Abstract
Epsilon-near-zero (ENZ) materials are promising candidates in the fields of sensing technologies, solar energy harvesting, and electromagnetic absorbers, and most research on ENZ materials is focused at visible, infrared, and terahertz wavelengths. However, the report about ENZ materials at radio frequency is rare. In this work, flexible polystyrene/graphene (PS/GR) metacomposites exhibiting ENZ properties at radio-frequency region were fabricated by solution mixing assisted with non-solvent induced phase separation (NIPS) strategy and the hot press method. The NIPS strategy greatly improved the dispersion and distribution of GR nanosheets in PS matrix, allowing GR nanosheets to disperse in PS solution without delamination within 72 h. The microstructure, crystalline structure, chemical composition, mechanical properties, and electrical and dielectric properties were investigated. When GR content reached 30 wt%, the continuous conductive GR network was formed, and the epsilon-near-zero at around 920 kHz accompanied by the transition of permittivity from positive to negative was observed, ascribing to the resonance of the induced electric dipoles from GR nanosheets' surfaces. The equivalent circuit analysis showed that the appearance of inductors was significant for the realization of ENZ and negative permittivity. The flexible PS/GR composites with ENZ properties at radio frequency show great potentials in the fields of wearable materials such as invisibility cloak, drug delivery, and soft robotics.