Fabrication of flexible and sensitive resistance strain sensor by flexible TPU decorated with CQDs/TNC composite

Attaching flexible resistive strain sensors to human skin enables response detection of behaviours towards real-time physiological monitoring. However, current flexible resistive strain sensors hinder themselves from practical applications due to their low sensitivity, small linear working range, and poor wearing comfort. In this research, a conductive thermoplastic polyurethane (TPU) membrane is fabricated using TEMPO modified nanocellulose (TNC) decorated with carbon quantum dots (CQDs) to prepare flexible highly sensitive, and breathable strain sensors. Results show that the mechanical property and strain response range of the TPU membrane is significantly enhanced by CQDs-TNC. The TPU membrane also exhibits the highest sensitivity (GF= 49.4 in the 30∼80 % strain range) and a wide response range (0–80 %). At 5 %wt of CQDs-TNC, the membrane displays the highest elongation at break (389.8 %) with maximum breaking stress approaching 9.7 MPa. The CQDs-TNC/TPU membrane exhibits fast response and recovery times (85 ms and 93 ms), low hysteresis (8.9 %), and excellent dynamic cyclic strain performance (1000 stretch/release cycles). The CQDs/TMC/TPU-resistive strain sensor (CTT-RSS) sensor well conforms to human joints, and accurately produces real-time regular resistance strain responses based on human movements. In all, this study contributes a novel research design for fabricating flexible and sensitive sensor to the development of smart textiles.