Ultra broadband electromagnetic wave absorbing and scattering properties of flexible sandwich cylindrical water-based metamaterials

Water-based electromagnetic wave absorbers have attracted significant attention due to their potential applications for conformal absorbing structures. In this paper, a flexible broadband electromagnetic wave metamaterial absorber (MMA) based on sandwiched cylindrical water resonators is designed and prepared via the 3D printing, which realizes a low and high frequency cooperative electromagnetic absorption in 4–40 GHz. Additionally, the proposed absorber shows a comprehensive performance with temperature insensitivity and broad absorption characteristics at wide incidence angles. The broadband perfection electromagnetic absorption is discussed based on the improved impedance matching induced by the sandwiched water resonators, and the enhanced electromagnetic wave loss introduced by connected water resonators would further improve the absorption efficiency. Particularly, the radar cross section (RCS) of the designed flexible MMA with different curvature also shows excellent conformal absorption in the evaluated frequency range. Therefore, the proposed flexible ultra-broadband MMA based optimized 3D patterned cylindrical water resonators shows excellent comprehensive performances, which could be widely utilized in electromagnetic protection applications for conformal devices.