Dip-Coated Conductive Polyurethane Fibers Composited with Liquid Metal Particles and Multiwall Carbon Nanotubes for Multifunctional Applications

Currently, highly stretchable conductive fibers have become one of the most important components of flexible electronics due to their excellent conductivity, adaptability, and knittability. In this work, a conductive fiber was developed with a thermoplastic polyurethane (TPU) core and a composited conductive sheath of liquid metal particles (LMP) and multiwall carbon nanotubes (CNTs) by simply dip coating and then was permeated and encapsulated by a waterborne polyurethane (WPU) layer. After mechanical sintering, the resulting WPU/LMP-CNTs/TPU fiber (WLCTF) exhibited ultrahigh conductivity, reaching 1.15 × 106 S/m, along with remarkable linearity (R2 = 0.997) across a large strain range of 160%. The WLCTF was molded by thermoplastic process into stretchable helical electrodes, which provided a stable signal output at 1700% strain with an extremely high-quality factor of 5483.9 (helical index of 7). Notably, these fibers can be woven into fabric substrates to possess Joule heating capabilities and waterproof properties; in addition, the WLCTF is engineered with efficiency in recycling. With its consistent strain sensing capabilities, electrical conductivity, recyclability, and Joule heating properties, the WLCTF holds significant potential for advancement in the fields of flexible electronics and wearable technology.