Gallium‐Based Liquid Metals: Optical Properties, Applications, and Challenges

Abstract Originating from the intrinsic metallic and liquid natures, gallium‐based liquid metals (Ga‐based LMs) have been greatly developed in the research of soft electronics, chemical synthesis, and other fields due to their fascinating characteristics. Meanwhile, the development and application of metal optics can help modern medicine and industry reach rapid developmental stages, such as disease imaging, photothermal treatment, and sensor detection. However, Ga‐based LMs have been much less explored in terms of their optical properties, particularly liquid alloys, and few reviews have contributed to their photonic applications. Ga‐based LMs can achieve wideband‐tunable plasmonic resonance and exhibit characteristic optical responses owing to their unique polymorphisms, undercooling, and superior mobility. Ga‐based LMs have broad applications in optical switches and memory, optical sensors, light sources, light‐driven micro or nano‐robots, photoacoustic imaging, and controllable metamaterials. In this study, recent progress in the optical properties of Ga‐based LMs and their potential applications are summarized. Current challenges in optical applications and future perspectives in this research field are summarized and discussed.