Terminator-style stretchable metal created in lab © Alamy

Terminator-style stretchable metal created in lab

New droplets of liquid metal could be used in soft robots or flexible electronics.

Move over T-1000: engineers at Beihang University, Beijing have created a magnetic liquid metal that can stretch in three dimensions that mimics the liquid properties of the shapeshifting robot assassin from the future that scared the life out of us all in Terminator 2: Judgement Day.

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The shiny liquid metal can be stretched into shape using magnets and could one day be used to create a pliable, soft robot or more flexible electronic circuits, the team says. They created the material by combining three metals: gallium, which is still liquid as low as 30°C, indium, and tin, and then mixed in particles of iron to make the whole concoction magnetic.

Any magnetic liquid can be manipulated by magnets, but any movement is limited by its surface tension – the property that gives droplets of any liquid their shape. The higher the surface tension the more a liquid ‘wants’ to form into spheres – the shape with the smallest possible area for a given volume –  making it difficult to stretch or expand it.

The team got around this by immersing their liquid metal in hydrochloric acid. This caused a layer of gallium oxide to form on the liquids surface which lowered its surface tension enough to allow it to be stretched up to almost four times its original length in three dimensions.

They used the resulting material to connect together an electronic circuit and light up an LED bulb that was fully immersed in the acid, and also used it to connect a pair of electrodes – one that immersed in the acid and one that was outside of it.

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