Zhang Bin, Guo Liwei, Chen Hongyi, Ventikos Yiannis, Narayan Roger J, Huang Jie
Department of Mechanical Engineering, University College London, London, UK.
Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC, USA.
J Mech Behav Biomed Mater. 2020 Apr;104:103665. doi: 10.1016/j.jmbbm.2020.103665. Epub 2020 Jan 30.
Osteochondral (OC) defects usually involve the damage of both the cartilage and its underneath subchondral bone. In recent years, tissue engineering (TE) has become the most promising method that combines scaffolds, growth factors, and cells for the repair of OC defects. An ideal OC scaffold should have a gradient structure to match the hierarchical mechanical properties of natural OC tissue. To satisfy such requirements, 3D printing, e.g., direct ink writing (DIW), has emerged as a technology for precise and customized scaffold fabrication with optimized structures and mechanical properties. In this study, finite element simulations were applied to investigate the effects of pore geometry on the mechanical properties of 3D printed scaffolds. Scaffold specimens with different lay-down angles, filament diameters, inter-filament spacing, and layer overlaps were simulated in compressive loading conditions. The results showed that Young's moduli of scaffolds decreased linearly with increasing scaffold porosity. The orthotropic characteristics increased as the lay-down angle decreased from 90° to 15°. Moreover, gradient transitions within a wide range of strain magnitudes were achieved in a single construct by assembling layers with different lay-down angles. The results provide quantitative relationships between pore geometry and mechanical properties of lattice scaffolds, and demonstrate that the hierarchical mechanical properties of natural OC tissue can be mimicked by tuning the porosity and local lay-down angles in 3D printed scaffolds.
骨软骨（OC）缺损通常涉及软骨及其下方软骨下骨的损伤。近年来，组织工程（TE）已成为结合支架、生长因子和细胞修复OC缺损最具前景的方法。理想的OC支架应具有梯度结构，以匹配天然OC组织的分级力学性能。为满足此类要求，3D打印，例如直接墨水书写（DIW），已成为一种用于精确制造具有优化结构和力学性能的定制支架的技术。在本研究中，应用有限元模拟来研究孔隙几何形状对3D打印支架力学性能的影响。在压缩加载条件下模拟了具有不同铺放角度、细丝直径、细丝间距和层重叠的支架标本。结果表明，支架的杨氏模量随支架孔隙率的增加而线性降低。当铺放角度从90°减小到15°时，正交各向异性特征增加。此外，通过组装具有不同铺放角度的层，在单个构建体中实现了宽应变幅度范围内的梯度转变。这些结果提供了晶格支架孔隙几何形状与力学性能之间的定量关系，并证明通过调整3D打印支架的孔隙率和局部铺放角度，可以模拟天然OC组织的分级力学性能。
