Printed strain sensor based on silver nanowire/silver flake composite on flexible and stretchable TPU substrate

A novel printed strain sensor, based on metal-metal composite, was developed for applications in the biomedical and civil infrastructural industries. The sensor was fabricated by screen printing a silver nanowire (Ag NW)/silver (Ag) flake composite on a flexible and stretchable thermoplastic polyurethane (TPU) substrate in two design configurations: straight line and wavy line. The capability of the fabricated strain sensors was investigated by studying its electro-mechanical response towards varying elongations. Average resistance changes of 104.8%, 177.3% and 238.9%, over 100 cycles, and 46.8%, 141.4% and 243.6%, over 200 cycles, were obtained for the sensors with the straight and wavy line configurations at elongations of 1 mm, 2 mm and 3 mm, respectively. A sensitivity of 21% and 33%, in resistance change for every 1% strain, was calculated for the printed strain sensors with the straight and wavy line configurations, respectively. The results obtained thus demonstrate the feasibility of employing conventional addictive screen printing process for the development of strain sensors for applications that require a flexible and stretchable form factor.