Study On PDMS-Metal Film Friction Piezoelectric Conversion And Pressure Detection Performance

Pressure detection technology has a wide range of needs in the field of underwater engineering,such as ship draft detection,underwater robot state monitoring and so on.At present,people generally use solid materials with piezoelectric effect or polymer film materials represented by PVDF to transform pressure signal into electrical signal.However,solid materials are brittle,poor impact resistance and easy to fracture,and they are not suitable for movable mechanical joints.In order to produce piezoelectric effect,PVDF thin film needs to be polarized,and it is easy to be affected by other environmental parameters(such as temperature)besides pressure in use.In this thesis,a pressure signal conversion method based on the friction between PDMS and metal film under pressure is proposed,and its working mechanism is analyzed.By means of experiment and numerical simulation,the performance of pressure detection is studied systematically.The related research tasks are listed as follows:(1)A pressure detection system based on PDMS-metal film composite electrode is designed and experimental research is carried out.The results show that the output voltage of the electrode is directly proportional to the pressure applied on the electrode surface.When the load increases linearly from 0 to 5g,the output voltage of the 1mm thick composite electrode increases linearly from about OV to 0.08V,the slope of the output voltage curve is directly proportional to the change rate of the load.In addition,the amplitude of output voltage decreases with the increase of PDMS film thickness.When the thickness of PDMS film is 1O0?m and the speed of the injection pump is 0.7mL/min,the average output voltage of dynamic load detection is 0.9V,while when the thickness of PDMS is 1mm,the average output voltage of the same dynamic load is 0.3V.This is mainly because the thinner the PDMS,the smaller the deformation under the same load,the smaller the stored elastic potential energy,and the larger the corresponding electric potential energy increment.Because the capacitance of the double electric layer of the detection electrode is constant,the greater the increment of electric potential energy is,the greater the voltage is.(2)The deformation of PDMS layer of composite electrode was studied by numerical simulation and experiment.The results show that the PDMS shape variable increases with the increase of its thickness under the same load.This is mainly because the friction coefficient of PDMS surface increases with the decrease of thickness,and the smaller the thickness is,the less deformation is likely to occur.Specifically,when the pressure on PDMS film with thickness of 1mm and diameter of 2cm is 0.5N,the transverse extension of PDMS film is between 1 and 2?m and the compression is about 0.47?m.The numerical simulation results are in good agreement with the experimental results..In this thesis,the friction piezoelectric conversion method has the advantages of simple structure and high sensitivity.It provides a new idea and method for the development of new flexible pressure sensor with no power supply and pressure monitoring of unmanned underwater vehicle.