Flexible strain sensor based on CNT/TPU composite nanofiber yarn for smart sports bandage

As people pay more attention to physical health, smart textiles with motion detection functions are favored by consumers. Up to now, developing conductive composite yarns with high strain sensing performance that can be directly integrated into fabrics through textile technology is still a challenge. Here, we prepared a highly-stretchable carbon nanotube (CNT)/thermoplastic polyurethane (TPU) composite nanofiber yarn with a breaking elongation of up to 476% by dispersing CNTs uniformly into flexible TPU matrix and multi-needle liquid-bath electrospinning. The parameters about the preparation of the composite solution, electrospinning, and twisting were discussed and analyzed. On this basis, a highly-conductive dip-coating CNT/TPU composite nanofiber yarn (1.02 kΩ/cm) was developed by simply dip-coating CNT ink. The effects of coating methods on strain sensing performance and mechanism were explored according to the twisting structure of the yarn. This yarn-based strain sensor exhibited a high relative resistance change (440%) under 140% strain with satisfactory linearity and repeatability (1250 cycles). Finally, a smart sports bandage with sports auxiliary functions for badminton, basketball, running, and medical monitoring functions for heartbeat, respiration was developed by directly sewing the composite yarn into an elastic self-adhesive bandage. In the future, this yarn will be able to endow ordinary sportswears “intelligence” through simple sewing or embroidery.