A Research On Fabrication And Structural Optimization Of Electrode Type Flexible Pressure Sensor

Pressure sensors can transform physical pressure signal to electrical signal,so they have great potential for the applications in automatic control,medical diagnosis,smart robots and touch screens.Among the pressure sensors,the flexible pressure sensors using the PDMS film as substrate can be applied to curved surfaces and tolerate buckling,so can work effectively in the harsh situation.This thesis presents a resistance-type flexible pressure sensor with an air gap structure.To make the CNT/PDMS flexible conductive film,we disperse the CNT powder in SDS solution and synthesize the CNT film on the MCE filter membrane by the vacuum filtration method.In order to separate the CNT film from the filter membrane,the researcher immerse the filter membrane loaded with the CNT film in acetone solution to dissolve the filter membrane.And this thesis use the ground glass chips and smooth glass chips as templates to make smooth PDMS film and micro-patterned PDMS film.Finally,the CNT film can be transferred onto the PDMS films formed the flexible conductive film.In this thesis,we use the scanning electron microscope,Raman spectrometer,diamonds resistance instrument to analyze the properties of the CNT/PDMS film.According to the test results,the CNT/PDMS film using the smooth PDMS film as substrate is uniform,stable and has perfect conductivity.To analyze the influence of the air gap structure on the pressure sensor and compare the performance of the pressure sensors with different structures,this thesis has assembled four kinds pressure sensors(the traditional pressure sensor,the pressure sensor with air gap structure with one layer PDMS strips,the patterned pressure sensor,the pressure sensor with air gap structure with two layer PDMS strips).Then the thesis test performance index of responsivity,stability,sensitivity and the low detectable pressure limit of four kinds pressure sensors.Among different kinds of pressure sensors,the pressure sensor with one layer PDMS strips has the highest sensitivity(58.9 kPa-1 in the range of 1-5 Pa,0.66 KPa-1in the range of 5-100 Pa)and the smallest low detectable pressure limit(1 Pa).So the air gap structure can improve the pressure sensors' performance.To analyze the mechanism of the pressure sensor,the thesis has built up themathematical model of the pressure sensors with air gap structure.To obtain the simulated results of the mathematical model,the thesis use Matlab software to calculate the responsivity of pressure under different test pressure.The simulated results conform with the test result of pressure sensors.