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

This study presents a novel additive manufacturing (AM) technique, Photo switchable 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. Traditional vat photopolymerization methods, while known for their high precision, face significant challenges in balancing speed and resolution, requiring extensive support structures and dealing with material instability 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 research is the development of refined resin formulations that integrate azobenzene as a photo switchable molecule, enhancing the controllability of polymerization kinetics. UV-Vis spectrophotometry results showed that azobenzene extended the absorption spectrum into the blue region, with higher concentrations significantly increasing absorbance in the 380–500 nm range, confirming its potential as a photoinhibitor. Though the decreased tensile strength and elastic modulus due to agglomeration and chain disruption, the proposed P-DLP with dual wavelength light demonstrated effective curing of layers by inhibiting undesired curing in boundary and void regions, enabling high-resolution patterning with reduced overcuring artifacts. The advancements introduced in P-DLP make it particularly suited for applications requiring high precision and material integrity, such as optics, medical implants, and soft robotics. This approach represents a significant breakthrough in composite AM, addressing fundamental challenges of conventional methods and enabling faster, more accurate production of intricately detailed components across diverse industrial and biomedical applications.