Bio-inspired helical EGaIn/TPU conductive fibers fabricated by a twisted coating method for flexible electronics

Abstract

Flexible conductive fibers have garnered significant attention in the field of flexible electronics due to their knittability, breathability, and comfort. Inspired by the helical structure of the tendrils of climbing plants in nature, this study presents a method for fabricating flexible conductive fibers by coating twisted thermoplastic polyurethane (TPU) fibers with eutectic gallium–indium (EGaIn), using waterborne polyurethane (WPU) as a protective layer. This process enabled the production of single helix EGaIn/TPU conductive fibers (HETFs) and double-helix EGaIn/TPU conductive fibers (DHETFs). The HETFs demonstrate an outstanding electrical conductivity (2.68 × 10⁴ S cm⁻¹), excellent response to strain, ease of weaving, and good washability. These properties make them ideal for use as wearable flexible strain sensors that can accurately detect human motion. Additionally, according to the thermoplasticity of TPU fibers, they can be designed into a large helical structure combined with HETFs' helices to create novel fractal helical fibers. These fibers maintain excellent conductivity and stability under strains up to 1730%, with a quality factor of 2782, making them ideal for stretchable electrodes. The DHETFs not only have a strain response, but can also show a response to a finger in proximity, making them ideal for non-contact sensors. Overall, the helical EGaIn/TPU conductive fibers prepared by a twisted coating method show great potential for application in the fields of wearable electronics, flexible textiles, and non-contact sensing technologies.