Superior piezoresistive strain sensing behaviors of carbon nanotubes in one-dimensional polymer fiber structure

The fabrication of piezoresistive strain sensor with unified and balanced properties of high sensitivity, stretchability, and durability still remains a great challenge due to the oversimplified thin film structure of strain sensor. In this work, a high-performance strain sensor based on conductive poly(styrene-butadiene-styrene)/carbon nanotube fiber (SBS/CNT fiber, SCF) was prepared via wet-spinning. Then, the morphology, mechanical property, piezoresistive performance and sensing mechanism of the SCF-based sensors were systematically investigated. The resultant SCF-based sensors simultaneously demonstrated superior sensitivity (with a gauge factor of 175 under 50% deformation), wide workable range (>260%) and excellent durability due to the excellent flexibility of SBS polymer (the breaking elongation of pure SBS fiber > 1300%), high conductivity of CNT (10⁵ S/cm) and the strong π-π interaction between CNT and SBS. These properties make the composite fiber a perfect fit to monitor various large deformation in a wide range of applications. Moreover, the associated sensing mechanism was also systematically explained by tunneling theory and the evolution of the conductive network during the stretching-releasing process.