Gallium

Gallium is a class of liquid metal that can be attached to millimeter-scale robots to enhance their functionality. In our previous research, we discovered that gallium can exhibit highly reversible and switchable adhesion when it undergoes a solid–liquid phase transition. It has been demonstrated that this liquid metal can become highly adhesive when it freezes and it can conversely lose its adhesion when it melts. These adhesive properties had been characterized, and we experimentally show that gallium has good performance over a wide range of smooth and rough surfaces, under both dry and wet conditions.

Another critical advantage of gallium is that it has a natural layer of oxide, which acts like an elastic membrane surrounding the liquid metal. This oxide layer can effectively conserve the mass of gallium when it is in the liquid-state, and this in turn ensures that gallium can be used repeatedly as a reversible and switchable adhesive. The unique adhesive properties of gallium can therefore allow it to perform various pick-and-place tasks at small-scale (Videos G1 and G2), which are critical for numerous applications in transfer printing, robotics, electronic packaging, and biomedicine.

We believe there are still many interesting abilities in gallium, which have not been discovered yet. Therefore, we will continue to explore new abilities of this material and transform them into critical functions for miniature robots.

Relevant Publication:

Z. Ye*, G. Z. Lum*, S. Sukho, S. Rich and M. Sitti, "Phase change of gallium enables highly reversible and switchable adhesion", Advanced Materials, vol. 28, no. 25, May 2016, Pages 5088-5092. *Co-First Authors (Selected for Frontispiece Cover) [link]