Extrusion-based 3D bioprinting is a direct deposition approach used to create three-dimensional (3D) tissue scaffolds typically comprising hydrogels. Hydrogels are hydrated polymer networks that are chemically or physically cross-linked. Often, 3D bioprinting is performed in air, despite the hydrated nature of hydrogels and the potential advantage of using a liquid phase to provide cross-linking and otherwise functionalize the hydrogel. In this work, we print gelatin alginate hydrogels directly into a cross-linking solution of calcium chloride and investigate the influence of nozzle diameter, distance between nozzle and surface, calcium chloride concentration, and extrusion rate on the dimensions of the printed hydrogel. The hydrogel layer height was generally found to increase with increasing extrusion rate and nozzle distance, according to the increased volume extruded and the available space, respectively. In addition, the hydrogel width was generally found to increase with decreasing nozzle distance and cross-linking concentration corresponding to confinement-induced spreading and low cross-linking regimes, respectively. Width/height ratios of ~ 1 were generally achieved when the nozzle diameter and distance were comparable above a certain cross-linking concentration. Using these relationships, biocompatible 3D multilayer structures were successfully printed directly into calcium chloride cross-linking solution.

中文翻译：

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明胶藻酸盐水凝胶的液相3D生物打印：打印参数对水凝胶线宽和层高的影响

基于挤出的3D生物打印是一种直接沉积方法，用于创建通常包含水凝胶的三维（3D）组织支架。水凝胶是化学或物理交联的水合聚合物网络。尽管水凝胶具有水合性质，而且使用液相提供交联和以其他方式功能化水凝胶的潜在优势，但通常在空气中进行3D生物打印。在这项工作中，我们将明胶藻酸盐水凝胶直接印刷到氯化钙的交联溶液中，并研究喷嘴直径，喷嘴与表面之间的距离，氯化钙浓度和挤出速率对印刷水凝胶尺寸的影响。通常发现水凝胶层的高度随着挤出速率和喷嘴距离的增加而增加，根据增加的挤压量和可用空间。另外，通常发现水凝胶宽度随着喷嘴距离和交联浓度的减小而增加，分别对应于限制引起的扩散和低交联状态。当喷嘴直径和距离在一定的交联浓度以上相当时，通常可达到约1的宽/高比。利用这些关系，将生物相容性3D多层结构成功地直接打印到氯化钙交联溶液中。通常发现水凝胶宽度随着喷嘴距离和交联浓度的减小而增加，分别对应于限制引起的扩散和低交联状态。当喷嘴直径和距离在一定的交联浓度以上相当时，通常可达到约1的宽/高比。利用这些关系，将生物相容性3D多层结构成功地直接打印到氯化钙交联溶液中。通常发现水凝胶宽度随着喷嘴距离和交联浓度的减小而增加，分别对应于限制引起的扩散和低交联状态。当喷嘴直径和距离在一定的交联浓度以上相当时，通常可达到约1的宽/高比。利用这些关系，将生物相容性3D多层结构成功地直接打印到氯化钙交联溶液中。