AgNWs/TPU based Joule heating and strain sensing yarn with temperature visualization through the coordinated regulation of multiple conductive pathways for physical exercise and health monitoring

Flexible heating/strain sensing fiber devices have wide potential application in the fields of the real-time monitoring performance of human movement and physiological information and thermal management. However, there are still shortcomings in multi-functional integration and information visualization. In this work, the hollow thermoplastic polyurethane(TPU) nanofiber yarn was constructed by conjugate electrospinning technology, and Joule heating/strain sensing yarn was developed by continuous conductive treatment and twisting technology. Finally, the thermochromic sheath layer was constructed on the surface of the composite yarn to prepare the Joule heating/strain sensing yarn with the visible temperature(VHSY). The results showed that VHSY can detect both tensile and bending deformation. The excellent dynamic/static stability and durability were obtained as a flexible strain sensor. The GF values reached 23.08 in the strain range of 30 % and 170.02 in the strain range of 30 % to 50 %, respectively. In addition, VHSY exhibited a reversible color change of yellow-gray-blue-purple in the range of 25–60 °C, and the stable static and dynamic electric heating performance was obtained. The response times of heating and cooling temperature were 9.95 s and 10.62 s, respectively. VHSY held the excellent visualization function and strain sensing performance after 20 washes. This sensor has great potential applications for physical exercise and health monitoring. The work offers a novel strategy for the design of multifunctional yarn-based wearable devices and smart textiles.