Sustainable approaches in vat photopolymerization: advancements, limitations, and future opportunities

Vat photopolymerization (VP) is reshaping advanced manufacturing, yet its dependence on petrochemical-derived resins poses significant sustainability challenges. This review critically evaluates conventional photocurable formulations, highlighting the limitations of standard metrics such as the biobased carbon content (BCC%), and introduces the sustainable formulation score (SFS) as a comprehensive alternative. By integrating factors like atom economy, hazardous reagent usage, solvent selection, and end-of-life considerations, SFS offers a more holistic measure of environmental impact. The analysis encompasses diverse resin systems, including (meth)acrylated vegetable oil derivatives, biobased small molecules from lignin and other renewable sources, non-isocyanate urethanes, and thiol-ene formulations. For vegetable oil-based systems, a key trade-off is observed between achieving high biobased content and maintaining optimal mechanical properties, driven by variations in the degree of acrylation and processing conditions. In contrast, the synthesis of small biobased molecules often involves toxic reagents and less favorable atom economies, reducing their overall green appeal. Moreover, non-isocyanate urethanes and thiol-ene systems emerge as promising routes for improving sustainability while preserving performance. Overall, this review underscores the need for unified green metrics and optimized synthesis strategies to bridge the gap between environmental sustainability and material performance in photopolymer formulations, paving the way for more responsible and efficient additive manufacturing technologies.