CN112504518A - Flexible capacitive pressure sensor and preparation method thereof - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
- G01L1/142—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors
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- G—PHYSICS
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/12—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance, i.e. electric circuits therefor
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Abstract
The invention discloses a flexible capacitive pressure sensor and a preparation method thereof, wherein the preparation method comprises the following steps: s10, selecting a sensor material; s20, preparing a flexible substrate; s30, structuring the electrode layer or the dielectric layer, including adding a pyramid microstructure on the surface of the upper electrode layer; s40, preparing upper and lower electrode layers; s50, penetrating the electrode lead into the electrode film; and S60, the prepared upper electrode layer and the prepared lower electrode layer are placed in a crossed fit mode, electrode arrays arranged on the upper electrode layer and the lower electrode layer are perpendicular to each other, a dielectric layer is arranged between the upper electrode layer and the lower electrode layer, the upper electrode layer and the lower electrode layer are placed in an oven at the temperature of 80 ℃ for 2 hours to be cured, and the flexible capacitive pressure sensor with the sandwich structure is obtained after the upper electrode layer and the lower electrode layer are taken down. The invention can effectively improve the pressure measuring sensitivity performance of the pressure sensor, and has simple preparation process, higher sensitivity and short response time.
Description
Technical Field
The invention belongs to the technical field of pressure sensors, and particularly relates to a flexible capacitive pressure sensor and a preparation method thereof.
Background
At present, research on flexible electronic technology has entered into a substantial development stage from a starting stage, and the flexible electronic technology industry has always gained deep attention. The flexible pressure sensor has good performance in the aspects of information transmission and acquisition, is an important device, can convert the pressure sensed from the outside into signal data which can be directly measured electrically and optically, and reflects the size distribution condition of the pressure signal. The flexible sensor has the characteristics of free bending, small volume, thin thickness and the like, and has good compatibility with human skin, and the pressure sensor can also detect physiological parameters, environmental characteristics, motion postures and the like, so the flexible sensor has a great amount of applications in the aspects of medical equipment, electronic skin, wearable equipment and the like.
With the rapid development of organic electronics and electrical sensing technologies, the development of flexible pressure sensors has also made significant progress. The method has the characteristics of excellent flexibility, large elastic tensile strain, good compatibility and the like, is widely applied to the fields of human motion detection, health diagnosis and the like, and gradually improves the requirements on various performance parameters such as the accuracy, the sensitivity, the stability and the like of information measurement. Currently, flexible sensors exhibit limitations in some applications, including insufficient flexibility, response lag, low sensitivity and susceptibility to signal noise. The current preparation methods of the flexible pressure sensor mainly comprise the following steps:
the method comprises the following steps of performing magnetron sputtering Ag on a pre-stretched PDMS film substrate by a vacuum deposition method to serve as an electrode layer, preparing an electrode with a wavy microstructure, and enabling an intermediate dielectric layer to be composed of a polydimethylsiloxane/carbon nano tube (PDMS/CNT) composite material. The response time of the sensor is less than 200ms, and the sensor can be used for detecting distribution and position information of finger pressure.
The bionic rose petal is used for preparing a microscopic convex structure which is copied to the surface of the flexible PDMS film. Firstly, pouring a polyvinyl alcohol (PVA) solution on the surface of the rose petal, peeling to obtain a sunken PVA film which has a structure opposite to that of the petal, and spin-coating a mixed PDMS solution on a microstructure PVA film, namely, the peeled structure is matched with the petal structure. Copying silver-plated copper nanowires (Cu-AgNWs) to the surface of a PDMS film, and oppositely overlapping and packaging two microstructure conductive films to obtain the rose microstructure-imitated flexible pressure sensor. The sensor has high sensitivity and can be used for voice recognition, wrist pulse detection and the like.
The mixed PDMS and the cross-linking agent solution are coated on a conical groove structure array mould, heated at 70 ℃ for 30 minutes, kept stand for 30 minutes, and the PDMS membrane is separated from the mould. And forming the pre-processed carbon nano tube film on the micro-porous filtering membrane. The middle of the sensor is a carbon nano tube film, the lower electrode layer is a PDMS film with a conical array structure, and the upper electrode layer is a smooth PDMS film. The sensor improves the linearity, the minimum sensible pressure reaches 1mN, and the sensor has the characteristic of low power consumption.
