Transformable Liquid Metal Machine

Conventional robots consisting of rigid components have successfully freed human labor from repetitive mechanical operations. However, it is still challenging for these rigid machines to perform fine operations on soft and fragile objects. Similar to flexible machines, liquid machines should also have good transformation ability. Liquid robots have long been featured in some literature and science fiction works. An example is the T-1000 in the movie “Terminator 2,” which can flow at will, transform autonomously, and repair gunshot wounds. Although prototypes of such robots are fictional, rapid advances in science and technology are turning the idea into reality. Room temperature liquid metals have the combined characteristics of fluid and metal, which exhibit a variety of peculiar transformation phenomena under different stimuli. For example, the surface area of liquid metal machines can change hundreds of times rapidly under electric fields. They can also transform, combine, move, and rotate between different forms. These unusual transformation phenomena make it feasible for liquid metals to perform specific tasks in complex spaces. Until now, transformable machines based on liquid metals have already been used in preliminary applications in biomedicine, sensing, and other fields. This chapter aims to systematically sort out the research progress of liquid metal transformable machines. The wonderful properties and unique transformation ability of liquid metals lay the foundation for a new era of designing soft robots. The liquid metal convertible machine will have a broad scope for development in the future.