Physicochemical characteristics of bio-based thermoplastic polyurethane/graphene nanocomposite for piezoresistive strain sensor

Herein, we report the physicochemical characteristics and piezoresistive strain sensing performance of flexible thin film comprising graphene and bio-based thermoplastic polyurethane (TPU) prepared by solution cast method. A detailed analysis was carried to study the influence of graphene nanoplatelets on the morphological, thermal, mechanical, and electrical properties of TPU nanocomposite. Upon increasing the graphene nanoplatelets loading, the thermal stability and tensile properties improved remarkably, while glass transition temperature decreased slightly. Owing to better dispersion of graphene, the electrical conductivity was significantly increased, which broaden the utilization of the nanocomposite for various applications. The piezoresistive sensor was able to respond to various stress modes such as tapping, bending, and finger touch. The piezoresistive sensor was sensitive and achieved a gauge factor of 11. Sensor attached to finger, showed distinctive response upon bending at different angles and showed high stability and reproducibility even after >10,000 cycles under repetitive constant load. Also, the nanocomposite was able to detect any breakage or fracture in the form of change in electrical resistance. A combination of bio-based TPU and graphene offered improved physical properties and high sensing performance, which could be a potential material in flexible electronics and structural health monitoring systems.