Preparation method of multilayer transparent piezoelectric film sensor containing ZnO and rGO

Abstract

The invention relates to the field of sensors, and discloses a preparation method of a multilayer transparent piezoelectric film sensor containing ZnO and rGO. According to the invention, a small amount of propylene chain segments are introduced into a P (VDF-TrFE) molecular chain to improve the flexibility of the P (VDF-TrFE) molecular chain, and meanwhile, nano materials ZnO and rGO are added to greatly improve the piezoelectric property of the P (VDF-TrFE) after polarization; moreover, due to the introduction of ZnO, not only can the light and heat resistance of the piezoelectric film be improved, but also the color development of rGO can be reduced, so that the transparent performance of the piezoelectric film is better.

Description

Technical Field

[0001] The invention relates to the field of sensors, and in particular to a method for preparing a multilayer transparent piezoelectric film sensor containing ZnO and rGO. Background Art

[0002] Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) is a class of excellent ferroelectric and piezoelectric materials. It is semi-crystalline in nature and has good mechanical reliability. It is an excellent candidate material for electronic devices and can be widely used in electromechanical sensors, actuators, storage and other transducer devices. Piezoelectric film sensors have made significant progress in the past few decades. Various flexible sensors that simulate the tactile function of human skin and sensors for monitoring sound have been developed. They can sense the size of force, temperature, frequency, etc., and have great application prospects in wearable electronic devices, health and sports detection, biomedicine and other fields.

[0003] However, on the one hand, the piezoelectric performance and flexibility of the existing P (VDF-TrFE) piezoelectric film sensors are not ideal. On the other hand, the existing P (VDF-TrFE) piezoelectric film sensors have poor stability in extreme environmental environments and are easily affected by environmental factors such as light and heat. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a multilayer transparent piezoelectric film sensor containing ZnO and rGO. The present invention introduces a small amount of propylene segments into the P(VDF-TrFE) molecular chain to improve its flexibility, and adds nanomaterials ZnO and rGO to greatly improve its piezoelectric properties after polarization; and the introduction of ZnO can not only improve the light and heat resistance of the piezoelectric film, but also reduce the color development of rGO, making its transparent performance better.

[0005] The specific technical solution of the present invention is: a method for preparing a multilayer transparent piezoelectric film sensor containing ZnO and rGO, comprising:

[0006] Step 1): adding an initiator and water into a reactor, and degassing under vacuum under cooling; introducing gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene into the reactor at a molar ratio of 70-80:15-20:3-7, and copolymerizing after the gas is cooled and liquefied; cooling after the reaction, separating, washing and drying to obtain a terpolymer P (VDF-TrFE-P).

[0007] The present invention finds that introducing an appropriate amount of propylene segments into the P (VDF-TrFE) molecular chain can help improve the flexibility of the generated film; the feed molar ratio of vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers should be controlled within a reasonable range. If the molar percentage of each monomer is too high or too low, it will affect the piezoelectric properties or flexibility of the film.

[0008] Step 2): P(VDF-TrFE-P) is dissolved in N,N-dimethylformamide and ultrasonically stirred to obtain a P(VDF-TrFE-P) solution.

[0009] Step 3): P(VDF-TrFE-P), ZnO powder and rGO powder are dissolved in N,N-dimethylformamide in a mass ratio of 9.8-10.2:1:1.8-2.2, and ultrasonically treated, and then the obtained dispersion is ultrasonically stirred to finally obtain a ZnO / rGO / P(VDF-TrFE-P) dispersion.

[0010] The present invention controls the mass ratio of P(VDF-TrFE-P), ZnO powder and rGO powder to 9.8-10.2:1:1.8-2.2. If the amount of P(VDF-TrFE-P) is too much and the amount of ZnO powder and rGO powder is too little, the formed thin film sensor will be short-circuited and the sensing test cannot be performed; if the amount of P(VDF-TrFE-P) is too little and the amount of ZnO powder and rGO powder is too much, the nanomaterials will be agglomerated, affecting the performance of the thin film sensor, and the cost will be increased, which is not conducive to production. The mass ratio of ZnO powder and rGO powder should be controlled at 1:1.8-2.2. If the molar ratio is too high, the thermal and electrical conductivity of the film will be reduced, and the environmental stability will be reduced; if the molar ratio is too low, the film will be blackened and the transparency of the film will be reduced.

