Frequency-selective and tunable electromagnetic shielding effectiveness via the sandwich structure of silicone rubber/graphene composite

Abstract

Flexible electromagnetic interference (EMI) shielding materials are urgently required considering the rapid development of flexible electronics, such as foldable displays, fast-growing micro-robots, wearable devices, and sealing elements. In this study, a novel flexible sandwich-structured silicone rubber (SR)/graphene composite with a unique feature of frequency-selective EMI shielding effectiveness (SE) and insulation in shielding direction was achieved through the selective localization of graphene at the surface layers of SR. The average and maximum EMI SE values were 30.42 dB and 34.72 dB, respectively, with a graphene content of 3.00 wt%, indicating a 59.60% and 72.39% increase higher than those of their homogenous-structured composite counterparts. In addition, a frequency-selective EMI SE was observed in the sandwich-structured composite, which was ascribed to the Fabry–Pérot cavity resonance. The position of the shielding peak could be tuned by adjusting the thickness of the interlayer and graphene content in the surface layers. Moreover, it has been confirmed that the insulation of the interlayer is necessary for the appearance of the shielding peak. The flexible EMI shielding materials designed in this study will benefit the booming production of flexible electronic devices and offer a promising strategy for fabricating new-generation EMI shielding materials with frequency-selective and tunable EMI SE.