Preparation Method and Application of Flexible Pressure Film Based on Carbon Nanotube Composite Material

Abstract

The present invention belongs to the technical field of flexible pressure sensors, and discloses a preparation method and application of a flexible pressure film based on a carbon nanotube composite material. Using an iron alloy as a catalyst and acetylene as a carbon source, a carbon nanotube array is prepared by chemical vapor deposition; the carbon nanotube array is mixed and dispersed with commercially available carboxylated carbon nanotubes and PDMS, and a flexible pressure sensing film is obtained after scraping and curing; silver electrodes are printed on a PET film by screen printing, and an upper and lower electrode type packaging is adopted to prepare a flexible pressure sensor. The flexible pressure film with a carbon nanotube array / carboxylated carbon nanotube composite structure provided by the present invention can effectively improve the sensitivity and detection range of the flexible pressure sensor. The preparation process of the present invention is simple, and has good pressure sensing performance. The maximum pressure sensitivity can reach -2.586 kPa-1, and the detection range is 0 to 450 kPa, which has potential application value in technical fields such as electronic skin and intelligent medicine.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible pressure sensors, and particularly relates to a preparation method and application of a flexible pressure film based on a carbon nanotube composite material. Background Art

[0002] At present, with the continuous progress of science and technology and the rapid development of high-performance intelligent materials, flexible electronic products have a broader development prospect. Flexible wearable devices are an important branch of flexible electronic products. Flexible wearable electronic devices can achieve human-computer interaction and provide the possibility for the interaction between machines and the environment. Flexible pressure sensors in flexible wearable electronic devices have many advantages, including flexibility, light weight, easy preparation, etc. With the development of the field of human-computer interaction, the research and development of flexible pressure sensors have had a great impact on people's lives. Carbon-based materials are widely used in the manufacture of flexible force sensors due to their excellent electrical conductivity, general nanostructure, and good biocompatibility. Among many carbon-based materials, carbon nanotubes, as a material with low cost, good electrical conductivity, and mechanical properties, are widely used as sensitive materials for flexible pressure sensors. However, in order to achieve a greater resistance change in the carbon nanotube conductive network under pressure conditions, it is necessary to design the structure of the carbon nanotube conductive network. Materials such as carbon black, graphene nanosheets, and silver nanowires are used as materials for preparing flexible devices by compounding with carbon nanotubes due to their excellent electrical conductivity and stable composition. However, achieving highly sensitive pressure detection has always been a difficult problem faced by carbon-based flexible pressure sensors. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation of a flexible pressure sensor based on a composite structure of a carbon nanotube array and carboxylated carbon nanotubes in view of the defects existing in the background art. The present invention utilizes the high activity and wettability of carboxylated carbon nanotubes to disperse them well in a flexible substrate to form a basic conductive network, and prepares a carbon nanotube array by chemical vapor deposition. Based on the carboxylated carbon nanotube conductive network, due to the hollow structure and high orientation of the carbon nanotube array, when stress is applied, it is more likely to deform and change the conductive network structure with carboxylated carbon nanotubes, thereby reducing the resistance of the flexible pressure sensor and obtaining a higher pressure sensitivity and a wider pressure monitoring range.

[0004] The present invention is implemented as follows: using ferroalloy as a catalyst and acetylene as a carbon source, carbon nanotube arrays are prepared by chemical vapor deposition; then the carbon nanotube arrays are mixed and dispersed with commercial carboxylated carbon nanotubes and PDMS (polydimethylsiloxane), and a flexible pressure sensing film is obtained after scraping and curing; silver electrodes are printed on a PET film (polyethylene terephthalate) by screen printing, and an upper and lower electrode type packaging is adopted to prepare a flexible pressure sensor.

[0005] Furthermore, the preparation method of the flexible pressure film includes the following steps:

[0006] Step 1: Weigh 1 - 20 g of commercial ferroalloy powder as a catalyst, place it in the tube furnace cavity of the chemical vapor deposition equipment, and introduce 100 - 200 ml / min of inert gas to evacuate the air in the furnace cavity.

