Material extrusion, a filament-based three-dimensional (3D) bioprinting technique, is commonly adopted to fabricate many complex constructs for its high efficiency, compatibility with a variety of biomaterials, and easy realization. During extrusion bioprinting, the morphology (including the shape and size) of extruded filaments is of great interest since the filaments are the basic building blocks for printed 3D structures and the filament morphology determines the printing resolution, surface quality, and part mechanical strength. The objective of this study is to computationally analyze the printing performance of the jammed gelatin microgel-based composite ink during extrusion in terms of the filament cross-sectional morphology and the influence of ink yield-stress fluid property on the structural printability. As seen from the rheological measurements, the jammed gelatin microgel composite ink is a viscoplastic fluid with the shear-thinning property, and its yield-stress fluid property enables it for self-supported printing applications. The ink printing process has been computationally modeled by using a fitted Herschel–Bulkley model to simulate the behavior of the jammed gelatin microgel composite ink for the first time, resulting in good modeling performance. In particular, the filament cross-sectional morphology under different printing conditions has been satisfactorily modeled. It is found that the cross-sectional shape turns flat rectangular under a small normalized gap distance (less than 0.6). Furthermore, the achievable maximum length (without collapse) of the jammed gelatin microgel-based composite ink, deposited both between two supporting substrates and over a supporting substrate, has been satisfactorily estimated.

材料挤出是一种基于长丝的三维（3D）生物打印技术，由于其高效，与多种生物材料兼容且易于实现，因此通常被用来制造许多复杂的结构。在挤出生物打印过程中，由于长丝是打印的3D结构的基本构建基块，并且长丝的形态决定了打印分辨率，表面质量和零件机械强度，因此挤出长丝的形态（包括形状和尺寸）引起了人们的极大兴趣。这项研究的目的是根据长丝的横截面形态以及油墨屈服应力流体性质对结构可印刷性的影响，在挤出过程中通过计算分析堵塞的明胶微凝胶基复合油墨的印刷性能。从流变学测量可以看出，堵塞的明胶微凝胶复合油墨是具有剪切稀化特性的粘塑性流体，其屈服应力流体特性使其可用于自承式印刷应用。通过使用拟合的Herschel-Bulkley模型对油墨印刷过程进行了计算建模，首次模拟了堵塞的明胶微凝胶复合油墨的行为，从而获得了良好的建模性能。特别地，已经令人满意地模拟了在不同印刷条件下的长丝横截面形态。结果发现，在较小的归一化间隙距离（小于0.6）下，横截面形状变为扁平的矩形。此外，堵塞的明胶微凝胶基复合油墨可达到的最大长度（无塌陷），