阅读说明：本技术 一种基于石墨烯的柔性电容式压力传感器及其制备方法 (Flexible capacitive pressure sensor based on graphene and preparation method thereof ) 是由 张玉容 于 2020-12-26 设计创作，主要内容包括：本发明属于传感器技术领域,公开了一种基于石墨烯的柔性电容式压力传感器及其制备方法,本发明所述压力传感器包括上下两个平行设置的石墨烯电极层,两个石墨烯电极层之间设有多孔弹性体,所述多孔弹性体由热固化弹性材料和发泡材料混合后经过加热固化后形成,所述石墨烯电极层引出有银浆导线形成外围引线,所述外围引线绑定有柔性电路板。本发明解决了石墨烯与绝缘层之间的附着力问题,同时以多孔弹性体制备的绝缘层配合石墨烯电极材料,提高压力传感器的灵敏度和增加压力传感器高敏感性的压力范围。(The invention belongs to the technical field of sensors and discloses a flexible capacitive pressure sensor based on graphene and a preparation method thereof. The invention solves the problem of adhesive force between graphene and the insulating layer, and simultaneously improves the sensitivity of the pressure sensor and increases the pressure range of high sensitivity of the pressure sensor by matching the insulating layer prepared from the porous elastomer with the graphene electrode material.)

1. The utility model provides a flexible capacitive pressure sensor based on graphite alkene which characterized in that: including two upper and lower parallel arrangement's graphite alkene electrode layer, be equipped with porous elastomer between two graphite alkene electrode layers, graphite thick liquid wire formation peripheral lead wire has been drawn forth to graphite alkene electrode layer, peripheral lead wire is bound and is had flexible printed circuit board.

2. The flexible graphene-based capacitive pressure sensor of claim 1, wherein: the graphene electrode layer includes a flexible substrate and a graphene layer.

3. The flexible graphene-based capacitive pressure sensor of claim 2, wherein: the flexible substrate is made of a flexible high polymer material, and the high polymer material is one of polyimide, polyethylene terephthalate and polymethyl methacrylate.

4. The flexible graphene-based capacitive pressure sensor of claim 3, wherein: the porous elastomer is formed by mixing a thermosetting elastic material and a foaming material and then heating and curing the mixture.

5. The flexible graphene-based capacitive pressure sensor of claim 4, wherein: the thermosetting elastic material is polydimethylsiloxane.

6. The flexible graphene-based capacitive pressure sensor of claim 4, wherein: the foaming material is one of azodiisobutyronitrile, azodiisoheptonitrile, tosylhydrazide, oxidized bis (phenylsulfonyl-cool), sodium bicarbonate or ammonium bicarbonate.

7. The flexible graphene-based capacitive pressure sensor according to any one of claims 4 to 6, wherein: the mixing ratio of the thermosetting elastic material to the foaming material is 8:1-8: 3.

8. A method of manufacturing a flexible graphene-based capacitive pressure sensor according to claim 7, wherein: the method comprises the following steps:

s1: preparing a graphene layer on a metal substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a flexible substrate to form a graphene conductive film;

s3: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s4: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s5: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s6: coating PU-653 aqueous solution on the pattern areas of the upper and lower graphene electrode layers in a blade coating, spin coating or roller coating mode, and then placing in an oven for drying;

s7: weighing the thermosetting elastic material and the foaming material respectively and mixing the thermosetting elastic material and the foaming material uniformly;

s8: screen printing of the lower graphene electrode layer to thermoset a mixed solution of an elastic material and a foaming material;

s9: covering the upper graphene electrode layer on the lower graphene electrode layer printed with the thermosetting elastic material and the foaming material, and then integrally transferring the upper graphene electrode layer to an oven for heating.

S10: and binding the flexible printed circuit board in the binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing.

9. The method for manufacturing a flexible graphene-based capacitive pressure sensor according to claim 8, wherein in step S1, the metal is a copper foil or a nickel foil.

10. The preparation method of the flexible capacitive graphene-based pressure sensor according to claim 8, wherein the PU-653 water is a mixture of a PU-653 stock solution and water, and the mixing ratio of the PU-653 stock solution to the water is 1:100-1: 200.

Technical Field

The invention belongs to the technical field of sensors, and particularly relates to a flexible capacitive pressure sensor based on graphene and a preparation method thereof.

