Solvent frost heave-driven relaxation of conductive network in carbon blacks/polyurethane fibers towards highly sensitive sensor

Resistance-responsive fibers for detecting strain sensitively have drawn widespread attentions in human motion monitoring. In this work, carbon blacks/polyurethane (CBs/PU) fibers with sensitive strain-response were fabricated by precisely tuning the carbon black nanoparticles into a critical-formed conductive network. This was achieved by utilizing the frost heave of solvent inside the porous fibers, to drive the relaxation of percolation network. The fibrous sensor exhibited high sensitivity for detecting tensile strain with a detection limit of 0.1%, as well as a fast response (80 ms) and recovery (160 ms) time, excellent linearity (R2> 99%) in the strain range of 0–20% with a high Gauge Factor (GF) of 17.8. Moreover, it presented superior cyclic stability, revealing its potential applications in precise monitoring of tiny strains. This work provides a novel strategy basing on ice frost heave for precisely regulating conductive networks, which facilitates the design and fabrication of highly sensitive strain sensors.