A method for preparing a multilayer transparent piezoelectric film sensor containing ZnO and rGO

Abstract

The application relates to the field of sensors and discloses a preparation method of a multilayer transparent piezoelectric film sensor containing ZnO and rGO. A small amount of propylene segments are introduced into P(VDF-TrFE) molecular chains to improve the flexibility, nano materials ZnO and rGO are added to greatly improve the piezoelectric performance 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, so that the transparent performance is better.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sensors, in particular to a preparation method of a multilayer transparent piezoelectric film sensor containing ZnO and rGO. BACKGROUND

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

[0003] However, on the one hand, the piezoelectric performance and flexibility of the existing P(VDF-TrFE) piezoelectric film sensor are not ideal, and on the other hand, the stability of the existing P(VDF-TrFE) piezoelectric film sensor in extreme environments is poor, and it is easy to be affected by environmental factors such as light and heat. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a preparation method of a multilayer transparent piezoelectric film sensor containing ZnO and rGO. A small amount of propylene segment is introduced into the P(VDF-TrFE) molecular chain to improve its flexibility, and nano materials ZnO and rGO are added to greatly improve the piezoelectric performance after polarization. Moreover, the introduction of ZnO not only improves the light and heat resistance of the piezoelectric film, but also reduces the color development of rGO, making its transparent performance better.

[0005] The specific technical scheme of the present application is: a preparation method of a multilayer transparent piezoelectric film sensor containing ZnO and rGO, comprising:

[0006] Step 1): Add initiator and water to the reactor and vacuum degas under cooling; pass gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene into the reactor at a molar ratio of 70-80:15-20:3-7, and the gas is liquefied after meeting the cold liquid copolymerization reaction; after reaction, cooling, separation, washing and drying, a terpolymer P(VDF-TrFE-P) is obtained.

[0007] The present application finds that introducing a proper amount of propylene chain segment 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 monomer should be controlled within a reasonable range, and if the molar percentage of each monomer is too high or too low, the piezoelectric performance or flexibility of the film will be affected.

[0008] Step 2): P(VDF-TrFE-P) is dissolved in N,N-dimethylformamide, and ultrasonic stirring is performed 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 at a mass ratio of 9.8-10.2:1:1.8-2.2, ultrasonic treatment is performed, and then the obtained dispersion liquid is ultrasonic stirred to finally obtain a ZnO / rGO / P(VDF-TrFE-P) dispersion liquid.

[0010] In the present application, the mass ratio of P(VDF-TrFE-P), ZnO powder and rGO powder is controlled at 9.8-10.2:1:1.8-2.2, and 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 film sensor will be short-circuited and cannot be tested; 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 aggregated, affecting the performance of the film sensor, and increasing the cost, which is not conducive to production. The mass ratio of ZnO powder and rGO powder should be controlled at 1:1.8-2.2, and if the molar ratio is too high, the heat conduction and electrical conductivity of the film will be reduced, and the environmental stability will be decreased; and if the molar ratio is too low, the film will be blackened, reducing the transparency of the film.

[0011] Step 4): The ZnO / rGO / P(VDF-TrFE-P) dispersion liquid is cast on a substrate to form a film, and vacuum drying is performed to obtain a ZnO / rGO / P(VDF-TrFE-P) single-layer film.

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

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

[0014] The pure P(VDF-TrFE-P) as the intermediate layer can ensure the transparency of the film and significantly improve the piezoelectric performance of the film. The double-layer film has a piezoelectric coefficient greater than twice that of the pure P(VDF-TrFE-P) film after polarization, which can significantly improve the piezoelectric effect of the prepared sensor.

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

[0016] The pure P(VDF-TrFE-P) as the intermediate layer and ZnO / rGO / P(VDF-TrFE-P) as the outer layer can ensure the transparency of the film and significantly improve the piezoelectric performance of the film without the need for evaporation of other conductive layers. The three-layer film has a piezoelectric coefficient greater than three times that of the pure P(VDF-TrFE-P) film after polarization, which can significantly improve the piezoelectric effect of the prepared sensor.

