A flexible pressure sensor comprising CNT composite organic material and a preparation method thereof

Abstract

The present invention discloses a flexible pressure sensor comprising a CNT composite organic material, which relates to the field of flexible thin film sensors, and comprises from top to bottom a first flexible substrate, a first electrode, an active sensing layer, a second electrode and a second flexible substrate, wherein the active sensing layer is located between the first flexible substrate and the second flexible substrate, the first electrode and the second electrode are respectively fixed on the first flexible substrate and the second flexible substrate, and the first electrode and the second electrode are in a cross pattern; the active sensing layer material comprises multi-walled carbon nanotubes (CNT) and polymethyl methacrylate, and the active sensing layer is made by additive manufacturing. The present invention also discloses a method for preparing the above-mentioned flexible pressure sensor. The present invention selects an organic composite material resistant to high temperature and high pressure for the active sensing layer, optimizes the preparation process and printing process of the slurry, and meets the requirements for high temperature resistance, large range, and high-precision pressure perception in industry and consumer electronics.

Description

Technical Field

[0001] The present invention relates to the field of flexible thin film sensors, and in particular to a flexible pressure sensor comprising a CNT composite organic material and a preparation method thereof. Background Art

[0002] Sensors convert physical or environmental stimuli into detectable signals, playing an important role in the process of modern industrial automation and intelligence. Among them, flexible pressure sensors have the advantages of portability, flexibility, light weight, and thinness. They can be applied to different application scenarios and are widely used in electronic skin, artificial intelligence, soft robotics, health monitoring and other fields. They are one of the hot issues in current research.

[0003] As a one-dimensional carbon material, CNT has good electrical and mechanical properties. CNT has good deformation-induced resistance change characteristics, and its own strain coefficient is very high. The strain coefficient of pure CNT can be as high as 1000 or more; in addition, the resistance change caused by deformation of CNT is reversible. When the external force is removed, the resistance of CNT can return to the initial value. Therefore, using CNT as a sensitive active material can improve the sensitivity and durability of the sensor, and is an ideal material for preparing flexible resistive pressure sensors.

[0004] For flexible pressure sensors, the main performance parameters include sensitivity, sensing range, response time, relaxation time, hysteresis and stability. Sensitivity (S) refers to the slope of the curve of the relative change of resistance with the change of applied pressure, which is a key performance parameter that describes the ability of the pressure sensor to convert pressure signals into resistance signals; sensing range refers to the pressure sensor working within a pressure range, and the pressure signal within this range can be correctly converted into resistance signals; response time refers to the time required for the resistance signal of the flexible piezoresistive pressure sensor to reach 90% of the stable output value; relaxation time refers to the time required for the resistance signal of the flexible piezoresistive pressure sensor to change from the stable output value to the initial value after the applied pressure is removed; hysteresis refers to the phenomenon that the flexible piezoresistive pressure sensor cannot restore its electrical characteristics when the load pressure is removed; stability refers to the sensing ability of the flexible piezoresistive pressure sensor under multi-cycle use conditions. At present, high-sensitivity sensors often have a small sensing range, and it is necessary to reasonably select active materials and balance various parameters according to specific usage requirements.

[0005] Existing pressure sensors are classified by sensing principle, mainly into capacitive pressure sensors, resistive pressure sensors, piezoelectric pressure sensors and ionization pressure sensors. Compared with the other three types of pressure sensors, resistive pressure sensors have the characteristics of large pressure range, low process difficulty, low cost and fast response speed.

[0006] At present, flexible pressure sensors are mostly used in wearable devices, mobile medical, touch screens and intelligent robots. There are few flexible pressure sensors that can withstand high temperature and high pressure and can be used to detect the pressure consistency of hot presses. Although ordinary pressure sensors can work at high temperatures and the range meets the requirements, they are limited by the fixed physical shape and cannot be used for pressure detection of hot presses.

