Research On The Moisture Sensitivity Of Fe₂O₃-polyimide Flexible Composite Film

Polyimide?PI?is a good flexible moisture sensitive material.In recent years,more and more research and attention has been paid.Polyimide is used as a humidity sensitive film and it is made into a humidity sensor with a capacitance.Excellent characteristics,high sensitivity,short response time and good repeatability.Therefore,people pay more and more attention to PI film in the field of humidity measurement,which is called a flexible moisture sensitive material with unlimited future.Iron oxide?Fe₂O₃?,which is very sensitive to humidity signals,is widely used in the production of humidity sensors.In order to improve the moisture sensitivity of the material,it is usually achieved by controlling the material morphology,changing the particle size,and doping new materials.In this paper,two kinds of PI films were prepared by two-step method.Eight kinds of nano-Fe₂O₃ particles with different morphology were prepared by hydrothermal method.The flake-shaped,spherical,tire-like,rod-shaped nano-Fe₂O₃ particles were selected and different according to the way of body doping and surface doping.The doping concentration combines the nano Fe2O3 particles and the PI film to form a composite film.Based on the PI film moisture sensitive device test surface interdigital electrode structure and the capacitance characteristics of the upper and lower electrode plate capacitor structure,in response to recovery time,repeatability and other properties,after the experimental results,the aluminum interdigitated electrode was vapor-deposited on the surface of the composite film to prepare a wet Sensitive device.The devices prepared by different doping methods were tested for humidity.It is concluded that the humidity sensitivity of the tire-like Fe₂O₃-PI composite thin film device with 1%doping concentration is about 50 pF higher than that of the PI thin film humidity sensitive device.156%with a sensitivity of 1.87 pF/%RH.The response recovery time is not much different,the repeatability is good,and there is no large drift.The composite thin film device prepared by the surface doping method has a slightly poor effect on the humidity sensitivity,and the response time and repeatability are good.and the reproducible surface are good.