A highly stretchable and transparent silver nanowire/thermoplastic polyurethane film strain sensor for human motion monitoring

Due to the motion artifacts and mechanical mismatches between the conventional rigid sensor and soft skin, flexible sensors have received extensive attention in recent years. In this paper, a AgNW-based strain sensor on thermoplastic polyurethane (TPU) substrates was fabricated via a transfer-printing technique. The effects of AgNW content on the mechanical, electrical, transparency, and strain-sensing properties of the composite films were investigated. A highly transparent AgNW/TPU composite film with a sheet resistance of 20.8 Ω sq−1 possessed a higher GF above 1000 with a narrower tensile range of 50–60%. The composite strain sensor was used to detect large human motions such as finger, elbow and knee bending, as well as subtle muscle contractions. Additionally, the fast response of this strain sensor to an external stimulus was demonstrated. This work provides an easy operating and low-cost method to fabricate highly stretchable, electrically conductive and transparent films, which could be applied to wearable electronics and health monitoring.