A stretchable and transparent strain sensor based on sandwich-like PDMS/CNTs/PDMS composite containing an ultrathin conductive CNT layer

Stretchable and transparent strain sensors based on conductive polymer composites (CPCs) possess potential applications in a variety of fields, including electronic skin, wearable electronics, and human motion detection. However, it is still a challenge to prepare CPC-based strain sensors with both good transparency and broad sensing range by a low-cost, facile, and scalable fabrication method. Herein, we report a simple spray deposition and transfer method to fabricate a stretchable and transparent strain sensor based on the sandwich-like polydimethylsiloxane (PDMS)/carbon nanotubes (CNTs)/PDMS composite containing with an ultrathin and uniform conductive layer. The fabricated strain sensors exhibit superb stretchability, good optical transparency, and excellent sensing performances, which can detect both the subtle and large strains with outstanding stability and repeatability. For example, the strain sensor based on PDMS/CNTs/PDMS composite (containing 0.16 mg/cm2 CNTs on the conductive layer) presents a good optical transmittance of 53.1% at 550 nm, broad sensing range of over 130%, and the ability to monitor both the subtle motions of facial expressions and the large motions of human joints, which has great potential applications in human motion detection, wearable electronics, and electronic skin.