Research On Flexible Pressure Sensor Based On Carbon Nanotubes/PDMS

Flexible pressure sensor is an electronic device that can be attached to various irregular surfaces to measure pressure.It is widely used in wearable devices and health detection.Carbon nanotubes are one-dimensional nano-materials with high electron mobility and good mechanical strength.Polydimethylsiloxane?PDMS?sponge has the porous structure which makes it have the good compression-recovery performance.Its internal cross-linked network structure ensures that carbon nanotubes and other conductive filler can be loaded to prepare the conductive material which could be widely used in flexible pressure sensors.In this paper,firstly,the carbon nanotubes/PDMS and Ag-carbon nanotubes/PDMS flexible pressure sensors were prepared by the dip-drying method through which carbon nanotubes and Ag-carbon nanotubes were loaded into the PDMS sponge,respectively.The relevant process parameters have been improved to obtain a pressure sensor with high sensitivity.Secondly,the sensitivity,stability,response time,recovery time and hysteresis of the flexible pressure sensor were tested in a self-built test system.Finally,we chose the flexible pressure sensor with the best sensing performance to prepare the wearable pulse sensor.The main conclusions of this thesis are as follows:1.The carbon nanotubes/PDMS flexible pressure sensor prepared by freeze-drying method had higher sensitivity than the flexible pressure sensor made by heat-drying.When the content of carbon nanotubes was 3.5wt%,the sensitivity of the sensor reached the maximum value of 41.651kPa^-1.The temperature and pressure coupled experiments were performed by using this flexible pressure sensor.The results show that,the temperature coefficient of the flexible pressure sensor remained at-0.900?/°C in a certain pressure range?0²0kPa?,so that the sensor can be used to detect the temperature under a certain pressure2.Ag-carbon nanotubes/PDMS flexible pressure sensor had a maximum sensitivity of 71.831 kPa^-1 when the content of Ag-carbon nanotubes was 5.0wt%,and hysteresis error reached a minimum value of 3.39%The flexible pressure sensor had excellent cyclical stability,good hysteresis,fast responsiveness and restorability?the response time and recovery time were 1.14s and 0.41s,respectively?.These good performances result from the modification of Ag nanoparticles onto carbon nanotubes,making the carbon nanotubes with a good dispersion and reducing the contact resistance between the carbon nanotubes so as to improve the sensing performance of the flexible pressure sensor.3.The Ag-carbon nanotubes/PDMS flexible pressure sensor can be used to detect the subtle pressure quickly and accurately so that it was used as wearable sensor to measure the radial artery wave of a human body.The results showed that the pulse of the tester was 76 times per minute under normal condition,and increased to 119 times per minute after the exercise,demonstrating that the sensor can be employed to measure the pulse of a human body accurately,which has the potential application in health care and any other fields.