Space-Confined Graphene Films for Pressure-Sensing Applications

Transferring the inherent physicochemical properties of monolithic graphene to its macroassemblies requires reasonable and controllable structural engineering. The elasticity has been considered to be an exclusive property of graphene. Although the elasticities for three-dimensional porous graphene frameworks (aerogel, foam, and sponges) have been intensively explored, this property for two-dimensional (2D) porous graphene films has rarely been investigated. Here we present an ultrafast, controllable, and energy-efficient strategy to prepare porous elastic 2D graphene films via flame-induced foaming within a confined space. Three types of graphene films with disordered, cellular, and lamellar microstructures (namely, DGF, CGF, and LGF, respectively) were fabricated via tuning of the sp2–sp3 domains in graphene oxide by thermally driven phase transformation. CGF exhibits the highest conductivity, elasticity, cut resistance, and foldability. These characteristics endow the CGF-based pressure sensors with high sensitivity (12.55 kPa–1), good linearity (0–50 kPa), and fast response (18 ms) and recovery (7.1 ms) times as well as outstanding cycling stability (10000 cycles). The pressure sensors were further applied for the voice recognition and monitoring of pulse waveforms. Finally, the fabrication of pressure sensor arrays was demonstrated, confirming substantial potentials for the construction of flexible electronic skins.