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 above 30 °C), indium and tin. Dropped into an appropriate liquid—in these examples sodium hydroxide, but salt water works too—with a scrap of aluminum for fuel, it will run under its own steam for around an hour.
The motor's motion comes from two sources. First, those two liquids cause it to experience a charge imbalance, which creates a small pressure differences between two of its sides. That, in turn, pushes it in the direction of high to low pressure. Secondly, the aluminum 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 still, its motion allows it to act like a pump, which can move 50 millilitres of liquid per second.
It might not quite be as complex T-1000 yet, but the researchers hope to use 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]