(1. College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China) (2. Key Laboratory for LiquidSolid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China)
Dielectric permittivity, a fundamental parameter of materials, is generally considered to be positive for conventional materials. Inspired by the negative parameters in metamaterials, Fan and his coworkers focus on the negative permittivity of percolative composites consisting of conductive filler dispersed in the insulative matrix and pioneer the experimental and theoretical study on epsilonnegative materials. When the content of conductive fillers is above but still near the percolation threshold in the conductorinsulator composites, the negative permittivity will be achieved by the lowfrequency plasmonic state in the conductive percolative network with inductive character, while the frequency dispersion of negative permittivity can be effectively adjusted by the LC resonance due to the capacitive character of isolated conductive fillers. Percolative composites provide a more flexible method for the design and regulation of epsilonnegative property because the conductive fillers have many choices in phases, metal or carbon, and in the morphology of sheet, fiber or particle. Moreover, polymer or ceramics can both serve as matrix. The epsilonnegative materials have potential applications in electromagnetic attenuation, capacitor, microwave antenna, and wireless power transmission.