Biomimetic topology design of L-PBF-fabricated Zn-Cu alloy bone scaffolds for balancing mechanical performance and degradation behavior.

Balancing mechanical performance and degradation behavior remains a major challenge in the design of biodegradable porous scaffolds for load-bearing bone repair. Inspired by triply periodic minimal surface (TPMS)-like architectures found in nature and the hierarchical organization of cortical and cancellous bone, radially hybrid Diamond-Gyroid (GD) scaffolds with target porosities of 60%-75% were designed and fabricated from a biodegradable Zn-2Cu alloy using laser powder bed fusion (L-PBF). The outer D region and inner G core were integrated to provide complementary load-bearing and deformation functions, while porosity was varied to regulate mechanical performance and degradation behavior. At a target porosity of 60%, the GD scaffold exhibited a 0.2% offset compressive yield strength of 38.4 MPa and a compressive stress of 84.9 MPa at 50% strain. Its energy absorption reached 29.74 MJ m-3, corresponding to improvements of 50.6% and 119.5% over the D and G scaffolds, respectively. Increasing porosity reduced the yield strength, compressive stress at 50% strain, and elastic modulus, while the measured moduli of 1.11-1.78 GPa remained within the range of human cancellous bone. During the 28-day immersion in simulated body fluid, the degradation rates approached approximately 0.2 mm year-1, while electrochemical corrosion activity increased with porosity. The GD-70 scaffold extracts, tested at concentrations ranging from 5% to 50%, exhibited acceptable short-term in vitro cytocompatibility. This work demonstrates that topology fusion combined with porosity regulation offers an effective strategy for balancing the mechanical performance and degradation behavior of biodegradable Zn-based scaffolds, providing a promising design paradigm for next-generation biomimetic load-bearing bone implants.