Bioinspired gradient configurations: Multi-performance optimisation for additively manufactured bone implants

• Four gradient Gyroid structures were developed based on the gradient characteristics of the biological bone structure. • This structure mimics natural bone, achieving cortical bone‐level compressive strength with a low elastic modulus. • Compared with the homogeneous Gyroid structure, the Gyroid–LS structure facilitates nutrient transport and promotes cell adhesion and growth. As traditional bone implants encounter challenges such as stress shielding and inadequate osseointegration, it is imperative to investigate biomimetic gradient triply periodic minimal surface (TPMS) structures to enhance osseointegration performance and mitigate stress shielding effects. Four bioinspired gradient structures were designed based on the Gyroid structure: Gyroid Gradient (Gyroid-G), Gyroid Symmetric (Gyroid-S), Gyroid Large-to-Small (Gyroid-LS), and Gyroid Small-to-Large (Gyroid-SL). The corresponding samples were fabricated using Laser Powder Bed Fusion (LPBF) technology. Through numerical simulations and experimental tests, a comprehensive analysis was conducted on the stress distribution and permeability characteristics of these biomimetic gradient structures. The results indicate that, compared to homogeneous Gyroid structures, the Gyroid-SL structure exhibits over a 10% improvement in elastic modulus and more than a 3% enhancement in permeability. The Gyroid-S structure demonstrates over a 6% improvement in both elastic modulus and permeability compared to homogeneous Gyroid structures. In this study, the comparison of elastic modulus was based on experimental testing, while the permeability comparison was derived from CFD simulations. In vitro cell experiments further confirmed that all four strategies exhibit excellent cytocompatibility. The proposed biomimetic gradient design strategy effectively regulates the balance between mechanical properties and permeability, demonstrating significant potential for bone repair applications.