Gallium Liquid Metal: The Devil's Elixir

Gallium is a metal that literally melts in your hand. It has low toxicity, near-zero vapor pressure, and a viscosity similar to water. Despite possessing a surface tension larger than any other liquid (near room temperature), gallium can form nonspherical shapes due to the thin, solid native oxide skin that forms rapidly in oxygen. These properties enable new ways to pattern metals (e.g., injection and printing) to create stretchable and soft devices with an unmatched combination of mechanical and electrical properties. The oxide skin can be transferred to other substrates and manipulated electrochemically to lower the interfacial tension to near zero. The reactivity of gallium can drive a wide range of reactions. The liquid state of gallium makes it easy to break into particles for making colloids and soft composites that have unusual properties due to the deformable nature of the filler. This review summarizes the truly unique and exciting properties of gallium liquid metals.