Vat photopolymerization is a kind of 3D printing that entails pouring a light-reactive liquid resin right into a container after which solidifying particular areas with a laser or ultraviolet mild to create a form. Nevertheless, as a result of this technique solely works with light-sensitive polymers, its sensible makes use of are restricted.
Some researchers have developed strategies to show these printed polymers into stronger supplies like metals and ceramics, however Daryl Yee, who leads the Laboratory for the Chemistry of Supplies and Manufacturing at EPFL’s College of Engineering, says these approaches have main flaws. “These supplies are usually porous, which considerably reduces their power, and the components undergo from extreme shrinkage, which causes warping,” he says.
To handle these points, Yee and his group have launched a brand new method described of their paper printed in Superior Supplies. As an alternative of hardening a resin already combined with metallic compounds, the researchers first 3D print a framework utilizing a easy water-based gel often called a hydrogel. They then soak this “clean” construction in metallic salts, that are chemically transformed into tiny metal-containing nanoparticles that unfold all through the gel. Repeating this course of a number of occasions permits them to create composites with very excessive metallic content material.
After 5–10 of those “development cycles,” the remaining hydrogel is eliminated by way of heating, forsaking a dense metallic or ceramic object that exactly matches the form of the unique printed gel. As a result of the metallic salts are added solely after printing, the identical hydrogel template can be utilized to make quite a lot of completely different metals, ceramics, or composite supplies.
“Our work not solely allows the fabrication of high-quality metals and ceramics with an accessible, low-cost 3D printing course of; it additionally highlights a brand new paradigm in additive manufacturing the place materials choice happens after 3D printing, relatively than earlier than,” Yee summarizes.
Focusing on superior 3D architectures
For his or her examine, the group fabricated intricate mathematical lattice shapes known as gyroids out of iron, silver, and copper, demonstrating their method’s means to provide robust but advanced constructions. To check the power of their supplies, they used a tool known as a common testing machine to use growing stress to the gyroids.
“Our supplies may stand up to 20 occasions extra stress in comparison with these produced with earlier strategies, whereas exhibiting solely 20% shrinkage versus 60-90%,” says PhD scholar and first writer Yiming Ji.
The scientists say their method is very fascinating for the fabrication of superior 3D architectures that have to be concurrently robust, light-weight, and complicated, like sensors, biomedical gadgets, or gadgets for power conversion and storage. For instance, metallic catalysts are important for enabling reactions that convert chemical power into electrical energy. Different functions may embrace high-surface space metals with superior cooling properties for power applied sciences.
Trying forward, the group is engaged on enhancing their course of to facilitate uptake by business, notably by additional growing the density of their supplies. One other purpose is pace: the repeated infusion steps, whereas important for producing stronger supplies, make the strategy extra time-consuming in comparison with different 3D printing strategies for changing polymers to metals. “We’re already engaged on bringing the whole processing time down through the use of a robotic to automate these steps,” Yee says.