[0011] Step 4): Cast the ZnO / rGO / P(VDF-TrFE-P) dispersion on a substrate to form a thin film, and vacuum dry to obtain a ZnO / rGO / P(VDF-TrFE-P) single-layer thin film.

[0012] Compared with other molding methods, the film prepared by solution casting has the advantages of good transparency, uniform texture, and easy control. After vacuum heat treatment, the film will produce a self-crosslinking reaction, so that it will not swell when it comes into contact with water. The film has good transparency and certain toughness at a thickness of 10 to 15 μm. ZnO / rGO / P (VDF-TrFE-P) single-layer film can provide excellent performance and avoid the evaporation of the conductive layer. It is a conductive film with good transparency and piezoelectric properties.

[0013] Step 5): Casting the P(VDF-TrFE-P) solution on the obtained single-layer film to form a double-layer film, and vacuum drying to obtain a double-layer film.

[0014] Using pure P (VDF-TrFE-P) as the middle layer can not only ensure the transparency of the film, but also significantly improve the piezoelectric performance of the film. After polarization, the double-layer film has a piezoelectric coefficient greater than twice that of the pure P (VDF-TrFE-P) film, which can significantly improve the piezoelectric effect of the manufactured sensor.

[0015] Step 6): Casting the ZnO / rGO / P(VDF-TrFE-P) dispersion on the obtained double-layer film to form a three-layer film, and vacuum drying to obtain a multi-layer film.

[0016] Pure P (VDF-TrFE-P) is used as the middle layer and ZnO / rGO / P (VDF-TrFE-P) is used as the outer layer. No other conductive layer needs to be evaporated, which can ensure the transparency of the film and significantly improve the piezoelectric performance of the film. After polarization, the three-layer film has a piezoelectric coefficient that is three times greater than that of the pure P (VDF-TrFE-P) film, which can significantly improve the piezoelectric effect of the manufactured sensor.

[0017] Step 7): Annealing the multilayer film.

[0018] The formation of β phase during annealing makes the film have better piezoelectric properties. c and T m Annealing at a temperature between 300 and 500 °C is beneficial to both increasing the ferroelectric phase content and increasing the β phase content.

[0019] Step 8): polarize the multilayer film, maintain the polarization field strength and cool to room temperature.

[0020] Preferably, in step 2), the mass percentage of P(VDF-TrFE-P) in the obtained solution is 5-15wt%.

[0021] The present invention uses N,N-dimethylformamide as a solvent. N,N-dimethylformamide is a low-volatile solvent. Slow volatilization helps to improve the transparency of the obtained film. The mass percentage of the obtained pure P (VDF-TrFE-P) solution should be controlled at 5-15wt%. If the mass percentage is too low, the required solution volume will be too large, the solution viscosity will be too low, and it will be difficult to control the thickness of the generated film. If the mass percentage is too high, the required solution volume will be too small, the solution viscosity will be too high, and it will be difficult to cast the required film.

[0022] Preferably, in step 2), the ultrasonic stirring is carried out at room temperature for 4-8 hours.

[0023] Preferably, in step 3), the mass percentage of P(VDF-TrFE-P) in the obtained dispersion is 5-15wt%.

[0024] Preferably, in step 3), the ultrasonic treatment time is 1-3 h, the ultrasonic stirring temperature is room temperature, and the time is 8-12 h.

[0025] Preferably, in step 4) to step 6), the thickness of the thin film formed each time is 10 to 20 μm, and the optimal thickness is 15 μm.

[0026] Preferably, in step 4) to step 6), the vacuum drying temperature is 85-95°C and the time is 3-5h.

[0027] The evaporation temperature of N,N-dimethylformamide solvent is 80-90°C, so 85-95°C is selected for solvent distillation.

[0028] Preferably, in step 7), the annealing temperature is 110-150° C. (the optimal annealing temperature is 130° C.) and the time is 0.5-1.5 h.

[0029] The formation of β phase during annealing makes the film have better piezoelectric properties. c and T m Annealing at a temperature between 100°C and 200°C is beneficial to increasing both the ferroelectric phase content and the β phase content, and 130°C is in this range and is the preferred annealing temperature.

