Formation of simple and compound drops in microfluidic devices
Formation of simple and compound drops in microfluidic devices
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DOI：
10.1063/1.2353116
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发表时间：
2006-09
影响因子：
4.6
通讯作者：
Chunfeng Zhou;P. Yue;James J. Feng
中科院分区：
文献类型：
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作者：
Chunfeng Zhou;P. Yue;James J. Feng
这项工作的动机是最近的实验发展的微流体流动聚焦装置，产生高度单分散的简单或复合液滴。使用自适应网格的扩散界面框架中的有限元，我们模拟了简单和复合射流在同向流动条件下的破碎，并探讨了在不同参数范围内盛行的流态。此外，我们还研究了粘弹性对界面破裂和液滴夹断的影响。简单液滴的形成在相对低的流速下表现出滴落状态，在较高的流速下表现出喷射状态。在这两种情况下，由于毛细管不稳定性和粘性阻力的综合作用，液滴形成。液滴尺寸随内流体流量的增加而增大，随外流体流量的增加而减小。在滴相的粘弹性增加滴的大小在滴落制度，但减少它在喷射制度。复合液滴的形成是一个微妙的过程，发生在一个狭窄的窗口的流动和流变参数。内部液滴的封装关键取决于内外界面上毛细波的协调。
This work is motivated by the recent experimental development of microfluidic flow-focusing devices that produce highly monodisperse simple or compound drops. Using finite elements with adaptive meshing in a diffuse-interface framework, we simulate the breakup of simple and compound jets in coflowing conditions, and explore the flow regimes that prevail in different parameter ranges. Moreover, we investigate the effects of viscoelasticity on interface rupture and drop pinch-off. The formation of simple drops exhibits a dripping regime at relatively low flow rates and a jetting regime at higher flow rates. In both regimes, drops form because of the combined effects of capillary instability and viscous drag. The drop size increases with the flow rate of the inner fluid and decreases with that of the outer fluid. Viscoelasticity in the drop phase increases the drop size in the dripping regime but decreases it in the jetting regime. The formation of compound drops is a delicate process that takes place in a narrow window of flow and rheological parameters. Encapsulation of the inner drop depends critically on coordination of capillary waves on the inner and outer interfaces.