Accuracy Improvement Of Piezoresistive Flexible Pressure Sensors And Application

With the rapid development of technologies such as artificial intelligence and the Internet of Things,flexible pressure sensors have attracted much attention due to their wide application in human-computer interaction,health monitoring,and electronic skin.Flexible pressure sensors can convert external pressure into electrical signals,and have excellent adaptability to the human body.Flexible pressure sensors can be divided into piezoresistive,capacitive and piezoelectric.At present,sensors require external power sources such as batteries.Based on thermoelectric to realize the self-powering of the flexible pressure sensor has the characteristics of continuous and stable energy supply.However,flexible thermoelectric devices remain the problem of low output voltage.Under the condition of low output voltage of flexible thermoelectric devices,the self-powering of flexible pressure sensors encounters new challenges.The organic conductive materials used in the flexible pressure sensor have the Seebeck effect,which will generate thermoelectric potential in an environment with temperature differences.The thermoelectric potential will cause deviations in the resistance measurement of the piezoresistive flexible pressure sensor and affect the accuracy of its pressure sensing.In this paper,in order to solve the problems in the practical application of the resistive flexible pressure sensor,we improved the sensing ability of the resistive flexible pressure sensors.By studying the self-powered flexible pressure sensor based on the thermoelectric principle,we analyzed the errors caused by the thermoelectric potential.Through suppressing the thermoelectric effect of the sensor by adjusting the Seebeck coefficient,the maximum error of 18.75%is successfully eliminated.Besides,a self-powered flexible pressure sensor based on the thermoelectric principle and the resistive sensing principle is prepared.The main research contents are as follows:First,using the high elasticity of the porous structure of the melamine sponge and single-walled carbon nanotubes which is easy to control the Seebeck coefficient,the single-walled carbon nanotube/melamine composite conductive sponge was prepared by dip coating process.The polyethyleneimine was used as a dopant to adjust the Seebeck coefficient of the composite sponge.We compared and analyzed the Seebeck coefficient of the composite conductive sponge under different doping process conditions,and successfully reduced the Seebeck coefficient of the composite conductive sponge from 13.12?V·K^-1 to-0.72?V·K^-1 by optimizing the process.A sandwich structure is used to assemble the piezoresistive flexible pressure sensor,and then the sensing properties of the resistive flexible pressure sensor including sensitivity,response time,minimum detection limit(LOD)and others were tested.Among them,we emphases on the influence of thermoelectric potential on sensitivity and pressure-resistance correspondence,and explain the reasons for the deviations caused by thermoelectric potential.Then,by suppressing the thermoelectric effect of the resistive flexible pressure sensor,the 18.75%resistance measurement error is successfully eliminated,and the sensing accuracy of piezoresistive flexible pressure sensor is improved under self-powered conditions.Through the doping effect of polyethyleneimine on single-walled carbon nanotubes,an N-type composite conductive sponge with a Seebeck coefficient of-16.12?V·K^-1was obtained.Using the N-type composite sponge and the undoped P-type composite sponge,a flexible thermoelectric device was assembled as the power supply.The flexible self-powered pressure sensor was installed in different parts of the human body for testing,which verified its application under low voltage working condition.