[0007] Step 2: Introduce 50 - 300 ml / min of carbon source gas for reaction, and clean the iron aluminum alloy with an acidic solution to obtain carbon nanotube arrays.

[0008] Step 3: Mix carboxylated carbon nanotubes in a dispersant solution in a certain proportion, shear and stir for 20 - 60 min, and perform cell crushing and dispersion for 20 - 60 min to obtain a well-dispersed carboxylated carbon nanotube solution.

[0009] Step 4: Mix the solution obtained in Step 3 with the carbon nanotube arrays obtained in Step 2, add polydimethylsiloxane, and stir magnetically to obtain a conductive paste of carbon nanotube arrays / carboxylated carbon nanotubes.

[0010] Step 5: Place the conductive paste obtained in Step 4 in a vacuum environment and let it stand to obtain a paste.

[0011] Step 6: Print conductive silver paste on the PET film by screen printing, and then place it in an oven for curing to obtain a silver electrode path.

[0012] Step 7: Paste transparent glue on the surface of the silver electrode, leaving a space of 1 cm * 1 cm. Coat the paste obtained in Step 5 on the PET film in Step 6, and then place it in an electrothermal blast drying oven for curing at 100 - 120 °C. Then peel off the transparent glue, and at the same time peel off the excess flexible film, leaving only a 1 cm * 1 cm flexible film, and finally obtain a three-layer structure of PET film - silver electrode - flexible film.

[0013] Step 8: Cut and fit the two groups of three-layer structures obtained in Step 7 to obtain a six-layer structure of PET film - silver electrode - flexible film - flexible film - silver electrode - PET film.

[0014] Further, the inert gas in Step 1 is one or more of nitrogen, argon, and hydrogen.

[0015] Further, the carbon source gas in Step 2 is acetylene and methane, the acidic solution is hydrochloric acid and nitric acid, and the reaction time for introducing the carbon source gas is 40 - 120 min.

[0016] Further, the dispersant in Step 3 is one of chloroform, dichloromethane, and cyclohexane.

[0017] Further, the mass proportion of the carboxylated carbon nanotubes in polydimethylsiloxane in Step 4 is 4%, and the mass ratio of the carbon nanotube array to the carboxylated carbon nanotubes is adjusted to 4:1, 2:1, 1:1; magnetic stirring for more than 12 h gives the conductive paste of the carbon nanotube array / carboxylated carbon nanotubes.

[0018] Another object of the present invention is to provide a flexible pressure sensor prepared by using the preparation method of the flexible pressure film described above.

[0019] Another object of the present invention is to provide an application of the flexible pressure sensor in the fields of electronic skin, wearable electronic devices, and intelligent medical technology.

[0020] Combined with the above technical solutions and the solved technical problems, the advantages and positive effects of the technical solution to be protected by the present invention are as follows:

[0021] First, aiming at the technical problems existing in the above prior art and the difficulty of solving this problem, closely combining the technical solution to be protected by the present invention and the results and data in the R & D process, etc., analyze in detail and deeply how the technical solution of the present invention solves the technical problems and the creative technical effects brought after solving the problems. The specific description is as follows:

[0022] The present invention uses ferroalloy as a catalyst and acetylene as a carbon source to prepare a carbon nanotube array by chemical vapor deposition; then the carbon nanotube array is mixed and dispersed with commercially available carboxylated carbon nanotubes and PDMS, and after scraping and curing, a flexible pressure sensing film is obtained. The silver electrode is printed on the PET film by screen printing, and the upper and lower electrode type packaging is adopted to obtain a flexible pressure sensor. The preparation process of the present invention is simple and has good pressure sensing performance. The maximum pressure sensitivity can reach -2.586 kPa -1 , the detection range is 0 - 450 kPa, and it has potential application value in the fields of electronic skin, intelligent medical treatment, etc.

