High conductive free-written thermoplastic polyurethane composite fibers utilized as weight-strain sensors

Abstract Many stretchable conductive composite fibers exhibit high elongation at break, but most of them do not have a large workable strain range towing to the low conductivity when used as strain sensors. In this paper, we fabricated a highly conductive silver nanowire (Ag NW)/multi-walled carbon nanotube (MWCNT)/thermoplastic polyurethane (TPU) fiber via a wet-spinning process to improve the workable strain range of composite fibers. TPU was used as a matrix material to introduce superior stretchability. MWCNTs act as sensing elements and Ag NWs were used to increase conductivity. We investigated the effect of Ag NW content on the mechanical, electrical, and strain-sensing performance of the fiber-type strain sensors. The optimal content of Ag NWs extended the workable strain range as higher as 254% with an electrical conductivity of 0.803 S/cm. A weight-to-strain cloth sensor was assembled by writing Ag NW/MWCNT/TPU fibers in the coagulation solution. Furthermore, such composite fiber can be free-written into any designed pattern, which can be used to prepare fiber-based devices.