[0017] Step 7): Annealing the multi-layer film.

[0018] The formation of the β phase during annealing makes the film have better piezoelectric performance, and the T c and T m Annealing at a temperature between T

[0019] Step 8): Polarizing the multi-layer film, maintaining the polarization field strength and cooling 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 application uses N,N-dimethylformamide as a solvent, which is a low-volatility solvent, and slow evaporation 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, it will result in too much solution volume and too low solution viscosity, making it difficult to control the thickness of the generated film. If the mass percentage is too high, the solution volume is too small and the solution viscosity is too high, making it difficult to cast the required film.

[0022] Preferably, in step 2), the ultrasonic stirring temperature is room temperature and the time is 4-8h.

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

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

[0025] As preferred, in steps 4) to 6), the thickness of the film formed each time is 10-20 μm, and the optimal thickness is 15 μm.

[0026] As preferred, in steps 4) to 6), the temperature of the vacuum drying is 85-95℃, and the time is 3-5 h.

[0027] The evaporation temperature of the N,N-dimethylformamide solvent is 80-90℃, and therefore 85-95℃ is selected for the evaporation of the solvent.

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

[0029] The formation of the β phase in the annealing process makes the film have better piezoelectric properties, and the piezoelectric properties of the film are better than those of the film annealed at 130℃. c and T m Annealing at a temperature between T c and T m is beneficial to both the increase of the ferroelectric phase content and the increase of the β phase content, and 130℃ is in this interval and is the preferred annealing temperature.

[0030] As preferred, in step 8), the polarization conditions are: a polarization electric field intensity of 135-145 MV / m, a polarization temperature of 85-95℃, and a polarization time of 0.5-1.5 h.

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

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

[0033] (2) The present application adds the nano material rGO in P(VDF-TrFE-P), which can greatly improve the piezoelectric properties after polarization, improve the toughness and stability of the sensor; adds the nano material ZnO, which can greatly improve the piezoelectric properties after polarization, improve the sensitivity of the sensor to ultraviolet rays, gas, humidity, etc. and thus improve its stability, and also can reduce the opacity caused by the addition of rGO.

[0034] (3) The application adopts a preparation method of a sandwich type multilayer film sensor, taking P(VDF-TrFE-P) film as an intermediate layer and ZnO / rGO / P(VDF-TrFE-P) as an outer layer, which can greatly improve the piezoelectric effect, stability and toughness of the sensor, and also well maintain the transparency of the film itself.

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

[0036] The application will be further described below in combination with examples.

[0037] Example 1

[0038] Step 1): 0.15 g of potassium persulfate (K2S2O8) and 100 mL of deionized water were added to a 300 ml stainless steel container. The container was sealed and placed in a liquid nitrogen bath (-140℃), and then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers were pumped into the container and instantaneously liquefied at liquid nitrogen temperature. The feed molar ratio of the monomers was 76:19:5, which was controlled by the pumping time of each gas, and the reaction was carried out at 90℃ for 6 hours. After the reaction was completed, the container was cooled to room temperature, and the excess gas was carefully removed. The separated polymer was repeatedly washed with deionized water and methanol, and dried at 50℃ under vacuum, thereby obtaining 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 ultrasonic stirring was carried out at room temperature for 6h to obtain a 10wt% 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, ultrasonic treatment was carried out for 2h, then the obtained dispersion was ultrasonic stirred at room temperature for 10h, and finally a ZnO / rGO / P(VDF-TrFE-P) dispersion with a P(VDF-TrFE-P) concentration of 10wt% was obtained;

[0041] Step 4): Preparation of single-layer film: ZnO / rGO / P(VDF-TrFE-P) dispersion liquid was cast on the substrate to form a film, which was dried at 90℃ under vacuum for 4h to obtain a ZnO / rGO / P(VDF-TrFE-P) single-layer film with a thickness of 15μm;

[0042] Step 5): Preparation of double-layer film: P(VDF-TrFE-P) solution was cast on the single-layer film obtained in step 4) to form a double-layer film, which was dried at 90℃ under vacuum for 4h to obtain a double-layer film with a thickness of 30μm;

[0043] Step 6): Preparation of multi-layer film: ZnO / rGO / P(VDF-TrFE-P) dispersion liquid was cast on the double-layer film obtained in step 5) to form a three-layer film, which was dried at 90℃ under vacuum for 4h to obtain a multi-layer film with a thickness of 45μm;

[0044] Step 7): Annealing of multi-layer film: the multi-layer film was annealed at 130℃ for 1h.