[0007] Due to the fixed physical shape, traditional pressure sensors mainly use a combination of metal shell and thin film, and their application areas are very limited. They cannot solve the problem of pressure sensors on various curved surfaces and narrow spaces. In terms of sensing range, other types of flexible thin film pressure sensors on the market are often limited in range due to the principle of the sensing material used, and cannot meet the industry's demand for high pressures exceeding 10MPa. In terms of operating temperature, it is generally below 100℃.

[0008] Therefore, technicians in this field are committed to developing a flexible pressure sensor containing CNT composite organic materials and a preparation method thereof. The present invention uses the optimal organic composite material resistant to high temperature and high pressure as the active sensing layer, improves the slurry preparation process, optimizes the flexible electronic printing process, and specifically solves the problems of industrial process optimization and the demand for large-range and high-precision pressure perception in consumer electronics. Summary of the invention

[0009] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to improve the measuring range and high temperature and high pressure resistance of the flexible pressure sensor, and how to optimize its preparation process to provide more flexibility for the device appearance, reduce costs, and improve the applicability of the process, thereby facilitating its large-scale production.

[0010] To achieve the above-mentioned objectives, the present invention provides a flexible pressure sensor comprising a CNT composite organic material, comprising from top to bottom a first flexible substrate, a first electrode, an active sensing layer, a second electrode and a second flexible substrate, wherein the active sensing layer is located between the first flexible substrate and the second flexible substrate, the first electrode and the second electrode are respectively fixed on the first flexible substrate and the second flexible substrate, and the first electrode and the second electrode are in a cross mode; the active sensing layer material comprises multi-walled carbon nanotubes and polymethyl methacrylate, and the active sensing layer is made by additive manufacturing.

[0011] Furthermore, the active sensing layer is made by using active sensing layer slurry through template printing or screen printing, and the first electrode and the second electrode are made by using screen printing or inkjet printing.

[0012] Furthermore, the active sensing layer slurry includes multi-walled carbon nanotubes, polymethyl methacrylate, a dispersing solvent and a dispersant.

[0013] Furthermore, the dispersing solvent is diethylene glycol butyl ether acetate, and the dispersing agent is butyl acetate.

[0014] Furthermore, carbon black and / or graphene are added to the active sensing layer slurry.

[0015] Furthermore, the first flexible substrate and the second flexible substrate are made of the same material, which is one of polyimide, PET or PDMS, and the first electrode and the second electrode are both silver electrodes.

[0016] The present invention also provides a method for preparing a flexible pressure sensor, wherein the flexible pressure sensor is a flexible pressure sensor comprising a CNT composite organic material, comprising the following steps:

[0017] Step 1: cutting the first flexible substrate and the second flexible substrate;

[0018] Step 2, printing the first electrode and the second electrode on the first flexible substrate and the second flexible substrate respectively, checking for missing prints and thickness of the first electrode and the second electrode after each printing, and annealing;

[0019] Step 3, preparing the active sensing layer slurry;

[0020] Step 4, first align the position of the active sensing layer on the second electrode, then print the active sensing layer on the basis of the second electrode, check the missing printing and the thickness of the active sensing layer after each printing, and dry;

[0021] Step 5: Bonding: Using a mature dispensing process, drop epoxy glue around the second electrode and the active sensing layer, and then bond the first flexible substrate and the second flexible substrate together.

[0022] Furthermore, the printing method of the first electrode and the second electrode in step 2 is screen printing or inkjet printing; the annealing process in step 2 is specifically: annealing at 120°C in an oven for 20 minutes, and the drying process in step 4 is specifically: heating at 120°C in an oven for 15 minutes.

[0023] Furthermore, the preparation of the active sensing layer slurry in step 3 comprises the following steps:

[0024] Step 3.1, adding high molecular weight PMMA into diethylene glycol butyl ether acetate at a ratio of 5%-55%, heating at 100°C with magnetic stirring to dissolve it relatively quickly and form a PMMA solution;

[0025] Step 3.2, using a homogenizer to perform high-speed stirring to disperse the multi-walled carbon nanotubes in butyl acetate to form a butyl acetate-based multi-walled carbon nanotube solution;

[0026] Step 3.3, adding 10-80% of the butyl acetate-based multi-walled carbon nanotube solution to the PMMA solution;

[0027] Step 3.4: Use the homogenizer to perform high-speed stirring to obtain the active sensing layer slurry.

