Electrically Induced Transformations of Liquid Metal Among Different Morphologies

Abstract

As an emerging multifunctional material, the room temperature liquid metals own many intriguing properties that had never been anticipated before. Over the long year’s exploration of liquid metal as a soft machine, the present lab (Sheng et al. in Adv Mater 26: 6036–6042, 2014 [1]) found for the first time that through applying an external electrical field on the liquid metals sprayed with or immersed in water, a group of very unusual transformation phenomena of liquid metal among different morphologies and configurations can be induced. These basic machine effects and roles include transformation from a large-sized liquid metal film into a tiny sphere (over one thousand times variation in specific surface area), quick mergence of separate metal droplets, controlled self-rotation, and planar locomotion under different conditions. Further, a series of novel phenomena were observed, such as the self-rotating liquid metal sphere induced accompanying water vortexes nearby, and liquid metal droplet moving across the channel bridge under programmable external electrical fields, etc. In addition, the shape, size, voltage, orientation, and geometry of the electrodes would play important roles in controlling the liquid metal morphologies and transformations. Such soft machine capabilities were hard to achieve on rigid metal or conventional liquid objects otherwise. These findings have both fundamental and practical significances which suggest a generalized way of making smart soft machine in the coming time, collecting discrete metal fluids, as well as flexibly manipulating liquid metal objects or machines. This chapter is dedicated to illustrate the basics about driving the liquid metal soft machine among different configurations.