Flexible, graphene-based films with three-dimensional conductive network via simple drop-casting toward electromagnetic interference shielding

Abstract

Fabricating flexible and large-scale graphene-based films through a simple process to achieve excellent electromagnetic interference (EMI) shielding performance is still a daunting challenge. Herein, the flexible and large-area EMI shielding films with ultrathin coating thickness (i.e., 10 μm) and low coating density (i.e., 2.4 mg/cm2) were fabricated through a simple drop-casting approach by using graphene-based conductive ink at room temperature. With the aid of electromagnetic simulation, the optimal square resistance of conductive film for desirable EMI shielding effectiveness is predicted, avoiding the unnecessary costs of error and trial. To solve the vital issue of poor conductivity of reduced graphene oxide (RGO) arising from defects and the serious agglomeration of each filler in ink, a three-dimensional network was constructed by connecting RGO with flexible one-dimensional (1D) conductive fibers (i.e., carbon nanotubes (CNT) and Ag nanowire (AgNW)). The square resistance of the RGO/CNT@Epoxy/AgNW composite film could reach as low as 1.94 ± 0.63 Ω/sq, which exhibited the shielding effectiveness value of 40 dB at a minimum in 8.2–12.5 GHz. These attributes could satisfy the EMI shielding and flexibly conformal demands of most communication equipment.