[0023] Second, regarding the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are specifically described as follows:

[0024] The present invention provides a flexible pressure film with a carbon nanotube array / carboxylated carbon nanotube composite structure, a preparation method and an application thereof, which can effectively improve the sensitivity and detection range of a flexible pressure sensor. The flexible pressure film with the carbon nanotube array / carboxylated carbon nanotube composite structure of the present invention can be rapidly prepared with a wide pressure detection range and high pressure response sensitivity, and is applied to the field of wearable electronic devices.

[0025] Thirdly, as the creative auxiliary evidence of the claims of the present invention, it is also reflected in the following several important aspects:

[0026] The expected benefits and commercial value after the transformation of the technical solution of the present invention are as follows: The present invention has a low cost, good pressure sensitivity, a wide pressure detection range, and a complete packaging structure, and can be directly applied to the commercial field. According to the number of conductive paths required by the actual application, an FPC cable with the corresponding number of channels is used to complete the transmission of electrical signals such as voltage and resistance between the flexible pressure sensor of the present invention and the data acquisition system, and a structural design of flexible pressure sensor → data acquisition system → host computer is formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments of the present invention. Obviously, the following described drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0028] Figure 1 is a flowchart of the preparation method of the flexible pressure film provided in Embodiments 1 to 3 of the present invention;

[0029] Figure 2A is the SEM of the carbon nanotube array provided in Embodiments 1 to 3 of the present invention and Comparative Example 1 Figure 1 ;

[0030] Figure 2B is the SEM diagram 2 of the carbon nanotube array provided in Embodiments 1 to 3 of the present invention and Comparative Example 1;

[0031] Figure 3 is the pressure sensitivity test diagram of the flexible pressure film with a pure carboxylated carbon nanotube composite structure provided in Comparative Example 2 of the present invention;

[0032] Figure 4 is the pressure sensitivity test diagram of the flexible pressure film with different filler ratios of the carbon nanotube array / carboxylated carbon nanotube composite structure provided in Embodiments 1 to 3 of the present invention;

[0033] Figure 5It is the repeated pressure response test chart of the flexible pressure film of the carbon nanotube array / carboxylated carbon nanotube composite structure provided in Embodiment 2 of the present invention. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with Embodiment 1. It should be understood that the specific Embodiment 1 described herein is only used to explain the present invention and is not used to limit the present invention.

[0035] Aiming at the problems existing in the prior art, the present invention provides a preparation method and application of a flexible pressure film based on a carbon nanotube composite material, and the present invention will be described in detail below in conjunction with the accompanying drawings.

[0036] In order to enable those skilled in the art to fully understand how the present invention is specifically implemented, this part is an explanatory embodiment that expands and explains the technical solutions of the claims.

[0037] As Figure 1 shown, the preparation method of the flexible pressure film provided in the embodiment of the present invention includes the following steps:

[0038] S101, using an iron alloy as a catalyst and acetylene as a carbon source, preparing a carbon nanotube array by chemical vapor deposition;

[0039] S102, mixing and dispersing the carbon nanotube array with commercially available carboxylated carbon nanotubes and PDMS, and obtaining a flexible pressure sensing film after scraping and curing;

[0040] S103, printing silver electrodes on a PET film by screen printing, and adopting an upper and lower electrode type packaging to prepare a flexible pressure sensor.

[0041] As a preferred Embodiment 2, the preparation method of the flexible pressure film provided in Embodiment 2 of the present invention specifically includes the following steps:

[0042] Step 1, weighing a certain amount of iron-aluminum alloy powder and placing it in the tube furnace cavity of the chemical vapor deposition equipment, and then introducing an inert gas to evacuate the air in the furnace cavity;

[0043] Step 2, introducing a carbon source gas, reacting for 40-60 minutes, and then cleaning the iron-aluminum alloy with a hydrochloric acid solution to obtain a carbon nanotube array;

[0044] Step 3, mixing carboxylated carbon nanotubes in a dispersant solution in a certain proportion, shearing and stirring for 30 minutes, and performing cell crushing and dispersion to obtain a well-dispersed carboxylated carbon nanotube solution;

