Bicontinuous Bilayer Metacomposites Containing Corncob‐Derived Carbon and Polyaniline for Tunable Epsilon‐Near‐Zero and Epsilon‐Negative Responses

Metacomposites can achieve epsilon-negative (ɛ' <0, EN) and epsilon-near-zero (ɛ' ≈ 0, ENZ) responses below the GHz band, thus providing a brand-new design principle for developing meta-structure electronic components. However, its negative response presently cannot fully cover the kHz-MHz band and is thus constrained by an unclear regulation mechanism. This study offers a corncob-derived carbon/polyaniline (CC/PANI) metacomposite featuring a bicontinuous bilayer architecture to match the electromagnetic response in the frequency band of 10 kHz-45 MHz. The elaborately designed structure has achieved precisely controllable EN values of the order of 10⁵ and ENZ effect within the range of ≈123 to ≈189 kHz. The variable bicontinuous characteristics arise from the random CC network and the conductive PANI network, enabling tunable ENZ and EN properties of metacomposites. The ENZ responses are modulated by the bicontinuous bilayer structure due to the competition between the dielectric resonance of electric dipoles and the plasmonic state of free electrons. Additionally, the incorporation of randomly CC enhances the hydrophobicity, corrosion resistance, and thermal insulation of metacomposites. The work provides an attractive strategy for the recovery of biomass and their effective utilization in the field of metamaterials, also effectively helps expanding the EN response band and clarify its regulation mechanism.