Although the flexible pressure sensor can sense the pressure applied from the outside, the flexible pressure sensor has the following defects: the sensor based on the wave-shaped structure has insufficient stability and is suitable for sensing micro pressure; the detection range based on the bionic rose petal structure is small, and the phenomenon of response lag can occur; the PDMS sensor based on the cone structure has low sensitivity and is easily interfered by noise.
Disclosure of Invention
Based on this, there is a need for a flexible pressure sensor with short response time, high sensitivity, simple manufacturing process and low manufacturing cost.
In order to achieve the above object, the present invention provides a method for manufacturing a flexible capacitive pressure sensor, comprising the steps of: s10, selecting a sensor material;
s20, preparing a flexible substrate as a dielectric layer;
s30, structuring the electrode layer or the dielectric layer, including adding a pyramid microstructure on the surface of the upper electrode layer;
s40, preparing upper and lower electrode layers;
s50, penetrating the electrode lead into the electrode film;
and S60, the prepared upper electrode layer and the prepared lower electrode layer are placed in a crossed fit mode, electrode arrays arranged on the upper electrode layer and the lower electrode layer are perpendicular to each other, a dielectric layer is arranged between the upper electrode layer and the lower electrode layer, the upper electrode layer and the lower electrode layer are placed in an oven at the temperature of 80 ℃ for 2 hours to be cured, and the flexible capacitive pressure sensor with the sandwich structure is obtained after the upper electrode layer and the lower electrode layer are taken down.
Preferably, the selective sensor material includes polydimethylsiloxane as a base material and carbon nanotube powder as a conductive material.
Preferably, the preparing the flexible substrate comprises the following steps:
s21, weighing liquid polydimethylsiloxane and a polydimethylsiloxane curing agent, mixing and stirring the liquid polydimethylsiloxane and the polydimethylsiloxane curing agent according to the mass ratio of 10:1, mixing the liquid polydimethylsiloxane and deionized water according to the mass ratio of 3:1, and stirring the two mixed solutions together;
s22, dripping the solution on the surface of a cleaned glass sheet, spin-coating for 20S, curing for half an hour in an oven at 60 ℃ to obtain a semi-cured flexible substrate polydimethylsiloxane film, and cutting the flexible substrate into a square shape of about 6cm x 6 cm;
and S23, adding dilute nitric acid into the carbon nano tube powder, stirring by a magnetic stirrer, performing ultrasonic dispersion treatment, adding deionized water for dilution, standing, and filtering to remove supernatant to obtain the carbon nano tube oxide.
Preferably, the preparing the upper and lower electrode layers comprises the following steps:
s41, preparing an upper electrode layer with a pyramid microstructure, manufacturing a silk screen printing plate according to an electrode array and a lead diagram, and printing a conductive material on a polydimethylsiloxane film of a semi-solidified microstructure by utilizing a silk screen printing process;
s42, preparing a lower electrode layer, printing the carbon oxide nanotubes on a smooth basement membrane, and drying to obtain the electrode layer, wherein the electrode array of the prepared lower electrode layer is 4-6 parallel strips with 0.5cm by 5cm and the spacing between the strips is 4-6 mm.
Preferably, the dielectric layer is a polydimethylsiloxane film.
Preferably, when pressure is applied to the manufactured flexible capacitive pressure sensor with the sandwich structure, deformation occurs, and the capacitance value changes accordingly, wherein the capacitance expression is as follows:
wherein epsilon0＝8.854×10-12F/m represents the absolute dielectric constant in vacuum, εrIs the relative dielectric constant, S, of the dielectric layerζD is the initial thickness between the upper electrode layer and the lower electrode layer, and Delta D is the distance between the layers.
Based on the above purpose, the invention also provides a flexible capacitive pressure sensor prepared by the preparation method, which is characterized by comprising an upper electrode layer, a dielectric layer and a lower electrode layer from top to bottom, wherein the upper electrode layer is a carbon oxide nanotube film with a pyramid microstructure, the dielectric layer is a polydimethylsiloxane film, and the lower electrode layer is a smooth conductive planar electrode.