[0028] Furthermore, the process of high-speed stirring of the homogenizer used in step 3.2 and step 3.4 is: mixing at a speed of 1000-1500 r / min for 15 min, cooling, and then vacuum stirring at a speed of 300 r / min for 3 min.

[0029] In a preferred embodiment of the present invention, the nanocomposite sensing layer is transferred onto the electrode and the flexible substrate by template printing using additive manufacturing, thereby forming a high temperature resistant flexible pressure sensor with a composite "sandwich" structure. Improvements have been made in the active sensing layer material, using an organic long-chain copolymer as the skeleton of the pressure-sensitive material, and filling the skeleton with conductive materials such as carbon nanotubes. When the piezoresistive sensing material is subjected to external force (pressure signal stimulation), the pressure-sensitive material therein will produce a slight deformation, changing the distribution and state of the carbon-based material inside the pressure-sensitive material, thereby causing the resistance of the pressure-sensitive material to change regularly. In the active sensing layer material slurry system, diethylene glycol butyl ether acetate is mainly used as a dispersing solvent, and polymethyl methacrylate as a supporting skeleton is dispersed therein. Diethylene glycol butyl ether acetate is a diol ether ester solvent containing multiple functional groups, and is used as a slurry solvent because of its low volatility and high boiling point. Finally, multi-walled carbon nanotubes are added to increase the conductivity of the pressure-sensitive material, while improving its melting point and mechanical properties, especially Young's modulus and tensile strength. Among them, the incorporation ratio of multi-walled carbon nanotubes can be changed according to performance requirements. In order to improve the uniformity of the overall slurry system, butyl acetate is used as a dispersant, and a homogenizer is used to form a stable and uniform printing slurry to prepare for the next printing and coating process. Using butyl acetate as a dispersant and a homogenizer can effectively disperse multi-walled carbon nanotubes in the solution; and avoid the damage to the microstructure of carbon nanotubes caused by ultrasonic stirring, thereby maintaining the excellent performance of the composite organic material. After the multi-walled carbon nanotubes are dispersed, the vacuum degassing performed by the homogenizer is used again to remove the bubbles brought by polymethyl methacrylate in the slurry. The above process makes the slurry reach the best state for printing.

[0030] In another preferred embodiment of the present invention, carbon black, graphene, etc. can also be added to the slurry. Carbon black is cheaper and easier to mix. Graphene has excellent mechanical properties and high linearity of resistivity change with strain. Multi-walled carbon nanotubes have the highest sensitivity. Using screen-printed high-precision silver electrodes, the electrode coating thickness is reduced to a minimum, and the electrode resistance is consistently 11.395 μΩ / cm. The printing process reduces the material cost and physical volume of the device, improves the reliability of the device under physical impact (bending, stretching, etc.), and can effectively carry out low-cost large-scale production. High-precision silver electrodes can also be prepared by inkjet printing, which has higher precision. Template printing solves the problem of missing active sensing layer slurry and too thin thickness in screen printing, and the printing position can be accurately located by CCD. The active sensing layer can also be prepared by screen printing, and the obtained active sensing layer is thinner.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] 1. The present invention can improve the measurement range of the flexible sensor and work at a high temperature of 150 degrees Celsius;

[0033] 2. The test data does not need to be processed, and the pressure value can be directly obtained through the linear relationship;

[0034] 3. The array can be combined for large-area testing;

[0035] 4. Using flexible electronic printing technology, the device shape can be changed and fully customized; the process has low requirements on the working environment and working conditions, low process cost, and maximizes the efficiency of industrial resource utilization;

[0036] 5. The printing process reduces the material cost and physical volume of the device, improves the reliability of the device under physical impact (bending, stretching, etc.), and can effectively carry out low-cost large-scale production.

