Seehanam Saran, Chanchareon Wares, Promoppatum Patcharapit
Center for Lightweight Materials, Design, and Manufacturing, Department of Mechanical Engineering, Faculty of Engineering, King Mongkut's University of Technology Thonburi (KMUTT), Bangmod, Bangkok, 10140, Thailand.
Princess Srisavangavadhana College of Medicine, Chulabhorn Royal Academy, Bangkok, 10210, Thailand.
Heliyon. 2023 Apr 25;9(5):e15711. doi: 10.1016/j.heliyon.2023.e15711. eCollection 2023 May.
In the field of medical engineering, Triply Periodic Minimal Surfaces (TPMS) structures have been studied widely owing to their physical attributes similar to those of human bones. Computational Fluid Dynamics (CFD) is often used to reveal the interaction between structural architectures and flow fields. Nevertheless, a comprehensive study on the effect of manufacturing defects and non-Newtonian behavior on the fluid responses in TPMS scaffolds is still lacking. Therefore, the present study fabricated Gyroid TPMS with four relative densities from 0.1 to 0.4. Non-destructive techniques were used to examine surface roughness and geometric deviation. We found that the manufacturing defects had a minor effect on fluid responses. The pressure drop comparison between defect-containing and defect-free models could be differed up to 7%. The same comparison for the average shear stress showed a difference up to 23%, in which greater deviation between both models was observed at higher relative density. On the contrary, the viscosity model played a significant role in flow prediction. By comparing the Newtonian model with Carreau-Yasuda non-Newtonian model, the resulting pressure drop and average wall shear stress from non-Newtonian viscosity could be higher than those of the Newtonian model by more than a factor of two. In addition, we matched the fluid-induced shear stress from both viscosity models with desirable ranges of shear stresses for tissue growth obtained from the literature. Up to 70% from the Newtonian model fell within the desirable range while the matching stress reduced to lower than 8% for the non-Newtonian results. Furthermore, by correlating geometric features with physical outputs, the geometric deviation was seen associated with surface curvature while the local shear stress revealed a strong correlation with inclination angle. Overall, the present work emphasized the importance of the viscosity model for CFD analysis of the scaffolds, especially when resulting fluid-induced wall shear stress is of interest. In addition, the geometric correlation has introduced the alternative consideration of structural architectures from local perspectives, which could assist the further comparison and optimization among different porous scaffolds in the future.
在医学工程领域，三重周期极小曲面（TPMS）结构因其与人体骨骼相似的物理属性而受到广泛研究。计算流体动力学（CFD）常被用于揭示结构架构与流场之间的相互作用。然而，关于制造缺陷和非牛顿行为对TPMS支架中流体响应影响的全面研究仍然缺乏。因此，本研究制造了相对密度从0.1到0.4的四种Gyroid TPMS。采用无损技术检测表面粗糙度和几何偏差。我们发现制造缺陷对流体响应影响较小。含缺陷模型和无缺陷模型之间的压降比较差异可达7%。平均剪应力的相同比较显示差异可达23%，其中在较高相对密度下两种模型之间的偏差更大。相反，粘度模型在流动预测中起着重要作用。通过将牛顿模型与Carreau-Yasuda非牛顿模型进行比较，非牛顿粘度产生的压降和平均壁面剪应力可能比牛顿模型高出两倍多。此外，我们将两种粘度模型的流体诱导剪应力与文献中获得的组织生长所需剪应力范围进行了匹配。牛顿模型高达70%的结果落在所需范围内，而非牛顿结果的匹配应力降至低于8%。此外，通过将几何特征与物理输出相关联，发现几何偏差与表面曲率相关，而局部剪应力与倾斜角有很强的相关性。总体而言，本研究强调了粘度模型在支架CFD分析中的重要性，特别是当关注由此产生的流体诱导壁面剪应力时。此外，几何相关性从局部角度引入了对结构架构的另一种考虑，这有助于未来不同多孔支架之间的进一步比较和优化。
