm and a thickness of 25 μm.

[0043] When flexible electronic devices of various shapes are attached to complex curved surfaces, mismatched strains may occur in the devices, which may lead to non-conformal contact in the interface or have a significant impact on the performance of the electronic devices. When analyzing the conformal contact state, the energy minimization method is often used. The total energy of the system includes the bending energy of the film (the film-substrate shear stress is ignored, and the film energy is ignored), the elastic energy stored in the deformed substrate, and the film-substrate interface adhesion energy. For any type of film, when the length of the film is relatively small, the curvature of the substrate is relatively large, and the product of the length curvature of the film and the substrate is large, conformality requires greater energy. Hexagonal films are easier to reach a conformal state than other films with the same area. Compared with rectangular, elliptical and hexagonal films of the same area, the hexagonal film requires the least energy to contact the hard substrate, has the smallest dimensionless strain energy, and is better at maintaining stable conformality.

[0044] The present invention forms a dielectric layer with microspheres of different diameters arranged alternately on one side of the dielectric layer close to the top copper electrode layer. Figure 2The gradient microstructure shown in the figure is equivalent to staggered distribution of microspheres of different diameters, which makes the effective utilization rate of the dielectric layer area higher. When there is no external pressure, the dielectric layer has fewer contact points with the top copper electrode layer, the contact area is small, and only a small amount of EDL capacitance is formed at the top copper electrode layer. At this time, the capacitance value of the sensor is mainly composed of the non-contact C EDL1 The capacitance is determined by the distance between the dielectric layer and the top copper electrode layer, so C EDL2 The capacitance value is small, and the initial capacitance value of the sensor is low, so the rate of change of the capacitance value has a very high upper limit. As the pressure increases, the microspheres are compressed, and the contact area between the microspheres and the top copper electrode layer increases. More ions in the dielectric layer gather at the junction of the dielectric layer and the top copper electrode layer due to the electric field, forming a larger and more EDL capacitance. At this time, the capacitance value of the sensor is basically composed of C EDL2 The capacitance determines the EDL1 The capacitance value can be ignored, so the capacitance value of the sensor is also positively correlated with the contact area between the dielectric layer and the electrode. Based on the above analysis, it can be seen that the ion capacitive sensor based on the gradient microstructure has extremely high sensitivity.

[0045] The geometry of the dielectric layer is designed to enhance the compressibility of the dielectric layer and improve the performance of the capacitive pressure sensor. The microstructure can be designed as a microcolumn, a pyramid, a microsphere, etc. The microcolumn has buckling instability. Under a small applied force, the contact area increases significantly. When further deformed, the sensitivity of the pressure sensor drops sharply, resulting in nonlinearity and rapid saturation. The pyramid structure is characterized by uneven stress distribution. When the pyramid is deformed, the stress is concentrated at the top. When the pressure is initially applied, the large local stress concentration leads to a large change in the contact area, but as the pressure increases, it gradually tends to saturation. The stress concentration at the tip of the microsphere structure is greater, and it has greater compressibility. Under a given applied pressure, when comparing pyramids with the same base length and microsphere diameter, the microsphere shape bears less stress, but the contact area changes more. Therefore, the microsphere structure will have a 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 by two-dimensional finite element analysis (FEA). The pressure-induced capacitance change of the EDL-based capacitive sensor mainly comes from the change in the electrode / dielectric interface contact area (ΔA / A0). For a microstructure with uniform microspheres (diameter 500μm) of the same height, the contact area gradually tends to saturation as the pressure increases, as shown in Figure 3. Unlike the uniform microsphere microstructure of the same height, in the technical solution of the present invention, when the pressure is small at the beginning, only the higher microspheres will contact the top copper electrode layer, thereby generating a certain EDL capacitance. As the pressure gradually increases, the gradient structure is gradually compressed from high to low, and the degree of deformation becomes higher and higher, resulting in a gradual increase in the contact area between the top copper electrode layer and the dielectric layer interface. As the pressure continues to increase, it becomes increasingly difficult for the higher microspheres (750μm in diameter) to deform, causing the area change rate of the interface capacitance to decrease. At the same time, due to the movement of the top copper electrode layer, the lower microspheres (500μm in diameter) will gradually contact the upper electrode plate to form EDL capacitance. Since these microspheres are just beginning to contact the upper electrode plate, they are easier to deform than the higher microspheres before, and it is easier to obtain new interface capacitance increments. Therefore, these new interface capacitance increments will make up for the previous decrease in the area change rate of the interface capacitance of the higher microspheres, thereby maintaining a high level of sensor sensitivity.

[0047] The prediction of FEA is verified by experimental results. Compared with the existing uniform microsphere structure with the same height, the relative contact area of ​​the sensor of the gradient microstructure of the present invention changes the most when pressure is loaded, such as Figure 4 In addition, the gradient microstructure of the present invention has higher sensitivity than the existing isotropic microsphere structure, such as Figure 5 As shown in b, within the range of 0-100 kPa, 3.39 kPa can be obtained -1 (R 2 =0.997) and a sensitivity of 1.69 kPa in an ultra-wide range of 100-1500 kPa -1 (R 2 =0.999), the experiment verifies that the present invention can realize ultra-wide range detection.

