Many 3D printers work via a system called photopolymerizationin which a liquid resin solidifies using UV or laser light. The problem? It only works with light-sensitive polymerstherefore no metals or ceramics.
Some alternative methods try to turn a printed polymer into a more solid material. But often the result is not very compact and full of holeswith objects that they shrink and deform too.
The professor’s team Daryl Yeewho leads the ALCHEMY laboratory at EPFL, has chosen a completely different approach. We start from one simple and transparent hydrogel3D printed with the desired shape. Then it is immersed in a solution containing metal salts. These salts enter the gel and transform into tiny metal particles.
The step is repeated several times, in cycles called “growth cycles”to increase the quantity of metal. Eventually, with heat, the gel evaporates and only the metal or ceramic remainswith the perfect shape of the original model, as Yee points out:
Instead of already printing with the metal, we print the shape first, and choose the material later. This makes the technique much more flexible and accessible.
Test on complex shapes: up to 20 times more resistant and with less deformations
To prove the effectiveness of their method, the researchers printed gyroidscomplex geometric structures that are also found in nature. They made them using different metals like copper, iron and silver. Then they subjected them to mechanical resistance tests.
As he explains Yiming Jidoctoral student and first author of the study, the results speak clearly:
Our structures withstood pressures 20 times higher than similar materials obtained with other techniques.
And yes they are narrowed by only 20%against an average ranging from 60 to 90%.
This means that the resulting pieces are not only more resistant, but also more stable and precise.
Practical applications
The potential of this discovery is concrete, not theoretical. The new technique is ideal for producing 3D objects that need to be resistant, light and with complex shapes. And this is exactly what is needed in many key sectors:
The next steps? The EPFL team is working for speed up the processwhich today requires several immersion cycles. This is why they are developing a automatic robot which could handle the slower phases, thus paving the way for industrial-scale production.
Our goal is to make this technique quick and economical, to get it out of the laboratories and into companies.
