Design exploration of staggered hybrid minimal surface magnesium alloy bone scaffolds

• Published in: International journal of mechanical sciences 2024-11, Vol.281, p.109566, Article 109566
• Main Authors: Li, Kun, Liao, Ruobing, Zheng, Qingcui, Zuo, Chunlin, Yin, Bangzhao, Ji, Chen, Liang, Haisong, Wen, Peng, Jiang, Bin, Pan, Fusheng, Murr, Lawrence E.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Bone tissue engineering; Magnesium alloy scaffolds; Porous structures; Staggered hybrid structures; Triply periodic minimal surface
• ISSN: 0020-7403
• DOI: 10.1016/j.ijmecsci.2024.109566

•Novel implicit modeling method with offset functions precisely controls TPMS geometry and properties, enabling freeform deformation and avoiding Boolean operation errors.•SH-TPMS optimizes the balance between volume fraction and surface area, demonstrating a 50% increase in specific surface area over traditional TPMS.•SH-TPMS exhibits superior fluid dynamics and tunable mechanical properties, including anisotropy.•Successful fabrication of Mg alloy SH-TPMS bone scaffolds using LPBF technology, matching human bone properties with hierarchical porous structures. Bone implant design faces multifaceted challenges, requiring the simultaneous optimization of hierarchical porous structures, large surface areas, and appropriate elastic moduli. Triply Periodic Minimal Surface (TPMS) structures show promise but are limited in their design space, making it difficult to comprehensively and precisely control these properties. This study introduces a novel implicit modeling method for reconstructing TPMS structures, breaking longstanding limitations of design freedom in bone implant design. This innovative approach uses an offset function to precisely manipulate discrete points on the isosurface, achieving unprecedented controllable freeform deformation while avoiding errors in conventional Boolean operations. Building on this breakthrough, new staggered hybrid TPMS (SH-TPMS) porous structures are developed that effectively balance and optimize volume fraction and surface area. Subsequently, magnesium alloy SH-TPMS bone scaffolds have been successfully fabricated using laser powder bed fusion (LPBF) technology. The resulting SH-TPMS structures feature multi-level controllable channel architectures. Compared to conventional TPMS structures, these staggered hybrid designs maintain consistent elastic modulus and deformation patterns through optimized mass distribution while achieving an average increase of 50 % in specific surface area at equivalent volume fractions. Mechanical performance tests confirm that the elastic moduli of the SH-Gyroid and SH-Diamond scaffolds are 4.56 GPa and 8.40 GPa, respectively, comparable to that of human bone. This work presents a promising new strategy for fabricating optimized bone implants, offering a balance between enhanced surface area and tailored mechanical properties. [Display omitted]