Stretchable and ultrasensitive strain sensor from carbon nanotube-based composite with significantly enhanced electrical and sensing properties by tailoring segregated conductive networks

Excellent electrical and sensing properties are highly desirable for flexible strain sensors based on conducting polymer composites (CPCs) aimed for wearable devices and soft robotics. Herein, a novel and simple but very effective strategy is developed to significantly enhance the electrical and sensing performance of flexible strain sensor through tailoring the segregated conductive networks (SCNs) of CPCs. First, thermally expanded microspheres (TEMs) are incorporated into CNT/Ecoflex (CE) composites to construct CPCs with unique SCN structures. The internal microstructures of the resultant TEM/CNT/Ecoflex (TCE) composites are further tailored through post-processing, thereby causing the reconstitution of the SCNs and improving their electrical and sensing performance. It is found that the electrical conductivity, percolation threshold, and sensitivity of the TCE composite strain sensor are all effectively improved through tailoring the SCNs. Specifically, the electrical conductivity is increased over 15 times, and the gauge factor (GF) is significantly improved by approximately 2465 times from a value of 176 to an extra-high value of 433992 at the strain of 130%. Finally, various application demonstrations are conducted in human motion monitoring and soft robotics. The post-processing concept introduced here presents a universal technology platform to further advance the electrical and sensing performance of CPCs for practical applications.

Automated summary

This article introduces a new strategy to significantly enhance the electrical and sensing performance of flexible strain sensors by tailoring the segregated conductive networks (SCNs) structure. By incorporating thermally expanded microspheres (TEMs) into CNT/Ecoflex composites and post-processing the internal microstructures, the SCNs are reconstituted, leading to greatly improved electrical conductivity, percolation threshold, and sensitivity. The post-processing concept presented here offers a universal technology platform for enhancing the performance of conducting polymer composites (CPCs) in practical applications.