[0045] Step 4: Then mix the solution obtained in Step 3 with the carbon nanotube array obtained in Step 2, add polydimethylsiloxane, and magnetically stir for more than 12 hours to obtain a conductive paste of carbon nanotube array / carboxylated carbon nanotube;

[0046] Step 5: Place the paste obtained in Step 4 in a vacuum environment and let it stand for 30 min to remove air bubbles;

[0047] Step 6: Print the conductive silver paste on the PET film by screen printing, and then cure it in an oven at a temperature of 120 °C to obtain a silver electrode path, and the contact area between the electrode and the film is 1 cm * 1 cm;

[0048] Step 7: Spread the paste obtained in Step 5 on the PET film in Step 6, and then cure it in a thermostatic air blast drying oven to obtain a three-layer structure of PET film - silver electrode - flexible film;

[0049] Step 8: Cut and fit the three-layer structure obtained in Step 7 to obtain a six-layer structure of upper and lower electrode type: PET film - silver electrode - flexible film - flexible film - silver electrode - PET film.

[0050] The catalyst in Step 1 provided in Example 2 of the present invention can be iron oxide, magnesium oxide, etc.

[0051] The carbon source gas in Step 2 provided in Example 2 of the present invention is acetylene, methane, etc.

[0052] The acidic solution in Step 2 provided in Example 2 of the present invention is hydrochloric acid, nitric acid, etc.

[0053] The dispersant in Step 3 provided in Example 2 of the present invention can be chloroform, dichloromethane, etc.

[0054] In Step 4 provided in Example 2 of the present invention, the mass ratio of the carboxylated carbon nanotube in polydimethylsiloxane is 4%, and the mass ratio of the carbon nanotube array to the carboxylated carbon nanotube is adjusted to 4:1, 2:1, 1:1.

[0055] To prove the creativity and technical value of the technical solution of the present invention, this part is an application example 2 of the technical solution of the claim on a specific product or related technology.

[0056] Step 1: Weigh 1 - 20 g of commercial ferroalloy powder as a catalyst, place it in the tube furnace cavity of the chemical vapor deposition equipment, and introduce 100 - 200 ml / min of inert gas to evacuate the air in the furnace cavity;

[0057] Step 2: introducing a carbon source gas at a flow rate of 50 to 300 ml / min for a reaction of 90 minutes, and washing the iron alloy powder with a diluted hydrochloric acid solution (the volume ratio of commercial concentrated hydrochloric acid to water is 1:3) to obtain a carbon nanotube array;

[0058] Step 3, mixing 0.08 g of carboxylated carbon nanotubes into a dispersant solution, shearing and stirring for 20 to 60 minutes, and performing cell crushing and dispersion for 20 to 60 minutes to obtain a well-dispersed carboxylated carbon nanotube solution;

[0059] Step 4: Mix the solution obtained in step 3 with the carbon nanotube array obtained in step 2 at a mass ratio of 2:1, then add polydimethylsiloxane, and magnetically stir for more than 12 hours at a speed of 700 r / min. Then, add a polydimethylsiloxane curing agent at a volume ratio of 10:1, and then magnetically stir again at 700 r / min for more than 30 minutes to obtain a conductive slurry of carbon nanotube array / carboxylated carbon nanotubes;

[0060] Step 5, placing the conductive paste obtained in step 4 in a vacuum environment and allowing it to stand to obtain a paste;

[0061] Step 6: Print the conductive silver paste on the PET film by screen printing, and then place it in an electric hot air drying oven for curing. The curing temperature is set to 120 degrees and the curing time is 2 hours to obtain a silver electrode path cured on the PET film;

[0062] Step 7: Apply transparent tape to the surface of the silver electrode from step 6, leaving a 1cm*1cm space. Apply the slurry from step 5 to the surface of the silver electrode by scraping. Curing the slurry in an electric hot air drying oven at 60°C for 4 hours is then performed. The transparent tape and the excess flexible film are then peeled off, leaving only a 1cm*1cm area of flexible film. This results in a three-layer structure of PET film, silver electrode, and flexible film.

