Researchers from Lawrence Livermore National Laboratory and the University of California, Santa Barbara, have developed a dual-wavelength resin system for digital light processing (DLP) 3D printing. Published in ACS Central Science, the study demonstrates a method for simultaneously printing permanent structures and degradable supports using a one-pot resin formulation. The technique eliminates the need for resin swaps or manual support removal and is enabled by a custom-built dual-wavelength DLP printer.
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A one-pot solution for unsupported geometries
Unsupported features such as overhangs, bridges, and free-floating elements typically require support structures, which are often printed from the same material and removed manually. This process can damage parts and limit design freedom. To address these challenges, the researchers developed a one-pot resin system that responds to two different wavelengths of light: UV (365 nm) and visible (405 nm). The UV-curable epoxy forms the final permanent structure, while the visible-light-cured (meth)acrylate creates sacrificial supports. After printing and thermal post-processing, the supports are removed via degradation in a basic aqueous solution, leaving the primary structure intact.
Custom dual-wavelength DLP printer
Central to this advancement is a patented dual-wavelength negative imaging (DWNI) DLP printer, developed by co-author Bryan Moran. The printer uses a single digital micromirror device (DMD) to project both UV and visible light simultaneously. By adjusting the tilt of the micromirrors, the system selects which wavelength is projected to each pixel, allowing two materials to be patterned in a single layer without optical overlap.
This setup reduces print time by up to 50% compared to sequential dual-wavelength systems and removes the need for alignment between multiple DMDs. It also improves print resolution by enabling simultaneous exposure of both structural and support regions.
Optimizing resin chemistry and print performance
The resin formulation combines epoxy monomers for structural rigidity with methacrylated sebacic acid (MSA) for degradable supports. Real-time FTIR spectroscopy confirmed that visible light selectively polymerizes the (meth)acrylate network, while UV light triggers both cationic and radical polymerization to form a robust epoxy matrix.
Thermal post-processing improved the epoxy conversion rate, and base degradation effectively removed the sacrificial features without damaging the primary part. Despite a 35% reduction in cross-link density following degradation, mechanical tests showed the final epoxy-dominant parts retained high modulus values.
Complex geometries with dissolvable supports
To demonstrate the method’s capabilities, the researchers fabricated several intricate structures, including interlocking rings, a ball-in-a-cage, and a helix enclosing two spheres. The degradable supports stabilized unsupported features during printing and were easily removed post-cure.
The dual-wavelength approach improved shape fidelity and surface finish. Surface roughness remained low after degradation, and resolution studies confirmed the method’s precision and effectiveness.
Dissolvable supports in vat photopolymerization
Recent innovations in vat photopolymerization have focused on simplifying support removal through wavelength-selective resin systems. Researchers at MIT developed a dual-cure resin that switches mechanical properties depending on light exposure, allowing dissolvable supports to be printed alongside durable structures using UV and visible light.
Meanwhile, a multicolor DLP breakthrough from the University of Texas enabled the creation of freestanding parts with supports that dissolve in ethyl acetate, preserving fine features and smooth surfaces. These developments reflect a growing industry trend toward reducing post-processing complexity and expanding design freedom in resin-based additive manufacturing.
The ability to embed unsupported geometries without resin swapping or mechanical removal opens new opportunities in freeform additive manufacturing. This technique could be especially useful in biomedical, fluidic, and aerospace applications where internal features and delicate structures are common.
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Feature image shows support removal method comparison. Image via ACS Central Science.
