Liquid Metal Transformable Machines

ConspectusConventional robots can accomplish defined tasks but often encounter troubles when handling irregular objects under unstructured environments. Soft robots, with supercompliance, large transformation, and high environmental adaptability, hold big promise for delicate manipulations such as grasping soft objects or delivering precious biomedical samples. Even a step further, if soft robots are endowed with the extraordinary behaviors to freely transform among different morphologies and constructions just like those already existing in literature and science fiction films, more fantastic challenges can be tackled. Representing one of the most potential robotic soft materials, liquid metals have been given sufficient expectations on realizing the transformable machines that might fundamentally reform modern daily life. Accordingly, inspiring discoveries on controllable transformations of the liquid metal have been obtained surprisingly and tremendous efforts have been made over the past decade, indicating a significant step toward such a formidable dream. It is clear that the discovery of liquid metal-based large-scaled transformation with several hundred-fold fast change on the surface area opens a brand new direction of manufacturing future transformable machines. Even unusual findings on a self-fueled liquid metal with biological life-like behavior to freely explore the unknown space that solves the energy supply issue also came into being, holding big promise for making bionic transformable robots. This Account aims to systematically sort out the developmental history of liquid metal transformable machines with special focus on the fundamental scientific discoveries, the underlying mechanisms, and the potential applied scenarios based on liquid metal enabled solid–liquid hybrids. The fantastic properties and unique transformation capabilities of liquid metals have built the basis for a new era of designing soft robotics and we believe that liquid metal transformable machines are evolving into new forms of soft robots.