Stretchable and Highly Sensitive Braided Composite Yarn@Polydopamine@Polypyrrole for Wearable Applications.

Flexible wearable devices for various applications have attracted research attention in recent years. To date, it is still a big challenge to fabricate strain sensors with a large workable strain range while maintaining their high sensitivity. Herein, we report the fabrication of highly sensitive wearable strain sensors from braided composite yarns (BYs) by in-situ polymerization of polypyrrole (PPy) on the surface of yarns after polydopamine templating (BYs-PDA). The electromechanical performance and strain sensing properties of the fabricated braided composite yarn@polydopamine@polypyrrole (BYs-PDA-PPy) were investigated. Due to the unique braided structure of BYs, the BYs-PDA-PPy strain sensors exhibit fascinating performance, including a large workable strain range (up to 105 % strain), high sensitivity (gauge factor of 51.2 in strain of 0%-40% and of 27.6 in strain of 40%-105%), long-term stability and great electrical heating performance. Furthermore, the BYs-PDA-PPy sensors can be used in real-time monitoring subtle and large human motions. The BYs-PDA-PPy strain sensors can also be woven into fabrics for large area electric heating. These results demonstrate the potential of BYs-PDA-PPy in wearable electronics.