[0037] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of a flexible pressure sensor comprising CNT composite organic material according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0040] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0041] The present invention provides a flexible pressure sensor based on a composite material of carbon nanotubes and polymethyl methacrylate, the structure of which is as follows: Figure 1 As shown, it includes: a first flexible substrate 1, a first electrode 2, an active sensing layer 3, a second electrode 4 and a second flexible substrate 5. The active sensing layer 3 contains carbon nanotubes and polymethyl methacrylate; the first electrode 2 and the second electrode 4 are silver electrodes, which are transferred to the first flexible substrate 1 and the second flexible substrate 5 respectively by screen printing, and the active sensing layer 3 is made by template printing. Template printing solves the problem of missing printing and too thin thickness of the active sensing layer slurry in screen printing, and the printing position can be accurately located by CCD. Screen printing high-precision silver electrodes, the electrode coating thickness is minimized, and the electrode resistance is consistent at 11.395μΩ / cm. The printing process reduces the material cost and physical volume of the device, improves the reliability of the device under physical impact (bending, stretching, etc.), and can effectively carry out low-cost large-scale production.

[0042] Embodiment 1

[0043] The flexible pressure sensor containing CNT composite organic materials consists of 5 layers, namely the upper part consisting of a polyimide flexible substrate and a high-precision silver electrode fixed on the substrate, and the lower part consisting of an active sensing layer, a high-precision silver electrode and a polyimide flexible substrate. The electrodes in the upper and lower parts are in a cross pattern. The polyimide substrate film has excellent stability, insulation and mechanical properties, and its temperature resistance is relatively good. It can adapt to temperature changes in a large range and also has good corrosion resistance. The active sensing layer includes multi-walled carbon nanotubes and polymethyl methacrylate.

[0044] The specific preparation process is as follows: First, laser cut the polyimide flexible substrate into a 30×18cm rectangle. Spread the cut polyimide substrate on the workbench, then install the screen printing screen on the screen clamp, and adjust the screen position to ensure that the pattern is completely printed on the substrate. Adjust the printing parameter settings, ink return knife pressure 22.5kPa, speed 250mm / s, scraper pressure 20kPa, speed 110mm / s, screen spacing 3mm, and off-plate delay 2s. The scraper starting position is adjusted according to the printed pattern and screen position, and the parameter setting can be adjusted according to the printing effect. After the parameter setting is completed, take the nano silver paste out of the refrigerator, stir it evenly with a small scraper, and spread it between the printed pattern and the scraper starting point. After determining the position of the substrate on the workbench, adjust the printing to semi-automatic and automatic ink return on the main page of the control system. After each electrode is printed, check the missing print and thickness, and then transfer it to the oven for annealing at 120℃ for 20 minutes. This is the process of the upper part of the sensor.

[0045] The lower part is based on the upper part, and the active sensing layer is transferred and covered on the electrode through template printing. The specific operation steps are: after the electrode printing is completed, remove the silk screen and replace it with the template. First, manually align the position of the active sensing layer on the electrode, check whether the center of the circle coincides after printing the active sensing layer on the electrode, and then use CCD to accurately determine the position of the learning mark point. After successful learning, the workbench will automatically adjust the position so that the electrode position is consistent with the position of the first manual alignment. After each piece is printed, check for missing prints and thickness, and then transfer it to the oven and heat it at 120°C for 15 minutes to evaporate the solvent and surfactant. This is the additive manufacturing process of the upper part of the sensor based on the upper part.

[0046] The next step is the bonding process, which involves using a mature dispensing process to drop epoxy glue around the electrode and the active sensing layer to bond the upper and lower parts of the sensor together.

[0047] Embodiment 2

[0048] The flexible pressure sensor containing CNT composite organic materials of the present invention is composed of 5 layers, namely, the upper part is composed of a PDMS flexible substrate and a high-precision silver electrode fixed on the substrate, and the lower part is composed of an active sensing layer, a high-precision silver electrode and a PDMS flexible substrate. The electrodes of the upper part and the lower part are in a cross pattern. The advantages of the PDMS film are: low Young's modulus, good flexibility and stretchability, strong corrosion resistance, good transparency and stability in a wide range of operating temperatures, and can be used as a substrate material for large-area transparent flexible electronic devices or thermal stability devices; it is easy to combine with electronic materials so that the electronic materials are fixed on its surface, and the PDMS can be prepared into a structure with a certain geometric shape as needed to improve its ductility and meet the requirements of the coplanar structure; the preparation process is simple and easy to operate. The active sensing layer material includes carbon nanotubes and polymethyl methacrylate.

