World's first Terminator-like self-propelled liquid metal robot that can power itself

A Chinese research team has developed shape-shifting, liquid metal machines which can power themselves.

Jing Liu from the Tsinghua University said that the soft machine looks rather intelligent and can deform itself according to the space it voyages in, just like the Terminator does from the science-fiction film and these unusual behaviours perfectly resemble the living organisms in nature.

The motor is made from galinstan - an alloy made from gallium, indium and tin (68.5 percent, 21.5 percent and 10 percent respectively) that has a melting point of -19 degrees Celsius, meaning it stays liquid at room temperature.

When placed in a Petri dish with sodium hydroxide, or even brine, and left in contact with a flake of aluminium, which the alloy utilizes as fuel, the liquid motor can move around on its own for about an hour, prompting its inventors to raise some new questions about the definition of life, the research group has likened their creation to a bio-mimetic mollusc.

Puzzled by the underlying mechanism of the functioning motor, the team carried out several experiments that revealed two primary drivers of propulsion: some of it comes from a charge imbalance across the drop, which in turn creates a pressure differential between the front and the back, while the rest is created by hydrogen bubbles that form as the aluminium reacts with the sodium hydroxide.

Building on previous research that suggested a stationary drop of gallium can act as a pump in an electric field, Liu has demonstrated that their self-powered motor, too, becomes a pump if held still, and is capable of shifting around 50 millilitres of water per second. According to the team, this could have immediate applications in many fields, such as moving liquid through a cooling device without the need for an external source of power.

Thanks to the alloy's "large surface tension, desirable flexibility, high electrical conductivity and low toxicity," it can move in a straight line, run around the circular dish and squeeze through complex shapes, a robot based on a similar device could soon be used to monitor the environment, deliver materials through pipes, or even move substances through blood vessels.

Combined with 2014's findings, which revealed that electricity makes galinstan take complex forms, Liu believes their research could be used in tandem to change the drop's velocity or coordinate a swarm of individual drops.

The study appears in the journal Advanced Materials.