Fig. 1. Concurrent, two-color photoinitiation and photoinhibition.
(A) Optical setup for two-color SLA by concurrent photopolymerization and photoinhibition. Near UV (365 nm) is superimposed onto patterned blue (458 nm) with a dichroic mirror and projected through a transparent window into a photopolymerizable resin vat. Structures of (B) photoinitiator CQ, (C) co-initiator EDAB, and (D) photoinhibitor o-Cl-HABI. (E) UV-visible spectra of CQ (solid blue line) and o-Cl-HABI (dashed violet line) in tetrahydrofuran (THF). The UV and blue wavelengths used by the two-color AM system are highlighted by the violet and blue vertical bars, respectively. (F) Solid block M (left) and tug boat [model detailed in (31)] (right) printed using the two-color photopolymerization/photoinhibition stereolithography system at 500 and 375 mm/hour, respectively. (G) The polymerization inhibition volume thickness is affected by varying intensity ratios of the incident irradiation wavelengths (IUV,0/Iblue,0) and resin absorbance (hUV).