Spontaneous Dispersion and Large-Scale Deformation of Gallium-Based Liquid Metal Induced by Ferric Ions

A gallium-based liquid metal (LM) exhibits the largest interfacial tension among all the room-temperature liquids, which gives it strong deformability and promises its role in the field of soft machines. Paradoxically, such a material always remains nearly spherical in solution because of large interfacial tension, which in turn hinders the construction of LM-based soft machines. Consequently, it is of significant theoretical and practical value to regulate the interfacial tension of a LM in order to carry out richer deformation. In this study, spontaneous dispersion and large-scale deformation of a bulk LM were disclosed to be induced by ferric ions. It was found that the bulk LM immersed in the FeCl₃ solution can spontaneously disperse into a large amount of droplets. In addition, the dispersed LM droplets could move and deform by increasing the concentration of the solution or adding acids. The mechanisms behind the untraditional phenomena lie in the nonuniform interfacial tension over the entire surface of the LM, which is associated with the space-time distribution of the FeCl₃ solution. Further, directional locomotion and periodic oscillation occur because of the nonuniform interfacial tension, which leads to the autonomous dispersion and deformation of the LM. Overall, the unique redox reactions between the LM and the FeCl₃ solution play an essential role in ensuring the continuity of deformation. The present spontaneous dispersion and deformation capability of the LM signify a paradigm shift and open up new possibilities for the development of chemistry-enabled soft machines in the future.