Although there are several methods of 3D-printing metal objects, all of them involve the application of heat – which isn't conducive to producing certain heat-sensitive electronics, among other things. A new gel, however, can be used to print such items at room temperature.
Created by a team of scientists at North Carolina State University, the material starts out as a solution consisting of copper microparticles suspended in water. Microparticles of another metal, known as eutectic gallium indium alloy (EGaIn) are then added, as is hydrochloric acid.
The latter sets the pH of the water to 1.0, removing oxides from the EGaln and thus temporarily turning it to a liquid-metal state. This causes the EGaln particles (now globules) to cling to the firmer copper particles, forming a network of copper particles connected by EGaln bridges. Methylcellulose is also added, to bulk up the mixture.
The resulting viscous gel can be extruded from the nozzle of an ordinary 3D printer at room temperature, building an item up one layer at a time. When the finished object is left to dry – at that same temperature – the water and hydrochloric acid evaporate. The end result is a rigid, highly electrically conductive three-dimensional object which is up to 97.5% metal (the rest being methylcellulose).
Additionally, based on the manner in which the particles are aligned as the gel is extruded, the object will change shape in a predictable fashion if heat is applied while it's drying. This phenomenon could be utilized in the production of items which ultimately need to take on a complex shape, but are easier to print as a flat pattern. In the video below, you can see how the gel was used to 3D-print a spider that 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."
A paper on the research was recently published in the journal Matter.
Source: North Carolina State University
