Novel "Panchromatic Polymer" Resins Let 3D Printers Ditch the Ultraviolet for Visible Light

Future resin-based 3D printers could work with simple visible light, rather than ultraviolet light, thanks to work from researchers at the University of Texas at Austin on dramatically improving curing times.

"Light-driven 3D printing to convert liquid resins into solid objects (i.e., photocuring) has traditionally been dominated by engineering disciplines, yielding the fastest build speeds and highest resolution of any additive manufacturing process. However, the reliance on high-energy UV/violet light limits the materials scope due to degradation and attenuation (e.g., absorption and/or scattering)," the research team notes in the abstract to its paper. "Chemical innovation to shift the spectrum into more mild and tunable visible wavelengths promises to improve compatibility and expand the repertoire of accessible objects, including those containing biological compounds, nanocomposites, and multimaterial structures."

The biggest problem with the shift, though: Resins that cure based on visible light, rather than the more energetic ultraviolet light used in existing resin-based printers, take far too long to cure. The solution: A new type of resin, dubbed a "panchromatic polymer," with a significantly improved curing time.

"The combination of electron-deficient and electron-rich coinitiators was critical to overcoming the speed-limited photocuring with visible light. Furthermore, azo-dyes were identified as vital resin components to confine curing to irradiation zones, improving spatial resolution," the team explains. "A unique screening method was used to streamline optimization (e.g., exposure time and azo-dye loading) and correlate resin composition to resolution, cure rate, and mechanical performance.

"Ultimately, a versatile and general visible-light-based printing method was shown to afford (1) stiff and soft objects with feature sizes <100 μm, (2) build speeds up to 45 mm/h, and (3) mechanical isotropy, rivaling modern UV-based 3D printing technology and providing a foundation from which bio- and composite-printing can emerge."

The American Chemical Society, in whose journal the work has been published, notes that the new resin combined with printers set up for visible light curing could improve printing costs, improve biocompatibility of the finished print for medical use-cases, and could even open up entirely new applications for 3D printing — "such as," the Society notes, "making opaque composites, multi-material structures or hydrogels containing live cells."

The team's work has been published under open-access terms in the journal ACS Central Science.