[0030] Preferably, in step 8), the polarization conditions are: polarization electric field strength 135-145 MV / m, polarization temperature 85-95° C., and polarization time 0.5-1.5 h.

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

[0032] (1) The present invention introduces an appropriate amount of propylene monomer into the P(VDF-TrFE) copolymer molecular chain, which can increase the flexibility of the generated thin film sensor and is beneficial to the application in the field of wearable sensors.

[0033] (2) The present invention adds nanomaterial rGO to P(VDF-TrFE-P), which can greatly improve its piezoelectric properties after polarization and improve the toughness and stability of the sensor; adding nanomaterial ZnO can greatly improve its piezoelectric properties after polarization, enhance the sensitivity of the sensor to ultraviolet rays, gas, humidity, etc., thereby improving its stability, and at the same time reduce the opacity caused by the addition of rGO.

[0034] (3) The present invention adopts a method for preparing a sandwich multilayer thin film sensor, with P (VDF-TrFE-P) film as the middle layer and ZnO / rGO / P (VDF-TrFE-P) as the outer layer, which can greatly improve the piezoelectric effect, stability and toughness of the sensor, and can well maintain the transparency of the film itself.

[0035] (4) The film prepared by the solution casting method of the present invention has the advantages of good transparency, uniform texture, and easy control. After the film is subjected to vacuum heat treatment, a self-crosslinking reaction will occur, so that it will not swell when it comes into contact with water. The film has good transparency and certain toughness at a thickness of 10 to 20 μm. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the embodiments.

[0037] Example 1

[0038] Step 1): Add 0.15g potassium persulfate (K2S2O8) and 100mL deionized water to a 300ml stainless steel container. The container is sealed and placed in a liquid nitrogen bath (-140°C), and then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers are pumped into the container and liquefied instantly at liquid nitrogen temperature. The feed molar ratio of the monomers is 76:19:5, which is controlled by the pumping time of each gas, and the reaction is carried out at 90°C for 6 hours. After the reaction is completed, the container is cooled to room temperature and the excess gas is carefully removed. The separated polymer is repeatedly washed with deionized water and methanol and vacuum dried at 50°C to obtain P (VDF-TrFE-P) powder.

[0039] Step 2): Preparation of pure P(VDF-TrFE-P) solution: P(VDF-TrFE-P) powder was dissolved in N,N-dimethylformamide and ultrasonically stirred at room temperature for 6 h to obtain a 10 wt% pure P(VDF-TrFE-P) solution;

[0040] Step 3): Preparation of ZnO / rGO / P(VDF-TrFE-P) dispersion: P(VDF-TrFE-P) powder, ZnO powder and rGO powder were dissolved in N,N-dimethylformamide at a mass ratio of 10:1:2, and ultrasonically treated for 2 h. The obtained dispersion was then ultrasonically stirred at room temperature for 10 h to obtain a ZnO / rGO / P(VDF-TrFE-P) dispersion with a P(VDF-TrFE-P) concentration of 10 wt%;

[0041] Step 4): Preparation of a single-layer film: cast a ZnO / rGO / P (VDF-TrFE-P) dispersion on a substrate to form a film, and vacuum dry it at 90° C. for 4 h to obtain a ZnO / rGO / P (VDF-TrFE-P) single-layer film with a thickness of 15 μm;

[0042] Step 5): Preparation of a double-layer film: Casting a pure P (VDF-TrFE-P) solution on the single-layer film obtained in step 4) to form a double-layer film, and vacuum drying at 90° C. for 4 h to obtain a double-layer film with a thickness of 30 μm;

[0043] Step 6): Preparation of a multilayer film: Casting the ZnO / rGO / P(VDF-TrFE-P) dispersion on the double-layer film obtained in step 5) to form a three-layer film, and vacuum drying at 90°C for 4h to obtain a multilayer film with a thickness of 45 μm;

[0044] Step 7): Annealing of the multilayer film: anneal the multilayer film at 130° C. for 1 h.

[0045] Step 8): Polarization of the multilayer film: Set the polarization parameters: polarization electric field strength 140MV / m, polarization temperature 90°C, polarization time 1h, perform polarization, and finally maintain the polarization field strength and cool to room temperature.

