Deformation hysteresis of a water nano-droplet in an electric field
Deformation hysteresis of a water nano-droplet in an electric field
复制标题
电场中纳米水滴的变形滞后
DOI：
10.1140/epje/i2019-11885-8
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发表时间：
2019
影响因子：
1.8
通讯作者：
Yang Qingzhen
中科院分区：
文献类型：
--
作者：
Song Fenhong;Ju Dapeng;Fan Jing;Chen Qicheng;Yang Qingzhen
摘要电场是微纳米尺度下操纵液滴的有效手段，在电场与流体流动的相互作用下，发现了各种各样的物理现象。在这项研究中，我们开发了一个分子动力学模型来研究纳米液滴在均匀电场中的变形行为。纳米液滴最初被限制在两个板之间，然后在下板上润湿（即，衬底）直到平衡状态，之后在垂直方向上向系统施加均匀电场。在电场力的作用下，液滴开始变形，直到达到新的平衡状态，并记录了动态过程。通过比较不同电场强度下的平衡状态，发现了变形滞后现象，即，当增大和减小电场时，获得不同的变形。具体而言，需要较大的电场（E= 0.57 V ·nm^-1）来拉伸纳米液滴以使其接触上板，而相对较低的电场（E= 0.40 V ·nm^-1）足以使其与板保持接触。在变形滞后的同时，还发现了纳米液滴中水分子平均偶极取向的分布滞后现象，这种滞后现象是由液滴与平板之间的电流体动力学相互作用引起的，这一研究结果可以加深我们对液滴在电场中变形的理解。
AbstractElectric field is an effective method to manipulate droplets in micro/nano-scale, and various physical phenomena have been found due to the interaction of electric field and fluid flow. In this study, we developed a molecular dynamic model to investigate the deforming behavior of a nano-droplet in a uniform electric field. The nano-droplet was initially confined between two plates and then wetted on the lower plate (i.e., substrate) until an equilibrium state, after that a uniform electric field in vertical direction was imposed to the system. Due to the electrical force, the droplet started to deform until achieving a new equilibrium state and the dynamic process is recorded. By comparing the equilibrium state under different electric field strength, we found a deformation hysteresis phenomenon,i.e., different deformations were obtained when increasing and decreasing the electric field. To be specific, a large electric field (E= 0.57 V ·nm^-1) is needed to stretch the nano-droplet to touch the upper plate, while a relatively lower field (E= 0.40 V ·nm^-1) is adequate to keep it contacting with the plate. Accompanied by the deformation hysteresis, a distribution hysteresis of the average dipole orientations of water molecules in the nano-droplet is also found. Such a hysteresis phenomenon is caused by the electrohydrodynamic interactions between droplet and plates, and the findings of this study could enhance our understanding of droplet deformation in an electric field.Graphical abstract