Comprised entirely of liquid metal, the robot assassin T-1000 from Terminator 2 seems a creature straight out of science fiction — and at the time the film was released, it was. However, now researchers at North Carolina State University have successfully have successfully tested 3D-printing of free-standing structures out of a similar liquid metal substance at room temperature.
Normally, it is very difficult to create such structures with liquid due to liquid's tendency to bead, but the team discovered that a liquid metal alloy of gallium and indium reacts to oxygen in the air at room temperature and forms a sort of skin — this allows the structures printed with the liquid metal to retain their shapes.
The research team worked on multiple techniques for creating these structures, including stacking droplets of liquid metal on top of each other — similar to how oranges are stacked at the supermarket. The droplets adhere to one another, but manage to retain their shape, rather than merge into a big blob of liquid (see video below).
A second technique injects the liquid metal into a polymer template so that the metal takes on a specific shape. The template dissolves, leaving only the liquid metal in its intended form. The researchers also worked with creating liquid metal wires, which also hold their shape when held perpendicular to the substrate. The team is now exploring how to further develop these methods, as well as how they can be used in applications involving electronics with existing 3D printing technologies.
Although we're not yet at the stage where we can create an assassin robot of liquid metal, the scientists involved with the project think that these new techniques could be specifically handy with creating more flexible parts for electronics.