A double-sided gradient microstructure array electric double layer capacitor flexible sensor and a preparation method and application thereof

Abstract

This invention relates to a double-sided gradient microstructure array double-layer capacitive flexible sensor, its fabrication method, and its applications, belonging to the field of flexible sensor technology. On one hand, the invention employs an ion-gel film as the dielectric layer, utilizing its ability to form a thin double layer at the electrode interface to impart high intrinsic sensitivity to the device. On the other hand, it modulates the double-sided gradient micro-pyramid array coated with ion-gel. Through gradient design of microstructure size and array distribution density, large-size micro-pyramids preferentially respond at low pressure, ensuring high sensitivity. As pressure increases, double-sided gradient micro-pyramids of different sizes gradually participate in contact, causing the effective contact area to continuously increase with pressure, thereby significantly widening the sensor's detection range. This invention effectively solves the problem of the mutual constraint between sensitivity and detection range in flexible capacitive sensors, providing an effective approach for developing flexible sensors with both high sensitivity and wide detection range.

Description

Technical Field

[0001] This invention belongs to the field of flexible sensors. Specifically, it relates to a double-sided gradient microstructure array double-electric-layer capacitive flexible sensor, its fabrication method, and its application. The aim is to solve the technical bottleneck of existing flexible capacitive sensors that are difficult to balance high sensitivity and wide detection range. Background Technology

[0002] In recent years, with the increasing public awareness of health and the aging population, the pressure on the medical system has been growing daily. Since many people only seek medical attention when they feel unwell, latent diseases are easily discovered too late. Therefore, disease prevention and real-time monitoring are particularly important, and the development of electronic devices capable of continuously monitoring the human body's physiological state is of significant practical importance. However, traditional rigid electronic devices commonly used in hospitals are mostly made of hard materials, making it difficult to fit snugly against the skin, leading to inaccurate monitoring signals. At the same time, these devices are bulky and time-consuming, failing to meet the clinical demand for long-term dynamic monitoring. To address these pain points, flexible wearable electronic devices have emerged. With their excellent flexibility, bendability, and portability, these devices have been widely used in fields such as healthcare and fitness. Flexible sensors, as the core component of flexible wearable electronic devices, are the key carrier for achieving two-way information interaction between the human body and external devices. High sensitivity and wide measurement range are essential prerequisites for flexible sensors to achieve long-term accurate pressure monitoring in various practical application scenarios. However, current flexible sensors on the market still face challenges in balancing high sensitivity and wide measurement range performance, which has become a major bottleneck restricting their large-scale application. Summary of the Invention

[0003] To address the aforementioned challenges, this invention proposes a multi-level strain regulation strategy and a synergistic mechanism with ionogel membranes to fabricate an array of bifacial gradient elastic microstructures coated with ionogel. This dual mechanism achieves a performance breakthrough: firstly, the ionogel membrane serves as the dielectric layer, leveraging its ability to form a thin electric double layer at the electrode interface to impart high intrinsic sensitivity to the device; secondly, by controlling the structural size and array density of the bifacial gradient micropyramids coated with ionogel, a high contact area change rate is achieved using low-density, large-size micropyramids during the low-pressure phase, ensuring high sensitivity. As the pressure increases, bifacial gradient micropyramids of different sizes participate in contact at different levels, effectively broadening the detection range, ultimately achieving a synergistic improvement in both high sensitivity and wide detection range for the flexible sensor.

[0004] This invention proposes a synergistic mechanism between a multi-level strain regulation strategy and an ion-gel membrane, successfully fabricating an ion-gel-coated double-sided gradient elastic microstructure array. This design solves the challenge of simultaneously achieving high sensitivity and a wide detection range in flexible capacitive sensors through a dual mechanism: First, an ion-gel membrane is used as the dielectric layer, leveraging its ability to form a thin electric double layer at the electrode interface to impart a highly sensitive intrinsic response to the device. Second, in the ion-gel-coated double-sided gradient elastic microstructure array, by controlling the structural size and array distribution density of the micro-pyramids (larger micro-pyramids have lower density), the sensor exhibits a higher rate of change in contact area during the low-pressure phase (i.e., initial pressure application), thus ensuring high sensitivity. As the pressure increases, the relatively smaller micro-pyramids sequentially participate in contact, continuously changing the contact area and significantly broadening the sensor's detection range. Therefore, the synergistic strategy of microstructure geometry control and ion-gel interface modification provides an effective approach to achieving flexible capacitive sensors with both high sensitivity and a wide detection range.