[0045] Step 8): Polarization of multi-layer film: the polarization parameters were set as follows: polarization electric field strength 140MV / m, polarization temperature 90℃, polarization time 1h, and then the polarization was carried out, and finally the polarization field strength was maintained and cooled to room temperature.

[0046] The static piezoelectric coefficient d 33 was tested by using a piezoelectric coefficient tester, and the piezoelectric coefficient d 33 ~116pC / N, indicating that it has excellent piezoelectric performance; the sensor was tested by using a sensor piezoelectric performance test system, and the maximum sensitivity ~745.12mV / N was obtained, indicating that it has excellent piezoelectric response performance; the transmittance was tested by using a transmittance tester, and it was found that the transmittance ~91% was obtained, indicating that it has excellent transparency; after being irradiated by ultraviolet light for 24h, it was found that it could still maintain an output voltage of ~30.67V, indicating that it has excellent light resistance; after being subjected to 150℃ cyclic temperature rise and fall, 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 by using a cyclic load test device, 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 breaking elongation was tested by using a breaking elongation tester, and it was found that the breaking elongation was ~280%, indicating that it has excellent flexibility.

[0047] Comparative Example 1

[0048] Step 1): 0.15 g of potassium persulfate (K2S2O8) and 100 mL of deionized water were added to a 300 ml stainless steel vessel. The vessel was 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 were pumped into the vessel and instantaneously liquefied at liquid nitrogen temperature. The feed molar ratio of monomers was 80:20, controlled by the pumping time of each gas, and the reaction was carried out at 90 °C for 6 hours. After the reaction was completed, the vessel was cooled to room temperature and the excess gas was carefully removed. The isolated polymer was repeatedly washed with deionized water and methanol and dried under vacuum at 50 °C, thereby obtaining P(VDF-TrFE) powder.

[0049] Step 2): Preparation of pure P(VDF-TrFE) solution: P(VDF-TrFE) powder was dissolved in N,N-dimethylformamide, 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, rGO powder were dissolved in N,N-dimethylformamide at a mass ratio of 10:1:2, ultrasonically treated for 2 h, and then the obtained dispersion was ultrasonically stirred at room temperature for 10 h, finally obtaining a ZnO / rGO / P(VDF-TrFE) dispersion with a P(VDF-TrFE-P) concentration of 10 wt%;

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

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

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

[0054] Step 7): Annealing of multi-layer thin film: the multi-layer thin film was annealed at a high temperature of 130 °C for 1 h.

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

[0056] Comparative Example 2

[0057] Step 1): 0.15 g of potassium persulfate (K2S2O8) and 100 mL of deionized water were added to a 300 ml stainless steel container. The container was sealed and placed in a liquid nitrogen bath (-140℃), and then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers were pumped into the container and instantaneously liquefied at liquid nitrogen temperature. The molar ratio of the monomer feed was 76:19:5, controlled by the pumping time of each gas, and the reaction was carried out at 90℃ for 6 hours. After the reaction was completed, the container was cooled to room temperature, and the excess gas was carefully removed. The separated polymer was repeatedly washed with deionized water and methanol, and dried at 50℃ under vacuum, thereby obtaining 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, ultrasonically stirred at room temperature for 6 h, 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, ZnO powder were dissolved in N,N-dimethylformamide at a mass ratio of 10:1, ultrasonically treated for 2 h, and then the obtained dispersion was ultrasonically stirred at room temperature for 10 h, finally obtaining a 10 wt% ZnO / P(VDF-TrFE) dispersion;

