Ionizing fabric-based pressure-volume sensor and preparation method thereof

Abstract

The invention belongs to the technical field of flexible pressure sensors, and particularly relates to an ionizing fabric-based pressure-volume sensor and a preparation method thereof. The pressure-volume sensor is composed of an upper electrode layer, a lower electrode layer and a dielectric layer, a flexible diaphragm layer is arranged between the electrode layers and the dielectric layer, and holes with certain density are formed in the flexible diaphragm layer. The ionizing fabric-based pressure-capacitance sensor is simple in structure and simple in preparation process, and meanwhile, accurate regulation and control and wide-range linear response of the ionizing contact area between the capacitance sensor electrode and the dielectric layer can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible pressure sensors, and particularly relates to a triboelectric fabric-based piezocapacitive sensor and a preparation method thereof. Background Art

[0002] At present, the rapid development of artificial intelligence and virtual reality technologies has put forward new requirements for signal acquisition and processing in the fields of human-computer interaction and the Internet of Things. As a key medium for signal acquisition, flexible pressure sensors have shown multi-directional application prospects in the fields of human health detection, intelligent real-time control, and artificial electronic skin. Pressure sensors can be classified into piezoresistive, piezoelectric, and piezocapacitive sensors according to their mechanisms. Among them, piezocapacitive sensors can stably detect steady-state pressure signals to achieve the above-mentioned multiple uses. At the same time, due to their excellent performance adjustability and low power consumption, piezocapacitive sensors with various morphologies have been widely studied. However, it has always been a huge challenge for piezocapacitive pressure sensors to simultaneously achieve a low detection limit and a wide linear response range. For this reason, researchers have proposed triboelectric piezocapacitive sensors, that is, introducing ion-conductive fillers into the dielectric layer, and inducing the enrichment of ions in the dielectric layer towards the two electrodes under the electric field during the use of the sensor to form a double-layer structure, so as to increase the capacitance change rate of the piezocapacitive sensor, thereby achieving high sensitivity under small stress.

[0003] At present, the common structural design method of triboelectric piezocapacitive sensors is to construct electrode layers or dielectric layers with different geometric structures, and to realize the change of the partial area of the double layer through the deformation of the geometric structure during the compression process, so as to regulate the sensing performance of the sensor. However, the fixed electrode or dielectric layer structure makes it difficult to regulate the performance of the piezocapacitive sensor. At the same time, the complex structural design greatly increases the difficulty of sensor production and preparation. In addition, the materials that can be used for additive or subtractive manufacturing often do not have good air permeability, which is not conducive to the wearing comfort of wearable flexible devices.

[0004] Regarding the contact area control of current triboelectric piezocapacitive sensors, researchers have realized the gradual change of the double-layer area during the compression process by designing the topological structure of the electrode or dielectric layer. Common methods include: using the template method to construct random microstructures, uniform microstructures, and gradient microstructures; 3D printing to manufacture microstructures; mechanical entanglement or stretching to construct microstructures. By deforming the microstructures during the compression process, the contact area between the electrode and the dielectric layer, that is, the double-layer area, is changed, thereby realizing the optimization of the piezocapacitive sensing performance. For example, Bai Ningning et al. reported a PVA / H 3 PO 4 ion-conductive dielectric layer with microstructures constructed by a sandpaper template, which was assembled with a deposited gold electrode to form a sensor, achieving ultra-high sensitivity (the sensitivity reached 3302.9 kPa under a pressure below 10 kPa -1) response and still maintain a sensitivity of 229.9 kPa under high pressure -1 Qin Yuxiang et al. reported a method for constructing a microstructural template by pre-stretching PDMS to prepare PVA / H 3 PO 4 dielectric layer, which was assembled with the PVA / H 3 PO 4 electrode loaded with silver wires to achieve a sensitivity of 37.7 kPa in the range of 0 - 4 kPa -1 However, through this method of constructing microstructures, although a highly sensitive triboelectric capacitive sensor can be obtained, the production of the sensor is difficult, and it is also difficult to achieve an adjustable wide-range linear response. Summary of the Invention

[0005] The purpose of the present invention is to provide a triboelectric fabric-based capacitive sensor and its preparation method, which can solve the problems existing in the prior art, such as complex electrode and dielectric layer structure design, difficult sensor production, or difficulty in achieving an adjustable wide-range linear response.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A triboelectric fabric-based capacitive sensor, the capacitive sensor is composed of upper and lower electrode layers and a dielectric layer, and a flexible diaphragm layer is arranged between the electrode layer and the dielectric layer, and a certain density of holes are formed on the flexible diaphragm layer.