[0049] The specific preparation process is as follows: First, laser cut the PDMS flexible substrate into a 30×18cm rectangle. Spread the cut PDMS substrate on the workbench, then install the screen printing screen on the screen clamp, and adjust the screen position to ensure that the pattern is completely printed on the substrate. Adjust the printing parameter settings, ink return knife pressure 22.5kPa, speed 250mm / s, scraper pressure 20kPa, speed 110mm / s, screen spacing 3mm, and plate departure delay 2s. The scraper starting position is adjusted according to the printed pattern and screen position, and the parameter setting can be adjusted according to the printing effect. After the parameter setting is completed, take the nano silver paste out of the refrigerator, stir it evenly with a small scraper, and spread it between the printed pattern and the scraper starting point. After determining the position of the substrate on the workbench, adjust the printing to semi-automatic and automatic ink return on the main page of the control system. After each electrode is printed, check for missing prints and thickness, and then transfer it to the oven for annealing at 120℃ for 20 minutes. This is the process of the upper part of the sensor.

[0050] The lower part is based on the upper part and continues to cover the active sensing layer on the electrode by screen printing. The specific operation steps are: continue to brush the active sensing layer slurry on the electrode layer, check the missing print and thickness after each brushing, and then transfer it to the oven and heat it at 120℃ for 15 minutes to evaporate the solvent and surfactant. This is the additive manufacturing process of the upper part of the sensor based on the upper part.

[0051] The next step is the bonding process, which involves using a mature dispensing process to drip epoxy glue around the electrode and the active layer, and then sticking the upper and lower parts of the sensor together.

[0052] Embodiment 3

[0053] The preparation process of the active sensing layer slurry is as follows: PMMA (5wt%) with high molecular weight can be dissolved relatively quickly in diethylene glycol butyl acetate under heating and magnetic stirring at 100°C; diethylene glycol butyl acetate is used as an ink solvent in the printing process due to its low volatility and high boiling point. Multi-walled carbon nanotubes are dispersed in butyl acetate using a homogenizer for high-speed stirring to form a butyl acetate-based multi-walled carbon nanotube solution. The detailed process of high-speed stirring of the homogenizer is to stir the mixed slurry at 1000r / min for 15 minutes, wait for the slurry to cool, and then vacuum stir for 3 minutes at a speed of 300r / min. A 10% butyl acetate-based multi-walled carbon nanotube (MWCNT) solution is then added to the PMMA solution. The dispersion of carbon nanotubes in resins has always been a challenge in the synthesis of their composite materials. The high aspect ratio and strong van der Waals interaction of carbon nanotubes lead to their easy entanglement and clustering in solvents. The surface energy of carbon nanotubes is different from that of common organic solvent matrices or polymer matrices; carbon nanotubes may not have chemical affinity for organic matrices. (The seamless surface of carbon nanotubes does not allow them to physically interact with organic matrices.) The physical adsorption of butyl acetate as an ester surfactant on the surface of carbon nanotubes reduces the surface tension of carbon nanotubes and effectively prevents the clustering of carbon nanotubes. Because multi-walled carbon nanotubes (MWCNT) are already uniformly dispersed in butyl acetate, we only need to prevent multi-walled carbon nanotubes (MWCNT) from clustering when mixed with PMMA solution; so we chose to use high-speed stirring of a homogenizer instead of ultrasonic stirring to better retain the various properties (conductive and mechanical) of multi-walled carbon nanotubes (MWCNT); and the homogenizer also has a degassing function, which can solve the problem of bubbles generated during mixing. The detailed process of high-speed stirring of the homogenizer is to stir the mixed slurry at 1000r / min for 15 minutes, wait for the slurry to cool, and then vacuum stir for 3 minutes at a speed of 300r / min.

