Multifunctional wrinkled nacreous all-carbon films for high-performance stretchable strain sensors and supercapacitors

Achieving high stretchability and sensitivity in strain sensors remains a challenge in the development of high-performance wearable devices. In this study, drawing inspiration from wavy nacre surfaces, we developed wrinkled “brick-and-mortar” composite structures by mixing reduced graphene oxide (rGO) sheets as “bricks” and carbon nanotubes (CNTs) as “mortar” to simultaneously address two conflicting sensing metrics: stretchability and sensitivity. While cracks formed on the rGO layers after the wrinkles were removed during stretching, the fractured rGO islands were bridged by long and entangled CNTs, maintaining electrical connections. Therefore, strain sensing using the wrinkled rGO/CNT film achieved a high stretchability of 617%, a high gauge factor of 1472, a detection limit as low as 0.5% strain, and high repeatability during 10 000 stretch-release cycles. Furthermore, the porous all-carbon structure of the rGO/CNT film was appropriate for constructing a stretchable supercapacitor. The solid-state symmetric supercapacitor with a gel electrolyte exhibited a high specific areal capacitance of 34 mF cm⁻² at 0%, 50%, and 100% strain. Because of the porous all-carbon structures with microscale wrinkles and nanoscale nacre-like configurations, the wrinkled rGO/CNT film has great potential as a multifunctional carbon film for various wearable devices.