Liquid Metal Marbles Bounce, Don't Splatter

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In the film Terminator 2, the evil robot from the future is made of a shape-shifting liquid metal that can survive getting hit with everything from shotgun shells to grenades. Building that kind of machine isn’t possible yet, but Australian scientists have taken a small step in that direction: they’ve created a liquid metal droplet that doesn’t splatter and retains its shape like a rubber ball.

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The advance could lead to self-healing liquid metal circuits whose wires simply flow back together if cut or frayed. Other applications are also possible, such as soft electronics that can be molded into any shape, semiconducting circuits or even liquid ball bearings.

Liquid metal is used in a number of applications already, such as the mercury switches in thermostats and roll sensors. Mercury is pretty toxic, though, and isn’t always a good fit for electronics.

Vijay Sivan, a research fellow at the Royal Melbourne Institute of Technology’s School of Electrical and Computer Engineering, along with his colleagues, coated a drop of galinstan — a mixture of gallium, indium and tin — with nanometer-sized particles of materials such as Teflon and carbon nanotubes.

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“It has a nanoparticle coating so it will not stick on the surface and also by having a functional material as a coating you can use it like a transistor.” Sivan told the Australian Associated Press.

The result was a droplet that could bounce. If split in two, the droplets retained their shape, but when merged, returned to their original size. Sound familiar? Lastly, these droplets did not transfer moisture to other surfaces. This was unusual for galinstan, which is notorious for wetting surfaces, including glass, and also corroding.

Sivan published his work in the most recent issue of Advanced Functional Materials.

Credit: RMIT University