Electric-field-guided 3D manipulation of liquid metal microfleas

Liquid metal micromotors have attracted mounting interest over the past decade, but their property of sticking to many surfaces has limited their controllable manipulation in three dimensions (3-D). In this work, we demonstrate a versatile and generic approach in manipulating Gallium-based liquid metal microfleas (LMMFs) on solid surfaces by strategically applied electric (E-) fields, in which the adhesion of LMMFs to solid surfaces is greatly reduced by tailoring the thickness of the oxide skins of the liquid metal. Numerical simulations and experimental demonstrations illustrate that the LMMFs can be readily driven to jump along prescribed trajectories with high localization accuracy (the order of ~10 microns). The prowess of the precision manipulation of LMMFs is further demonstrated in several practical applications, including the walking of LMMFs on the stairs, the micro-welding for cracked conducting wire, as well as the on-demand jumping of LMMFs on a “mini-piano.” Such a proposed approach provides a convenient, rather generic, E-field-based strategy for manipulation of LMMFs in non-liquid environments with a configurable, switchable, and programmable fashion, offering considerable potential for diverse practical applications in the near future.