[0054] Embodiment 4

[0055] The preparation process of the active sensing layer slurry is as follows: PMMA (15wt%) with high molecular weight can be dissolved relatively quickly in diethylene glycol butyl ether acetate under heating and magnetic stirring at 100°C; diethylene glycol butyl ether acetate is used as an ink solvent in the printing process due to its low volatility and high boiling point. Multi-walled carbon nanotubes and carbon black are dispersed in butyl acetate to form a butyl acetate-based multi-walled carbon nanotube solution using a homogenizer for high-speed stirring. The detailed process of the homogenizer high-speed stirring is to stir the mixed slurry at 1000r / min for 15 minutes, wait for the slurry to cool, and then vacuum stir for 3 minutes at a speed of 300r / min. Carbon black is cheaper and easier to mix. A 20% butyl acetate-based multi-walled carbon nanotube (MWCNT) solution is then added to the PMMA solution. The dispersion of carbon nanotubes in resins has always been a challenge in the synthesis of their composite materials. The high aspect ratio and strong van der Waals interaction of carbon nanotubes cause them to be easily entangled and clustered in solvents. The surface energy of carbon nanotubes is different from that of common organic solvent matrices or polymer matrices; carbon nanotubes may not have chemical affinity for organic matrices. (The seamless surface of carbon nanotubes does not allow them to physically interact with organic matrices.) The physical adsorption of butyl acetate as an ester surfactant on the surface of carbon nanotubes reduces the surface tension of carbon nanotubes and effectively prevents the clustering of carbon nanotubes. Because multi-walled carbon nanotubes (MWCNT) are already uniformly dispersed in butyl acetate, we only need to prevent multi-walled carbon nanotubes (MWCNT) from clustering when mixed with PMMA solution; so we chose to use high-speed stirring of a homogenizer instead of ultrasonic stirring to better retain the various properties (conductive and mechanical) of multi-walled carbon nanotubes (MWCNT); and the homogenizer also has a degassing function, which can solve the problem of bubbles generated during mixing. The detailed process of high-speed stirring of the homogenizer is to stir the mixed slurry at 1000r / min for 15 minutes, wait for the slurry to cool, and then vacuum stir for 3 minutes at a speed of 300r / min.

[0056] Embodiment 5

[0057] The preparation process of the active sensing layer slurry is as follows: PMMA (55wt%) with a high molecular weight can be dissolved relatively quickly in diethylene glycol butyl acetate under heating and magnetic stirring at 100°C; diethylene glycol butyl acetate is used as an ink solvent in the printing process due to its low volatility and high boiling point. Multi-walled carbon nanotubes and graphene are dispersed in butyl acetate to form a butyl acetate-based multi-walled carbon nanotube solution using a homogenizer for high-speed stirring. The detailed process of the high-speed stirring of the homogenizer is to stir the mixed slurry at 1000r / min for 15 minutes, wait for the slurry to cool, and then vacuum stir for 3 minutes at a speed of 300r / min. Graphene has excellent mechanical properties and high linearity of resistivity change with strain. The 80% butyl acetate-based multi-walled carbon nanotube (MWCNT) solution was then added to the PMMA solution. The dispersion of carbon nanotubes in resin has always been a challenge in the synthesis of its composite materials. The high aspect ratio and strong van der Waals interaction of carbon nanotubes lead to their easy entanglement and clustering in solvents. The surface energy of carbon nanotubes is different from that of common organic solvent matrices or polymer matrices; carbon nanotubes may not have chemical affinity for organic matrices. (The seamless surface of carbon nanotubes does not allow them to physically interact with organic matrices.) The physical adsorption of butyl acetate as an ester surfactant on the surface of carbon nanotubes reduces the surface tension of carbon nanotubes and effectively prevents the clustering of carbon nanotubes. Because multi-walled carbon nanotubes (MWCNT) are already uniformly dispersed in butyl acetate, we only need to prevent multi-walled carbon nanotubes (MWCNT) from clustering when mixed with PMMA solution; so we chose to use high-speed stirring of the homogenizer instead of ultrasonic stirring to better retain the various properties (conductive and mechanical) of multi-walled carbon nanotubes (MWCNT); and the homogenizer also has a degassing function, which can solve the problem of bubbles generated during mixing. The detailed process of high-speed stirring of the homogenizer is to stir the mixed slurry at 1500r / min for 15 minutes, wait for the slurry to cool, and then vacuum stir at a speed of 300r / min for 3 minutes.

