Marangoni-induced reversal of meniscus-climbing microdroplets
Marangoni-induced reversal of meniscus-climbing microdroplets
复制标题
马兰戈尼诱导的半月板攀爬微滴逆转
DOI：
10.1039/d2sm00979j
复制
发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Weisensee, Patricia B.
中科院分区：
文献类型：
--
作者：
Sun, Jianxing;Weisensee, Patricia B.
由于不平衡的毛细作用力，位于油的半月面上的小水滴或颗粒通常会爬上半月面。在这里，我们介绍了这种半月面攀升行为的大小相关的逆转，其中，当底层冷却时，不同大小的液滴同时在半月板上上升和下降。我们发现，油半月面内的微观Marangoni对流单元是造成这一现象的原因。虽然相对较大的水滴的动力学仍然受到不平衡的毛细管力的支配，因此上升到半月面，但较小的水滴被表面流动携带，因此下降到半月面。我们进一步证明了对流单体的大小和方向取决于半月面几何形状和衬底温度，并引入了一个修正的Marangoni数来很好地预测它们的强度。我们的发现为操纵液体半月面上的液滴提供了一种新的方法，这可能在材料自组装、生物传感和测试以及相变热传输方面有应用。
Small water droplets or particles located at an oil meniscus typically climb the meniscus due to unbalanced capillary forces. Here, we introduce a size-dependent reversal of this meniscus-climbing behavior, where upon cooling of the underlying substrate, droplets of different sizes concurrently ascend and descend the meniscus. We show that microscopic Marangoni convection cells within the oil meniscus are responsible for this phenomenon. While dynamics of relatively larger water microdroplets are still dominated by unbalanced capillary forces and hence ascend the meniscus, smaller droplets are carried by the surface flow and consequently descend the meniscus. We further demonstrate that the magnitude and direction of the convection cells depend on the meniscus geometry and the substrate temperature and introduce a modified Marangoni number that well predicts their strength. Our findings provide a new approach to manipulating droplets on a liquid meniscus that could have applications in material self-assembly, biological sensing and testing, or phase change heat transfer.