A facile structural strategy for a wearable strain sensor based on carbon nanotube modified helical yarns

Wearable sensors have gained considerable popularity due to the potential feasibility in flexible electronics. In this work, a facile fabrication strategy for a wearable strain sensor is presented based on a hierarchical-gap response mechanism. A double-helical-structured elastic string was employed as the stretchable substrate, and carbon nanotubes were chosen as the resistance-sensitive nanostructures. A CNT-modified elastic string (CES) was obtained by directly coating CNTs onto the substrate. After polydimethylsiloxane encapsulation, a fiber-shaped resistive-type strain sensor was fabricated. It was attached to different joints for human body motion monitoring. The double-helical structure could produce hierarchical gaps as the applied strain increased, which served as spatial complements to allow a well-connected structure to be formed. The CES sensor could accurately capture different levels of strain caused by physiological signals and joint motions. This facile fabrication strategy is expected to be used to produce large-scale strain sensors with ultra-sensitivity.