Twisted Conductive Fiber-Based Strain Sensor with High Sensitivity and Wide Working Range for Human Motion Recognition and Physiological Activity Monitoring

A strain sensor with high sensitivity and a wide working range is urgently required owing to its potential applications in wearable electronic devices. Nevertheless, high sensitivity, which includes a high gauge factor (GF) and a low detection limit, requires a noticeable structural variation even at a tiny deformation, while a wide working range requires maintaining morphological integrity under a large strain. The contradictory performances lead to a huge challenge to simultaneously acquire the aforementioned comprehensive performance. Herein, we prepared a twisted fiber-based strain sensor (TFSS) composed of a thermoplastic polyurethane (TPU)/silver nanoparticle (AgNP) fiber and a TPU/carbon nanotube (CNT) fiber. The special twisting structure and the synergistic effect of the different conductive materials endow TFSS with a high GF of 1.05 × 105 within a strain range of 250 ∼ 300%, ultralow detection limit (0.02% strain), large detection range (up to 300% strain), short response time (60 ms), and excellent sensing stability and durability (4000 stretching/releasing cycles under 50% strain). Moreover, the strain sensor can be used for diverse human movement recognition, microexpression detection, pulse/breath monitoring, and speech recognition, offering a promising strategy for designing high-performance and smart wearable devices.