Liquid metal manoeuvred into new applications

Developed at North Carolina State University, the technique is said to hinge on the fact that the oxide “skin” of the metal – which can be deposited or removed – acts as a surfactant, lowering the surface tension between the metal and the surrounding fluid.

The researchers used a liquid metal alloy of gallium and indium. In base, the bare alloy has a high surface tension of about 500 millinewtons (mN)/metre, which causes the metal to bead up into a spherical blob.

‘But we discovered that applying a small, positive charge – less than one volt – causes an electrochemical reaction that creates an oxide layer on the surface of the metal, dramatically lowering the surface tension from 500mN/meter to around 2mN/meter,’ said Dr Michael Dickey, an associate professor of chemical and biomolecular engineering at NC State and senior author of a paper describing the work. ‘This change allows the liquid metal to spread out like a pancake, due to gravity.’