[0048] The method for manufacturing the gradient microstructure ion capacitive pressure sensor comprises 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 into the beaker, using a mass ratio of 1:10 between polyvinylidene fluoride-hexafluoropropylene and dimethyl sulfoxide, then completely seal the beaker with tin foil, and finally place the beaker in an oil bath, and stir at a speed of 1000 r / min and heating at 120°C for 2 hours;

[0050] Step 2: After polyvinylidene fluoride-hexafluoropropylene is completely dissolved in dimethyl sulfoxide (DMSO) solution, ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl imide) salt is quickly added to the beaker, and the mass ratio of ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl imide) salt to polyvinylidene fluoride-hexafluoropropylene is 1:2, followed by stirring in an oil bath for 2 hours. After completion, an ion gel liquid is obtained, and a glass bottle with intact sealing performance is taken to store it;

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

[0052] Step 4: dripping the prepared polydimethylsiloxane (PDMS) solution onto the printed resin mold and curing it at 80°C for 1h, and peeling off to obtain a polydimethylsiloxane mold with a gradient microstructure array, wherein the mass ratio of the elastomer to the curing agent in the polydimethylsiloxane solution is preferably 10:1;

[0053] Step 5: The ion gel solution obtained in step 2 is applied to the polydimethylsiloxane mold, and then the polydimethylsiloxane mold is placed in a drying oven and dried at 80° C. for 1 hour to fully solidify the ion gel inside and form an ion gel film on the surface of the polydimethylsiloxane mold;

[0054] 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 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, and then use conductive tape to lead out from the top and bottom electrodes as wires to complete the production of the gradient microstructure-based ionic capacitive pressure sensor.

[0056] The ionic capacitive pressure sensor of the present invention is placed inside the helmet to monitor head impact. When a pressure of about 300 kPa is applied to the helmet from the outside, the sensor responds quickly, and its relative capacitance changes to a maximum of 647. Figure 6 shown.

[0057] The sensor is placed on the sole of the human foot during exercise, including standing, walking, and running. The rapid changes in plantar pressure and acceleration reveal three states of capacitance change on the sensor, with different amplitudes and frequencies to distinguish the three different states such as Figure 7shown.

[0058] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A wide range gradient microstructure ion capacitive pressure sensor, Features: It comprises an outer wrapping layer and a sensor main body; the sensor main body is encapsulated in the outer wrapping layer; the sensor main body is a multilayer composite 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 an ion gel, and the ion gel is a mixture of polyvinylidene fluoride-hexafluoropropylene and 1-ethyl-3-methylimidazoline bistrifluoromethylsulfonyl imide 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; a uniformly distributed gradient microstructure with a height difference is arranged on one side of the dielectric layer close to the top copper electrode.

2. The gradient microstructure ion capacitive pressure sensor according to claim 1, Features: The uniformly distributed gradient microstructure is composed of staggeredly distributed microspheres of different diameters.

3. The gradient microstructure ion capacitive pressure sensor according to claim 1, Features: The capacitive pressure sensor is in the shape of a regular hexagon, with a top polyimide circumscribed circle diameter of 52 mm and a thickness of 25 μm; a top copper electrode layer circumscribed circle diameter of 36 mm and a thickness of 12 μm; a dielectric layer circumscribed circle diameter of 42 mm and a thickness of 350 μm; a bottom copper electrode layer circumscribed circle diameter of 36 mm and a thickness of 12 μm; and a bottom polyimide film layer circumscribed circle diameter of 52 mm and a thickness of 25 μm.

4. A method for manufacturing a wide range gradient microstructure ionic capacitive pressure sensor according to any one of claims 1 to 3, Features: The steps include: Step 1: First, use tweezers to take an appropriate amount of polyvinylidene fluoride-hexafluoropropylene into a beaker, then add dimethyl sulfoxide solution into the beaker, using a mass ratio of 1:10 between polyvinylidene fluoride-hexafluoropropylene and dimethyl sulfoxide, then completely seal the beaker with tin foil, and finally place the beaker in an oil bath, and stir at a speed of 1000 r / min and heating at 120°C for 2 hours; Step 2: After the polyvinylidene fluoride-hexafluoropropylene is completely dissolved in the dimethyl sulfoxide solution, the ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl imide) salt is quickly added to the beaker, and the mass ratio of the ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl imide) salt to the polyvinylidene fluoride-hexafluoropropylene is 1:2, and then stirred in an oil bath for 2 hours. After completion, an ion gel liquid is obtained, and a glass bottle with intact sealing performance is taken to store it; Step 3: Design the required pattern using computer-aided modeling software, use a 3D printer to print a gradient microstructure resin mold, and customize the top polyimide film layer, the top copper electrode layer, the bottom copper electrode layer, and the bottom polyimide film layer; Step 4: drop the prepared polydimethylsiloxane solution on the printed resin mold and cure it at 80°C for 1h, and then peel off to obtain a polydimethylsiloxane mold with a gradient microstructure array; Step 5: The ion gel solution obtained in step 2 is applied to the polydimethylsiloxane mold, and then the polydimethylsiloxane mold is placed in a drying oven and dried at 80° C. for 1 hour to fully solidify the ion gel inside and form an ion gel film on the surface of the polydimethylsiloxane mold; 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 cleaner for ultrasonic cleaning 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 encapsulate them with 3M double-sided tape, and then use conductive tape to lead out from the top and bottom electrodes as wires to complete the production of the gradient microstructure-based ionic capacitive pressure sensor.

5. The method for manufacturing the wide range gradient microstructure ionic capacitive pressure sensor according to claim 4 based on any one of claims 1 to 3, Features: In step 4, the mass ratio of the elastomer to the curing agent in the polydimethylsiloxane solution is 10:1.

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