Background

Capacitive pressure sensor, mostly flat structure, constitute by two electrodes and middle insulating medium layer, exert pressure through the external world, extrude middle insulating medium, change the distance between two electrodes, and then change the capacitance value between two electrodes, this capacitance value is through measuring circuit, the device links to each other with the external world, utilize the capacitance sensing element to become the electric quantity output of certain relation with it by the conversion of measured pressure, it is fast to have reaction rate, the interference killing feature is strong, environmental suitability is good, the cost of manufacture is low, easily make characteristics such as transparent flexibility. Graphene, as a two-dimensional monoatomic layer thin film material, is the thinnest and hardest nano material known in the world, and is expected to be used for developing a new generation of flexible electronic elements with thinner and faster conduction speed due to its extremely low resistivity, extremely fast electron migration speed, and good optical property and flexibility.

In recent years, with the rapid development of society and higher requirements of people on products, the graphene-based capacitive flexible pressure sensor has received great attention, and especially has a wide market prospect in the fields of future flexible, transparent, wearable devices and the like. However, how to apply graphene to a flexible capacitive pressure sensor is a technology concerned by the prior art, and at present, many technical barriers still exist. Graphene is a problem of adhesion between upper and lower electrode layers and an insulating layer provided between the upper and lower electrode layers, and when a deflection or a large pressure extrusion occurs, peeling between the electrode layers and the insulating layer or a void is often generated, that is, the bonding state between the graphene layer and the insulating layer is poor, so that this technique cannot cope with a complicated pressure situation. The prior art also has the problem that in order to realize the lightness and thinness of the pressure sensor, the thickness of the insulating layer needs to be reduced, and the distance between the electrodes is inevitably influenced, so that the sensitivity of the pressure sensor and the pressure range with high sensitivity of the pressure sensor are lower.

Disclosure of Invention

The invention aims to overcome the defects of the background technology, and provides a flexible capacitive pressure sensor based on graphene and a preparation method thereof, so that the problem of adhesion between the graphene and an insulating layer is solved, and meanwhile, the insulating layer prepared from a porous elastomer is matched with a graphene electrode material, so that the sensitivity of the pressure sensor is improved, and the pressure range of high sensitivity of the pressure sensor is enlarged.

The purpose of the invention is realized as follows:

the invention provides a flexible capacitive pressure sensor based on graphene, which comprises an upper graphene electrode layer and a lower graphene electrode layer which are arranged in parallel, wherein a porous elastomer is arranged between the two graphene electrode layers, silver paste leads are led out of the graphene electrode layers to form a peripheral lead, and a flexible printed circuit board is bound to the peripheral lead.

Further, the graphene electrode layer comprises a flexible substrate and a single graphene layer, wherein the sheet resistance of the graphene electrode layer is 150-300 Ω/□, and the light transmittance is 85-92%. The single graphene layer is grown on a metal substrate by CVD and then transferred to a flexible substrate support by a conventional wet process, where the flexible substrate also serves as a pressure cover plate for the capacitive pressure sensor.

Further, the flexible base material is made of a flexible high polymer material, and the flexible high polymer material is one of polyimide, polyethylene terephthalate and polymethyl methacrylate.

Further, the porous elastomer is formed by mixing a thermosetting elastic material and a foaming material and then heating and curing the mixture.

Further, the thermosetting elastic material is polydimethylsiloxane.

Further, the foaming material is one of azobisisobutyronitrile, azobisisoheptonitrile, tosylhydrazide, bis (phenylsulfonyl-cool) oxide, sodium bicarbonate or ammonium bicarbonate.

Further, the mixing ratio of the thermosetting elastic material to the foaming material is between 8:1 and 8: 3.

The invention also provides a preparation method of the flexible capacitive pressure sensor based on graphene, which comprises the following main steps:

s1: preparing a graphene layer on a metal substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a flexible substrate to form a graphene conductive film;

s3: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s4: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s5: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s6: coating PU-653 aqueous solution on the pattern areas of the upper graphene electrode layer and the lower graphene electrode layer in a blade coating, spin coating or roller coating mode, and then placing the obtained product in an oven for drying;

s7: weighing the thermosetting elastic material and the foaming material respectively and mixing the thermosetting elastic material and the foaming material uniformly;

s8: screen printing of the lower graphene electrode layer to thermoset a mixed solution of an elastic material and a foaming material;

s9: covering the upper graphene electrode layer on the lower graphene electrode layer printed with the thermosetting elastic material and the foaming material, then integrally transferring the upper graphene electrode layer to an oven for heating, wherein the foaming material generates gas in the heating process and simultaneously solidifies along with the thermosetting material to form a porous structure.

