Digital Light Processing 3D Printing of Polymer Composites Based on Tunable Curing Resins with Photoswitchable Molecules.

Abstract

This study presents an additive manufacturing (AM) technique, photoswitchable direct light processing (P-DLP), which utilizes a dynamic mask imaging photoinitiation approach to mitigate light-scattering effects caused by filler particles like silicon carbide (SiC) in composite printing. Vat photopolymerization AM process offers high precision but faces significant challenges in balancing speed and resolution, material instability, and requiring extensive support structures during fabrication. The P-DLP technique overcomes these limitations by employing a dynamic masking system, where ultraviolet (UV) light initiates photopolymerization and visible (blue) light selectively inhibits undesired polymerization. This mechanism allows for precise control over the curing process, enabling the fabrication of complex high-resolution structures while minimizing scattering-induced distortions. A key aspect of this work is the resin formulation incorporating azobenzene as a photoswitchable additive, enhancing the controllability of the polymerization kinetics. UV-vis spectrophotometry results showed that azobenzene extended the absorption spectrum into the blue region, with higher concentrations significantly increasing the absorbance in the 380-500 nm range, confirming its potential as a photoinhibitor. Despite reductions in mechanical properties, the proposed dual-wavelength P-DLP method demonstrated robust control over layer curing, successfully inhibiting unwanted polymerization in the boundary and void regions. This enabled high-resolution printing with minimal overcuring artifacts. The advancements in P-DLP make it well-suited for applications demanding high precision and structural integrity, including optical, medical implants, and soft robotics. Overall, this approach marks a significant advancement in composite AM by overcoming key limitations of conventional methods and enabling the faster, more accurate fabrication of complex components for industrial and biomedical use.