A flexible PTI-CNT strain sensor with high stretchable and sensitive for human movement and vocal cord vibration monitoring

Flexible strain sensors possess significant application potential in wearable electronics, as they enable the monitoring of physical signals from extensive human movements and subtle motions. Despite the increasing demand for conductive and elastic materials in strain-sensing applications for wearable electronic devices, attaining exceptional and balanced mechanical performance while maintaining high conductivity remains challenging. In this work, we developed a novel polyurethane elastomer sensor material (referred to as PTI-CNTs) composed of polycaprolactone triol (PCT-L), isophorone diisocyanate (IPDI) and carbon nanotubes (CNTs). The elongation at break of the PTI-CNTs 3% material can reach 866.70%, representing a 44.00% increase compared to pure PTI. The PTI-CNTs 3% sensors exhibited high sensitivity (GF = 23.12) and excellent stability (with the cycle stretching time exceeding 5000 s). The flexible sensors displayed a satisfactory response time of 300 ms, enabling the detection of extensive human movements, including bending of the finger, wrist, elbow, knee, and ankle, as well as subtle motions like swallowing and phonation. Due to the easy and economical fabrication process, high sensitivity, and good reversibility of PTI-CNTs 3% sensors, they have great potential for use in wearable health monitoring devices applications.