[0005] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a method for fabricating a double-sided gradient microstructure array double-electric-layer capacitive flexible sensor, comprising the following steps: Step 1: Place the silicon wafer in acetone, ethanol and deionized water in sequence and sonicate them respectively. Then dry it in a nitrogen atmosphere. Use photolithography to prepare a mask pattern on the surface of the dried silicon wafer. Then place it in a buffer oxide etching solution to remove the silicon dioxide layer that is not protected by the photoresist. After that, put the patterned silicon wafer into a mixed solution of potassium hydroxide and isopropanol for anisotropic etching. Then use a buffer oxide etching solution to remove the residual silicon dioxide layer on the surface of the silicon wafer to obtain the silicon template. Step 2: After plasma treatment and fluorination of the silicon template surface in an oxygen atmosphere, the hydrophobic silicon template is obtained after natural cooling. Step 3: Spin-coat the PDMS prepolymer onto the surface of the hydrophobic silicon template, vacuum degas it, cure it and peel it off to obtain a gradient pyramid microstructure array film, and then treat it with plasma. Step 4: Then spin-coat the PDMS prepolymer onto the flat surface of the plasma-treated gradient pyramid microstructure array film. Subsequently, symmetrically assemble another plasma-treated gradient pyramid microstructure array film with it, and after curing, obtain a double-sided gradient microstructure array film. Step 5: Then, plasma treatment; Step 6: Mix 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, N,N-dimethylacetamide and polyvinylidene fluoride, heat and stir until fully dissolved to obtain a precursor solution, and uniformly spin-coat the precursor solution onto the surface of the double-sided gradient microstructure array film and dry it. Step 7: After cutting to the preset appropriate size, attach the electrode material to the two surfaces of the double-sided gradient microstructure array film processed in step 6 to obtain the double-layer capacitive flexible sensor.

[0006] Further specifying, in step 1, the buffer oxide etching solution has the following composition: NH4F:HF = 7:1, v / v; and the volume ratio of KOH to isopropanol is 5:1.

[0007] Further specifying, in step 2, the 30 W plasma treatment and fluorination treatment are carried out in 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane vapor at 200 °C.

[0008] Further specifying, in step 3, curing is performed at 90 °C.

[0009] Further defining the gradient pyramid microstructure array, the microstructure units are arranged in a regular rectangular grid, with the same size within the same row, exhibiting a gradient change from top to bottom, meaning the base side length and height of the pyramid decrease sequentially. Specifically, the base side lengths of the largest, middle, and smallest pyramids are 206 ± 2 μm, 156 ± 2 μm, and 106 ± 2 μm, respectively, corresponding to heights of 145.4 ± 2 μm, 110.1 ± 2 μm, and 74.8 ± 2 μm, respectively.

[0010] Further specifying, in step 4, curing is performed at 100 °C.

[0011] Further specifying, in step 5, the plasma processing power is 30 W.

[0012] Further specifying, in step 6, the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, N,N-dimethylacetamide and polyvinylidene fluoride is 8:34:6.

[0013] Another objective of this invention is to provide a double-sided gradient microstructure array double-electric-layer capacitive flexible sensor prepared by any of the above methods.

[0014] Another objective of this invention is to provide the use of the double-sided gradient microstructure array double-electric-layer capacitive flexible sensor prepared by any of the above methods for the detection of dynamic finger bending.

