Flexible liquid metal electromagnetic shielding materials

The demand for flexible shielding has been rapidly growing in recent years. Shielding materials using solid metals, carbon materials, or MXenes as shielding units usually have difficulty in combining high shielding and flexibility (stretching and bending characteristics), and thus they gradually fail to meet the shielding needs of flexible electronics. Therefore, shielding materials with both flexibility and high conductivity are urgent to fill this gap. Gallium-based room temperature liquid metal (LM) is an emerging functional material with a low melting point, low viscosity, low modulus, and easy modification. However, due to wettability and compatibility issues, it is difficult to apply bulk LMs directly in the field of electromagnetic shielding (EMS). The article reviews the fabrication methods, performance, and applications of LMs EMS materials from three perspectives: Macroscopic LMs, micro/nano-LMs, and LM-based composites. The gallium-based liquid EMS materials demonstrate the characteristics of high shielding performance with stretchability and a wide shielding band. In this review, different types of gallium-based LM materials are described from macroscopic to microscopic, from liquid to semi-solid, from high density to low density, from room temperature to ultra-low temperature, and from monolayer structure to multilayer structure. The prospect of LM materials as amorphous high-performance EMS materials is demonstrated in various applications, such as mobile communication, astronomical observation, radar, and medical detection, showing tremendous potential in the EMS field.