从仿生的角度设计用于指导构建组织支架的单元细胞模块、有限元分析以及3D打印工艺路径规划

Biomimetic modeling and analysis of computer aided bone tissue scaffolds, an exact copy of tissue anatomical structure may produce the optimal design. However, the limitations of computing and fabrication techniques make such replication impossible. One key area in tissue engineering is the design of three-dimensional bone tissue scaffolds. The micro-architecture of the scaffold greatly influences cell proliferation, migration, and differentiation, which is required for proper bone function and morphogenesis. Scaffolds have several complicated biological constraints, including the integrity of the scaffold structure, micro-structure, and scaffold manufacturability. The complexity of scaffolds requires new approaches and computational algorithms to match the desired criteria for internal permeability, pore size, and connectivity. The project intends to make full use of the interdisciplinary integration advantages of tissue engineering, solid modeling, computational design methods, as well as mechanical and biomedical engineering, By obtaining the biological, biomechanical and biochemical information of the tissue, systematically and deeply from the point of view of bionic design to guide the construction of tissue scaffold unit cell module, analysis and fabrication, including tissue scaffold bionic modeling, anatomical structure reconstruction, quantifying QCT analysis, finite element analysis, 3D printing process path planning based on combination mapping technology and support free extruding deposition for fabrication of tissue scaffolds. Modeling accuracy and competence, scaffold structural integrity and stability, manufacturability will be verified by experiment.

计算机辅助骨组织支架仿生建模与分析中，精确地复制组织解剖结构可以获得最优设计结果，由于计算与制造技术限制使这种精确复制难以实现。组织工程研究领域中一个关键问题是三维骨组织支架设计。支架微结构极大地影响细胞增殖、迁移和分化。支架具有复杂生物约束，包括支架结构完整性、微结构和支架可制造性。支架的复杂性决定了需要研究新的设计方法和计算算法构建符合组织结构内部渗透率、孔隙率和连通性等要求的计算模型。项目拟充分利用组织工程、实体建模、计算设计方法及力学与生物医学多学科交叉融合优势，通过获取组织的生物学、生物力学及生物化学信息，系统而深刻地从仿生的角度设计用于指导构建组织支架的单元细胞模块、分析与制作，包括组织支架仿生建模、解剖结构重建、定量QCT分析、有限元分析、基于组合映射技术的3D打印工艺路径规划和支架自由挤压沉积制作。从建模精度与能力、支架结构完整性和稳定性以及可制造性等方面进行实验验证。

人体硬组织支架仿生原型构建的关键问题为组织微结构孔隙率、渗透率、内部连通性和密度以及生物力学约束和生物学评价，实现几何相容性与生物适应性。项目从仿生的角度设计用于指导构建组织支架的单元细胞模块，以人体胫骨近端为研究对象，首先基于Micro-CT扫描获取0.03mm层厚的DICOM格式数据文件，采用二值化和去噪处理，获取非规则且孔隙与椭圆具有高度相似性的微断层图像；采用最小二乘法椭圆拟合图像孔隙，并对椭圆几何参数进行数据统计分析，探讨相应孔隙上椭圆分布规律，实验得到椭圆短半径趋于0.24mm，长半径趋于0.48mm；选取椭球为多孔支架构建单元体，基于极值点分析三维空间椭圆蜂窝结构，并在此基础上提出了CAD建模与计算机程序设计相结合的快速建模方法；基于四面体结构空间排布方式，通过支柱表面镜像和空间阵列，设计了两种四面体微结构单元体，并建立支架晶格仿生模型；以1×2×2晶胞单元的四面体模型为例，采用钛合金（Ti6Al4V）材料，分析线性静态结构力学性质，并优化微结构参数，建立不同孔隙率下四面体单元支柱直径、支柱长度、弹性模量与最大应力之间的数学模型，使其满足结构力学性能要求；分析四面体结构对支架性能的影响，为进一步优化设计提供理论支撑。