In Terminator 2, T-1000 was that science fiction dream-come-nightmare: a shape-shifting robot made from liquid metal. Now, scientists have actually developed a self-powered liquid metal motor.
It isn't anything fancy, as New Scientist reports: just a small drop of a metal alloy, whose constituents are gallium (which is liquid below 30 °C), indium and tin. Dropped into an appropriate liquid—in these examples sodium hydroxide, but salt water works too—with a scrap of aluminium for fuel, it will run independently for around an hour.
The motor's thrust comes from two sources. First, it experiences a charge imbalance when it's in either of those two liquids, which creates a small pressure differences between two of its sides, pushing it in the direction of high to low pressure. Secondly, the aluminium reacts with the surrounding liquid to form hydrogen bubbles, which, combined with the pressure forces, serve to push it forward faster.
The researchers that created the device have shown that it can easily move along a constrained path, be it a straight line, curved maze or the edge of a Petri dish. Forced to sit stationary, its motion allows it to act like a pump, which moves 50 millilitres of liquid per second. They've also shown in the past that applied electric fields force the drop to change shape—while removing them sees the liquid metal return to its simple, drop-like form.
It might not quite be as complex T-1000 yet, but the researchers hope to use those electric fields to create a swarm of independent drops that can work together. Less like Hollywood, then, but equally as exciting. [Advanced Materials via New Scientist]