[0015] Based on specific implementation methods, the fabrication method of the double-sided gradient microstructure array double-electric-layer capacitive flexible sensor of the present invention is achieved through the following steps: (1) Preparation of silicon template First, the silicon wafer was sequentially placed in acetone, ethanol, and deionized water, and ultrasonically treated for approximately 15 minutes each, followed by drying pretreatment under a nitrogen atmosphere. Next, a mask pattern was fabricated on the pretreated silicon wafer surface using photolithography. To remove the unprotected silicon dioxide (SiO2) layer, the silicon wafer was treated in a buffered oxide etching solution (NH4F:HF = 7:1, v / v). Then, the patterned silicon wafer was immersed in a mixed solution of potassium hydroxide (KOH, 35 wt%) and isopropanol (KOH:isopropanol = 5:1, v / v) and anisotropically etched at 80 °C with vigorous stirring. Finally, the remaining SiO2 layer on the silicon wafer surface was removed again using the buffered oxide etching solution to obtain the target silicon template. Notably, the silicon template is reusable, which provides favorable conditions for the large-scale production of sensors.

[0016] (2) Preparation of hydrophobic silica template To facilitate the smooth transfer of the subsequently prepared flexible film from the silicon template surface, the silicon template needs to be hydrophobically treated. The specific operation is as follows: First, the silicon template surface is subjected to plasma treatment in an oxygen atmosphere at 30 W for 3 min. Then, the silicon template is placed in 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane vapor and fluorinated at 200 °C. After natural cooling, the hydrophobic silicon template can be obtained.

[0017] (3) Preparation method of double-sided gradient microstructure array film PDMS prepolymer was spin-coated onto the surface of a hydrophobically treated silicon template, and the PDMS prepolymer was then degassed under vacuum to eliminate the influence of air bubbles on the preparation quality. The silicon template coated with PDMS prepolymer was then cured at 90 °C for 3 h. After curing, it was peeled off to obtain a PDMS film with a gradient pyramid microstructure array. The back side of the obtained PDMS film with gradient pyramid microstructure array was plasma-treated (30 W, 2 min); after treatment, a layer of PDMS prepolymer was spin-coated onto this side. Another PDMS film with a gradient pyramid microstructure array was assembled with it, using the PDMS prepolymer surface as the bonding interface; after assembly, it was placed in a 100 °C oven for curing for 1 h, finally obtaining a double-sided gradient microstructure array film.

[0018] (4) Preparation of ion gel composite double-sided gradient microstructure array film First, 8 g of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 34 g of N,N-dimethylacetamide, and 6 g of polyvinylidene fluoride were weighed out according to the specified proportions. The three raw materials were mixed evenly and stirred at 60 °C for 40 min to ensure complete dissolution and uniform mixing, resulting in a homogeneous and stable ion gel precursor solution. Next, the double-sided gradient microstructure array membrane was subjected to plasma treatment at a power of 30 W for 2 min. Then, a spin-coating process was used to uniformly spin-coat the ion gel precursor solution onto the surface of the double-sided gradient microstructure array membrane at a speed of 2000 r / min for 20 s. Finally, the spin-coated film was dried in an 80 °C oven for 15 min, thus completing the preparation of the ion gel composite double-sided gradient microstructure array membrane (see [link to documentation]). Figure 3 ).

[0019] (5) Assembly of flexible double-layer capacitive sensor First, the previously prepared ion-gel double-sided gradient microstructure array film was precisely cut to a predetermined size according to actual assembly requirements and subsequent application scenarios. Then, conductive tape with excellent conductivity, flexibility, and strong adhesion to the ion-gel array film surface was selected as the electrode material. Finally, the conductive tape was precisely adhered to the upper and lower surfaces of the ion-gel double-sided gradient microstructure array film. During the adhesion process, it was necessary to ensure that the conductive tape adhered precisely to the array film surface without air bubbles or misalignment, ensuring stable contact between the electrodes and the array film. This assembly method then constructs a double-layer capacitive flexible sensor, laying the foundation for subsequent performance testing and practical applications.

