Combined impact of geometric and process-induced dual-grading on the mechanical performance of 3D-Printed TPMS meta-biomaterials

Triply periodic minimal surface architectures have emerged as promising candidates for advanced structural applications. However, uniform triply periodic minimal surface structures often exhibit global instabilities, such as diagonal shear band formation, which limit their energy absorption efficiency and failure predictability. This study proposes a novel dual-grading strategy that integrates mathematical geometric grading, including relative density and cell size gradients, with a process-induced ultraviolet-exposure gradient during masked stereolithography three-dimensional printing. Using a flexible dental gingiva resin, three fundamental topologies were fabricated and subjected to quasi-static compression with in situ failure monitoring. Results demonstrate that the Diamond topology provides the highest Specific Surface Area-to-Volume ratios and load-bearing capacity. Crucially, the dual-grading strategy effectively mitigated the adverse 45° diagonal shear bands observed in uniform specimens, forcing a stable, sequential layer-by-layer collapse mechanism initiated from the softer upper regions. The dual graded with cell size Diamond configuration achieves a peak Specific Energy Absorption of 32.4 J/g, representing a ∼30% improvement in structural efficiency. Moreover, scaling law analysis indicated that this dual-grading strategy shifts the structural deformation mechanism from a bending-dominated regime toward a more efficient stretching-dominated response. Overall, the proposed approach provides a robust and tunable design framework for next-generation load-bearing meta-biomaterials.