[0063] Step 8: Cut and bond the two groups of three-layer structures obtained in step 7 to obtain a six-layer structure of PET film-silver electrode-flexible film-flexible film-silver electrode-PET film.

[0064] The embodiments of the present invention have achieved some positive results during the development or use process, and indeed have great advantages over the existing technology. The following content describes them in conjunction with data, charts, etc. from the experimental process.

[0065] Example 1

[0066] The method for preparing a flexible pressure film of a carbon nanotube array / carboxylated carbon nanotube composite structure provided by an embodiment of the present invention comprises the following steps:

[0067] Step 1: Weigh a certain amount of ferroalloy powder and place it in the tube furnace cavity of the chemical vapor deposition equipment. Then, introduce an inert gas to evacuate the air in the furnace cavity.

[0068] Step 2: Introduce acetylene gas and react for 40 - 60 minutes. Then, clean it with 30% hydrochloric acid solution to remove the catalyst and obtain a carbon nanotube array.

[0069] Step 3: Mix 0.08 g of commercial multi-walled carbon nanotubes obtained in Step 2 with 8 g of cyclohexane solution. Stir shear for 30 minutes and cell crush for 20 minutes to obtain a well-dispersed carboxylated carbon nanotube cyclohexane solution.

[0070] Step 4: Mix polydimethylsiloxane with the carbon nanotube array in Step 2 and the carboxylated carbon nanotube cyclohexane solution obtained in Step 3. Control the mass ratio of the carbon nanotube array to the carboxylated carbon nanotubes to be 1:1 and magnetically stir at room temperature for more than 4 hours to fully mix the fillers.

[0071] Step 5: Place the solution obtained in Step 4 in a vacuum environment and let it stand for 1 hour to remove air bubbles.

[0072] Step 6: Print conductive silver paste on the PET film by screen printing, and then cure it in an oven at a temperature set to 120 degrees to obtain a silver electrode path. The contact area between the electrode and the film is 1 cm * 1 cm.

[0073] Step 7: Knife-coat the slurry obtained in Step 5 on the PET film in Step 6, and then cure it in an electrothermal blast drying oven to obtain a three-layer structure of PET film - silver electrode - flexible film.

[0074] Step 8: Cut and laminate the three-layer structure obtained in Step 7 to obtain a six-layer structure of upper and lower electrode type: PET film - silver electrode - flexible film - flexible film - silver electrode - PET film.

[0075] Example 2

[0076] Compared with Example 1, the difference in this example of the present invention is that in Step 4, 0.08 g of carboxylated carbon nanotubes and 0.04 g of carbon nanotubes are dispersed in 7 g of cyclohexane solution, that is, the mass ratio of the carbon nanotube array to the carboxylated carbon nanotubes is controlled to be 1:2; the remaining steps are the same as those in Example 1.

[0077] Example 3

[0078] Compared with Example 1, the difference in this example of the present invention is that in Step 4, 0.08 g of carboxylated carbon nanotubes and 0.02 g of carbon nanotubes are dispersed in 6 g of cyclohexane solution, that is, the mass ratio of the carbon nanotube array to the carboxylated carbon nanotubes is controlled to be 1:4; the remaining steps are the same as those in Example 1.

[0079] Comparative Example 1

[0080] Compared with Example 1 of the present invention, the difference lies in that in Step 4, 0.08 g of carbon nanotube arrays are dispersed in 6 g of cyclohexane solution, that is, the sensitive material is only carbon nanotube arrays; the remaining steps are the same as those in Example 1.

[0081] Comparative Example 2

[0082] Compared with Example 1 of the present invention, the difference lies in that in Step 4, 0.08 g of carboxylated carbon nanotubes are dispersed in 6 g of cyclohexane solution, that is, the sensitive material is only carboxylated carbon nanotubes; the remaining steps are the same as those in Example 1.

