Research On Flexible Pressure Array Sensor Based On Piezoresistivity Of Carbon Nanotubes/PDMS Composites

Flexible sensors as the basic core components of flexible electronics,are widely used in medical detection,sports health and other fields.Carbon Nanotubes/silicone rubber composites as sensitive materials for flexible pressure sensors is a new research direction.In this paper,a flexible pressure sensor array is designed and fabricated,aiming at the problems of complex structure,cumbersome fabrication process and not easy to fabricate in large area of flexible pressure sensors.The fabrication process,electrical and piezoresistive characteristics of the sensitive materials and the information of the sensors are also discussed.The data acquisition system has been studied.CNTs/PDMS conductive composites with piezoresistive effect were prepared by solution method using carbon nanotubes(CNTs)as conductive fillers and polydimethylsiloxane(PDMS)as matrix.The effects of preparation parameters such as concentration of CNTs/chloroform,ultrasonic power,ultrasonic time and temperature during dispersion on the conductivity of CNTs/PDMS composites were studied.The optimum preparation process of CNTs/PDMS composites with high flexibility and conductivity was obtained.The conduction mechanism in composites was analyzed by using macro conductive path theory and micro tunnel effect theory.The effects of CNTs concentration on the electrical and force-sensitive properties of CNTs/PDMS composites were studied.The percolation threshold of CNTs in PDMS was 4wt%,and the percolation area was from4wt%to 8wt%.The composites with different CNTs concentration were prepared in the percolation region and their piezoresistive properties were tested.The composites exhibited obvious positive piezoresistive effect in a certain pressure range.The composites with 6wt%CNTs concentration were the most suitable sensitive materials for sensors.Based on bulk resistance effect and interface piezoresistance effect,a 4x4 flexible array pressure sensor based on CNTs/PDMS composite material was designed and fabricated on flexible polyimide substrate fabricated by FPCB process.The size of the flexible array pressure sensor is 42x42mm~2,about 1mm thick.The design scheme and fabrication process were proposed.The scanning circuit of array resistance signal is designed by zero-potential method.The influence of circuit parameters on the error of scanning circuit is analyzed.A sensor testing system including hardware circuit and Lab VIEW software development is built.The signal reading and display are realized.The static characteristics of the sensor array are tested by the system.The application example shows that the flexible array pressure sensor and signal processing system can realize real-time monitoring of pressure distribution and size,which can provide reference for the design and preparation of flexible array pressure sensor.