Preferably, the height of the pyramid microstructure is 0.2mm, and the thickness of the prepared oxidized carbon nanotube film is 200-400 μm.
Preferably, the electrode arrays arranged on the upper electrode layer and the lower electrode layer are both in a parallel strip shape, and the electrode arrays on the upper electrode layer and the lower electrode layer are arranged in a vertically crossed structure.
Preferably, each electrode in the electrode array is 0.5cm by 5cm in size, spaced 0.5cm apart from each other.
The invention has the beneficial effects that: the flexible capacitive pressure sensor prepared by the formula has the characteristics of high heat dissipation, high insulation, high temperature resistance, strong flexibility and the like, the heat conductivity is 2.8-3.0W/m.K, and the peel strength is 1.08-1.28 kN/m. The preliminarily positioned polymer colloid is used, and boron nitride in a system is mutually connected through coating, semi-curing and hot-pressing curing, so that a heat conduction network in the polymer is established, and the heat conductivity of the insulating layer is improved.
Drawings
In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:
FIG. 1 is a flow chart illustrating steps in a method of making a flexible capacitive pressure sensor in accordance with an embodiment of the present invention;
FIG. 2 is a cross-sectional view of the overall structure of a flexible capacitive pressure sensor in accordance with an embodiment of the present invention;
FIG. 3 is an overall block diagram of a flexible capacitive pressure sensor in accordance with an embodiment of the present invention;
FIG. 4 is a cross-sectional view of a pyramidal microstructure mold of a flexible capacitive pressure sensor in accordance with an embodiment of the present invention;
FIG. 5 is a diagram of an electrode array of an upper electrode layer and a lower electrode layer of a flexible capacitive pressure sensor according to an embodiment of the present invention
Fig. 6 is a simulation diagram of a microstructure of the flexible capacitive pressure sensor according to the embodiment of the invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The flexible pressure sensor is an electronic device capable of sensing external pressure change, has various structural types, and has important application in the aspects of Internet of things, wearable electronics, electronic skins, intelligent robots and the like. When the pressure sensor is prepared, the performance index of the pressure sensor is improved, and the method is an effective method for further researching the microstructure of the pressure sensor. In addition, in order to solve the problem of complex preparation process, the process needs to be further simplified, and the manufacturing cost needs to be reduced, so that the sensor can be put into application in a large scale.
Method example 1
Referring to fig. 1, the method comprises the following steps: s10, selecting a sensor material;
s20, preparing a flexible substrate as a dielectric layer;
s30, structuring the electrode layer or the dielectric layer, including adding a pyramid microstructure on the surface of the upper electrode layer;
s40, preparing upper and lower electrode layers;
s50, penetrating the electrode lead into the electrode film;
and S60, the prepared upper electrode layer and the prepared lower electrode layer are placed in a crossed fit mode, electrode arrays arranged on the upper electrode layer and the lower electrode layer are perpendicular to each other, a dielectric layer is arranged between the upper electrode layer and the lower electrode layer, the upper electrode layer and the lower electrode layer are placed in an oven at the temperature of 80 ℃ for 2 hours to be cured, and the flexible capacitive pressure sensor with the sandwich structure is obtained after the upper electrode layer and the lower electrode layer are taken down.
S10, selecting a sensor material including polydimethylsiloxane as a base material and carbon nanotube powder as a conductive material.
S20, preparing a flexible substrate, comprising the following steps:
s21, weighing liquid polydimethylsiloxane and a polydimethylsiloxane curing agent, mixing and stirring the liquid polydimethylsiloxane and the polydimethylsiloxane curing agent according to the mass ratio of 10:1, mixing the liquid polydimethylsiloxane and deionized water according to the mass ratio of 3:1, and stirring the two mixed solutions together;
s22, dripping the solution on the surface of a cleaned glass sheet, spin-coating for 20S, curing for half an hour in an oven at 60 ℃ to obtain a semi-cured flexible substrate polydimethylsiloxane film, and cutting the flexible substrate into a square shape of about 6cm x 6 cm;
and S23, adding dilute nitric acid into the carbon nano tube powder, stirring by a magnetic stirrer, performing ultrasonic dispersion treatment, adding deionized water for dilution, standing, and filtering to remove supernatant to obtain the carbon nano tube oxide.