[0020] like Figure 1 As shown, the complete fabrication process of the flexible sensor is illustrated in detail. Figure 2 The sensing mechanism of the double-layer capacitive flexible sensor is explained: the double layer formed at the ionogel interface acts as a highly sensitive "signal amplifier," while the stepwise contact behavior of the bifacial gradient micropyramid array acts as a "regulator" to broaden the detection range. By modulating the pressure-contact area response curve through gradient microstructure, combined with the high capacitance of the ionogel, both high sensitivity and a wide detection range are ultimately achieved. Figure 3 The image shows a scanning electron microscope (SEM) image of an ion gel gradient microstructure array and its magnification. The micro pyramid structures with different gradients are arranged in an orderly manner, which provides favorable support for improving the stability and sensitivity of the sensor. Figure 4The sensitivity data for the double-layer capacitive flexible sensor are shown. Based on the sensor's response signal characteristics under different pressure conditions, its sensitivity was calculated as follows: Within the pressure ranges of 30.09 Pa ~ 2576.55 Pa and 5.15 kPa ~ 150 kPa, the sensitivities of this pressure sensor are 8.43 nF / kPa and 0.13 nF / kPa, respectively. Furthermore, under the same applied pressure, the sensor's sensing signal shows almost no change, indicating good stability. Figure 5 This provides an important guarantee for its practical application. Finally, the sensor was successfully applied to the dynamic bending detection of the finger. Figure 6 This has important practical significance for the field of human health monitoring.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a multi-level strain regulation strategy and a synergistic mechanism with an ion-gel membrane to fabricate an ion-gel-coated double-sided gradient elastic microstructure array. The ion-gel membrane serves as the dielectric layer, leveraging its ability to form a thin electrical double layer at the electrode interface to impart high intrinsic sensitivity to the device. Simultaneously, by controlling the structural size and array distribution density of the double-sided gradient micropyramids, large-sized micropyramids maintain high sensitivity at low pressure, while relatively smaller micropyramids sequentially participate in contact at high pressure, achieving a wide detection range. The fabrication process includes silicon template preparation, hydrophobic silicon template preparation, double-sided gradient microstructure array membrane preparation, ion-gel composite membrane preparation, and sensor assembly. The resulting sensor exhibits sensitivities of 8.43 nF / kPa and 0.13 nF / kPa in the 30.09 Pa ~ 2576.55 Pa and 5.15 kPa ~ 150 kPa ranges, respectively, demonstrating good stability. It can be successfully applied to the detection of dynamic finger bending, providing technical support for long-term accurate monitoring of human physiological states, and is suitable for fields such as medical health and sports fitness.

[0022] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the fabrication of a double-sided gradient microstructure array double-electric-layer capacitive flexible sensor; Figure 2 This is a schematic diagram of the sensing mechanism of a double-layer capacitive flexible sensor; Figure 3 A scanning electron microscope image of an array of microstructures with ion-gel gradients; Figure 4 Sensitivity data for a double-layer capacitive flexible sensor; Figure 5 Stability data for double-layer capacitive flexible sensors; Figure 6 This is used to monitor real-time response data of finger bending using a double-layer capacitive flexible sensor. Detailed Implementation

[0024] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0025] Example 1 (1) Preparation of silicon template First, the silicon wafer was sequentially placed in acetone, ethanol, and deionized water, and ultrasonically treated for approximately 15 minutes each, followed by drying pretreatment under a nitrogen atmosphere. Next, a mask pattern was fabricated on the pretreated silicon wafer surface using photolithography. To remove the unprotected silicon dioxide (SiO2) layer, the silicon wafer was treated in a buffered oxide etching solution (NH4F:HF = 7:1, v / v). Then, the patterned silicon wafer was immersed in a mixed solution of potassium hydroxide (KOH, 35 wt%) and isopropanol (KOH:isopropanol = 5:1, v / v) and anisotropically etched at 80 °C with vigorous stirring. Finally, the remaining SiO2 layer on the silicon wafer surface was removed again using the buffered oxide etching solution to obtain the target silicon template.

[0026] (2) Preparation of hydrophobic silica template The surface of the silicon template was subjected to plasma treatment in an oxygen atmosphere at 30 W for 3 min. Subsequently, the silicon template was placed in 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane vapor and fluorinated at 200 °C. After natural cooling, the hydrophobic silicon template was obtained.

