Most of us know what 3D printing is, and we also understand that even when we say 3D printing, the actual printing process takes place in multiple 2D layers deposited one above the other. This is what bothered a group of researchers from the Rowland Institute at Harvard and they decided to make 3D printing, truly 3D. They have developed a new upconversion process as a solution.
The researchers now present a new method with upconversion process to assist printers in living up to their names and delivering “true” 3D printing. They describe a volumetric 3D printing technique that goes beyond the bottom-up, layered approach in a new paper published in Nature (Triplet fusion upconversion nanocapsules for volumetric 3D printing). This new process also eliminates the need for support structures as the resin produces in the process is self-supporting.
Upconversion Process
First, let’s look at how 3D printing works: The printers layer flat layers of resin, which hardens into plastic when exposed to laser light, on top of each other from the bottom to the top. The object, such as a skull, eventually takes shape. However, if a piece of the print overhangs, such as a bridge or a plane wing, it requires some type of flat support structure to print, or the resin will fall apart.
“What we were wondering is, could we actually print entire volumes without needing to do all these complicated steps? Our goal was to use simply a laser moving around to truly pattern in three dimensions and not be limited by this sort of layer-by-layer nature of things.”
– Daniel N. Congreve, an assistant professor at Stanford and former fellow at the Rowland Institute
The key component in their novel design is the conversion of red light to blue light via a upconversion process added to the resin, the light reactive liquid used in 3D printers that hardens into plastic.
Resin hardens in a flat and straight line along the path of the light in 3D printing. The researchers use nano capsules to add chemicals that only react to a specific type of light — a blue light at the focal point of the laser created by the upconversion process. Because this beam is scanned in three dimensions, it prints without needing to be layered onto anything. The resulting resin has a higher viscosity than the traditional method, allowing it to stand alone once printed.
Daniel N. Congreve added, “We designed the resin, we designed the system so that the red light does nothing. But that little dot of blue light triggers a chemical reaction that makes the resin harden and turn into plastic. Basically, what that means is you have this laser passing all the way through the system and only at that little blue do you get the polymerization, [only there] do you get the printing happening. We just scan that blue dot around in three dimensions and anywhere that blue dot hits it polymerizes and you get your 3D printing.”
The researchers used their printer to create a 3D Harvard logo, a Stanford logo, and a small boat, which is a standard but difficult test for 3D printers due to the boat’s small size and fine details such as overhanging portholes and open cabin spaces.
The researchers, which included Christopher Stokes from the Rowland Institute, intend to continue developing the system for speed and finer detail printing. When it reaches its full potential, volumetric 3D printing is expected to be a game changer because it will eliminate the need for complex support structures and dramatically speed up the process. Consider the “replicator” from “Star Trek,” which materialises multiple objects at once.
However, the researchers are aware that they still have a long way to go and they are just beginning.
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