S40, preparing upper and lower electrode layers, comprising the following steps:
s41, preparing an upper electrode layer with a pyramid microstructure, manufacturing a silk screen printing plate according to an electrode array and a lead diagram, and printing a conductive material on a polydimethylsiloxane film of a semi-solidified microstructure by utilizing a silk screen printing process;
s42, preparing a lower electrode layer, printing the carbon oxide nanotubes on a smooth basement membrane, and drying to obtain the electrode layer, wherein the electrode array of the prepared lower electrode layer is 4-6 parallel strips with 0.5cm by 5cm and the spacing between the strips is 4-6 mm.
The dielectric layer is a polydimethylsiloxane film.
When pressure is applied to the flexible capacitive pressure sensor with the sandwich structure manufactured in the step S60, deformation occurs, and a capacitance value changes accordingly, where an expression of the capacitance is:
wherein epsilon0＝8.854×10-12F/m represents the absolute dielectric constant in vacuum, εrIs the relative dielectric constant, S, of the dielectric layerζD is the initial thickness between the upper electrode layer and the lower electrode layer, and Delta D is the distance between the layers.
Example 2
S10, selecting materials, the carbon material as the conductive filler of the flexible sensor has many advantages, the carbon nano tube has large specific surface area, excellent conductive performance and mechanical performance, and because of the special tubular structure, the carbon nano tube can be compatible with large-area solution processing technology, and the oxidized carbon nano tube is deposited on the flexible substrate by adopting the processing technology. The substrate material is also an important influencing factor of the sensor, and needs to have key indexes such as lightness and thinness, good stretchability, flexibility and the like, and Polydimethylsiloxane (PDMS) has the characteristics of low modulus, good flexibility, high elasticity and the like, is simple and easy to obtain, has stable chemical properties, and meets the requirement for preparing the flexible sensor.
S20, a preparation method of the flexible substrate PDMS film. Measuring liquid PDMS and PDMS curing agent, mixing and stirring the liquid PDMS and the PDMS curing agent according to the optimal ratio of 10:1, mixing the PDMS solution and deionized water according to the ratio of 3:1, and stirring the two mixed solutions together.
Dripping the solution on the surface of a clean glass sheet, spin-coating for 20s at a certain speed, curing for half an hour in an oven at 60 ℃ to obtain a semi-cured flexible substrate PDMS film, and cutting the flexible substrate into about 6 x 6cm2Is square in shape.
Adding dilute nitric acid into carbon nano tube powder, stirring by a magnetic stirrer, performing ultrasonic dispersion treatment, adding deionized water for dilution, standing for a period of time, and filtering to remove supernatant to obtain the carbon nano tube oxide.
S30, in order to improve the performance of the sensor, a microstructure is designed in the upper electrode layer of the flexible sensor, and the characteristic that the sensor is easy to deform under the action of micro pressure can be met.
In the design, a micro pyramid structure is added on the surface of an upper electrode layer of the sensor, the sensor with the micro structure is realized through the same manufacturing process under the same material, when the sensor is stressed, the pyramid structure is contacted with the electrode, the stress area is relatively concentrated, the capacitance change rate is relatively large, the material can obtain larger deformation, the sensitivity of the sensor is improved, and a 3D printing technology is used for preparing the die. The expression of the sensitivity is as follows:
in the above formula,. DELTA.C represents the amount of change in capacitance, CξRepresenting the initial capacitance value and F the pressure value to which the sensor is subjected per unit area. It can be seen from the equation that when pressure is applied, the sensitivity increases as the capacitance change increases.
And S40, preparing upper and lower electrode layers of the flexible pressure sensor. The preparation of the electrode layer is carried out on the basis of a flexible substrate, and a silk-screen printing technology with simple preparation process flow and lower cost is adopted. And (3) manufacturing a mold by using a 3D printing technology, wherein the sectional view of the mold is shown in figure 4.
