Fabrication of superior conductive composite yarn with 3D continuous CNT/WPU structure for high-performance stretchable heater and sensor

Composite yarns based on coating are suitable for broad application fields and massive production due to the flexibility, efficient fabrication, and economic feasibility. However, challenges remain for composite yarns to simultaneously meet the stringent requirements for stretchability, durability, and functionality in practical application. Herein, we report the fabrication of carbon nanotube (CNT)/waterborne polyurethane (WPU) composite yarn (C/WCY) by inducing CNT/WPU composite ink to construct a 3D continuous conductive structure in draw texturing yarn (DTY) through the capillary effect. Consequently, a high loading of 49 wt% CNTs and conductivity of over 2.3 × 103 S/m were achieved, which enabled C/WCY fast thermal response (120 °C within 8 s), long-term durability, superb electrothermal conversion efficiency (hr+c = 1.38 mW/°C), and excellent electrical properties. The stretchable heater and wearable sensors based on C/WCY were further achieved by braiding and weaving technology. This work offered new opportunities for scalable, fast, and low-cost fabrication of wearable electric devices.