[0060] Step 4): Preparation of single-layer film: ZnO / P(VDF-TrFE-P) dispersion was cast on a substrate to form a film, which was dried at 90℃ under vacuum 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 double-layer film: pure P(VDF-TrFE-P) solution was cast on the single-layer film obtained in step 4) to form a double-layer film, which was dried at 90℃ under vacuum for 4 h, to obtain a double-layer film with a thickness of 30 μm;

[0062] Step 6): Preparation of multilayer film: ZnO / P(VDF-TrFE-P) dispersion was cast on the double-layer film obtained in step 5) to form a three-layer film, which was dried at 90℃ under vacuum for 4 h, to obtain a multilayer film with a thickness of 45 μm;

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

[0064] Step 8): Polarization of the multilayer film: The polarization parameters were set as follows: polarization electric field strength 140 MV / m, polarization temperature 90 °C, polarization time 1 h, and finally the polarization field strength was maintained and cooled to room temperature.

[0065] Comparative Example 3

[0066] Step 1): 0.15 g of potassium persulfate (K2S2O8) and 100 mL of deionized water were added to a 300 ml stainless steel container. The container was sealed and placed in a liquid nitrogen bath (-140 °C), then degassed by a vacuum pump. Gaseous vinylidene fluoride (VDF), trifluoroethylene (TrFE) and propylene monomers were pumped into the container and instantaneously liquefied at liquid nitrogen temperature. The feed molar ratio of monomers was 76:19:5, controlled by the pumping time of each gas, and the reaction was carried out at 90 °C for 6 hours. After the reaction was completed, the container was cooled to room temperature, and the excess gas was carefully removed. The isolated polymer was repeatedly washed with deionized water and methanol, and vacuum dried at 50 °C, thereby obtaining 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, ultrasonically stirred at room temperature for 6 h, 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, rGO powder were dissolved in N,N-dimethylformamide at a mass ratio of 5:1, ultrasonically treated for 2 h, then the obtained dispersion was ultrasonically stirred at room temperature for 10 h, finally a 10 wt% rGO / P(VDF-TrFE-P) dispersion was obtained;

[0069] Step 4): Preparation of single-layer film: The rGO / P(VDF-TrFE-P) dispersion was cast on a substrate to form a film, which was vacuum dried 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 double-layer film: The pure P(VDF-TrFE-P) solution was cast on the single-layer film obtained in step 4) to form a double-layer film, which was vacuum dried at 90 °C for 4 h to obtain a double-layer film with a thickness of 30 μm;

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

[0072] Step 7): Annealing of multilayer film: The multilayer film was annealed at a high temperature of 130°C for 1h.

[0073] Step 8): Polarization of multilayer film: The polarization parameters were set as follows: polarization electric field strength 140MV / m, polarization temperature 90°C, polarization time 1h, and the polarization was carried out, and finally the polarization field strength was maintained and cooled to room temperature.

[0074] Comparative Example 4

[0075] Step 1): 0.15g of potassium persulfate (K2S2O8) and 100mL of deionized water were added to a 300ml stainless steel container. The container was 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 were pumped into the container and instantaneously liquefied at liquid nitrogen temperature. The feed molar ratio of the monomers was 76:19:5, which was controlled by the pumping time of each gas, and the reaction was carried out at 90°C for 6 hours. After the reaction was completed, the container was cooled to room temperature, and the excess gas was carefully removed. The isolated polymer was repeatedly washed with deionized water and methanol, and vacuum dried at 50°C, thereby obtaining P(VDF-TrFE-P) powder.

[0076] Step 2): Preparation of ZnO / rGO / P(VDF-TrFE-P) dispersion: P(VDF-TrFE-P) powder, ZnO powder, rGO powder were dissolved in N,N-dimethylformamide at a mass ratio of 10:1:2, ultrasonic treatment for 2h, then the obtained dispersion was ultrasonically stirred at room temperature for 10h, finally the ZnO / rGO / P(VDF-TrFE-P) dispersion with a P(VDF-TrFE-P) concentration of 10wt% was obtained;

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

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

[0079] Step 5): Preparation of the multilayer film: The ZnO / rGO / P(VDF-TrFE-P) dispersion was cast on the double-layer film obtained in step 4) to form a three-layer film, which was dried at 90℃ under vacuum for 4h to obtain a multilayer film with a thickness of 45μm;

[0080] Step 6): Annealing of the multilayer film: The multilayer film was annealed at a high temperature of 130℃ for 1h.

