A robot made of liquid metal that changes shape and moves around of its own accord... this was one of the scenes from Terminator 2: Judgment Day which impressed many viewers.

Now we are a step closer to this kind of robot. Chinese scientists have made a drop of metal that is able to propel itself through liquid and change its shape to fit through a narrow aperture.

The research team recently published their findings in the journal "Advanced Materials" and announced that exceptional phenomena such as transformation from a film into a sphere, rapid merging of separate objects, controlled self-rotation, and planar locomotion, have been observed in liquid metals for the first time.

To produce the phenomenon the Chinese scientists use a drop of metal alloy made mostly of gallium – which is liquid at just under 30 °C – along with some indium and tin. When the drop is placed in a solution of sodium hydroxide, or even brine, and kept in contact with a flake of aluminum for "fuel", it moves around for about an hour at a speed of 5 centimeters per second. It can travel in a straight line, run around the outside of a circular dish, or squeeze through complex shapes.

"The soft machine looks almost intelligent, and can deform itself according to the space it is traveling in, just like the Terminator in the science-fiction film," says Liu Jing. "These unusual behaviors mirror living organisms in nature."

Liu Jing and his research team have given the liquid metal machine the affectionate name of "mollusk" because of the unusual features it presents, which are already quite close to the natural simplicity of the software creatures.

The research team has produced liquid metal machines of different sizes, ranging from tens of microns to several centimeters and verified their autonomous movement in different environments such as alkaline, acidic and neutral solution.

Liu Jing explains that as a new functional material, liquid metal has several novel physical properties which conventional materials lack. Liquid metal could be used to produce robot vessels, shape-changing robots, or even humanoid robots, performing tasks in outer space in microgravity or zero gravity environments.

Edited and translated from Chinese version of 《我国科学家研发出世界首台自驱动液态金属机器》， source: People’s Daily.