Mass production of carbon nanotube fibers and hybrid yarns for high-performance helical auxetic yarn strain sensors

With the spectacular physical properties of electrical conductivity, mechanical strength and thermal conductivity, carbon nanotube (CNT) fibers are favored in many fields such as energy storage devices, sensing, electromagnetic shielding and structural reinforcement, especially in flexible sensing devices. However, the lower tensile properties of CNT fibers limit their further application in stretchable strain sensors, especially when monitoring large deformation variables. Here, large-scale continuous production of CNT fibers has achieved through floating catalytic chemical vapor deposition (FCCVD) technology. In the meantime, the CNT fibers were hybrid with Kevlar fibers to obtain hybrid CNT yarns with the strength of 168.4 MPa and the electrical conductivity of 7.78 x 104 S m-1. The strength of the hybrid CNT yarns produced by this method is higher than that of 40 count cotton yarns, which is perfectly suited for the fabrication of textile devices. Through knitting with three-dimensional elastic fabrics, the textile-based sensors exhibit promising sensing ability, washability, weather tolerance and sweat resistance, owing to the excellent physical and chemical properties of the hybrid CNT yarns. Moreover, stretchable strain sensors exhibit fast response and cycle stability, which provides unique opportunities in designing smart textiles with fast response and environmental durability.