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

Gallium-based liquid metal owns the largest interfacial tension among all the room temperature liquid, 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 due to large interfacial tension, which in turn hinders the construction of liquid metal-based soft machines. Consequently, it is of significant theoretical and practical value to regulate the interfacial tension of liquid metal in order to carry out richer deformation. In this study, spontaneous dispersion and large-scale deformation of the bulk liquid metal were disclosed to be induced by ferric ions. It was found that the bulk liquid metal immersed in the FeCl3 solution can spontaneously disperse into tremendous droplets. And the dispersed liquid metal droplets could move and deform through increasing the concentration of the solutions or adding acids. The mechanisms lying behind the untraditional phenomena lie in the non-uniform interfacial tension over the entire surface of liquid metal, which is associated with the space-time distribution of FeCl3 solutions. Further, directional locomotion and periodic oscillation occur due to the non-uniform interfacial tension, which leads to the autonomous dispersion and deformation of liquid metal. Overall, the unique redox reactions between liquid metal and FeCl3 solutions play an essential role in ensuring the continuity of deformation. The present spontaneous dispersion and deformation capability of liquid metal signify a paradigm shift and open up new possibilities for making the chemistry-enabled soft machines in the coming time.