[0027] (3) Preparation method of double-sided gradient microstructure array film PDMS prepolymer was spin-coated onto the surface of a hydrophobically treated silicon template, and the PDMS prepolymer was then degassed under vacuum to eliminate the influence of air bubbles on the preparation quality. The silicon template coated with PDMS prepolymer was then cured at 90 °C for 3 h. After curing, it was peeled off to obtain a PDMS film with a gradient pyramid microstructure array. The back side of the obtained PDMS film with gradient pyramid microstructure array was plasma-treated (30 W, 2 min); after treatment, a layer of PDMS prepolymer was spin-coated onto this side. Another PDMS film with a gradient pyramid microstructure array was assembled with it, using the PDMS prepolymer surface as the bonding interface; after assembly, it was placed in a 100 °C oven for curing for 1 h, finally obtaining a double-sided gradient microstructure array film.

[0028] (4) Preparation of ion gel composite double-sided gradient microstructure array film First, 8 g of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 34 g of N,N-dimethylacetamide, and 6 g of polyvinylidene fluoride were weighed out according to the specified proportions. The three raw materials were mixed evenly and stirred at 60 °C for 40 min to ensure complete dissolution and uniform mixing, resulting in a homogeneous and stable ion gel precursor solution. Next, the double-sided gradient microstructure array membrane was subjected to plasma treatment at a power of 30 W for 2 min. Then, a spin-coating process was used to uniformly spin-coat the ion gel precursor solution onto the surface of the double-sided gradient microstructure array membrane at a speed of 2000 r / min for 20 s. Finally, the spin-coated film was dried in an 80 °C oven for 15 min, thus completing the preparation of the ion gel composite double-sided gradient microstructure array membrane (see [link to documentation]). Figure 3 ).

[0029] (5) Assembly of flexible double-layer capacitive sensor The previously prepared ion-gel double-sided gradient microstructure array film was precisely cut to a predetermined size according to actual assembly requirements and subsequent application scenarios. Then, conductive tape with excellent conductivity, flexibility, and strong adhesion to the ion-gel array film surface was selected as the electrode material. Finally, the conductive tape was precisely adhered to the upper and lower surfaces of the ion-gel double-sided gradient microstructure array film. During the adhesion process, it was necessary to ensure that the conductive tape adhered precisely to the array film surface without air bubbles or misalignment, ensuring stable contact between the electrodes and the array film. This assembly method was then used to construct a double-layer capacitive flexible sensor.

[0030] like Figure 1 As shown, the complete fabrication process of the flexible sensor is illustrated in detail. Figure 2The sensing mechanism of the double-layer capacitive flexible sensor is explained: the double layer formed at the ionogel interface acts as a highly sensitive "signal amplifier," while the stepwise contact behavior of the bifacial gradient micropyramid array acts as a "regulator" to broaden the detection range. By modulating the pressure-contact area response curve through gradient microstructure, combined with the high capacitance of the ionogel, both high sensitivity and a wide detection range are ultimately achieved. Figure 3 The image shows a scanning electron microscope (SEM) image of an ion gel gradient microstructure array and its magnification. The micro pyramid structures with different gradients are arranged in an orderly manner, which provides favorable support for improving the stability and sensitivity of the sensor. Figure 4 The sensitivity data for the double-layer capacitive flexible sensor are shown. Based on the sensor's response signal characteristics under different pressure conditions, its sensitivity was calculated as follows: Within the pressure ranges of 30.09 Pa ~ 2576.55 Pa and 5.15 kPa ~ 150 kPa, the sensitivities of this pressure sensor are 8.43 nF / kPa and 0.13 nF / kPa, respectively. Furthermore, under the same applied pressure, the sensor's sensing signal shows almost no change, indicating good stability. Figure 5 This provides an important guarantee for its practical application. Finally, the sensor was successfully applied to the dynamic bending detection of the finger. Figure 6 This has important practical significance for the field of human health monitoring.

