Graphene and graphene-based materials gifted with high electrical conductivity are potential alternatives in various related fields. However, the electrical conductivity of the macro-graphene materials is much lower than their metal counterparts. Herein, we improved the electrical conductivity of reduced graphene oxide (rGO) based graphene assembled films (GAFs) by applying a series of compressive stress and systematically investigated the relationship between the compressive stress and the electrical conductivity. The result indicates that with increasing applied compressive stress, the sheet resistance increased as well, while the thickness decreased. Under the combined effect of these two competing factors, the number of charge carriers per unit volume increased dramatically, and the conductivity of compressed GAFs (c-GAFs) showed an initial increasing trend as we applied higher pressure and reached a maximum of 5.37 × 105 S/m at the optimal stress of 450 MPa with a subsequent decrease with stress at 550 MPa. Furthermore, the c-GAFs were fabricated into strain sensors and showed better stability and sensitivity compared with GAF-based sensors. This work revealed the mechanism of the tunable conductivity and presented a facile and universal method for improving the electrical conductivity of macro-graphene materials in a controllable manner and proved the potential applications of such materials in flexible electronics like antennas, sensors, and wearable devices.
Keywords: fabrication process; graphene assembled film; high electrical conductivity; strain sensor.