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Metals & Alloys

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Mini Motor Made Only of Liquid Metal

Posted March 18, 2015 3:55 PM by HUSH

Last week there were some dubious media reports that scientists were a step closer to T-1000 technology. Being the avid Terminator fan that I am, I immersed myself in coverage of this development.

Of course, I was disappointed when headlines gave way to a story about liquid galinstan droplets that use aluminum flakes as fuel to create propulsion when submerged in sodium hydroxide. There were zero reports of bodybuilders on motorcycles, time travel, or a biological vs. technological war, all of which might spice things up a bit.

Instead, the liquid gallium droplets were being compared to T-1000s because its structure allows it to navigate constricted passages and confined spaces, similar to how the T-1000 was able to liquefy its "mimetic polyalloy" to slip under closed doors, or as in this scene, shape shift from dispersed puddles into a well-sculpted Robert Patrick.

Galinstan is an alloy of gallium, indium and tin with a melting point of -2┬░ F. Placing a droplet of galinstan in a solution of sodium hydroxide and then feeding the galinstan drop with a flake of aluminum provides locomotion for the liquid alloy droplet. A charge differential is created across the droplet to provide spin (known as electrowetting), while the reaction between aluminum and the solution creates hydrogen bubbles. The spinning droplet uses the bubbles for traction, and the result is a single material engine.

What does this mean for practical applications? First, micro- and nano-sized pumps can be developed without an external power supply or mechanical components. Not only can complicated pump components be eliminated, but a pump could be complete enclosed. Currently, the galinstan droplets are powered for 30 minutes by a single flake of aluminum, but it's not hard to imagine technological or refueling improvements that could create a permanent motor.

Experiments have showed that the droplet can navigate obstacles and even elongate and change shapes to get through environments. For this reason, there is hope that these materials could be harnessed to deliver materials to pipes as well as blood vessels. Now to create a Robert Patrick-esque Terminator, researchers demonstrated that the galinstan balls can create complex shapes in the presence of an electrical field. As of now liquid galinstan has only a few uses: as a replacement for mercury in thermometers or as a thermal conductor or coolant.

Yet it's also not going to be coagulating into robots or anything else. Galinstan droplets are a long way from being useful at all, let alone from becoming a science fiction threat. Instead, creating threats from pools of liquid materials comes from the world of 3D printing. Peachy Printer and continuous liquid interface production are two example technologies that are much closer to delivering T-1000s. That's not to discount the reveal of the self-propelled galinstan droplet, only to note that we're not closer to Skynet doomsday than the last time I wrote about it.


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