Rapid, High-Resolution Visible-Light DLP 3D Printing Using 4DP-IPN Photoredox Chemistry and a Liquid-Cooled Vat

This research presents a visible-light-based digital light processing (DLP) 3D printing platform that combines a 4DP-IPN-mediated multicomponent initiating system with thermal and optical control strategies to achieve rapid printing while maintaining high resolution. A N,N-dimethylacrylamide/isobornyl acrylate/trimethylolpropane triacrylate resin was formulated with 4DP-IPN as an organic photoredox catalyst and iodine/borate as co-initiators, enabling efficient radical generation and deep curing under 450 nm irradiation at low catalyst loading. To mitigate the severe exotherm associated with ultrafast curing, a liquid-cooled vat was integrated into the printer architecture, providing direct mechanical cooling of the resin during layer-by-layer fabrication and thereby stabilizing viscosity, refractive index, and dimensional fidelity under high-intensity exposure. In parallel, Sudan I was employed as a visible-light absorber and TEMPO as a radical scavenger to confine the polymerization zone, suppress overcuring and sharpen feature boundaries in both the lateral and vertical directions. This combination of photoredox catalyst design, active thermal management, and optical/radical modulation enabled significantly accelerated build speeds without sacrificing fine feature definition, reducing line broadening, surface roughness, and warpage in benchmark test structures. The results demonstrate a coherent materials-process engineering strategy for overcoming the trade-off between speed and resolution in visible-light DLP printing and highlight the potential of 4DP-IPN-based systems for next-generation high-throughput, high-precision additive manufacturing.