A new gel has been developed by scientists at North Carolina State University that allows 3D printing of metal objects without the need for heat. The gel is made by combining copper microparticles, a metal called eutectic gallium indium alloy (EGaIn), and hydrochloric acid in water.
The addition of hydrochloric acid lowers the pH of the water, removing oxides from the EGaIn and making it temporarily liquid metal. This causes the EGaIn particles to stick to the copper particles, creating a network of copper connected by EGaIn bridges. Methylcellulose is also added to thicken the mixture.
The resulting gel has a thick consistency and can be printed at room temperature using a regular 3D printer. Each layer of the object is built up as the gel is extruded from the printer’s nozzle.
After printing, the object is left to dry at the same temperature, causing the water and hydrochloric acid to evaporate.
This results in a solid three-dimensional object made of up to 97.5% metal, with the remaining portion being methylcellulose.
Moreover, the way the particles align during extrusion allows the object to change shape predictably when heat is applied during the drying process. This property can be utilized to create complex-shaped items that are initially printed as flat patterns.
The video below demonstrates how the gel was used to 3D print a spider, which rises up on its legs as it dries while heated.
“3D printing has revolutionized manufacturing, but we’re not aware of previous technologies that allowed you to print 3D metal objects at room temperature in a single step,” said Dickey. “This opens the door to manufacturing a wide range of electronic components and devices.”