[0008] Furthermore, the holes are uniformly arranged on the flexible diaphragm layer, the number of holes is not less than 8, and the opening area accounts for 7 - 64% of the area of the diaphragm layer.

[0009] Furthermore, the holes are arranged in an array;

[0010] Taking the diaphragm layer as 2 cm × 2 cm as an example, the array can be arranged in 3×3, 5×5, 7×7, 9×9.

[0011] The thickness of the flexible diaphragm layer is 25 - 150 μm.

[0012] There are no special requirements for the flexible diaphragm material, but polyimide film is more preferably used.

[0013] When preparing the above-mentioned triboelectric fabric-based capacitive sensor, the existing technology can be used to process holes on the flexible diaphragm, and after processing, it is ultrasonically cleaned in ethanol and deionized water in sequence, and then dried.

[0014] Specifically, a UV laser engraving machine can be used, etc. The subsequent cleaning is mainly to remove the carbon impurities and stains left by laser drilling.

[0015] Ultrasonic cleaning for about 10 minutes is sufficient, and drying can be carried out in an oven at 60 °C for 1 hour.

[0016] The ion-conductive dielectric layer can be prepared by, but not limited to, the following method: Clean and dry a cotton fiber cloth, then immerse it in 100 μL of ionic liquid for 5 minutes, and wipe off the excess ionic liquid on the surface with filter paper to obtain the ion-conductive dielectric layer.

[0017] The electrode layer can be prepared according to the existing technology.

[0018] Different from the existing technology where the capacitive pressure sensor mainly realizes the change in the area of the double electric layer during the compression process through the microstructure design of the electrode and the dielectric layer, the processing of the microstructure often relies on complex additive or subtractive manufacturing, which increases the preparation cost and difficulty of the capacitive pressure sensor. At the same time, the fixed structure is difficult to regulate the performance of the sensor. The present invention realizes the precise regulation and wide-range linear response of the off-contact area between the electrode and the dielectric layer of the capacitive sensor by introducing a diaphragm with adjustable pore density and thickness.

[0019] Compared with the existing technology, the present invention has the following advantages:

[0020] The off-contact fabric-based capacitive pressure sensor of the present invention has a simple structure and a simple preparation process. At the same time, it can realize the precise regulation and wide-range linear response of the off-contact area between the electrode and the dielectric layer of the capacitive sensor, and the linear response interval is 0 - 200 kPa. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the sensor structure of the present invention;

[0022] Figure 2 It is a physical diagram of the diaphragm (50 μm thick) prepared in Example 1;

[0023] Figure 3 It is the initial capacitance of the sensor regulated by diaphragms with different thicknesses and pore densities;

[0024] Figure 4 It is a curve of the capacitance change rate of the sensor varying with pressure obtained by using diaphragms with a pore density of 5×5 and different thicknesses;

[0025] Figure 5 It is a curve of the capacitance change rate of the sensor varying with pressure obtained by using diaphragms with a thickness of 50 μm and different pore densities and its sensitivity;

[0026] Figure 6 It is a curve of the capacitance change rate of the sensor varying with pressure obtained by using PDMS diaphragms with a thickness of 75 μm and different pore densities and its sensitivity. Detailed Embodiments

[0027] The technical solutions of the present invention will be described below by specific embodiments, but the protection scope of the present invention is not limited thereto:

[0028] The materials used in the embodiments of the present invention are as follows:

[0029] The polyimide film PI film was purchased from Quanzhou Jue Aluminum Technology Co., Ltd., polydimethylsiloxane (PDMS-Sylgard 184) was purchased from Dow Corning Corporation of the United States, carbon cloth (WOS1011) was purchased from Suzhou Shengnuoke Technology Co., Ltd., cotton fiber cloth was purchased from Shenzhen PurCotton Times Technology Co., Ltd., and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) was purchased from Beijing Innochem Technology Co., Ltd. The above listing is only a specific description of the materials used in the embodiments of the present invention, and does not constitute a specific limitation on the materials used in the present invention, nor does it affect the effects of the embodiments due to changes in the specific brands of the materials.

[0030] Example 1

[0031] Select polyimide (PI) films with different thicknesses (25, 50, 75, 100, 125, 150 μm), set the parameters of the ultraviolet laser engraving machine as speed 1100 mm / s, power 50%, engraving 120 times, process the PI separator with different hole densities (3×3, 5×5, 7×7, 9×9), the hole diameter is 1 mm, and the separator is a square with a side length of 25 mm. After processing, ultrasonically clean in ethanol and deionized water in sequence, and then dry.

[0032] Ultrasonically clean the cotton fiber cloth in ethanol and deionized water in sequence, and then immerse the cleaned cotton fiber cloth with a side length of 20 mm in 100 μL of ionic liquid for 5 min, and wipe off the excess ionic liquid on the surface with filter paper to make an ion-conductive dielectric layer.

