Development Of A Flexible Humidity Sensor Based On PVDF

As an important physical quantity related to people's daily life,humidity affects us in the fields of agriculture,medicine,industrial manufacturing,meteorological observation,and artificial intelligence.Humidity usually refers to the content of water vapor in the air.People can detect the specific value of environmental humidity by using humidity sensors made of humidity-sensitive materials.For humidity-sensitive materials,most of the researches based on rigid materials on the market are relatively mature,but with the increasing demand for sensors and the development of wearable,human-computer interaction,electronic skin and other technologies,rigid humidity-sensitive materials Limitations in applications such as mechanical properties have gradually emerged.Humidity sensors based on flexible humidity-sensitive materials have received extensive attention from recent researchers due to their good mechanical properties,low cost,easy integration,and easy human-computer interaction.Not only that,researchers also hope to integrate temperature,humidity,pressure and other parameters closely related to people's lives on the same device,so as to further realize a multifunctional flexible sensor based on the same material.In flexible sensors,polymers are often used as sensitive materials.As a hydrophobic material,the moisture-sensitive properties of PVDF have always been difficult to develop,and the moisture-sensitive properties have become the main obstacle to the further multi-functionalization of PVDF.This article starts with the hydrophilic modification of PVDF,researches and analyzes the flexible humidity sensor based on PVDF,and after successfully fabricating the device,realizes the readout circuit of the device,and completes the design of the whole machine based on the PVDF flexible hygrometer.The main work of this paper is as follows.Preparation and characterization of PVDF composite film modified by PVDF doping to study its moisture-sensitive properties.Using polymer PVDF as the matrix material,doping PVA and Li Cl two humidity sensitive materials respectively,using spin coating to prepare PVDF composite film,and doping the film through FTIR,XRD,scanning electron microscope,deionized water droplet contact angle The humidity sensitivity characteristics before and after were analyzed,and the optimal doping ratio was found.The test results show that by doping PVA,the hydrophilic group(-OH)can be introduced into the PVDF film,and the surface of the PVDF film can be roughened to increase the specific surface area;at the same time,doping with Li Cl can enhance the ionization ability of the PVDF film to water.And because of phase inversion,a large number of microporous structures are brought about.When the two dopants are added at the same time,the contact angle of the deionized water droplets of the PVDF composite humidity-sensitive film can reach as low as32.8°,indicating that the PVDF composite humidity-sensitive film has the best affinity at this doping concentration.Water-based.Preparation of flexible humidity sensor based on PVDF composite humidity-sensitive film and various performance tests and research.The silver interdigital electrode was prepared on the PVDF composite humidity-sensitive film using magnetron sputtering and hard mask method,and the preparation of the flexible humidity sensor based on PVDF was completed.A humidity performance test platform was built to test and evaluate the sensitivity and hysteresis,response time and repeatability of the device,and the resistance to temperature changes of the device.And it has been applied to the detection of human respiratory frequency.The test results show that the flexible humidity sensor based on PVDF composite humidity-sensitive film has improved hydrophilicity and humidity sensitivity compared with devices prepared from undoped films,and has higher sensitivity and faster adsorption/desorption.The advantages of time and low hysteresis.Among them,the maximum sensitivity of the device with the best overall performance(PVDF:PVA:Li Cl=10:1:0.5)under the doping concentration(PVDF:PVA:Li Cl=10:1:0.5)is up to 441,the response time reaches12 s,and the hysteresis is 2.3%RH.The capacitance readout circuit based on the PVDF flexible humidity sensor was designed using the multi-resonant circuit,and the HS1101 commercial humidity sensor was used for theoretical verification before the combination,and finally the STM32 single-chip microcomputer minimum system board was used in the software combined with the look-up table method to realize the The whole machine design of the hygrometer of the PVDF flexible humidity-sensitive film has completed the actual design and application from the device to the whole machine.The test results show that the relative humidity of the PVDF-based flexible hygrometer for the relative humidity measurement of the environment and the commercial hygrometer is only 1.4%,which confirms the feasibility of this scheme.The test results show that the relative humidity of the PVDF-based flexible hygrometer for environmental relative humidity measurement and the commercial hygrometer is only 1.4%,and the measurement results are basically the same.