Liquid Metal Vacuoles

Abstract Conventional bubbles are generally made of an outside water film and the interior air, and their formation and rupture involve rich scientific knowledge. An intriguing question is what would happen if the water film and air of such bubbles were replaced by completely different fluids? Here, a high‐surface‐tension liquid metal‐solution bilayer is introduced into the two‐phase interface system, and a new conceptual hybrid vacuole consisting of a liquid metal outer membrane and inner solution core is proposed and demonstrated for the first time. Through tuning the filling volume of the liquid metal, various vacuolar structures with diverse interfacial morphologies are constructed. Such vacuoles can maintain long‐term stability via adjusting the composition of the solution, which is a mixture of surfactant and alkali. If switching glass substrate to graphite, liquid metal vacuoles would become more robust and exhibit further abundant individual and collective behaviors, which are mainly attributed to the firmer bonding strength between the two‐phase interfaces. In addition to interpreting the generation and maintenance mechanisms of the vacuole, different rupture processes are also presented and disclosed. The current findings on the liquid metal‐solution hybrid vacuoles are expected to enrich the content of liquid metal interfacial science, and will stimulate further promising applications in the emerging engineering fields.