S10: and binding the flexible circuit board in the binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing.

Preferably, the metal in S1) is a copper foil or a nickel foil.

Preferably, the PU-653 aqueous solution is a mixed solution of PU-653 raw solution and water, wherein the PU-653 raw solution is produced by Dutch Sttar, and the mixing ratio of the PU-653 raw solution to the water is 1:100-1: 200.

The invention has the beneficial effects that:

1. the graphene film disclosed by the invention is flexible and has extremely strong bending resistance, can bear large pressure by being matched with the porous elastomer, and cannot be brittle and broken.

2. According to the invention, the surface treatment is carried out on the lap joint area and the edge area through the ultraviolet laser, so that the silver paste line can be well attached to the flexible graphene electrode layer and can be well bound with the flexible circuit board, and meanwhile, the graphene conducting layer and the porous elastomer are packaged between the upper substrate and the lower substrate, and the reliability of the sensor is ensured.

3. Further surface treatment is carried out on the graphene electrode layer through a PU-653 aqueous solution, the graphene electrode layer and the porous elastic body have strong binding force, the porous elastic film is bonded between the two flexible graphene electrode layers through thermosetting treatment, and compared with the prior art, the bonding material between the porous elastic body and the two flexible electrode layers is reduced, and the cost of the sensor is lower.

4. The existence of the plurality of holes in the porous elastic film enables the film to have larger thickness deformation under the action of pressure, the capacitance value variation of the capacitor is increased, the sensitivity of the sensor to the pressure is increased, and meanwhile, the porous elastic film can be compacted only by applying large pressure, so that the pressure range of the high sensitivity of the pressure sensor is increased.

Drawings

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings, in which:

fig. 1 is a front view of a flexible graphene-based capacitive pressure sensor according to an embodiment of the present invention;

fig. 2 is a top view of a flexible graphene-based capacitive pressure sensor according to an embodiment of the present invention;

FIG. 3 is a graph illustrating the response of a flexible graphene-based capacitive pressure sensor to pressure according to example 1, wherein Δ C/C₀Is the rate of change of capacitance, the amount of change in capacitance after Δ C is applied, C₀Is a parametric capacitance value.

The labels in the figure are: flexible substrate 1, graphite alkene layer 2, porous elastomer 3, flexible circuit board 4.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

As shown in fig. 1-2, the flexible capacitive pressure sensor based on graphene provided by the invention comprises an upper graphene electrode layer and a lower graphene electrode layer which are arranged in parallel, a porous elastomer is arranged between the two graphene electrode layers, a silver paste lead is led out from the graphene electrode layers to form a peripheral lead, a flexible circuit board is bound to the peripheral lead, the capacitive pressure sensor is used for collecting pressure and transmitting collected information to a control circuit flexible circuit board, and the control circuit flexible circuit board converts and calculates information obtained by the sensor and transmits the result to an intelligent main control device.

The graphene electrode layer comprises a substrate and a single-layer graphene layer, wherein the sheet resistance of the graphene layer is 150-300 omega/□, and the light transmittance is 85-92%. The graphene layer is transferred by conventional wet methods onto a flexible substrate support, which here also serves as a pressure cover plate for the capacitive pressure sensor.

The flexible substrate is made of a flexible high polymer material, and the flexible high polymer material is one of polyimide, polyethylene terephthalate and polymethyl methacrylate.

The porous elastomer is formed by mixing a thermosetting elastic material and a foaming material and then heating and curing the mixture.

The thermally cured elastomeric material is Polydimethylsiloxane (PDMS).

The foaming material is one of azodiisobutyronitrile, azodiisoheptonitrile, tosylhydrazide, oxidized bis (phenylsulfonyl-cool), sodium bicarbonate or ammonium bicarbonate.

The mixing ratio of the thermosetting elastic material to the foaming material is between 8:1 and 8: 3.

