A capacitive pressure sensor based on honeycomb graded porous carbon material and preparation method thereof

Abstract

A method for preparing a capacitive pressure sensor based on a honeycomb graded porous carbon material comprises: washing the waste biomass material of white broccoli, placing it in a vacuum freeze dryer, then taking it out, adding an alkaline solution, and placing it in an oven for drying; placing the dried material in a tube furnace for carbonization under an inert atmosphere; adding a hydrochloric acid solution to the carbonized black powder, placing it in an oven for drying, and obtaining a honeycomb graded porous carbon material; then mixing and curing the PDMS component, a curing agent, and an organic solvent of n-hexane with the honeycomb graded porous carbon material to obtain an electrode layer; cutting two polyimide films, adhering a copper electrode in the middle, placing the electrode layer between one of the polyimide films and the copper electrode, and sealing the capacitive pressure sensor by a plastic sealing machine. The present invention prepares a capacitive pressure sensor with high sensitivity and strong stability by improving the microstructure, specific surface area, conductivity, and deformation capacity of the electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitive pressure sensors, and in particular relates to a capacitive pressure sensor based on honeycomb graded porous carbon material and a preparation method thereof. Background Art

[0002] Flexible pressure sensors can output external pressure in the form of electrical signals and can be applied to real-time online monitoring fields such as wearable devices and smart products. Sensors can be divided into four categories according to the sensing mechanism: capacitive, piezoelectric, piezoresistive, and triboelectric. Among them, capacitive pressure sensors have the advantages of simple processing, low cost, and low power consumption, and have attracted much attention. However, the problems of capacitive pressure sensors being not sensitive enough and being greatly affected by environmental factors such as temperature have limited their development prospects. Among them, the electrode layer of the capacitive pressure sensor is the key factor affecting the capacitive pressure sensor.

[0003] At present, the materials commonly used for the electrode layer in capacitive pressure sensors are carbon materials, conductive polymers and metal compounds. Compared with conductive polymers and metal compounds, the preparation process of carbon materials is simpler, more environmentally friendly and cheaper, and has certain advantages. Among them, activated carbon is a type of carbon material, which is mainly derived from the high-temperature carbonization of cheap, easy-to-obtain, non-toxic, environmentally friendly, and carbon-rich biomass. However, existing carbon material capacitive pressure sensors still have the disadvantages of low sensitivity and weak stability. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a capacitive pressure sensor based on honeycomb graded porous carbon material and a preparation method thereof. The prepared capacitive pressure sensor has high sensitivity and strong stability.

[0005] The present invention is achieved in that:

[0006] A method for preparing a capacitive pressure sensor based on a honeycomb hierarchical porous carbon material comprises the following steps:

[0007] Step S1: Wash the waste biomass material of white broccoli, place it in a vacuum freeze dryer for 36 to 72 hours, then take it out, weigh 5 to 8 g of the waste biomass material and place it in a beaker, add 0.8 to 1.2 M alkaline solution, stir for 8 to 12 hours, filter, and place it in a 50 to 80 ° C oven to dry for 12 to 14 hours; place the dried material in a tube furnace, and carbonize it at a temperature of 600 to 850 ° C for 2 to 5 hours under an inert atmosphere; place the carbonized black powder in a beaker, add 0.8 to 1.2 M hydrochloric acid solution, stir for 1 to 3 hours, filter, and place it in a 50 to 80 ° C oven to dry for 12 to 14 hours to obtain a honeycomb graded porous carbon material;

[0008] Step S2: The PDMS component and the curing agent tetramethyltetravinylcyclotetrasiloxane are mixed uniformly in a mass ratio of 8 to 11:1, 3 to 5 mL of n-hexane organic solvent is added for dilution, the mixed solution is mixed with 8 to 10 mg of honeycomb graded porous carbon material, and vacuum degassing is performed at 80 to 120° C. for 4 to 8 hours to remove the organic solvent n-hexane, and the high-toughness elastomer is cured to form an electrode layer;

[0009] Step S3: Cut two polyimide films, adhere a copper electrode between the two polyimide films, place the electrode layer prepared in step S2 between one of the polyimide films and the copper electrode, and use a plastic sealing machine to seal the capacitive pressure sensor based on the honeycomb graded porous carbon material.

