Highly flexible and multifunctional CNTs/TPU fiber strain sensor formed in one-step via wet spinning

Elastic conductive fiber, owing to its soft and stretchable capability, makes it an ideal material for a wearable strain sensor. However, the incompatibility between the ultra-stretchable polymer matrix and the rigid inorganic conductors results in poor stretchability, low conductivity stability, and complex operation process. To overcome these drawbacks, high-stretched carbon nanotubes/thermoplastic polyurethane (CNTs/TPU) composite fibers have been fabricated through wet spinning in a simple one-step approach. By introducing rotating aqueous dispersion of CNTs as coagulating bath, the squeezed out TPU spinning solution could sufficiently adhere surrounding CNTs during double diffusion process of solvent and non-solvent medium. It has been demonstrated that the strain performance, strain sensing performance, and stability could be promoted by optimizing the rotation speed of the solidification bath. After being drafted and solidified in the bath with a rotation speed of 800 r/min (S-8), the obtained fiber has exhibited an outstanding working strain range of 200%, short response time of ≈ 0.18 s, and cyclic strain sensing performance. Besides, the obtained fiber has also exhibited exceptional Joule heating performance.