Wet-adaptive strain sensor based on hierarchical core-sheath yarns for underwater motion monitoring and energy harvesting

Bifunctional flexible electronics with motion monitoring and energy harvesting have broad application prospects in day-to-day activities of human society. Nevertheless, conventional electronics are difficult to adapt to the wear comfortability and anti-sensing interference properties in wet environments. Herein, a wet-adaptive spandex/graphene@cotton/polyurethane yarn (SGCPY) sensor is fabricated with excellent sensing and triboelectric performance, which comprises core layer of spandex fibers, middle layer of graphene@cotton sensing fibers and outer layer of spindle-knotted polyurethane nanofibers. Benefiting from its unique structure, as-prepared SGCPY sensor exhibits high mechanical properties (∼80 %), superhydrophobic performance (>130°), good strain sensitivity (1.82) and fatigue resistance (12,000 cycles) even under water condition. The usage of the SGCPY sensor is demonstrated for the stable monitoring of human body motions and human-machine interaction in both air and water environments. When SGCPY sensor weave as plain fabric, the textile also can convert various mechanical energy into electric power for driving electronic device, showing a maximum voltage of ∼3.9 V and ∼0.7 V with solid-solid and liquid-solid contact. This work fosters the in-depth study of textile-based electronics for underwater applications and highlights the promising prospects of multi-functional flexible electronics based on textiles.