[0083] Test Example

[0084] The detection process is as follows: Use the L series color screen linear programmable power supply of Dongguan Bufan Electronic Technology Co., Ltd. as the input power supply, and obtain voltage and resistance data through the data acquisition card USB-3111 of Beijing Simai Kehua Technology Co., Ltd. Use the pressure testing machine of the Thin Film Manufacturing Department of Zhejiang Tsinghua Flexible Electronics Research Institute to set and obtain force data. First, place the film to be tested on the testing machine in an initial state without pressure, and then use the upper computer on the computer to test and set the pressing speed and pressing direction, where the pressure speed is always kept at 1 mm / min. After the test is completed, obtain the test data through the test software, and then present the data in the form of pictures by the Origin mapping software. The specific results are shown in Figure 3 、 Figure 4 。

[0085] Use the ZQ-990 testing machine of Dongguan Zhiqu Precision Instrument Co., Ltd. to set and obtain force data, and obtain resistance data through the KEITHLEY 2450 series digital source meters. First, place the film to be tested on the testing machine in an initial state without pressure, and then use the testing software on the computer to set parameters such as the pressing speed, pressing direction, and number of cycles, where the pressure speed is always kept at 10 mm / min. After the test is completed, obtain the test data through the test software, and then present the data in the form of pictures by the Origin mapping software. The specific results are shown in Figure 5 。

[0086] Figure 2A 、 Figure 2B is the SEM morphology characterization of the carbon nanotube arrays of Example 1 of the present invention, indicating that the array structure is good, and carbon nanotubes grow on both sides of the flaky catalyst and all have a consistent orientation.

[0087] Figure 3The pressure sensitivity test chart of Comparative Example 2 obtained for the present invention. As can be seen from the figure, the detection range of pure carboxylated carbon nanotubes is only 50 kPa, and the resistance change rate is too large. This is because after applying pressure, the distance between carbon nanotubes decreases, and at this time the tunneling current increases, but it is very weak. Due to the huge difference between the tube diameter and particle size, it is not easy to form a new effective conductive link in the conductive network, so the piezoresistive sensitivity is very small and reaches saturation under small stress.

[0088] Figure 4 The pressure sensitivity test chart of the flexible pressure film with different filler ratios of the carbon nanotube array / carboxylated carbon nanotube composite structure obtained for the present invention. Combining the comprehensive analysis of Comparative Example 1 and Comparative Example 2, the carbon nanotube array-based film in Comparative Example 1 is not conductive, which is mainly because of its unique array structure. The characteristic of its low aspect ratio makes it not easy to form a conductive path between carbon arrays, while the pressure detection range of pure carboxylated carbon nanotubes in Comparative Example 2 is very narrow; for the mixed structure of carbon nanotube arrays and carboxylated carbon nanotubes, in the film with a ratio of carbon nanotube arrays to carboxylated carbon nanotubes of 1:1 (Example 1), when a small pressure is applied, due to the sudden increase in the conductive network between carbon nanotube arrays and carbon nanotubes, it has a high pressure sensitivity. However, as the pressure increases, due to the excessive content of carbon nanotube arrays, the conductive network formed by them and carboxylated carbon nanotubes tends to be stable and unable to form a new path, resulting in a relatively narrow detection range and poor overall linearity, which is not conducive to practical applications. When the ratio of carbon nanotube arrays to carboxylated carbon nanotubes is 1:4 (Example 3), due to the too small content of carbon nanotube arrays, its influence on the piezoresistive performance of the film is limited, so a relatively narrow pressure detection range (0 - 150 kPa) is presented. When the ratio of carbon nanotubes to carboxylated carbon nanotubes is 1:2 (Example 2), the film presents a large detection range (0 - 450 kPa), and also shows excellent pressure sensitivity (up to -2.586 kPa -1 ), and compared with Example 1, it shows better linearity and is suitable for practical applications.

[0089] Figure 5 The repeated pressure response test chart of Example 2 of the present invention, that is, a 500 - time repeated loading - unloading pressure experiment was carried out on the film with a mass ratio of carbon nanotube arrays to carboxylated carbon nanotubes of 1:2 at 5 kPa - 100 kPa.

