Vat photopolymerization — a form of 3D printing is the process behind manufacturing hearing aids, mouth guards, dental implants, and other highly tailored structures. The process uses light patterns to shape and solidify a resin.
Vat photopolymerization (VP) begins with a 3D computer model, such as interlocking gears. The model features support structures to maintain its position during printing. This model is sliced into digital layers, which are sent to the printer.
A VP printer uses liquid resin and a light source. Each layer of the model is projected as a light pattern onto the resin, which solidifies. Layer by layer, the final structure forms. After printing, the finished part is lifted from the resin bath, cleaned, and manually freed from its temporary supports, which are then discarded, resulting in significant waste.
MIT engineers have developed a special resin that speeds up 3D printing by eliminating the need for manual support removal. The resin reacts differently to light—UV light makes it strong, while visible light creates easily dissolvable supports.
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During printing, UV light forms the main structure, and visible light creates temporary supports. Instead of breaking them off by hand, the printed part is dipped into a solution that dissolves the supports away. These supports can be recycled by mixing the dissolved material back into fresh resin for future prints.
The researchers created a resin that simplifies support removal and enables recycling. The material reacts differently to light—UV light creates a strong, durable structure, while visible light forms dissolvable supports.
They achieved this by mixing two common plastic monomers. When exposed to UV light, the monomers form a tough, interconnected solid. Under visible light, the monomers still solidify but remain loosely connected, allowing them to dissolve easily in specific solutions.
During tests, researchers confirmed that their resin could shift between insoluble and soluble states using ultraviolet and visible light. However, when applied to a 3D printer with dimmer LEDs, the UV-cured material failed—it wasn’t strong enough because the monomer strands weren’t fully linked.
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To fix this, they added a small amount of a third “bridging” monomer, which strengthened the UV-cured material by tightly linking the monomers. This allowed them to print both durable structures and dissolvable supports in a single run using precisely timed light pulses.
Graduate student Nicholas Diaco said, “With all these structures, you need a lattice of supports inside and out while printing. 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.”
Professor of mechanical engineering John Hart said, “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. 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.”
Journal Reference:
- Nicholas S. Diaco, Carl J. Thrasher, Max M. Hughes, Kevin A. Zhou, Michael N. Durso, Saechow Yap, Robert J. Macfarlane, A. John Hart. Dual-Wavelength Vat Photopolymerization With Dissolvable, Recyclable Support Structures. Advanced Materials Technologies. DOI: 10.1002/admt.202500650
