Flexible Metamaterial Absorber in Paper Substrate using Graphene Conductive Ink for WiMAX Applications

Graphene's unique electrical properties make it an ideal material for conductive inks, enabling efficient electromagnetic wave absorption at WiMAX (Worldwide Interoperability for Microwave Access) frequency bands. This paper presents the preparation of graphene-based conductive ink for use in flexible metamaterial absorbers on paper substrates, targeting WiMAX applications. The ink was synthesized to ensure homogeneous dispersion and excellent conductivity, suitable for printing on flexible, environmentally friendly paper substrates. The ink formulation consisted of 6% modified graphene, 0.75% cellulose acetate butyrate binder, and solvent. This ink formulation has a resistance value of approximately 22 Ω cm and sheet resistance of 7.6 Ω/square. The resistance of ink can be altered by changing the binder content for the different absorption ranges. The resulting metamaterial absorber demonstrated superior flexibility, light weight, and effective absorption performance within the WiMAX frequency range. The unit cell consists of a cross-shaped resonator and a thin layer of aluminum behind the ground layer. Cross-shaped layers of graphene ink are printed on Kodak printing paper, making them completely bendable along the surfaces. This flexible absorber is environmentally friendly because it does not waste chemicals and is biodegradable. A full-wave simulation was conducted for the graphene material absorber (GMA) prototype, and it was then fabricated using a two-axis computer numerical control (CNC) printer. The experimental results showed that the absorption of incident angle-insensitive GMA at 5.8 GHz reached 95%.