A high stretchability fiber based on a synergistic three-dimensional conductive network for wide-range strain sensing

Fiber strain sensors are promising for constructing high-performance wearable electronic devices due to their light weight, high flexibility and excellent integration. However, the conductivity of most reported fiber strain sensors is severely degraded, following deformation upon stretching, and it is still a considerable challenge to achieve both high conductivity and stretchability. Herein, we have fabricated a fiber strain sensor with high conductivity and stretchability by integrating the AgNPs into the multi-walled carbon nanotube/graphene/thermoplastic polyurethane (MWCNT/GE/TPU) fiber. The tunneling-effect dominated MWCNT/GE layer bridges separated AgNP islands, endowing conductive fibers with the integrity of conductive pathways under large strain. By means of the synergistic effect of a three-dimensional conductive network, the fiber strain sensor of AgNPs/MWCNT/GE/TPU presents not only a high conductivity of 116 S m^-1, but also a wide working range of up to 600% and excellent durability (8000 stretching-releasing cycles). Remarkably, benefiting from the crack propagation on the brittle AgNP layer, the fiber strain sensor exhibits a large resistance change in the strain range of 500-600%, and thus high sensitivity with a gauge factor of 545. This fiber strain sensor can monitor human physiological signals and body movement in real-time, including pulse and joint bending, which will contribute to the development of smart textiles and next-generation wearable devices.