Ti多孔结构选区激光熔化成型及性能研究

        3D打印技术也被称为增材制造，是根据三维模型数据，通过自动控制逐层增添材料，最终制得所需零件的制造方法，这使得3D打印受复杂几何形状的限制很少。因此，3D打印技术在骨科植入物领域的应用得到了快速发展，3D打印技术可以制备具有复杂多孔结构及内部结构的骨科植入物。然而，相同生物相容材料前提下，3D打印骨科植入物中不同类型多孔结构、同种多孔结构在不同几何结构参数的情况下，其对生物成骨细胞的生长影响规律尚未得到系统性的研究，在现有的技术流程中，仅依赖医生及设计人员的经验进行选择，这一定程度上降低了植入物的可靠性及科学性。本研究选取了十二面体晶格结构、金刚石晶格结构、螺旋十二面体、费舍诺克曲面、泰森多边形等五种多孔结构，通过计算机辅助设计技术进行了三维建模，并通过选区激光熔化技术，在N₂和Ar混合气氛围下制备了具有不同结构参数的20个氮气氛强化纯钛多孔结构样品。

        本论文对不同多孔结构样品进行了压缩试验，分析了孔隙率及单胞尺寸对弹性模量的影响规律，同时对屈服强度、极限强度、能量吸收能力等关键力学性能进行了测定，并与人体骨质相应参数对比，以表征其力学性能差异；对样品进行了成骨细胞培养实验，并进行了矿化，利用酶标仪对Ca含量进行半定量分析，对比了成骨细胞在不同多孔结构样品内的生长情况；通过活死细胞染色，研究了细胞在多孔结构中生长的情况及表面附着情况，以研究细胞在不同多孔结构中的生长状况差异；最后对样品进行了细胞增殖、毒性试验及溶血性试验，以更全面验证其生物性能。

        实验表明，通过合适的选区激光熔化工艺参数可以顺利成型介观尺度的多孔结构，且最优能量密度约为实体结构的0.4倍，通过调节不同能量密度，还可形成不同的微表面粗糙结构；氮气氛强化纯Ti多孔结构的性能可以通过其与孔隙率及单胞尺寸等参数的关系进行较好预测；Ti多孔结构的生物相容性及促进细胞融合生长性能优良，其中 螺旋十二面体型多孔结构样品综合性能最优；各种多孔结构弹性模量均在0.2~20 GPa范围内，符合人体骨质的模量范围，因此能很好减缓应力屏蔽效应，适合植入物应用。

3D printing technology, also known as additive manufacturing, is a manufacturing method of adding materials layer by layer through automatic control based on 3D model data to finally produce the required parts, which makes 3D printing less limited by complex geometries. Therefore, the application of 3D printing technology in the field of orthopedic implants has been rapidly developed. 3D printing technology can prepare orthopedic implants with complex porous structures and internal structures. However, under the premise of the same biocompatible materials, different types of porous structures in 3D printed orthopedic implants, the same porous structure in the case of different geometric structure parameters, its influence on the growth of biological osteoblasts has not been systematically studied. The existing technical process, only relies on the experience of doctors and designers for selection, which reduces the reliability and scientificity of implants to a certain extent. In this study, five porous structures such as Dodecahedron, Diamond, Gyroid, Fischer Koch S and Voronoi were selected, 3D modeling by computer-aided design technology and 20 samples with different structural parameters were prepared by selective laser melting under N₂ and Ar mixture atmosphere.

In this study, compression tests were carried out on samples with different porous structures, and the influence of porosity and unit cell length on the elastic modulus was analyzed. At the same time, key mechanical properties such as yield strength, ultimate strength, and energy absorption capacity were measured. The corresponding parameters of the bone were compared to characterize the difference in mechanical properties; the samples were subjected to osteoblast culture experiments and mineralization, and the Ca content was semi-quantitatively analyzed by a microplate reader, and the osteoblasts in different porous structures were compared. Growth in the sample through live and dead cell staining, the growth of cells in the porous structure and the ability to attach to the surface were studied to study the difference in the growth of cells in different porous structures. Finally, the samples were tested for cell proliferation and toxicity and hemolytic test to more comprehensively verify its biological properties.

The research shows that the mesoscopic-scale porous structure can be successfully formed by suitable selective laser melting process parameters, and the optimal energy density is about 0.4 times that of the solid structure. Different micro-surface rough structures can also be formed by adjusting different energy densities. The performance of pure Ti porous structure strengthened by nitrogen atmosphere can be well predicted by its relationship with parameters such as porosity and unit cell size. Among them, the Gyroid porous structure sample has the best comprehensive performance. The elastic modulus of various porous structures is in the range of 0.2~20 GPa, which is in line with the modulus range of human bone, so it can well reduce the stress shielding effect and is suitable for implant applications.

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