[0090] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a flexible pressure film, characterized in that, The preparation method of the flexible pressure film includes: using ferroalloy as a catalyst and acetylene as a carbon source, and preparing a carbon nanotube array by chemical vapor deposition; then mixing and dispersing the carbon nanotube array with commercial carboxylated carbon nanotubes and PDMS, and obtaining a flexible pressure sensing film after scraping and curing; printing silver electrodes on a PET film by screen printing, and adopting an upper and lower electrode type packaging to prepare a flexible pressure sensor; The preparation method of the flexible pressure film includes the following steps: Step 1, weigh a certain amount of ferroaluminum alloy powder and place it in the tube furnace cavity of the chemical vapor deposition equipment, and introduce an inert gas to evacuate the air in the furnace cavity; Step 2, introduce a carbon source gas for reaction, and wash the ferroaluminum alloy with an acidic solution to obtain a carbon nanotube array; Step 3, mix carboxylated carbon nanotubes in a dispersant solution in a certain proportion, shear and stir, and perform cell crushing dispersion to obtain a well-dispersed carboxylated carbon nanotube solution; Step 4, mix the solution obtained in Step 3 with the carbon nanotube array obtained in Step 2, add polydimethylsiloxane, and stir magnetically to obtain a conductive paste of carbon nanotube array / carboxylated carbon nanotubes; Step 5, let the conductive paste obtained in Step 4 stand in a vacuum environment to obtain a paste; Step 6, print conductive silver paste on a PET film by screen printing, and then place it in an oven for curing to obtain a silver electrode path; Step 7, scrape the paste obtained in Step 5 on the PET film in Step 6, and then place it in an electrothermal blast drying oven for curing to obtain a three-layer structure of PET film - silver electrode - flexible film; Step 8, cut and fit the three-layer structure obtained in Step 7 to obtain a six-layer structure of PET film - silver electrode - flexible film - flexible film - silver electrode - PET film.

2. The preparation method of the flexible pressure film according to claim 1, wherein The catalyst in Step 1 is iron oxide and magnesium oxide; The carbon source gases in Step 2 are acetylene and methane, the acidic solution is hydrochloric acid and nitric acid, and the reaction time for introducing the carbon source gas is 40 - 60 min.

3. The preparation method of the flexible pressure film according to claim 1, wherein, The dispersants in Step 3 are chloroform and dichloromethane, and the shear stirring time is 30 min.

4. The preparation method of the flexible pressure film according to claim 1, characterized in that, In Step 4, the mass proportion of carboxylated carbon nanotubes in polydimethylsiloxane is 4%, and the mass ratio of the carbon nanotube array to carboxylated carbon nanotubes is adjusted to 4:1, 2:1, 1:1; stir magnetically for more than 12 h to obtain a conductive paste of carbon nanotube array / carboxylated carbon nanotubes.

5. The preparation method of the flexible pressure film according to claim 1, characterized in that, The standing time in Step 5 is 30 min; The curing temperature in Step 6 is 120 °C, and the contact area between the electrode and the film is 1 cm * 1 cm.

6. The preparation method of the flexible pressure film according to claim 1, wherein, Step 7, paste transparent tape on the surface of the silver electrode, leaving a space of 1 cm * 1 cm; scrape the paste obtained in Step 5 on the PET film in Step 6, and then place it in an electrothermal blast drying oven for curing at 100 - 120 °C, and then peel off the transparent tape, and at the same time peel off the excess flexible film, only leaving a 1 cm * 1 cm flexible film, and finally obtain a three-layer structure of PET film - silver electrode - flexible film.

7. The preparation method of the flexible pressure film according to claim 1, characterized in that, Step 8, cut and fit the two groups of three-layer structures obtained in Step 7 to obtain a six-layer structure of PET film - silver electrode - flexible film - flexible film - silver electrode - PET film.

8. A flexible pressure sensor prepared by using the preparation method of the flexible pressure film as described in any one of claims 1 to 7.

9. An application of the flexible pressure sensor as described in claim 8 in the fields of electronic skin, wearable electronic devices, and intelligent medical technology.

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