Preparation And Research On The Performance Of Flexible Temperature And Humidity Sensors

Temperature and humidity are two important physical quantities in nature,and their measurements are very important.Temperature and humidity sensors have been widely used in industrial and agricultural production,meteorology,medicine and other fields.In recent years,the Internet of Things is rising gradually,and electronic devices are also developing towards the trend of bending and folding.Research on the flexibility of traditional temperature and humidity sensors has begun.In this paper,a resistive flexible temperature sensor based on graphene/ CNTs and a capacitive flexible humidity sensor based on polyimide(PI)were prepared.The sensitive materials of the sensors have characterized,and the performance of the sensors are studied The main research contents of this paper are as follows:1.In this paper,graphene/CNTs thermosensitive film was sprayed on polyimide(PI)flexible substrate,then annealed and encapsulated.Scanning electron microscope,energy dispersive spectrometer and Raman spectroscopy were used to characterize the thermosensitive films.The characterization results showed that the film is composed of carbon series materials with good electrical conductivity.There are many folds in the film,and the folds are obviously reduced after annealing.The performance test of the sensor showed that the sensor has good linearity and good repeatability with the increase of test times.Carbon films are sensitive to humidity.Reseach showed that the resistance was no longer affected by the environmental humidity after encapsulating.This indicates that the encapsulation was reliable.After bending the sensor for many times,the temperature sensitive performance is almost not affected by repeated bending,which indicates that the sensor has good flexibility.The test results show that the sensor has not only the basic temperature-sensitive performance,but also good bendability.2.In this paper,polyamidoic acid(PAA)solution was chosen to obtain polyimide(PI)moisture sensitive film by spin coating and imide process,and conductive silver paste was printed on the PI film as electrodes.Two kinds of humidity sensors were obtained by using such structures as cross finger electrode capacitor and parallel-plate capacitor.Fourier transform infrared spectroscopy was used to characterize PAA and PI obtained by different heating temperatures.The characterization results showed that the imide degree of PAA increased with the increase of heating temperature.In this paper,the humidity sensor with parallel plate capacitance structure is selected for subsequent research.Test results show that the flexible humidity sensor based on PI has good linearity and repeatability,and the hysteresis is not obvious.After bending the sensor for many times,the sensor still shows good humidity sensitivity.The test results show that the sensor has good bendability.Furthermore,PI/GO composite film was prepared by spraying GO solution on the surface of PI moisture sensitive film.The composite film was characterized by scanning electron microscopy,and the characterization results showed that GO can be successfully adhered to the surface of PI by spraying,while a uniform GO layer cannot be obtained by soaking.After testing the flexible humidity sensor based on PI/GO,we found that the introduction of GO can improve the humidity response of the humidity sensor.However,Comparing with the pure PI flexible humidity sensor,the hysteresis of PI/GO flexible humidity sensor is somewhat increased.