Topological transitions and graded wall thicknesses cooperatively boost mechanical and mass-transport behavior in TPMS Mg-scaffolds

Hybrid scaffolds combining various Triply Periodic Minimal Surface architectures enable coordinated functional performance. However, their direct assembly introduces geometric discontinuities at the interfaces, leading to compromised mechanical and fluidic properties. Here, a gradient transition region is designed to facilitate smooth topological evolution between Primitive and Gyroid structures, while a wall-thickness gradient modulates stiffness and pore characteristics. The scaffolds are fabricated via laser powder bed fusion using WE43 alloy. Results demonstrate that the hybrid scaffold achieved an elastic modulus of 1.20 GPa and a yield strength of 43.64 MPa, marking increases of approximately 39% and 56% over a uniform‑wall‑thickness hybrid counterpart. The results reveal that the graded structural distribution effectively disperses external loads across adjacent unit cells and the transition zone, suppressing local instabilities and delaying early interfacial failure. Meanwhile, the permeability reaches 9.6 × 10 − ⁹ m², approaching that of the highly permeable Gyroid scaffold, since the continuously evolving pore morphology mitigates velocity fluctuations and pressure accumulation caused by localized channel constrictions. These attributes establish a synergistic optimization mechanism, in which the Primitive region provides structural support and load transfer, the Gyroid region facilitates efficient mass transport, and the graded transition zone ensures mechanical and fluidic compatibility between them. This strategy alleviates the stiffness-permeability trade-off within the investigated design space by integrating the complementary functions of the two topologies within a continuously graded architecture.