Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD Delft, The Netherlands.
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD Delft, The Netherlands; Department of Orthopedics, University Medical Center Utrecht, Heidelberglaan100, 3584CX Utrecht, The Netherlands.
Acta Biomater. 2018 Jan;65:292-304. doi: 10.1016/j.actbio.2017.11.014. Epub 2017 Nov 8.
Additive manufacturing (AM) techniques enable fabrication of bone-mimicking meta-biomaterials with unprecedented combinations of topological, mechanical, and mass transport properties. The mechanical performance of AM meta-biomaterials is a direct function of their topological design. It is, however, not clear to what extent the material type is important in determining the fatigue behavior of such biomaterials. We therefore aimed to determine the isolated and modulated effects of topological design and material type on the fatigue response of metallic meta-biomaterials fabricated with selective laser melting. Towards that end, we designed and additively manufactured Co-Cr meta-biomaterials with three types of repeating unit cells and three to four porosities per type of repeating unit cell. The AM meta-biomaterials were then mechanically tested to obtain their normalized S-N curves. The obtained S-N curves of Co-Cr meta-biomaterials were compared to those of meta-biomaterials with same topological designs but made from other materials, i.e. Ti-6Al-4V, tantalum, and pure titanium, available from our previous studies. We found the material type to be far more important than the topological design in determining the normalized fatigue strength of our AM metallic meta-biomaterials. This is the opposite of what we have found for the quasi-static mechanical properties of the same meta-biomaterials. The effects of material type, manufacturing imperfections, and topological design were different in the high and low cycle fatigue regions. That is likely because the cyclic response of meta-biomaterials depends not only on the static and fatigue strengths of the bulk material but also on other factors that may include strut roughness, distribution of the micro-pores created inside the struts during the AM process, and plasticity.
Meta-biomaterials are a special class of metamaterials with unusual or unprecedented combinations of mechanical, physical (e.g. mass transport), and biological properties. Topologically complex and additively manufactured meta-biomaterials have been shown to improve bone regeneration and osseointegration. The mechanical properties of such biomaterials are directly related to their topological design and material type. However, previous studies of such biomaterials have largely neglected the effects of material type, instead focusing on topological design. We show here that neglecting the effects of material type is unjustified. We studied the isolated and combined effects of topological design and material type on the normalized S-N curves of metallic bone-mimicking biomaterials and found them to be more strongly dependent on the material type than topological design.
增材制造（AM）技术能够制造出具有前所未有的拓扑结构、力学和质量传递性能组合的仿生元生物材料。AM 元生物材料的力学性能直接与其拓扑设计有关。然而，目前尚不清楚在多大程度上材料类型对于确定此类生物材料的疲劳行为很重要。因此，我们旨在确定拓扑设计和材料类型对选择性激光熔化制造的金属元生物材料的疲劳响应的单独和调制影响。为此，我们设计并制造了具有三种重复单元和每种类重复单元三种至四种孔隙率的 Co-Cr 元生物材料。然后对 AM 元生物材料进行力学测试，以获得其归一化 S-N 曲线。将 Co-Cr 元生物材料的获得的 S-N 曲线与我们之前研究中具有相同拓扑设计但由其他材料制成的元生物材料（即 Ti-6Al-4V、钽和纯钛）的 S-N 曲线进行了比较。我们发现材料类型比拓扑设计在确定我们的 AM 金属元生物材料的归一化疲劳强度方面重要得多。这与我们对相同元生物材料的准静态力学性能的发现相反。在高循环和低循环疲劳区域，材料类型、制造缺陷和拓扑设计的影响是不同的。这很可能是因为元生物材料的循环响应不仅取决于大块材料的静态和疲劳强度，还取决于其他因素，例如支柱粗糙度、在 AM 过程中支柱内部形成的微孔的分布以及可塑性。
元生物材料是一类具有特殊性质的超材料，具有机械、物理（例如质量传递）和生物学特性的不寻常或前所未有的组合。拓扑复杂且增材制造的元生物材料已被证明可以改善骨骼再生和骨整合。此类生物材料的力学性能与它们的拓扑设计和材料类型直接相关。然而，以前对这些生物材料的研究在很大程度上忽略了材料类型的影响，而是侧重于拓扑设计。我们在这里表明，忽略材料类型的影响是不合理的。我们研究了拓扑设计和材料类型对金属仿生生物材料归一化 S-N 曲线的单独和综合影响，发现它们比拓扑设计更强烈地依赖于材料类型。
