Preparation And Application Of Non-Contact Pyroelectric Sensor Based On Polyvinylidene Fluoride

With the development and popularization of intelligent terminals,people have put forward higher requirements for the portability and effectiveness of human-machine interaction.Non-contact sensing,as a technology that can achieve information interaction without physical contact,is widely used in electronic products,such as smartphones,tablets,vehicle display equipments,and smart wearables.Recently,the development tendency for terminal products is gradually moving towards high-integration and lightweight,as well as intelligent terminals mostly use screens as carriers to realize the feedback of interactive information.Therefore,this thesis aims to develop PVDF-based pyroelectric sensors that possess the features of miniaturization,flexibility,foldability,self-power,and easily to integrate with screen,thus achieving the functions of non-contact sensing.Because the PVDF-based materials exhibit a lower pyroelectric property compared to single crystal materials and metal oxide ceramic materials,this thesis improved the pyroelectric performance of the material by selecting PVDF-based copolymers with different molecular structures,optimizing the film preparation process,and introducing 2D-BP for composite with copolymers.Based on the above,further research was conducted on the electrical properties of PVDF-based pyroelectric sensors and exploration in different application scenarios.The specific contents are as follows:Firstly,characterization and measurement of PVDF-Tr FE with different molar ratios(VDF and Tr FE)to screen the material with the strongest pyroelectric performance.Followed by optimizing the preparation process of PVDF-based copolymer films,and investigating the effects of the preparation process with different drying methods and temperatures on the pyroelectric property.Finally,2D-BP was added in the PVDF-based copolymer to facilitate the orientation of dipoles,effectively increasing the residual polarization strength of the composite film and thus strengthening the pyroelectric property.Subsequently,the electrical properties of PVDF-based pyroelectric sensors were investigated,the as-fabricated sensors revealed a detection limit as low as 0.5 ℃,and the intensity of output signal strengthens with the increase in temperature of heat source as well as a decrease in distance between sensor and heat source.Furthermore,the thesis demonstrates the application in diverse fields of levitation touch,gesture recognition,and respiratory monitoring.In the field of levitation touch,the “touch” behaviors without physical contact can be executed through the pyroelectric sensor to sense the heat radiation from the human body,while the body is gradually close to the sensor.In the field of gesture recognition,the monitoring of body movement trajectory can be achieved through the sensor array,because the output signal intensity of sensor is associated with the distance between the limbs and sensor.In the breath monitoring field,the sensor can be integrated into a mask to monitor breath,because the respiratory causes the flow of air with different temperatures,thus driving the operation of sensor.All experimental results indicate that the PVDF-based pyroelectric sensor has good electrical properties and promising application in the field of non-contact sensing.