Foldable Metamaterial Absorber with Liquid Metal Printing on Paper

Metamaterials, characterized by their unique artificial periodic structures, exhibit extraordinary abilities in controlling electromagnetic waves not found in natural materials. Metamaterial absorbers, for example, have been developed by patterning solid conductive materials on dielectric surfaces. However, the foldability limitations of solid conductors make them unsuitable as foldable metamaterial absorbers since they lose those desirable properties when folded. To address this challenge, various methods using liquid metals have emerged, but they either require often necessitate structural frames or are primarily suited for hard surfaces, limiting their foldability potential. This study proposes an innovative solution involving the deposition of liquid metal onto paper surfaces to overcome foldability constraints. We design a metamaterial absorber with a circular pattern using three sheets of printing paper bonded with a film, leveraging these adhesive properties of oxidized gallium-based liquid metal to waterproof agent coated printing paper while preventing adhesion to laser-printed toner surfaces. The experimental results show that this absorber achieves an absorption rate of more than 90% in the frequency range of 10.36-10.76 GHz while being insensitive to polarization and incidence angle. Surprisingly, our proposed absorber retains its excellent performance even after being folded and unfolded up to 50 times. This foldable metamaterial absorber made of liquid metal is a promising solution for electromagnetic wave management applications requiring flexibility and adaptability.