[0046] Using the static piezoelectric coefficient d 33 The piezoelectric coefficient d 33 ~116pC / N, indicating that it has excellent piezoelectric properties; the sensor was tested using a sensor piezoelectric performance test system, and the maximum sensitivity was ~745.12mV / N, indicating that it has excellent piezoelectric response performance; the transmittance tester was used for testing, and it was found that its transmittance was ~91%, indicating that it has excellent transparency; after 24h of ultraviolet light irradiation, it was found that it could still maintain an output voltage of ~30.67V, indicating that it has excellent light resistance; after 150℃ cyclic heating and cooling, it was found that it could still maintain an output voltage of ~30.02V, indicating that it has excellent heat resistance; the stability of the film was tested using a cyclic load tester, and it was found that after 6600 test cycles, it could still maintain an output voltage of ~30.47V without obvious attenuation, indicating that it has excellent stability; the elongation at break was tested using a elongation at break tester, and it was found that its elongation at break was ~280%, indicating that it has excellent flexibility.

[0047] Comparative Example 1

[0048] Step 1): Add 0.15g potassium persulfate (K2S2O8) and 100mL deionized water to a 300ml stainless steel container. The container is sealed and placed in a liquid nitrogen bath (-140°C), and then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF) and trifluoroethylene (TrFE) monomers are pumped into the container and liquefied instantly at liquid nitrogen temperature. The feed molar ratio of the monomers is 80:20, which is controlled by the pumping time of each gas, and the reaction is carried out at 90°C for 6 hours. After the reaction is completed, the container is cooled to room temperature and the excess gas is carefully removed. The separated polymer is repeatedly washed with deionized water and methanol and vacuum dried at 50°C to obtain P(VDF-TrFE) powder.

[0049] Step 2): Preparation of pure P(VDF-TrFE) solution: P(VDF-TrFE) powder was dissolved in N,N-dimethylformamide and ultrasonically stirred at room temperature for 6 h to obtain a 10 wt% pure P(VDF-TrFE) solution;

[0050] Step 3): Preparation of ZnO / rGO / P(VDF-TrFE) dispersion: P(VDF-TrFE) powder, ZnO powder and rGO powder were dissolved in N,N-dimethylformamide at a mass ratio of 10:1:2, and ultrasonically treated for 2 hours. The obtained dispersion was then ultrasonically stirred at room temperature for 10 hours to obtain a ZnO / rGO / P(VDF-TrFE) dispersion with a P(VDF-TrFE-P) concentration of 10 wt%;

[0051] Step 4): Preparation of a single-layer film: cast a ZnO / rGO / P(VDF-TrFE) dispersion on a substrate to form a film, and vacuum dry it at 90°C for 4 hours to obtain a ZnO / rGO / P(VDF-TrFE) single-layer film with a thickness of 15 μm;

[0052] Step 5): Preparation of a double-layer film: Casting a pure P(VDF-TrFE) solution on the single-layer film obtained in step 4) to form a double-layer film, and vacuum drying at 90° C. for 4 h to obtain a double-layer film with a thickness of 30 μm;

[0053] Step 6): Preparation of a multilayer film: Casting the ZnO / rGO / P(VDF-TrFE) dispersion on the double-layer film obtained in step 5) to form a three-layer film, and vacuum drying at 90°C for 4h to obtain a multilayer film with a thickness of 45 μm;

[0054] Step 7): Annealing of the multilayer film: anneal the multilayer film at 130° C. for 1 h.

[0055] Step 8): Polarization of the multilayer film: Set the polarization parameters: polarization electric field strength 140MV / m, polarization temperature 90°C, polarization time 1h, perform polarization, and finally maintain the polarization field strength and cool to room temperature.

[0056] Comparative Example 2

[0057] Step 1): Add 0.15g potassium persulfate (K2S2O8) and 100mL deionized water to a 300ml stainless steel container. The container is sealed and placed in a liquid nitrogen bath (-140°C), and then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers are pumped into the container and liquefied instantly at liquid nitrogen temperature. The feed molar ratio of the monomers is 76:19:5, which is controlled by the pumping time of each gas, and the reaction is carried out at 90°C for 6 hours. After the reaction is completed, the container is cooled to room temperature and the excess gas is carefully removed. The separated polymer is repeatedly washed with deionized water and methanol and vacuum dried at 50°C to obtain P (VDF-TrFE-P) powder.

