Phase Diagram of Pinch-off Behaviors During Drop-on-Demand Inkjetting of Alginate Solutions
Phase Diagram of Pinch-off Behaviors During Drop-on-Demand Inkjetting of Alginate Solutions
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DOI：
10.1115/1.4044252
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发表时间：
2019-06
期刊：
影响因子：
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通讯作者：
Changxue Xu;Zhengyi Zhang;Yong Huang;Heqi Xu
中科院分区：
文献类型：
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作者：
Changxue Xu;Zhengyi Zhang;Yong Huang;Heqi Xu
粘弹性聚合物溶液已被广泛用于喷墨打印的各种生物医学应用。粘弹性喷嘴的夹持是喷墨打印中产生液滴的关键一步。这一复杂的过程是由四种应力相互作用控制的，包括惯性应力、毛细应力、粘性应力和弹性应力。根据聚合物溶液的性质和工艺条件，在粘弹性海藻酸盐溶液的喷墨过程中观察到四种类型的夹断现象。本研究对不同浓度的藻酸盐溶液的物性进行了表征，并提出了三个无量纲数(Ohnesorge数oh、Deborah数De和Weber数We)来分析不同的夹断行为。根据这三个无量纲数构建了相图，以分类粘弹性海藻酸盐溶液喷墨过程中不同夹点类型的状态。结果表明：(1)在较低的De和OH值下，毛细管应力主要由惯性应力平衡，从而产生前沿收缩；(2)在中温区和低温区，随着WE的增加，夹点类型可能由前沿夹点到混合夹点再到出口夹点。(3)在低OH和高De条件下，毛细管应力主要由弹性应力平衡，产生出口收缩。(4)在较高的OH和De时，粘弹性效应占主导地位。随着WE的增加，由于成形液滴附近初始韧带直径的增加，中间收缩转变为出口收缩。
Viscoelastic polymer solutions have been extensively utilized in inkjet printing for a variety of biomedical applications. The pinch-off of viscoelastic jets is a key step toward the generation of droplets in inkjet printing. This complex process is governed by the interplay of four stresses, including inertial stress, capillary stress, viscous stress, and elastic stress. Depending on polymer solution properties and process conditions, four types of pinch-off phenomenon were observed during inkjetting of viscoelastic alginate solutions. In this study, material properties of alginate solutions with different concentrations have been characterized, and three dimensionless numbers (Ohnesorge number Oh, Deborah number De, and Weber number We) have been proposed to analyze different pinch-off behaviors. The phase diagram in terms of these three dimensionless numbers has been constructed to classify the regimes for different pinch-off types during inkjetting of viscoelastic alginate solutions. It is found that (1) at low De and Oh, the capillary stress is mainly balanced by the inertial stress, resulting in front pinching. (2) At medium De and low Oh, with the increase of We, the pinch-off type may change from front pinching to hybrid pinching to exit pinching. (3) At low Oh and high De, the capillary stress is mainly balanced by the elastic stress, resulting in exit pinching. (4) At high Oh and De, the viscoelastic effect is dominant. With the increase of We, middle pinching turns to be exit pinching due to the increase in the initial ligament diameter near the forming droplet.