[0010] Furthermore, the heating rate under the inert atmosphere is 5-8°C / min, and the atmosphere flow rate is 90-120 mL / min.

[0011] A capacitive pressure sensor based on a honeycomb graded porous carbon material is prepared by using the above-mentioned method for preparing a capacitive pressure sensor based on a honeycomb graded porous carbon material.

[0012] The invention has the advantages that a capacitive pressure sensor with high sensitivity and strong stability is prepared by improving the microstructure, specific surface area, conductivity and deformation capacity of the electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0014] Figure 1 It is a schematic flow chart of the method of the present invention.

[0015] Figure 2 The figure is a comparison of the waste biomass material (a) and the honeycomb-shaped hierarchical porous carbon material (b) of the present invention by scanning electron microscope (SEM).

[0016] Figure 3 3 is a thermogravimetric (TGA) graph of the honeycomb hierarchical porous carbon material of the present invention.

[0017] Figure 4 1 and 2 are nitrogen adsorption-desorption curves (a) and pore size distribution diagrams (b) of the honeycomb hierarchical porous carbon material of the present invention.

[0018] Figure 5 It is a schematic structural diagram of a capacitive pressure sensor based on honeycomb graded porous carbon material of the present invention. DETAILED DESCRIPTION

[0019] like Figure 1As shown, a method for preparing a capacitive pressure sensor based on a honeycomb hierarchical porous carbon material comprises the following steps:

[0020] Step S1: Wash the waste biomass material of white broccoli, place it in a vacuum freeze dryer for 36 to 72 hours, then take it out, weigh 5 to 8 g of the waste biomass material and place it in a 250 mL beaker, add 0.8 to 1.2 M (mol / L) alkaline solution (NaOH, KOH, etc.), stir for 8 to 12 hours, filter, and place it in a 50 to 80 ° C oven to dry for 12 to 14 hours; place the dried waste biomass in a tubular furnace, and carbonize it at a temperature of 600 to 850 ° C for 2 to 5 hours under an inert atmosphere; place the carbonized black powder in a 100 mL beaker, add 0.8 to 1.2 M hydrochloric acid solution, stir for 1 to 3 hours, filter, and place it in a 50 to 80 ° C oven to dry for 12 to 14 hours to obtain a honeycomb graded porous carbon material;

[0021] Step S2: The PDMS component (tetrakis(trimethylsiloxy)silane) and the curing agent (tetramethyltetravinylcyclotetrasiloxane) are mixed uniformly in a mass ratio of 8 to 11:1, 3 to 5 mL of n-hexane organic solvent is added for dilution, the mixed solution is mixed with 8 to 10 mg of honeycomb hierarchical porous carbon material, and vacuum degassing is performed at 80 to 120° C. for 4 to 8 hours to remove the organic solvent n-hexane, and the high-toughness elastomer is cured to form an electrode layer;

[0022] Step S3: Cut two polyimide films, adhere a copper electrode between the two polyimide films, place the electrode layer prepared in step S2 between one of the polyimide films and the copper electrode, and use a plastic sealing machine to seal the capacitive pressure sensor based on the honeycomb graded porous carbon material.

[0023] The morphology and structural changes of waste biomass materials before and after alkali activation and high-temperature carbonization were observed by scanning electron microscopy (SEM). Figure 2 (a) It can be seen that the surface of the waste biomass material that has not been activated by alkali and carbonized at high temperature is relatively smooth and has fewer holes. Figure 2 (b) It can be seen that the surface of the activated carbon material after alkali activation and high-temperature carbonization is rough, the pores are evenly distributed, and a honeycomb hierarchical porous carbon structure is formed by numerous dense pores and channels. The formation of this structure is related to the intercalation chemical activation of metal ions and the lattice expansion effect.

[0024] The thermal stability of honeycomb hierarchical porous carbon materials was analyzed by thermogravimetric analysis (TGA). Figure 3It can be seen that at 30-278°C, the water in the honeycomb graded porous carbon material evaporates and the internal heated gas volatilizes, resulting in a mass loss of 8.63%; at 278-800°C, the carbon in the honeycomb graded porous carbon material burns, resulting in a mass loss of 32.57%; when the honeycomb graded porous carbon material is heated to 800°C, its total residual weight is 58.78%; the above analysis proves that the material has excellent stability.