[0081] Step 7): Polarization of the multilayer film: The polarization parameters were set as follows: polarization electric field strength 140MV / m, polarization temperature 90℃, and polarization time 1h, and then polarization was performed, and finally the polarization field strength was maintained and cooled to room temperature.

[0082] Performance analysis

[0083]

[0084] From the above table data comparison can be seen:

[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, which is due to the introduction of a proper amount of propylene monomer in the polymer of Example 1, thereby improving the flexibility of the sensor.

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

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

[0088] Compared with Example 1, the piezoelectric coefficient d 33And the sensitivity is higher, which shows that the comparative example 4 has better piezoelectric performance, which is due to the middle layer also doped with rGO nanoparticles, which improves the piezoelectric performance of the sensor; The transparency of comparative example 4 is lower, which shows that example 1 has better transparency, which is due to the middle layer of comparative example 4 also doped with nanoparticles, thereby reducing the transparency of the sensor; The output voltage of comparative example 4 after 6600 cycles of load and the output voltage after various treatments are all higher, which shows that comparative example 4 has better light and heat resistance and stability, which is related to the piezoelectric coefficient and the doping of the middle layer of comparative example 4. The improvement of the piezoelectric coefficient causes the improvement of the output voltage, and the doping of the middle layer of ZnO nanoparticles slightly improves the light and heat resistance and stability.

Claims

1. A method for preparing a multilayer transparent piezoelectric thin film sensor containing ZnO and rGO, characterized by The application relates to a preparation method of a ZnO / rGO / P(VDF-TrFE-P) multilayer film. Step 1): adding an initiator and water into a reactor and vacuum degassing under cooling; Step 2): dissolving P(VDF-TrFE-P) in N, N-dimethylformamide and ultrasonically stirring to obtain a P(VDF-TrFE-P) solution; Step 3): dissolving P(VDF-TrFE-P), ZnO powder and rGO powder in N, N-dimethylformamide according to a mass ratio of 9.8-10.2:1:1.8-2.2, ultrasonically treating, then ultrasonically stirring the obtained dispersion liquid, and finally obtaining a ZnO / rGO / P(VDF-TrFE-P) dispersion liquid; Step 4): casting the ZnO / rGO / P(VDF-TrFE-P) dispersion liquid on a substrate to form a thin film and vacuum drying to obtain a ZnO / rGO / P(VDF-TrFE-P) single-layer 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 liquid 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): polarizing the multilayer film, keeping the polarization field intensity and cooling to room temperature. In step 2), the mass percentage of P(VDF-TrFE-P) in the obtained solution is 5-15wt%.

2. The method of claim 1, wherein: In step 2), the ultrasonic stirring temperature is room temperature and the time is 4-8h.

3. The method of claim 1, wherein: In step 3), the mass percentage of P(VDF-TrFE-P) in the obtained dispersion liquid is 5-15wt%.

4. The method of claim 1, wherein: In step 3), the ultrasonic treatment time is 1-3h and the ultrasonic stirring temperature is room temperature and the time is 8-12h.

5. The method of claim 1, wherein: In steps 4) to 6), the thickness of the film formed each time is 10-20mu.

6. The method of claim 1, wherein: In steps 4) to 6), the vacuum drying temperature is 85-95 DEG C and the time is 3-5h.

7. The method of claim 1, wherein: In step 7), the annealing temperature is 110-150 DEG C and the time is 0.5-1.5h.

8. The method of claim 1, wherein: In step 8), the polarization conditions are as follows: a polarization electric field intensity of 135-145MV / m, a polarization temperature of 85-95 DEG C and a polarization time of 0.5-1.5h.

9. The method of claim 1, wherein: ​

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