Piezoresistive effect of superelastic graphene aerogel spheres

Graphene aerogels have recently become one of the most attractive carbon metamaterials due to their unique properties such as ultralight weight, large specific surface area, high electrical conductivity and excellent compressibility. However, there still remain some challenges to efficiently fabricate superelastic graphene aerogels through the facile and cost-effective processes and assemble them into a well-designed unity for wider applications. Here we show superelastic grouped graphene/carbon nanotube (CNT) aerogel spheres (GCSs) for intelligent piezoresistive sensors by wet-spinning technique. With the synergistic effect of graphene and CNTs, such grouped GCSs with core-shell structure annealed at 1000 °C show excellent elasticity and fatigue resistance, which are comparable to those of graphene spheres annealed at 2500 °C. The grouped GCSs can fully recover after compression at 95% strain, and still retain 70% of maximum stress with negligible plastic deformation and structural damage even after 1000 cycles at 70% strain. Significantly, the robust, superelastic and conductive GCSs are suitable for pressure sensors, exhibiting extraordinary cycling stability and long working life. Due to intact and tough shells, the small-scale GCSs with high sensitivity can be easily assembled into stretchable piezoresistive sensors with pixel arrays for spatial pressure distribution measurement and object shape recognition.