Grayscale Color 3D/4D Printing via Orthogonal Photochemistry

Coloration is essential for enhancing visual aesthetics and facilitating information communication, but it is difficult to apply to highly complex surfaces. Efficient manufacturing of 3D printed colored products is particularly challenging, given the arbitrary nature of the surfaces. We accomplish this goal with 3D/4D color printing using a photoprintable resin containing a free radical initiator, photocurable monomers, a photoacid generator, and an acid-sensitive dye. The free radical initiator is activated with a long wavelength light (405 nm) for 3D/4D photoprinting. Independently, the photoacid generator is triggered with a shorter wavelength light (365 nm) to activate acid-sensitive dye for coloration. This allows decoupling 3D/4D printing with coloration to yield geometrically complex 3D objects with designable surface color patterns as a highly efficient yet simple way to produce colored 3D objects.