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). 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. Photochemistry at these longer wavelengths
currently suffers from slow reaction times precluding its utility.
Herein, novel panchromatic photopolymer resins were developed and
applied for the first time to realize rapid high-resolution visible
light 3D printing. 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. 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.