Transformable soft liquid metal micro/nanomaterials

Liquid metal is a liquid-state metallic material with a low melting point at or around room temperature. Owing to their high thermal or electrical conductivity, low viscosity and superior fluidity, liquid metals are emerging as a highly desirable candidate in a broad array of areas, such as flexible electronics, thermal management, soft machines and biomedical materials. However, bulk liquid metal is not readily utilized because of its high surface tension and large dimension-induced dexterity limitations. To address this challenge, liquid metals have been innovated with micro/nanotechnology to endow the bulk liquid metals with remarkably diversified performances. These new functional materials not only possess the softness of classical liquid metals but also have many outstanding properties, including great thermal conductivity, self-healing ability and stimuli-responsive deformability. Compared to rigid inorganic micro/nanoscale materials, soft liquid metal micro/nanoparticles demonstrate their unconventionally superior flexibility, compliance and tunability. This review is dedicated to summarize the state-of-the-art progress in fabricating methods, highlight unique features, and discuss applications of liquid metal micro/nanoparticles in biomedicine, soft electronics, thermal management and soft motors. Future outlooks, including both opportunities and scientific challenges of liquid metal micro/nanoparticles, are also presented here.