[0025] The specific surface area and pore structure of honeycomb hierarchical porous carbon materials were analyzed by nitrogen adsorption-desorption curve and pore size distribution diagram. Figure 4 (a) It can be seen that the curve is a type IV isotherm and has an H3 type hysteresis loop, indicating that the honeycomb hierarchical porous carbon material has microporous and mesoporous structures, and its specific surface area can reach 878m 2 / g. From Figure 4 (b) It can be seen that the curve has a strong PSD peak at 1.7 and 4.1 nm, which also shows that the honeycomb hierarchical porous carbon material has microporous and mesoporous structures, and its pore volume can reach 0.66 cm 3 / g.

[0026] The schematic diagram of the capacitive pressure sensor based on honeycomb hierarchical porous carbon material is shown in Figure 5 As shown. The present invention combines the honeycomb hierarchical porous carbon material with a flexible polymer (polydimethylsiloxane) and solidifies to generate a high-toughness elastomer; in addition, the present invention adheres a copper electrode between two polyimide films, places the high-toughness elastomer between the films and the copper electrode, and uses a plastic sealing machine to perform plastic sealing to obtain a capacitive pressure sensor based on the honeycomb hierarchical porous carbon material.

[0027] The present invention uses the waste biomass material of white brocade as a precursor. The material has the effect of clearing away heat and detoxifying, and is widely used in the food, beverage and pharmaceutical industries. However, it will generate a large amount of waste during the production process, causing serious environmental problems. The present invention uses the waste biomass material of white brocade to prepare an activated carbon material with a honeycomb hierarchical porous carbon structure, a large specific surface area, excellent conductivity, and good stability. The honeycomb hierarchical porous carbon material is combined with a flexible polymer (polydimethylsiloxane), and a high-toughness elastomer suitable for a capacitive pressure sensor is prepared through a curing reaction. Subsequently, the high-toughness elastomer is connected to a copper electrode and plastic-sealed to prepare a capacitive pressure sensor with high sensitivity and strong stability.

[0028] Activated carbon is combined with PDMS to generate a high-toughness elastomer with a rich porous structure, good stability and superelasticity, and is expected to be used in various sensing function fields such as pressure sensing, gas sensing, and environmental monitoring sensing.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a capacitive pressure sensor based on a honeycomb hierarchical porous carbon material, characterized in that: The steps include: Step S1: Wash the waste biomass material of white broccoli, place it in a vacuum freeze dryer for 36 to 72 hours, then take it out, weigh 5 to 8 g of the waste biomass material and place it in a beaker, add 0.8 to 1.2 M alkaline solution, stir for 8 to 12 hours, filter, and place it in a 50 to 80 ° C oven to dry for 12 to 14 hours; place the dried material in a tube furnace, and carbonize it at a temperature of 600 to 850 ° C for 2 to 5 hours under an inert atmosphere; place the carbonized black powder in a beaker, add 0.8 to 1.2 M hydrochloric acid solution, stir for 1 to 3 hours, filter, and place it in a 50 to 80 ° C oven to dry for 12 to 14 hours to obtain a honeycomb graded porous carbon material; Step S2: The PDMS component and the curing agent tetramethyltetravinylcyclotetrasiloxane are mixed uniformly in a mass ratio of 8 to 11:1, 3 to 5 mL of n-hexane organic solvent is added for dilution, the mixed solution is mixed with 8 to 10 mg of honeycomb graded porous carbon material, and vacuum degassing is performed at 80 to 120° C. for 4 to 8 hours to remove the organic solvent n-hexane, and the high-toughness elastomer is cured to form an electrode layer; Step S3: Cut two polyimide films, adhere a copper electrode between the two polyimide films, place the electrode layer prepared in step S2 between one of the polyimide films and the copper electrode, and use a plastic sealing machine to seal the capacitive pressure sensor based on the honeycomb graded porous carbon material.

2. A method for preparing a capacitive pressure sensor based on a honeycomb hierarchical porous carbon material as claimed in claim 1, characterized in that: The heating rate under the inert atmosphere is 5-8°C / min, and the atmosphere flow rate is 90-120mL / min.

3. A capacitive pressure sensor based on honeycomb graded porous carbon material, characterized in that : It is manufactured by the method for preparing a capacitive pressure sensor based on honeycomb graded porous carbon material as described in claim 1 or 2.

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