Highly conductive, durable, washable, and scalable composite yarn for multifunctional wearable electronic applications

Fiber-based electronics with excellent flexibility and functionality have recently attracted widespread attention in the field of wearable devices. However, it remains challenging to develop conductive fibers with high electrical conductivity, efficient fabrication yield, and excellent durability simultaneously. Herein, a scalable continuous capillary dip-coating strategy was proposed to prepare washable carbon nanotube (CNT)/waterborne polyurethane (WPU) composite yarns. By the optimized two-step dip-coating and heat-stretching procedure, we achieve yarns with a high loading of 60 wt% CNTs and electrical conductivity of over 3 x 103 S/m. The excellent interfacial interaction between the polyvinyl pyrrolidone (PVP) in conductive layer and WPU in protect layer enables the ultra-high durability and stability of yarns. Consequently, conductive yarn showed high reliability upon microenvironment change of wearable interfaces in various temperature, humidity, aqueous acid, and alkaline solutions. The response to bending, friction, and washing in practical application is also marginal, which enable conductive yarn to construct conveniently wearable electronic devices for various applications through braiding technology. This work provides a simple route for the development of fiber-based electronics and promises satisfactory application in wearable flexible fabric devices.