Vat Photopolymerization 3D Printing of Strain-Amplifying Mechanical-Luminescent Metamaterial of High-Concentration ZnS-Elastomeric Composites

Mechanoluminescent (ML) materials are promising for application in sensing, diagnostic and energy harvesting. The implementation of ML materials in high-resolution additive manufacturing (AM) processes remains restricted because of material and processing limitations. In this study, we introduce a copper-doped zinc sulfide (ZnS:Cu)-based ML photopolymer resin with high loading capacity for use in liquid crystal display based stereolithography (LCD-SLA). The optimization of tip-sonication time and process parameters enables the development of a UV-curable resin that can incorporate 50 wt% filler content while maintaining stable viscosity, effective photocuring properties, and high print quality. The material undergoes rheological, optical and mechanical tests to evaluate its printability and structural performance. Tensile testing and dynamic mechanical analysis (DMA) results show that the material has suitable stiffness and ductility for applications requiring flexibility and durability. The printing of various mechanical-luminescent metamaterial (MLM) geometries result in enhanced mechano-luminescence during deformation. Finite element modeling predicts strain distributions that matches the localized light emission patterns observed during mechanical loading. This study presents a method to incorporate high-filler ML composites into LCD-SLA printing while establishing guidelines for designing photopolymer-based optical sensors with geometric programming capabilities as well as new information on ML composite material properties.