Porous and anisotropic liquid metal composites with tunable reflection ratio for low-temperature electromagnetic interference shielding

Abstract Materials providing electromagnetic interference (EMI) shielding at low temperature are highly desirable for cryogenic electronic equipment. However, the structure of conventional shielding material may be affected by thermal stress at cryogenic conditions, which is harmful to their shielding performance. Here, we demonstrate the potential of a porous and anisotropic gallium-indium-alloy (liquid metal) based composite as low-temperature shielding materials (LTSMs). LTSMs at 77 K exhibited EMI shielding effectiveness of ∼80 dB, which is superior to that at 300 K (∼20 dB) in 8–12 GHz. This upsurge mainly originates from the newly-formed conductive path induced by expansile liquid metal particles after the liquid-solid phase change. Besides, the porous structure and anisotropy of conductivity offered by LTSMs enable them to alter the reflection coefficient from 40% to 85% by adjusting the direction of incident electromagnetic waves. This adjustable material provides a new option for shielding protection, especially at the cryogenic conditions.