生物凝胶微孔挤出胀大的有限元模拟与三维打印成形

由于挤出胀大现象的存在，在室温条件下通过三维打印技术(Three-dimensional printing，3DP)成形的凝胶组织工程支架与输入的目标支架原始模型相比，内部微观孔隙结构精度与孔隙率明显降低。针对这一问题，采用流体计算软件Polyflow对明胶-海藻酸钠共混体系交联形成的生物凝胶材料在挤出成形过程中通过喷头直径过渡段时流线的收缩与离开喷头后的挤出胀大现象进行有限元模拟，着重分析凝胶黏度与供料压力对挤出胀大的影响规律，并通过试验验证模拟的合理性。提出将挤出胀大引起的尺寸变形误差引入支架模型的设计过程。通过数值模拟与试验结果的对比，合理调整模型中纤维间距，利用得到的最佳工艺参数进行凝胶组织工程支架的三维打印成形。结果表明，支架内部的微观孔隙结构精度和孔隙率与理想支架要求近似吻合。通过对生物凝胶挤出胀大的模拟分析，可为凝胶组织工程支架的精确打印成形提供理论依据和技术指导。

Finite Element Simulation of Bio-gel Micropore Extrudate Swell and Three-dimensional Printing Manufacturing

Due to the extrudate swell effect, the accuracy of porous structure and porosity of the gel scaffold, which is fabricated by three-dimensional printing (3DP) at room temperature, are significantly lower than that of the designed scaffold model. To solve this problem, the CFD package Polyflow is used to simulate the streamline shrinkage and extrudate swell of bio-gel material flowing through the injecting nozzle. The influences of the viscosity and applied pressure on the extrudate swell are discussed, and the reliability of the simulation is verified by experiment. The bio-gel material is cross-linked by gelatin and sodium alginate. The compensation of the material size deformation in the forming process is considered in the design of scaffold model. According to comparison between the numerical simulation and the experimental results, the fiber spacing of the scaffold model is reasonably adjusted, and the gel scaffold is fabricated by utilizing the optimized process parameters. The results show that the accuracy of porous structure and porosity of the gel scaffold are proximate to the ideal scaffold. All the above work can provide the theoretical basis and technical guidance for the gel scaffold 3D printed process accurate control.