[0058] Step 2): Preparation of pure P(VDF-TrFE-P) solution: P(VDF-TrFE-P) powder was dissolved in N,N-dimethylformamide, and ultrasonically stirred at room temperature for 6 hours to obtain a pure P(VDF-TrFE-P) solution with a P(VDF-TrFE-P) concentration of 10 wt%;

[0059] Step 3): Preparation of ZnO / P(VDF-TrFE-P) dispersion: P(VDF-TrFE-P) powder and ZnO powder were dissolved in N,N-dimethylformamide at a mass ratio of 10:1, and ultrasonically treated for 2 hours, and then the obtained dispersion was ultrasonically stirred at room temperature for 10 hours to finally obtain a 10wt% ZnO / P(VDF-TrFE) dispersion;

[0060] Step 4): Preparation of a single-layer film: casting a ZnO / P (VDF-TrFE-P) dispersion on a substrate to form a film, and vacuum drying at 90° C. for 4 h to obtain a ZnO / P (VDF-TrFE-P) single-layer film with a thickness of 15 μm;

[0061] Step 5): Preparation of a double-layer film: Casting a pure P (VDF-TrFE-P) solution on the single-layer film obtained in step 4) to form a double-layer film, and vacuum drying at 90° C. for 4 h to obtain a double-layer film with a thickness of 30 μm;

[0062] Step 6): Preparation of a multilayer film: casting a ZnO / P (VDF-TrFE-P) dispersion on the double-layer film obtained in step 5) to form a three-layer film, and vacuum drying at 90° C. for 4 h to obtain a multilayer film with a thickness of 45 μm;

[0063] Step 7): Annealing of the multilayer film: anneal the multilayer film at 130° C. for 1 h.

[0064] Step 8): Polarization of the multilayer film: Set the polarization parameters: polarization electric field strength 140MV / m, polarization temperature 90°C, polarization time 1h, perform polarization, and finally maintain the polarization field strength and cool to room temperature.

[0065] Comparative Example 3

[0066] Step 1): Add 0.15g potassium persulfate (K2S2O8) and 100mL deionized water to a 300ml stainless steel container. The container is sealed and placed in a liquid nitrogen bath (-140°C), and then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers are pumped into the container and liquefied instantly at liquid nitrogen temperature. The feed molar ratio of the monomers is 76:19:5, which is controlled by the pumping time of each gas, and the reaction is carried out at 90°C for 6 hours. After the reaction is completed, the container is cooled to room temperature and the excess gas is carefully removed. The separated polymer is repeatedly washed with deionized water and methanol and vacuum dried at 50°C to obtain P (VDF-TrFE-P) powder.

[0067] Step 2): Preparation of pure P(VDF-TrFE-P) solution: P(VDF-TrFE-P) powder was dissolved in N,N-dimethylformamide, and ultrasonically stirred at room temperature for 6 hours to obtain a pure P(VDF-TrFE-P) solution with a P(VDF-TrFE-P) concentration of 10 wt%;

[0068] Step 3): Preparation of rGO / P(VDF-TrFE-P) dispersion: P(VDF-TrFE-P) powder and rGO powder were dissolved in N,N-dimethylformamide at a mass ratio of 5:1, and ultrasonically treated for 2 h. The obtained dispersion was then ultrasonically stirred at room temperature for 10 h to obtain a 10 wt% rGO / P(VDF-TrFE-P) dispersion.

[0069] Step 4): Preparation of a single-layer film: Cast the rGO / P (VDF-TrFE-P) dispersion on a substrate to form a film, and vacuum dry it at 90° C. for 4 h to obtain a rGO / P (VDF-TrFE-P) single-layer film with a thickness of 15 μm;

[0070] Step 5): Preparation of a double-layer film: Casting a pure P (VDF-TrFE-P) solution on the single-layer film obtained in step 4) to form a double-layer film, and vacuum drying at 90° C. for 4 h to obtain a double-layer film with a thickness of 30 μm;

[0071] Step 6): Preparation of a multilayer film: Cast the rGO / P(VDF-TrFE-P) dispersion on the double-layer film obtained in step 5) to form a three-layer film, and vacuum dry it at 90°C for 4h to obtain a multilayer film with a thickness of 45 μm;

[0072] Step 7): Annealing of the multilayer film: anneal the multilayer film at 130° C. for 1 h.