The first electrode layer is provided with a microstructure. And manufacturing a silk screen printing plate according to the electrode array and the wire pattern, and printing a conductive material on the PDMS film of the semi-cured microstructure by utilizing a silk screen printing process.
The last layer is a lower electrode layer, carbon oxide nanotubes are printed on a smooth basement membrane, and the electrode layer is prepared by drying, namely the prepared electrode array is 4 parallel strips with the length of 0.5 x 5cm, and the spacing is 5 mm.
S50, in order to facilitate the detection of the sensor, an electrode lead needs to be arranged, but the conductive stability and the connection firmness are guaranteed, so that the electrode lead directly penetrates into the electrode film, and the connection firmness is guaranteed.
And S60, vertically and crosswise placing the prepared upper and lower parallel electrode layers, placing the middle of the electrode layers to be a dielectric layer PDMS (polydimethylsiloxane) layer, placing the electrode layers in an oven at the temperature of 80 ℃ for two hours for curing, and taking down the sample to obtain the prepared sandwich structure sensor.
Sensor embodiments
Referring to fig. 2 and 3, the flexible capacitive pressure sensor prepared by the above preparation method includes an upper electrode layer 10, a dielectric layer 20 and a lower electrode layer 30 from top to bottom, wherein the upper electrode layer 10 is a carbon oxide nanotube film with a pyramid microstructure, the dielectric layer 20 is a polydimethylsiloxane film, and the lower electrode layer 30 is a smooth conductive planar electrode. When the pressure is sensed, the force-bearing area is increased due to the pyramid microstructure, namely the capacitance change rate is increased, so that the sensitivity of the sensor is improved.
The height of the pyramid microstructure is 0.2mm, and the thickness of the prepared carbon oxide nanotube film is 200-400 μm.
The electrode arrays arranged on the upper electrode layer 10 and the lower electrode layer 30 are both in a parallel strip shape, and the electrode arrays on the upper electrode layer 10 and the lower electrode layer 30 are arranged in a vertical crossing structure. Each electrode in the electrode array was 0.5cm by 5cm, spaced 0.5cm apart.
Detailed description of the preferred embodiments
The sensor is prepared by preparing a PDMS film with a pyramid microstructure, preparing a smooth PDMS film, preparing a conductive material oxidized carbon nanotube film electrode layer, and laminating the three layers. In other embodiments, the preparation sequence can be changed, and finally the flexible sensor is prepared by superposing the upper and lower electrode layers 10 and 30 and the dielectric layer 20.
By adding the microstructure on the surface of the electrode, the positive area of the electrode plate is increased and the distance between the electrode plate and the electrode plate is reduced under the stimulation of pressure, so that the capacitance change rate is higher, and the sensitivity is improved. In the design, the surface of the upper electrode layer is paved with micro pyramid shapes with the same size and the same distance, so that the pressure contact area is increased. The flexible upper electrode layer can be manufactured by adopting a 3D printing technology to print a die according to a pattern and laying a conductive material on the surface of the flexible substrate with the microstructure by applying a screen printing process.
Fig. 5 is a diagram of an electrode array. The electrode arrays of the upper and lower electrode layers are 0.5cm by 5cm square, the middle interval is 5mm, and the silk screen printing screen plate of the electrode arrays is prepared according to the designed model.
FIG. 6 is a simulation of the microstructure. When the same material and the same preparation process are adopted, the sensor with the microstructure is designed, the deformation amount is better than that of a sensor without the structure under the action of pressure, and the sensitivity is higher. From the angle analysis of mechanics, when receiving pressure, through pyramid and electrode contact, the lifting surface area is more concentrated, obtains the deformation volume bigger, has bigger electric capacity rate of change, so sensitivity is better. Simulation analysis is carried out by using COMSOL Multiphysics software, a micro cone structure is designed, and deformation quantity obtained by the same pressure action is larger than that of a sensor without a microstructure.
Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (10)
1. A preparation method of a flexible capacitive pressure sensor is characterized by comprising the following steps:
s10, selecting a sensor material;
s20, preparing a flexible substrate as a dielectric layer;
s30, structuring the electrode layer or the dielectric layer, including adding a pyramid microstructure on the surface of the upper electrode layer;
s40, preparing upper and lower electrode layers;
s50, penetrating the electrode lead into the electrode film;
and S60, the prepared upper electrode layer and the prepared lower electrode layer are placed in a crossed fit mode, electrode arrays arranged on the upper electrode layer and the lower electrode layer are perpendicular to each other, a dielectric layer is arranged between the upper electrode layer and the lower electrode layer, the upper electrode layer and the lower electrode layer are placed in an oven at the temperature of 80 ℃ for 2 hours to be cured, and the flexible capacitive pressure sensor with the sandwich structure is obtained after the upper electrode layer and the lower electrode layer are taken down.
2. The method of claim 1, wherein the selected sensor material comprises polydimethylsiloxane as a base material and carbon nanotube powder as a conductive material.
3. The method of making a flexible capacitive pressure sensor according to claim 1, wherein said making a flexible substrate comprises the steps of:
s21, weighing liquid polydimethylsiloxane and a polydimethylsiloxane curing agent, mixing and stirring the liquid polydimethylsiloxane and the polydimethylsiloxane curing agent according to the mass ratio of 10:1, mixing the liquid polydimethylsiloxane and deionized water according to the mass ratio of 3:1, and stirring the two mixed solutions together;
s22, dripping the solution on the surface of a cleaned glass sheet, spin-coating for 20S, curing for half an hour in an oven at 60 ℃ to obtain a semi-cured flexible substrate polydimethylsiloxane film, and cutting the flexible substrate into a square shape of about 6cm x 6 cm;
and S23, adding dilute nitric acid into the carbon nano tube powder, stirring by a magnetic stirrer, performing ultrasonic dispersion treatment, adding deionized water for dilution, standing, and filtering to remove supernatant to obtain the carbon nano tube oxide.
4. The method for preparing a flexible capacitive pressure sensor according to claim 1, wherein the preparing of the upper and lower electrode layers comprises the following steps:
s41, preparing an upper electrode layer with a pyramid microstructure, manufacturing a silk screen printing plate according to an electrode array and a lead diagram, and printing a conductive material on a polydimethylsiloxane film of a semi-solidified microstructure by utilizing a silk screen printing process;
s42, preparing a lower electrode layer, printing the carbon oxide nanotubes on a smooth basement membrane, and drying to obtain the electrode layer, wherein the electrode array of the prepared lower electrode layer is 4-6 parallel strips with 0.5cm by 5cm and the spacing between the strips is 4-6 mm.
5. The method of making a flexible capacitive pressure sensor of claim 1, wherein the dielectric layer is a polydimethylsiloxane film.
6. The method for manufacturing a flexible capacitive pressure sensor according to claim 1, wherein the flexible capacitive pressure sensor with a sandwich structure is deformed when pressure is applied to the flexible capacitive pressure sensor, and the capacitance value of the flexible capacitive pressure sensor changes accordingly, wherein the capacitance expression is as follows:
wherein epsilon0＝8.854×10-12F/m represents the absolute dielectric constant in vacuum, εrIs the relative dielectric constant, S, of the dielectric layerζD is the initial thickness between the upper electrode layer and the lower electrode layer, and Delta D is the distance between the layers.
7. A flexible capacitive pressure sensor prepared by the preparation method of any one of claims 1 to 6, comprising an upper electrode layer, a dielectric layer and a lower electrode layer from top to bottom, wherein the upper electrode layer is a carbon oxide nanotube film with a pyramid microstructure, the dielectric layer is a polydimethylsiloxane film, and the lower electrode layer is a smooth conductive planar electrode.
8. The flexible capacitive pressure sensor of claim 7, wherein the pyramidal microstructure has a height of 0.2mm and the thickness of the carbon nanotube oxide film is 200-400 μm.
9. The flexible capacitive pressure sensor according to claim 7, wherein the electrode arrays disposed on the upper electrode layer and the lower electrode layer are parallel strips, and the electrode arrays disposed on the upper electrode layer and the lower electrode layer are disposed in a vertically crossing structure.
10. The flexible capacitive pressure sensor of claim 9, wherein each electrode in the array of electrodes is 0.5cm by 5cm in size and 0.5cm apart from each other.
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