Sub-regional design of the bionic bone scaffolds using macrostructural topology

With the increasing demand for bone repair, the bionic bone scaffolds have become a research hotspot. A sub-regional design method of the bionic bone scaffolds, using macrostructural topology, is proposed in this paper, aiming to provide a functionally enhanced region division method for the gradient design. The macrostructural topology was carried out by the bi-directional evolutionary structural optimization (BESO), dividing the predefined design domain into sub-region A and sub-region B. Subsequently, a combined probability sphere model and a distance-to-scale coefficient mapping model are established to implement the graded porosification based on the Voronoi tessellation. This approach takes geometric and mechanical continuity into fully account and assures a reasonable distribution of characteristic parameters, yielding to improve the mechanical strength under specific stress conditions. Finally, the scaffolds were fabricated by the laser powder bed fusion (LPBF) process using the Ti-6Al-4V powder. The results of compression tests are satisfactory, showing that the as-built specimens implement sub-regional functionality. The apparent elastic modulus and the ultimate strength range, respectively, between 1.50 GPa and 7.12 GPa (for the first module) and between 38.55 MPa and 268.03 MPa (for the second module), which conform to the required level of natural bone, providing a possibility for clinical application.