[0073] Step 8): Polarization of the multilayer film: Set the polarization parameters: polarization electric field strength 140MV / m, polarization temperature 90°C, polarization time 1h, perform polarization, and finally maintain the polarization field strength and cool to room temperature.

[0074] Comparative Example 4

[0075] Step 1): Add 0.15g potassium persulfate (K2S2O8) and 100mL deionized water to a 300ml stainless steel container. The container is sealed and placed in a liquid nitrogen bath (-140°C), and then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers are pumped into the container and liquefied instantly at liquid nitrogen temperature. The feed molar ratio of the monomers is 76:19:5, which is controlled by the pumping time of each gas, and the reaction is carried out at 90°C for 6 hours. After the reaction is completed, the container is cooled to room temperature and the excess gas is carefully removed. The separated polymer is repeatedly washed with deionized water and methanol and vacuum dried at 50°C to obtain P (VDF-TrFE-P) powder.

[0076] Step 2): Preparation of ZnO / rGO / P(VDF-TrFE-P) dispersion: P(VDF-TrFE-P) powder, ZnO powder and rGO powder were dissolved in N,N-dimethylformamide at a mass ratio of 10:1:2, and ultrasonically treated for 2 hours. The obtained dispersion was then ultrasonically stirred at room temperature for 10 hours to obtain a ZnO / rGO / P(VDF-TrFE-P) dispersion with a P(VDF-TrFE-P) concentration of 10 wt%;

[0077] Step 3): Preparation of a single-layer film: cast a ZnO / rGO / P (VDF-TrFE-P) dispersion on a substrate to form a film, and vacuum dry it at 90° C. for 4 h to obtain a ZnO / rGO / P (VDF-TrFE-P) single-layer film with a thickness of 15 μm;

[0078] Step 4): Preparation of a double-layer film: casting the ZnO / rGO / P(VDF-TrFE-P) solution on the single-layer film obtained in step 3) to form a double-layer film, and vacuum drying at 90°C for 4h to obtain a double-layer film with a thickness of 30 μm;

[0079] Step 5): Preparation of a multilayer film: Casting the ZnO / rGO / P(VDF-TrFE-P) dispersion on the double-layer film obtained in step 4) to form a three-layer film, and vacuum drying at 90°C for 4h to obtain a multilayer film with a thickness of 45 μm;

[0080] Step 6): Annealing of the multilayer film: anneal the multilayer film at 130° C. for 1 h.

[0081] Step 7): Polarization of the multilayer film: Set the polarization parameters: polarization electric field strength 140MV / m, polarization temperature 90°C, polarization time 1h, perform polarization, and finally maintain the polarization field strength and cool to room temperature.

[0082] Performance Analysis

[0083]

[0084] From the comparison of the data in the above table, we can see that:

[0085] Compared with Example 1, the elongation at break of Comparative Example 1 is lower, indicating that the film obtained in Example 1 has better flexibility. This is because an appropriate amount of propylene monomer is introduced into the polymer of Example 1, thereby improving the flexibility of the sensor.

[0086] Compared with Example 1, the piezoelectric coefficient d of Comparative Example 2 is 33 and lower sensitivity, indicating that Example 1 has better piezoelectric properties, which is due to the lack of rGO in the film of Comparative Example 2, and the doping of rGO can improve the piezoelectric properties of the sensor to a certain extent; the transmittance of Comparative Example 2 is lower, indicating that Example 1 has better light transmittance, which is due to the lack of the synergistic effect of ZnO and rGO in Comparative Example 2; the output voltage of Comparative Example 2 after 6600 cycles of loading and the output voltage after various treatments are slightly reduced, which is related to the piezoelectric coefficient of Comparative Example 2, and the reduction of the piezoelectric coefficient leads to a reduction in the output voltage.

