Liquid Metal–Tannic Acid-Modified Cotton Yarn Prepared with Twist-Assisted Deposition Technique for Textile Electronics

The past decade has witnessed the rapid growth of electronic textiles with a variety of textile-based smart devices being developed. However, the development of one-dimensional conductors that exhibit both excellent mechanical and electrical properties, while being compatible with conventional textile techniques, remains a challenge. Herein, a conductive cotton yarn was constructed using liquid metal as the conductive filler and tannic acid (TA) as the immobilizing linker via a twist-assisted deposition technique, in which eutectic gallium-indium alloy (EGaIn) droplets were effectively modified on cotton plies by using TA, followed by moderate twisting. By fully utilizing internal spaces between the adjacent fibers, the as-prepared EGaIn-TA-yarn exhibits high conductivity, with an average resistance of 11.20 Ω at a 10 cm length. When further wrapped with cotton fibers, the conductive yarn shows superior wash resistance, long-term stability, and excellent flexibility. It can withstand 25 washes, 3000 bending or twisting cycles, and 90 days of storage at ambient conditions without significant loss of conductivity. The cotton-wrapped EGaIn-TA-yarn could be used as a bendable, knottable, and sewable conductor to connect light-emitting diodes (LEDs) to power sources for lighting. This work could provide a simple, cost-effective approach to developing highly conductive yarns as promising candidates to replace traditional metal wires in textile electronics.