North Carolina State University researchers are developing a metal 3D printing technology that can create small structures from a room temperature liquid metal.
Most 3D printers can print using plastics, resins, ceramics and rubber materials. Currently the only 3D printers that can produce objects in metal use a laser sintering process to create a solid object from powdered material, which isn’t a true “printing” process.
The NCSU team, consisting of Collin Ladd, Ju-Hee So, John Muth, and Michael D. Dickey, use a binary eutectic alloy of gallium and indium (EGaIn, 75% Ga 25% In by weight) which is liquid at room temperature. Once exposed to the oxygen in the air the alloy forms a thin (~1nm) skin composed of gallium oxide. This allows the material to retain its shape.
“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,” explained Dr. Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State.
The team have developed a few different techniques for creating metal structures including stacking liquid metal droplets onto one another. The droplets stick to each other but don’t merge into a single blob. The team also inject the liquid metal into a template made of a polymer which can be dissolved leaving the metal shape behind. The video below also shows how the liquid metal can be formed into wires (as the metal can conduct electricity). This 3D printing technique has immediate applications in the manufacture of electronic circuits but it will be a while before it can be used to make larger parts in metal that can currently be 3D printed in plastic.