Graphene oxide/graphite nanosheets composite thin films for wearable strain sensors

Facile fabrication of highly flexible and sensitive strain sensors is essential for emerging applications such as wearable electronics. Nanomaterials have been extensively explored as sensing elements to fabricate highly sensitive and stretchable strain sensors. Unfortunately, it is still a formidable challenge to develop a facile, low-cost, scalable approach to fabricate ultrasensitive strain sensors with excellent stretchability. Graphite nanosheets (GNs) consisting of multilayered graphene with a high electrical conductivity offer potential to producing wearable strain sensors at low cost due to its large-scale process via intercalation and expansion of natural graphite. We utilize the readily available graphene oxide (GO) and GNs as sensing materials to fabricate high-performance strain sensors using a simple, cost-effective and solution processable strategy. It is of interest to note that GO and GN sheets tended to self-adjust their basal plane parallel to the substrate and form partially aligned layers. The sensitivity and working range were controlled by adjusting the GO content. By controlling the content of GO, GO/GN composite strain sensors were endowed with tunable sensitivity and stretchability. With an addition of 15 wt% GO, the gauge factor considerably increased by ~1400% from 10 (without addition of GO) to 153 under 7% stretching deformation. This reported fabrication method can be extended to other 2D materials for many emerging practical applications, such as artificial intelligence, electronic skins, personalized health monitoring and human-machine interface.