Highly sensitive flexible strain sensor based on carbon nanotube/styrene butadiene styrene@ thermoplastic polyurethane fiber with a double percolated structure

The combination of a high sensitivity and a wide strain detection range in conductive polymer composites-based flexible strain sensors is still challenging to achieve. Herein, a double-percolation structural fiber strain sensor based on carbon nanotubes (CNT)/styrene butadiene styrene (SBS)@thermoplastic polyurethane (TPU) composite was fabricated by a simple melt mixing and fused filament fabrication strategy, in which the CNT/SBS and TPU were the conductive and insulating phases, respectively. Compared with the sensor without the double percolated structure, the CNT/SBS@TPU sensor achieved a lower percolation threshold (from 2.0 to 0.5 wt%, a reduction of 75%), and better electrical and sensing performance. It is shown that the strain detection range of the CNT/SBS@TPU sensor increases with increasing CNT loading. An opposite trend was observed for the sensitivity. The 1%-CNT/SBS@TPU sensor exhibited a high conductivity (1.08 x 10(-3) S/m), high sensitivity (gauge factor of 2.65 x 10(6) at 92% strain), wide strain detection range (0.2%-92% strain), high degree of linearity (R-2 = 0.954 at 0-10% strain), broad monitoring frequencies (0.05-0.5 Hz), and excellent stability (2000 cycles). Moreover, the CNT/SBS@TPU sensor was shown to successfully monitor a range of human physiological activities and to be capable of tactile perception and weight distribution sensing.

Automated summary

A double-percolation structural fiber strain sensor based on CNT/SBS@TPU composite was fabricated, showing lower percolation threshold and better performance, achieving high sensitivity and wide strain detection range. The sensor exhibited high conductivity, sensitivity, broad strain detection range, and excellent stability, successfully monitoring a range of human physiological activities and demonstrating tactile perception and weight distribution sensing capabilities.