[0058] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A flexible pressure sensor comprising a CNT composite organic material, characterized in that: The invention comprises, from top to bottom, a first flexible substrate, a first electrode, an active sensing layer, a second electrode and a second flexible substrate, wherein the active sensing layer is located between the first flexible substrate and the second flexible substrate, the first electrode and the second electrode are fixed on the first flexible substrate and the second flexible substrate respectively, and the first electrode and the second electrode are in a cross mode; the active sensing layer material comprises multi-walled carbon nanotubes and polymethyl methacrylate, and the active sensing layer is made by additive manufacturing; the active sensing layer is made by template printing or screen printing using the active sensing layer slurry, and the first electrode and the second electrode are made by screen printing or inkjet printing; the active sensing layer slurry comprises multi-walled carbon nanotubes, polymethyl methacrylate, a dispersing solvent and a dispersant; the dispersing solvent is diethylene glycol butyl ether acetate, and the dispersant is butyl acetate; wherein PMMA with a high molecular weight is mixed at a ratio of 5% to 55%. The ratio of 1:1 to 2:1 is added to diethylene glycol butyl ether acetate, and heated at 100° C. with magnetic stirring to make it dissolve relatively quickly and form a PMMA solution; a homogenizer is used to stir at high speed to disperse the multi-walled carbon nanotubes in butyl acetate to form a butyl acetate-based multi-walled carbon nanotube solution; Adding 10% to 80% of the butyl acetate-based multi-walled carbon nanotube solution to the PMMA solution; The active sensing layer slurry is obtained by high-speed stirring using the homogenizer.

2. The flexible pressure sensor comprising CNT composite organic material according to claim 1, characterized in that: Carbon black and / or graphene are added to the active sensing layer slurry.

3. The flexible pressure sensor comprising CNT composite organic material according to claim 1, characterized in that: The first flexible substrate and the second flexible substrate are made of the same material, which is one of polyimide, PET or PDMS, and the first electrode and the second electrode are both silver electrodes.

4. A method for preparing a flexible pressure sensor, characterized in that: The flexible pressure sensor is a flexible pressure sensor comprising a CNT composite organic material according to any one of claims 1 to 3, comprising the following steps: Step 1: cutting the first flexible substrate and the second flexible substrate; Step 2, printing the first electrode and the second electrode on the first flexible substrate and the second flexible substrate respectively, checking for missing prints and thickness of the first electrode and the second electrode after each printing, and annealing; Step 3, preparing the active sensing layer slurry; Step 4, first align the position of the active sensing layer on the second electrode, then print the active sensing layer on the basis of the second electrode, check the missing printing and the thickness of the active sensing layer after each printing, and dry; Step 5: Bonding: Using a mature dispensing process, drop epoxy glue around the second electrode and the active sensing layer, and then bond the first flexible substrate and the second flexible substrate together.

5. The method for preparing the flexible pressure sensor according to claim 4, characterized in that: The printing method of the first electrode and the second electrode in step 2 is screen printing or inkjet printing; the annealing process in step 2 is specifically: annealing in an oven at 120° C. for 20 minutes, and the drying process in step 4 is specifically: heating in an oven at 120° C. for 15 minutes.

6. The method for preparing the flexible pressure sensor according to claim 5, characterized in that: The process of high-speed stirring using a homogenizer is as follows: mixing at a speed of 1000 - 1500 r / min for 15 minutes, cooling, and then vacuum stirring at a speed of 300 r / min for 3 minutes.

Images