Capillary-flow dynamics in open rectangular microchannels
Capillary-flow dynamics in open rectangular microchannels
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DOI：
10.1017/jfm.2020.986
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发表时间：
2021-01-28
影响因子：
3.7
通讯作者：
Kumar, Satish
中科院分区：
文献类型：
--
作者：
Kolliopoulos, Panayiotis;Jochem, Krystopher S.;Kumar, Satish
狭窄空间中液体的自发毛细管流动在众多应用中发挥着关键作用，包括芯片实验室设备、热管、航天器中的推进剂管理设备和柔性印刷电子制造。在这项工作中，我们结合理论和实验来研究开放矩形微通道中的毛细管流动动力学，这种微通道经常出现在这些应用中。扫描电子显微镜和轮廓测定法用于突出自由表面形态的复杂性。我们开发了一种基于自相似润滑理论的模型来解释这种复杂性，并将模型预测与广泛使用的修改后的 Lucas-Washburn 模型进行比较，以及对各种通道纵横比 lambda 和平衡接触角 theta(0) 的实验观察。我们证明，对于较大的 lambda，两个模型预测是无法区分的，而对于较小的 lambda，基于润滑理论的模型与实验更加吻合。基于润滑理论的模型也被证明与较小 theta(0) 下的实验具有更好的一致性，尽管当 theta(0) -> pi/4 时，它无法解释对自由表面的重要轴向曲率贡献并且一致性恶化。最后，我们表明基于润滑理论的模型还可以定量预测延伸到半月板之前的手指的动力学。这些发现阐明了修改后的卢卡斯-沃什伯恩模型的局限性，并证明了考虑复杂自由表面形态对开放矩形微通道中毛细管流动动力学影响的重要性。
Spontaneous capillary flow of liquids in narrow spaces plays a key role in a plethora of applications including lab-on-a-chip devices, heat pipes, propellant management devices in spacecrafts and flexible printed electronics manufacturing. In this work we use a combination of theory and experiment to examine capillary-flow dynamics in open rectangular microchannels, which are often found in these applications. Scanning electron microscopy and profilometry are used to highlight the complexity of the free-surface morphology. We develop a self-similar lubrication-theory-based model accounting for this complexity and compare model predictions to those from the widely used modified Lucas-Washburn model, as well as experimental observations over a wide range of channel aspect ratios lambda and equilibrium contact angles theta(0). We demonstrate that for large lambda the two model predictions are indistinguishable, whereas for smaller lambda the lubrication-theory-based model agrees better with experiments. The lubrication-theory-based model is also shown to have better agreement with experiments at smaller theta(0), although as theta(0) -> pi/4 it fails to account for important axial curvature contributions to the free surface and the agreement worsens. Finally, we show that the lubrication-theory-based model also quantitatively predicts the dynamics of fingers that extend ahead of the meniscus. These findings elucidate the limitations of the modified Lucas-Washburn model and demonstrate the importance of accounting for the effects of complex free-surface morphology on capillary-flow dynamics in open rectangular microchannels.