Harnessing detachment of an aqueous droplet via electrowetting on a flat surface has been of considerable interest for potential practical applications, ranging from self-cleaning to novel optical and digital microfluidic devices, due to the wettability of the droplet on a solid substrate enhanced by applying an electric voltage between the droplet and the insulated substrate. However, a quantitative understanding of the detachment process and an accurate prediction on the thresholds of applied voltage for droplet detachment on curved surfaces are still lacking. In this paper, based on energy conservation, we derive a critical condition theoretically for electrowetting-induced droplet detachment from a hydrophobic curved surface. Furthermore, phase diagrams are constructed in terms of droplet volume, viscosity, the Ohnesorge number, friction coefficient at contact line, surface curvature, surface wettability, and electrowetting number. The deduced critical condition offers a general and quantitative prediction on when the detachment occurs, a criterion enabling us to gain more insights into how to accurately manipulate the electrowetting-induced detachment of an aqueous droplet on a curved surface. The results obtained in this paper also imply that the detachable regimes of the phase diagrams can be enlarged through increasing droplet volume and surface curvature and reducing liquid viscosity, friction coefficient, the Ohnesorge number, and wettability of substrates.

中文翻译：

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电润湿诱导液滴脱离的曲率效应

通过在平面上进行电润湿来利用水滴的分离对于潜在的实际应用具有相当大的兴趣，从自清洁到新型光学和数字微流体设备，由于液滴在固体基板上的润湿性通过应用增强液滴和绝缘基板之间的电压。然而，仍然缺乏对脱离过程的定量理解和对曲面上液滴脱离施加电压阈值的准确预测。在本文中，基于能量守恒，我们从理论上推导出电润湿诱导液滴从疏水曲面脱离的临界条件。此外，相图是根据液滴体积、粘度、Ohnesorge 数、接触线处的摩擦系数、表面曲率、表面润湿性和电润湿数。推导出的临界条件提供了关于何时发生脱离的一般和定量预测，该标准使我们能够更深入地了解如何准确操纵曲面上水滴的电润湿诱导脱离。在本文中获得的结果还意味着相图的可分离区域可以通过增加液滴体积和表面曲率以及降低液体粘度、摩擦系数、Ohnesorge 数和基材的润湿性来扩大。一个标准使我们能够更深入地了解如何准确地操纵水滴在曲面上的电润湿诱导分离。在本文中获得的结果还意味着相图的可分离区域可以通过增加液滴体积和表面曲率以及降低液体粘度、摩擦系数、Ohnesorge 数和基材的润湿性来扩大。一个标准使我们能够更深入地了解如何准确地操纵水滴在曲面上的电润湿诱导分离。在本文中获得的结果还意味着相图的可分离区域可以通过增加液滴体积和表面曲率以及降低液体粘度、摩擦系数、Ohnesorge 数和基材的润湿性来扩大。