Kernmantle structured stretchable strain sensors for biomechanical sensing in amphibious environments

The burgeoning field of flexible wearable electronics, crafted from lightweight and stretchable yarns, has captured widespread attention due to their promising roles in human health monitoring and personal health management. The quintessential wearable devices demand not only exceptional comprehensive performance but also a harmonious integration of conductive yarns into an assortment of apparel to ensure comfort while capturing different signals from the human body. However, producing yarns that can accommodate high loadings of functional materials and retain superb elasticity presents an inevitable challenge. To surmount this obstacle, here, a three-dimensional (3D) braided structure is developed to achieve contact -separation between the MXene-based thermoplastic polyurethane (TPU) fiber and silver nanowires (AgNWs)-based cotton fiber. This innovative structure preserves the inherent stretchability of the TPU while enabling the integration of functional materials. The resultant kernmantle yarn sensor (KMYS) features a low strain detection limit (0.01%), high sensitivity (gauge factor up to 948.16), ultrafast response time (71 ms), wide strain detection range (0-165%), and excellent reliability and stability (>10,000 cycles). These impressive strain -sensing properties empower the KMYS to accurately track both subtle and significant strain fluctuations in real-time - ranging from the delicate pulse signals at a fingertip to the pronounced movements of joints and the pressure exerted by the foot. This work is anticipated to establish a groundbreaking and viable approach for the large-scale production of highly sensitive strain sensors, tailored for monitoring human physiological and kinematic signals under different environmental conditions.