Low-profile reconfigurable saline water-based ultrawideband metamaterial absorber

Abstract Saline water solutions are widely used in the design of electromagnetic absorbers due to their high dielectric loss. However, most of the saline water solution-based absorbers are not reconfigurable. In this work, we propose a low-profile, reconfigurable saline water-based ultra-wideband metamaterial absorber. Two types of dielectric resonators, pyramid-shaped and cube-shaped cavities, are filled with saline water to create multi-frequency resonances and realize ultra-wideband absorption. We fabricate an absorber sample with 3D-printing technology and conduct experiments. It is demonstrated that the absorber exhibits an absorptivity of over 90% for electromagnetic waves within 6.7~63GHz, with a relative bandwidth of 161.5%. The absorption performance remains stable under different incident angles of different polarizations, and the absorber can maintain a high absorbing capacity at different temperatures. Emptying the saline water causes complete reflection of all electromagnetic waves from 1GHz to 53GHz. Furthermore, the infrared radiation of the absorber can be effectively controlled at a low level by introducing cryogenic saline water. This saline-based reconfigurable absorber can find potential applications in electromagnetic camouflage and protection in military scenarios.