In the science-fiction classic, Terminator 2: Judgement Day, the T-1000 is a robotic assassin with a liquid metal endoskeleton that can assume the form of any object or person. Its liquid nature makes it immune to attack by bullets and impervious to mechanical damage in general.
The T-1000 is an entirely fictional device that might as well be magic as far as conventional manufacturing techniques are concerned. And yet this might be about to change thanks to the pioneering work of Lei Sheng, Jie Zhang and Jing Liu at Tsinghua University in Beijing.
These guys have taken the first tentative steps to making liquid machines that work like the T-1000. Their first attempts can assume various shapes, move around and then transform into other shapes more or less without limit. And they say the work has profound implications for the design of robots, future machines and the nature of manufacturing.
While the most familiar liquid metal is the toxic mercury, there are other metals and alloys that are liquid at room temperature and much more benign. In particular, a gallium-indium-selenium alloy, with a melting point of around 10°C, has received much recent attention because it can be used for cooling microprocessors and even for liquid metal printing techniques.
Now Lei Sheng and co have made this liquid metal assume simple shapes by placing a thin film of it in water and applying an electric field.
With careful arrangement of the voltages and electrode geometries, these guys can make the metal form into a sphere. They say this is the result of the balance between the surface tension in the liquid metal and the electronic forces applied to its surface.