Fabrication and characterization of carbon nanotube–polyimide composite based high temperature flexible thin film piezoresistive strain sensor

• Piezoresistive effect was studied for carbon nanotube–polymer nanocomposite.
• Nanocomposite was also studied for its high temperature performance.
• Strain sensors based on the nanocomposite thin films using interdigital electrodes were fabricated and used to measure the static strain.
• The results were validated by theoretical calculation and measurements by impedance spectroscopy.

A high temperature strain sensor based on polyimide/single-wall carbon nanotube (SWCNT) composites was proposed. Sensors with different SWCNT contents ranging from 0.07 to 2.0 wt% were prepared. The electrical property of the composites was investigated by direct current (DC) resistance and electrical impedance spectroscopy. A simple equivalent model was used to estimate the resistance of the composite, and percolation theory was adopted to analyze the electrical property transition from insulator to conductor. The experiment results suggested the percolation threshold to be 1 wt%. Several strain sensors with different CNT concentrations in and above the percolation threshold range are characterized, and the test results show the optimum CNT concentration for the sensor to be 1.4 wt%. The strain sensors are also characterized under different temperature up to 265 °C for future high temperature application.