Picture: MIT News
A research team from the Massachusetts Institute of Technology (MIT) has developed a new process for optimizing 3D printing with synthetic resin that significantly simplifies post-processing. The focus is on a specially formulated photopolymer resin mixture whose physical properties can be specifically controlled using different light sources. Depending on the wavelength, the material solidifies into either a robust component or an easily soluble support material.
“You can now print — in a single print — multipart, functional assemblies with moving or interlocking parts, and you can basically wash away the supports,” says graduate student Nicholas Diaco. “Instead of throwing out this material, you can recycle it on site and generate a lot less waste. That’s the ultimate hope.”
The process is based on vat photopolymerization, in which a liquid resin is cured layer by layer using light patterns. Usually, this also creates temporary support structures made of the same material, which have to be removed manually after printing and then disposed of. The new resin formulation, on the other hand, allows stable structures to be created using UV light, while visible light simultaneously forms soluble support structures. After the printing process, an immersion bath in a suitable solution – such as baby oil – is sufficient to dissolve the supports without leaving any residue.
“With all these structures, you need a lattice of supports inside and out while printing,” Diaco says. “Removing those supports normally requires careful, manual removal. This shows we can print multipart assemblies with a lot of moving parts, and detailed, personalized products like hearing aids and dental implants, in a way that’s fast and sustainable.”
In contrast to previous processes, the dissolved material can also be fed back into the printing process. This not only reduces waste, but also opens up the possibility of a closed material cycle. The researchers demonstrated the method on functional objects such as gears and filigree lattice structures. Tests with commercially available monomers showed that the desired selectivity can be achieved by combining UV and visible light and adding a third crosslinking agent.
“We’ll continue studying the limits of this process, and we want to develop additional resins with this wavelength-selective behavior and mechanical properties necessary for durable products,” says professor of mechanical engineering John Hart. “Along with automated part handling and closed-loop reuse of the dissolved resin, this is an exciting path to resource-efficient and cost-effective polymer 3D printing at scale.”
