Researchers from North Carolina State University have developed a technique for controlling the surface tension of liquid metals by applying very low voltages. They liken it to the liquid metal Terminator from Terminator 2, although it may be very far from that sophisticated it’s still pretty fascinating.
They used a liquid metal alloy of gallium and indium. In base, alloy has a remarkably high surface tension (~500 millinewtons (mN)/meter), which causes the metal to bead up into a spherical blob.
“But we discovered that applying a small, positive charge – less than 1 volt – causes an electrochemical reaction that creates an oxide layer on the surface of the metal, dramatically lowering the surface tension from 500 mN/meter to around 2 mN/meter,” says 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.”
So what can this be used for, besides building a terminator?
“The resulting changes in surface tension are among the largest ever reported, which is remarkable considering it can be manipulated by less than one volt,” Dickey says. “We can use this technique to control the movement of liquid metals, allowing us to change the shape of antennas and complete or break circuits. It could also be used in microfluidic channels, MEMS, or photonic and optical devices. Many materials form surface oxides, so the work could extend beyond the liquid metals studied here.”
You can see a video at the source