[0033] Stack the carbon fiber cloth electrode, PI separator, cotton fiber cloth dielectric layer, PI separator and carbon fiber cloth electrode in sequence to form a tunable fabric-based piezocapacitive sensor. The schematic diagram is as Figure 1 shown, and the above are all achievable by conventional technical means.

[0034] The following, Table 1 shows the initial capacitance values of the sensors obtained by different thicknesses and hole arrangement combinations, the test frequency of the LCR meter is 100 kHz; Table 2 shows the capacitance change rates of the sensors obtained by different thicknesses and hole arrangement combinations, the pressure change range is 0-200 kPa, and the test frequency of the LCR meter is 100 kHz; Table 3 shows the sensitivities of the sensors obtained by different thicknesses and hole arrangement combinations, the pressure change range is 0-200 kPa, and the test frequency of the LCR meter is 100 kHz;

[0035] Table 1

[0036]

[0037]

[0038] Table 2

[0039]

[0040] Table 3

[0041]

[0042] Example 2

[0043] Prepare a mixed solution with a mass ratio of PDMS precursor to curing agent of 10:1, stir for 10 min, put the stirred mixed solution into a vacuum oven, and evacuate the air bubbles at room temperature. Use a doctor blade to set different thicknesses (25, 50, 75, 100, 125, 150 μm), scrape the PDMS solution to the corresponding thickness, place it on a hot stage at 80 °C for curing for 2 h to obtain PDMS membranes with different thicknesses. Set the parameters of the ultraviolet laser engraving machine: speed 1100 mm / s, power 50%, engraving 150 times, process the PDMS diaphragm with different hole densities (3×3, 5×5, 7×7, 9×9) to make a diaphragm with a side length of 25 mm and a pore diameter of 1 mm.

[0044] Replace the PI diaphragm with the PDMS diaphragm, and the others are the same as in Example 1.

[0045] From Figure 6 It can be seen that the PDMS diaphragm sample (thickness 75 μm) and the PI diaphragm sample have the same regulation trend. Due to the difference in the dielectric properties of the materials, although it is impossible to achieve exactly the same sensitivity change range, it does not affect the regulation of the sensing performance.

Claims

1. An ionization type fabric-based pressure-capacitive sensor, the pressure-capacitive sensor is composed of an upper and lower electrode layer and a dielectric layer, characterized in that: A flexible diaphragm layer is arranged between the electrode layer and the dielectric layer, and holes with a certain density are opened on the flexible diaphragm layer.

2. The ionization type fabric-based pressure-capacitive sensor according to claim 1, characterized in that: The holes are evenly distributed on the flexible diaphragm layer, the number of the holes is not less than 8, and the opening area accounts for 7-64% of the area of ​​the diaphragm layer.

3. The ionization type fabric-based pressure-capacitive sensor according to claim 2, characterized in that: The holes are arranged in an array; Optionally, taking the membrane layer of 2 cm×2 cm as an example, the arrays are arranged as 3×3, 5×5, 7×7, and 9×9.

4. The ionization type fabric-based pressure-capacitive sensor according to claim 2, characterized in that: The thickness of the flexible diaphragm layer is 25-150 μm.

5. The ionization type fabric-based pressure-capacitive sensor according to claim 1, characterized in that: The flexible diaphragm is a polyimide film.

6. The method for preparing the ionization type fabric-based pressure-capacitive sensor according to any one of claims 1 to 5, characterized in that: A flexible diaphragm with holes of a certain density is arranged between the upper electrode layer and the dielectric layer and between the dielectric layer and the lower electrode layer.

7. The method for preparing the ionization type fabric-based pressure-capacitive sensor according to claim 6, characterized in that: The holes are evenly arranged on the flexible diaphragm layer, the number of holes is not less than 8, and the opening area accounts for 7-64% of the area of ​​the diaphragm layer; Optionally, the holes are arranged in an array; Optionally, taking the membrane layer of 2 cm×2 cm as an example, the arrays are arranged as 3×3, 5×5, 7×7, and 9×9.

8. The method for preparing the ionization type fabric-based pressure-capacitive sensor according to claim 6, characterized in that: The thickness of the flexible diaphragm layer is 25-150 μm.

9. The method for preparing the ionization type fabric-based pressure-capacitive sensor according to claim 6, characterized in that: The flexible membrane is a polyimide film.

10. The method for preparing the ionizing fabric-based pressure-capacitive sensor according to any one of claims 6 to 9, characterized in that: After the holes are processed, the flexible membrane is ultrasonically cleaned in ethanol and deionized water in sequence, and then dried.

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