Green-to-red photopolymerization via Dual-Role Dyes for Transparency-Tunable 3D-Printed Hydrogels

Speed and resolution of light-based 3D printing typically relies on multicomponent photopolymer formulations. Here, we present a unique single-dye system that not only controls printing speed and resolution but also tunes the final optical properties of the printed constructs. Photobleaching behavior and photorheology of five dyes in the green-to-red light region were investigated. To gain deeper insight into the printing mechanism and resulting optical properties, one dye (methylene blue) was selected and studied across a series of concentrations to evaluate curing depth, curing resolution, and environmental photobleaching under different light and pH conditions. Together, these results establish a simple route to traceless visible-light DLP hydrogels with tunable optical properties and high print fidelity for biomedical applications.