The invention relates to a preparation method of a flexible capacitive pressure sensor based on graphene, which comprises the following steps:

s1: preparing a graphene layer on a copper foil or nickel foil substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a flexible substrate to form a graphene conductive film;

s2: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s3: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s4: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s5: coating PU-653 aqueous solution with the mixing ratio of PU-653 raw solution to water being 1:100-1:200 on the pattern areas of the upper and lower graphene electrode layers in a blade coating, spin coating or roller coating mode, and then placing the solution in an oven for drying;

s6: weighing the thermosetting elastic material and the foaming material respectively and mixing the thermosetting elastic material and the foaming material uniformly;

s7: screen printing of the lower graphene electrode layer to thermoset a mixed solution of an elastic material and a foaming material;

s8: covering the upper graphene electrode layer on the lower graphene electrode layer printed with the thermosetting elastic material and the foaming material, and then integrally transferring the upper graphene electrode layer to an oven for heating, wherein the foaming material generates gas and simultaneously solidifies along with the thermosetting material in the heating process to form a porous structure;

s9: and binding the flexible circuit board in binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing to form the flexible capacitive pressure sensor.

The following describes a method for manufacturing a flexible capacitive pressure sensor based on graphene by using specific embodiments.

Example 1

In the embodiment, a copper foil is used as a metal substrate for graphene growth, polyethylene terephthalate is used as a flexible base material of a graphene electrode layer, a thermosetting elastic material is dimethyl siloxane, and a foaming material is azobisisobutyronitrile.

The preparation of the flexible capacitive pressure sensor based on graphene is completed through the following specific steps:

s1: preparing a graphene layer on a copper foil substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a polyethylene terephthalate flexible substrate to form a graphene conductive film;

s3: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s4: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s5: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s6: coating a PU-653 aqueous solution with the mixing ratio of PU-653 stock solution to water being 1:100 on the pattern areas of the upper graphene electrode layer and the lower graphene electrode layer in a roller coating mode, and then placing the solution in an oven for drying;

s7: respectively weighing dimethyl siloxane and azodiisobutyronitrile in a ratio of 8:1, and uniformly mixing the dimethyl siloxane and the azodiisobutyronitrile to form a mixed solution;

s7: screen printing a mixed solution of dimethyl siloxane and azodiisobutyronitrile on the lower graphene electrode layer;

s8: covering the upper graphene electrode layer on the mixed melt of dimethyl siloxane and azodiisobutyronitrile, then transferring to an oven for heating, and curing the foaming material along with the thermocuring material while generating gas in the heating process to form a porous structure.

S9: and binding the flexible circuit board in the binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing.

In this embodiment, as shown in fig. 3, a pressure test is performed on a flexible capacitive pressure sensor based on graphene, and the pressure sensitivity coefficient of the prepared flexible capacitive pressure sensor based on graphene is about-1.1 kPa-1, and the pressure test range can reach 85 kPa.

Example 2

In the embodiment, a copper foil is used as a metal substrate for graphene growth, polyethylene terephthalate is used as a flexible base material of a graphene electrode layer, a thermosetting elastic material is dimethyl siloxane, and a foaming material is azobisisobutyronitrile.

The preparation of the flexible capacitive pressure sensor based on graphene is completed through the following specific steps:

s1: preparing a graphene layer on a copper foil substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a polyethylene terephthalate flexible substrate to form a graphene conductive film;

s3: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s4: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s5: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s6: coating a PU-653 aqueous solution with the mixing ratio of PU-653 stock solution to water being 1:150 on the pattern areas of the upper graphene electrode layer and the lower graphene electrode layer in a roller coating mode, and then placing the solution in an oven for drying;

s7: respectively weighing dimethyl siloxane and azodiisobutyronitrile in a ratio of 8:1, and uniformly mixing the dimethyl siloxane and the azodiisobutyronitrile to form a mixed solution;

s7: screen printing a mixed solution of dimethyl siloxane and azodiisobutyronitrile on the lower graphene electrode layer;

s8: covering the upper graphene electrode layer on the mixed melt of dimethyl siloxane and azodiisobutyronitrile, then transferring to an oven for heating, and curing the foaming material along with the thermocuring material while generating gas in the heating process to form a porous structure.

S9: and binding the flexible circuit board in the binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing.

Example 3

In the embodiment, a copper foil is used as a metal substrate for graphene growth, polyethylene terephthalate is used as a flexible base material of a graphene electrode layer, a thermosetting elastic material is dimethyl siloxane, and a foaming material is azobisisoheptonitrile.

