Comprehensive Formulation Strategy for 316L Stainless Steel Paste: Optimizing Printability, Curing, and Stability in Digital Light Processing

Metal digital light processing (MDLP) has emerged as a promising route for high-precision metal additive manufacturing (AM), owing to its capability to produce parts with excellent surface quality and fine geometric features. However, its practical application remains limited by the persistent trade-off among curing depth, solid loading, and feedstock stability, particularly for high-density, optically absorptive metal systems. Herein, we report a formulation-driven strategy to address these coupled challenges by simultaneously tailoring the printability, photocuring performance, and stability of a 316L stainless steel (316L SS) photosensitive paste, without relying on particle surface modification, auxiliary heating, or real-time mixing. A high solid loading of 50 vol% was achieved while maintaining a sufficient curing depth of approximately 56 μm through photoinitiator–wavelength matching and resin functionality optimization. Meanwhile, long-term feedstock stability for more than 24 h was realized by incorporating a shear-reversible thixotropic network, which enabled uniform recoating under blade-induced shear and effectively suppressed sedimentation during rest periods. As a result, complex 316L SS parts with high dimensional accuracy and excellent surface quality were successfully fabricated. After debinding and sintering, the parts exhibited a tensile strength of 511.2 ± 22.0 MPa and a fracture elongation of 69.1 ± 9.3%, demonstrating a favorable strength–ductility combination compared with reported values for indirectly additively manufactured 316L SS parts. This work establishes a practical and scalable paste-based formulation strategy for MDLP and provides guidance for extending vat photopolymerization to high-density, optically absorptive metal systems.