A team of researchers from North Carolina State University has developed three-dimensional (3-D) printing technology able to create free-standing structures made of liquid metal, which can be used to connect electronic components.
While it is relatively easy to pattern metal "in plane" - or, all on the same level - the newly-developed liquid metal structures, which can be created at room temperature, also form shapes that reach up or down.
"It's difficult to create structures out of liquids, because liquids want to bead up. But we've found that a liquid metal alloy of gallium and indium reacts to the oxygen in the air at room temperature to form a 'skin' that allows the liquid metal structures to retain their shapes," said Dr. Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State and co-author of a paper describing the work, "3-D Printing of Free Standing Liquid Metal Microstructures," which was published online in the journal Advanced Materials.
The work was supported by a National Science Foundation award and the National Science Foundation's engineering research center at NC State.
One technique for building the 3-D structures involved stacking droplets of liquid metal on top of each other, similar to a display of oranges at the supermarket.
During experimentation, liquid metal droplets adhered to one another, but retained their shape, and didn't merge into a single, larger droplet (see video below).
Another technique injected liquid metal into a polymer template, in order for the metal to assume a specific shape. The template was then dissolved, leaving the bare, liquid metal in the prescribed shape.
The researchers also developed ways for creating liquid metal wires that retained their shapes, even when held perpendicular to another surface.
Dickey said his team is has now started exploring how to enhance the new techniques, in particular, how to implement them with various electronics applications and in connection with established 3-D printing technologies.