Terminator 2

It's not quite as advanced as in Terminator 2, but a way of 3D printing liquid metal could offer a new range of flexible electronics.

An alloy of metals gallium and indium that is liquid at room temperature forms a thin skin when exposed to air, which is strong enough to hold the liquid's shape.

Michael Dickey of North Carolina State University in Raleigh and colleagues put the alloy in a syringe and were able to squeeze out wires, about a centimetre tall, that stood vertically despite their liquid centre.

Bendy electronics

'The fact that they are liquid means you could surround them with another material like rubber to make metallic structures that you can stretch and deform,' says Dickey. This would be useful for creating bendy electronics. The team also created towers of liquid metal droplets, all held together by the skin, illustrating how the metal can form 3D structures.

It should be easy to swap the syringe for the nozzle of a 3D printer, potentially letting you print plastic objects containing metal wiring with a single device. 'You could include this as a functional ink that you use with a 3D printer,' says Dickey.

Unlike materials such as liquid mercury, the metal is non-toxic so should be safe for commercial use, but the liquid metal won't come cheap, says Dickey - it is roughly 100 times the cost of 3D printing plastic.

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