Somewhere on campus at North Carolina State University, an interesting thing happened. Researchers took a liquid metal alloy of gallium and indium at room temperature and made more than just a puddle. They made a 3D figure. They made a wire. They even made tiny letters. The remarkable occurrence was that it all held together.
The researchers have spent years developing a method of 3D-printing liquid metal at room temperature. The resulting paper, "3D Printing of Free Standing Liquid Metal Microstructures," was recently published in the journal Advanced Materials.
The process uses a syringe needle to dollop tiny spheres of metal together. A thin oxide skin holds it all together and prevents the printed structures from just collapsing into metal blobs. It can be used to create extruded metal wires or put together tiny structures crafted from spheres.
The extruded wires are both flexible and stretchable, opening up possibilities for 3D-printing connections between electronic components. "The thin oxide layer on the surface of the metal allows for the formation of mechanically stable structures strong enough to stand against gravity and the large surface tension of the liquid," the paper says.
One of the researchers discussed the project on Reddit, saying, "The part that's so cool (from a scientific standpoint and really why we got a paper out of this) is that liquids don't behave this way normally. My wires should break up into a rain of droplets, and my structures should just melt into a puddle."
The incredibly thin oxide layer, however, seems to be working quite well. One of the more unusual tests of the process involved printing metal antennae on an insect.
This liquid metal printing method could open up some interesting uses for electronics and even applications like headphone wires where flexibility and the ability to self-heal could improve durability.