Stretchable strain sensors based on conductive coating cracks with improved interfacial adhesion by wet phase separation treatment

Abstract

Stretchable strain sensors have drawn plenty of attention due to their importance and necessity in high-technology areas. In this study, we fabricated a series of thermoplastic polyurethane (TPU) film-based stretchable strain sensors with a conductive hybrid sensing layer of reduced graphene oxide (RGO) and multiwalled carbon nanotubes (CNT) by simple coating methods. Meanwhile, we developed a kind of roughening method based on wet phase separation to form interpenetrating micropores on the surface of the TPU film, which overcomes the sliding and overlapping of the RGO/CNT sensing layer by improving the mechanical interlocking between the hybrid sensing layer and the elastic substrate. Owing to the improved adhesion between the sensing layer and the elastomeric substrate, the stretchable sensor shows good sensitivity (gauge factor (GF) = 75 at 50% strain), linearity (logarithmic GF = 10 during 0–50% strain), and stability (more than 1000 stretching–releasing cycles at a strain of 50%). These high performances suggest the potential application of our strain sensor in the detection of human body movements, personal health monitoring, and other kinds of human–machine interfaces.