ZnO nanowires–polyimide nanocomposite piezoresistive strain sensor

In this paper, we report a significant piezoresistive effect found in ZnO nanowires–polyimide nanocomposite. ZnO nanowires were synthesized through a simple hydrothermal route and subsequently mixed with polyimide matrix to form ZnO nanowires–polyimide nanocomposite. Electrical properties of the nanocomposite films, such as electrical conductivity, relative dielectric permittivity, impedance spectrum and electrical I–V curve, change with weight ratio of ZnO nanowires were characterized. Electrical measurement results indicated that the percolation threshold of the nanocomposite is about 15% weight ratio of ZnO nanowires. Piezoresistive effect of the nanocomposite was investigated and large gauge factor was observed for this nanocomposite. Strain sensors based on the nanocomposite thin films using interdigital electrodes were fabricated and used to measure the static and dynamic strain in a cantilever beam and the results were validated by theoretical calculation and measurements by other technique. With excellent flexibility, simple fabrication process, and large piezoresistive gauge factor, this novel ZnO nanocomposite can be used for strain sensors in many mechanical, civil, aerospace, and medical applications.