The preparation of the flexible capacitive pressure sensor based on graphene is completed through the following specific steps:

s1: preparing a graphene layer on a copper foil substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a polyethylene terephthalate flexible substrate to form a graphene conductive film;

s3: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s4: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s5: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s6: coating a PU-653 aqueous solution with the mixing ratio of PU-653 stock solution to water being 1:100 on the pattern areas of the upper graphene electrode layer and the lower graphene electrode layer in a roller coating mode, and then placing the solution in an oven for drying;

s7: respectively weighing dimethyl siloxane and azodiisoheptanonitrile in a ratio of 8:2, and uniformly mixing the dimethyl siloxane and the azodiisoheptanonitrile to form a mixed solution;

s7: screen printing a mixed solution of dimethyl siloxane and azodiisoheptonitrile on the lower graphene electrode layer;

s8: covering the upper graphene electrode layer on the mixed melt of dimethyl siloxane and azodiisoheptanonitrile, then transferring to an oven for heating, wherein the foaming material generates gas in the heating process and simultaneously solidifies along with the thermocuring material to form a porous structure.

S9: and binding the flexible circuit board in the binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing.

Example 4

In the embodiment, a copper foil is used as a metal substrate for graphene growth, polymethyl methacrylate is used as a flexible base material of a graphene electrode layer, a thermosetting elastic material is dimethyl siloxane, and a foaming material is azodiisoheptonitrile.

The preparation of the flexible capacitive pressure sensor based on graphene is completed through the following specific steps:

s1: preparing a graphene layer on a copper foil substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a polymethyl methacrylate flexible substrate to form a graphene conductive film;

s3: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s4: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s5: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s6: coating a PU-653 aqueous solution with the mixing ratio of PU-653 stock solution to water being 1:100 on the pattern areas of the upper graphene electrode layer and the lower graphene electrode layer in a roller coating mode, and then placing the solution in an oven for drying;

s7: respectively weighing dimethyl siloxane and azodiisoheptanonitrile in a ratio of 8:2, and uniformly mixing the dimethyl siloxane and the azodiisoheptanonitrile to form a mixed solution;

s7: screen printing a mixed solution of dimethyl siloxane and azodiisoheptonitrile on the lower graphene electrode layer;

s8: covering the upper graphene electrode layer on the mixed melt of dimethyl siloxane and azodiisoheptanonitrile, then transferring to an oven for heating, wherein the foaming material generates gas in the heating process and simultaneously solidifies along with the thermocuring material to form a porous structure.

S9: and binding the flexible circuit board in the binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing.

Example 5

In the embodiment, a copper foil is used as a metal substrate for graphene growth, polymethyl methacrylate is used as a flexible base material of a graphene electrode layer, a thermosetting elastic material is dimethyl siloxane, and a foaming material is sodium bicarbonate.

The preparation of the flexible capacitive pressure sensor based on graphene is completed through the following specific steps:

s1: preparing a graphene layer on a copper foil substrate by adopting tubular CVD equipment;

s2: transferring the graphene layer to a polymethyl methacrylate flexible substrate to form a graphene conductive film;

s3: etching up and down corresponding patterns on the graphene conductive film through an infrared laser etching machine so as to form an upper graphene electrode layer and a lower graphene electrode layer;

s4: carrying out surface treatment on a binding region and an edge region of the graphene electrode layer through ultraviolet laser;

s5: conducting silver paste is screen-printed in the overlapping areas of the upper graphene electrode layer and the lower graphene electrode layer and is solidified, one end of the conducting silver paste is overlapped on the graphene of the graphene electrode layer, and the other end of the conducting silver paste extends to the binding area of the graphene electrode layer;

s6: coating a PU-653 aqueous solution with the mixing ratio of PU-653 stock solution to water being 1:200 on the pattern areas of the upper graphene electrode layer and the lower graphene electrode layer in a roller coating mode, and then placing the solution in an oven for drying;

s7: respectively weighing dimethyl siloxane and sodium bicarbonate with the ratio of 8:2, and uniformly mixing the dimethyl siloxane and the sodium bicarbonate to form a mixed solution;

s7: screen printing a mixed solution of dimethyl siloxane and sodium bicarbonate on the lower graphene electrode layer;

s8: covering the upper graphene electrode layer on the mixed solution of dimethyl siloxane and sodium bicarbonate, then transferring to an oven for heating, wherein in the heating process, the foaming material generates gas and simultaneously solidifies along with the thermocuring material to form a porous structure.

S9: and binding the flexible circuit board in the binding regions of the upper graphite electrode layer and the lower graphite electrode layer through hot pressing.

The flexible capacitive pressure sensor based on graphene and the preparation method thereof provided by the invention are described in detail above. The specific embodiments are only intended to help the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.