[0087] Compared with Example 1, the transmittance of Comparative Example 3 is lower, indicating that Example 1 has better transparency. This is because the film of Comparative Example 3 does not contain ZnO and lacks the synergistic effect of ZnO and rGO. The output voltage of Comparative Example 3 after 6600 cycles of loading and the output voltage after various treatments are both lower, indicating that the film obtained in Example 1 has better light and heat resistance and stability. This is because ZnO has good light and heat resistance and stability, and its absence reduces the light and heat resistance and stability of the sensor.

[0088] Compared with Example 1, the piezoelectric coefficient d of Comparative Example 4 is 33The higher the sensitivity, the more accurate the comparison example 4 is, and the better the piezoelectric performance is. This is because the middle layer is also doped with rGO nanoparticles, which improves the piezoelectric performance of the sensor. The lower the transparency of the comparison example 4 is, the more accurate the comparison example 4 is, and the better the piezoelectric performance is. This is because the middle layer of the comparison example 4 is also doped with nanoparticles, which reduces the transparency of the sensor. The output voltage after 6600 cycles of loading and the output voltage after various treatments of the comparison example 4 are both high, which shows that the comparison example 4 has better light and heat resistance and stability, which is related to the piezoelectric coefficient of the comparison example 4 and the doping of the middle layer. The increase in the piezoelectric coefficient causes the increase in the output voltage, and the doping of ZnO nanoparticles in the middle layer slightly improves the light and heat resistance and stability.

Claims

1. A method for preparing a multilayer transparent piezoelectric film sensor containing ZnO and rGO, characterized in that include: Step 1): Add initiator and water into the reactor and degas under vacuum while cooling; Gaseous vinylidene fluoride, trifluoroethylene and propylene are introduced into a reactor at a molar ratio of 70-80:15-20:3-7, and the gas is cooled and liquefied and then copolymerized; after the reaction, the reaction is cooled, separated, washed and dried to obtain a terpolymer P (VDF-TrFE-P); Step 2): dissolving P(VDF-TrFE-P) in N,N-dimethylformamide and stirring with ultrasonic to obtain a P(VDF-TrFE-P) solution; Step 3): P(VDF-TrFE-P), ZnO powder and rGO powder are dissolved in N,N-dimethylformamide in a mass ratio of 9.8-10.2:1:1.8-2.2, and ultrasonically treated, and then the obtained dispersion is ultrasonically stirred to finally obtain a ZnO / rGO / P(VDF-TrFE-P) dispersion; Step 4): casting the ZnO / rGO / P(VDF-TrFE-P) dispersion on a substrate to form a thin film, and vacuum drying to obtain a ZnO / rGO / P(VDF-TrFE-P) single-layer thin film; Step 5): casting the P(VDF-TrFE-P) solution on the obtained single-layer film to form a double-layer film, and vacuum drying to obtain a double-layer film; Step 6): casting the ZnO / rGO / P(VDF-TrFE-P) dispersion on the obtained double-layer film to form a three-layer film, and vacuum drying to obtain a multilayer film; Step 7): annealing the multilayer film; Step 8): polarize the multilayer film, maintain the polarization field strength and cool to room temperature.

2. The preparation method according to claim 1, characterized in that: In step 2), the mass percentage of P(VDF-TrFE-P) in the obtained solution is 5-15wt%.

3. The preparation method according to claim 1, characterized in that: In step 2), the temperature of ultrasonic stirring is room temperature and the time is 4-8h.

4. The preparation method according to claim 1, characterized in that: In step 3), the mass percentage of P(VDF-TrFE-P) in the obtained dispersion is 5-15wt%.

5. The preparation method according to claim 1, characterized in that: In step 3), the ultrasonic treatment time is 1-3 hours, the ultrasonic stirring temperature is room temperature, and the time is 8-12 hours.

6. The preparation method according to claim 1, characterized in that: In step 4) to step 6), the thickness of the thin film formed each time is 10 to 20 μm.

7. The preparation method according to claim 1, characterized in that: In step 4) to step 6), the vacuum drying temperature is 85-95°C and the time is 3-5h.

8. The preparation method according to claim 1, characterized in that: In step 7), the annealing temperature is 110-150° C. and the time is 0.5-1.5 h.

9. The preparation method according to claim 1, characterized in that: In step 8), the polarization conditions are: polarization electric field strength 135-145 MV / m, polarization temperature 85-95° C., and polarization time 0.5-1.5 h.

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