[0031] This invention achieves a performance breakthrough through a dual-mechanism synergy. On one hand, an ionogel film is used as the dielectric layer, leveraging its ability to form a thin electric double layer at the electrode interface to impart a highly sensitive intrinsic response to the device. On the other hand, the double-sided gradient micropyramid array coated with ionogel is modulated. Through gradient design of microstructure size and array distribution density, large-size micropyramids preferentially respond at low pressure, ensuring high sensitivity. As pressure increases, double-sided gradient micropyramids of different sizes gradually participate in contact, causing the effective contact area to continuously increase with pressure, thereby significantly widening the sensor's detection range. Therefore, the synergistic strategy of microstructure geometry control and the electric double layer effect at the ionogel interface effectively solves the problem of the mutual constraint between sensitivity and detection range in flexible capacitive sensors, providing an effective approach for developing flexible sensors with both high sensitivity and wide detection range.

[0032] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A method for fabricating a double-sided gradient microstructure array double-layer capacitive flexible sensor, characterized in that, Includes the following steps: Step 1: Place the silicon wafer in acetone, ethanol and deionized water in sequence and sonicate them respectively. Then dry it in a nitrogen atmosphere. Use photolithography to prepare a mask pattern on the surface of the dried silicon wafer. Then place it in a buffer oxide etching solution to remove the silicon dioxide layer that is not protected by the photoresist. After that, put the patterned silicon wafer into a mixed solution of potassium hydroxide and isopropanol for anisotropic etching. Then use a buffer oxide etching solution to remove the residual silicon dioxide layer on the surface of the silicon wafer to obtain the silicon template. Step 2: After plasma treatment and fluorination of the silicon template surface in an oxygen atmosphere, the hydrophobic silicon template is obtained after natural cooling. Step 3: Spin-coat the PDMS prepolymer onto the surface of the hydrophobic silicon template, vacuum degas it, cure it and peel it off to obtain a gradient pyramid microstructure array film, and then treat it with plasma. Step 4: Then spin-coat the PDMS prepolymer onto the flat surface of the plasma-treated gradient pyramid microstructure array film. Subsequently, symmetrically assemble another plasma-treated gradient pyramid microstructure array film with it, and after curing, obtain a double-sided gradient microstructure array film. Step 5: Then, plasma treatment; Step 6: Mix 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, N,N-dimethylacetamide and polyvinylidene fluoride, heat and stir until fully dissolved to obtain a precursor solution, and uniformly spin-coat the precursor solution onto the surface of the double-sided gradient microstructure array film and dry it. Step 7: After cutting to the preset appropriate size, attach the electrode material to the two surfaces of the double-sided gradient microstructure array film processed in step 6 to obtain the double-layer capacitive flexible sensor.

2. The method according to claim 1, characterized in that, In step 1, the buffer oxide etching solution has the following composition: NH4F:HF = 7:1, v / v; and the volume ratio of KOH to isopropanol is 5:

1.

3. The method according to claim 1, characterized in that, In step 2, the fluorination treatment is carried out in 30 W plasma at 200 °C in 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane vapor.

4. The method according to claim 1, characterized in that, In step 3, the product is cured at 90 °C.

5. The method according to claim 1, characterized in that, The gradient pyramid microstructure array is arranged in a regular rectangular grid. The microstructure units in the same row have the same size and show a gradient change from top to bottom, that is, the bottom side length and height of the pyramid decrease successively. Among them, the bottom side lengths of the largest, middle and smallest pyramids are 206 ± 2 μm, 156 ± 2 μm and 106 ± 2 μm, respectively, and the corresponding heights are 145.4 ± 2 μm, 110.1 ± 2 μm and 74.8 ± 2 μm, respectively.

6. The method according to claim 1, characterized in that, In step 4, the product is cured at 100 °C.

7. The method according to claim 1, characterized in that, In step 5, the plasma processing power is 30 W.

8. The method according to claim 1, characterized in that, In step 6, the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, N,N-dimethylacetamide, and polyvinylidene fluoride is 8:34:

6.

9. A double-sided gradient microstructure array double-electric-layer capacitive flexible sensor prepared by any one of claims 1-8.

10. A double-sided gradient microstructure array double-electric-layer capacitive flexible sensor prepared by any one of claims 1-8 for detecting dynamic bending of the finger.

Images