Dielectrophoretic stretching of drops of silicone oil: Experiments and multi-physical modeling
Dielectrophoretic stretching of drops of silicone oil: Experiments and multi-physical modeling
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DOI：
10.1063/5.0087219
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发表时间：
2022-04
影响因子：
4.6
通讯作者：
R. Granda;Gen Li;Vitaliy Yurkiv;F. Mashayek;A. Yarin
中科院分区：
文献类型：
--
作者：
R. Granda;Gen Li;Vitaliy Yurkiv;F. Mashayek;A. Yarin
实验表明，两种不同粘度的纯硅油滴在聚丙烯基材上对面内电场不发生反应。在相对湿度为80%的潮湿气氛中预处理硅油，使油中含有与水有关的离子，在面内电场的作用下，导致随后的液滴轻微拉伸。这些现象表明，原始硅油不包含任何离子和反离子的足够浓度的任何库仑力或麦克斯韦应力的出现，这将导致液滴拉伸。然而，实验证明，当5 wt. %的[公式：见文]颗粒悬浮在油中时，受面内电场作用，聚丙烯基板上的硅油滴拉伸更强。这些粒子表现为电偶极子，当受到非线性对称电场的作用时，它们会受到介电力的作用，这将它们吸引到空气和油中的两个电极上。负载TiO2颗粒的硅油滴在介质电泳驱动下的三维模拟也显示了在电极间方向上明显的液滴拉伸，与实验数据定性一致。尽管如此，数值模拟预测了一个无界的拉伸，两个舌头在两个下降的侧面发展。这一预测与实验不一致，在实验中，介电驱动的拉伸停止，无舌的稳态液滴结构得到了实现。这种分歧可能与实验中的事实有关，[公式：见文本]颗粒沉降到基片上，并受到显著的额外摩擦力，这可能最终阻止它们。
It is shown experimentally that drops of two pure silicone oils of different viscosities on a polypropylene substrate do not react to the in-plane electric field. Pre-treatment of silicone oil in a humid atmosphere at 80% relative humidity enriches oil with water-related ions and results in subsequent drop slight stretching under the action of the in-plane electric field. These phenomena demonstrate that the original silicone oils do not contain a sufficient concentration of any ions and counter-ions for the appearance of any Coulomb force or Maxwell stresses, which would result in drop stretching. However, a stronger stretching of silicone oil drops on the polypropylene substrate subjected to the in-plane electric field was experimentally demonstrated when 5 wt. % of [Formula: see text] particles was suspended in oil. The particles behave as electric dipoles and, when subjected to a nonlinear symmetric electric field, experience dielectrophoretic force, which attracts them to both electrodes in air and oil. 3D simulations of the dielectrophoretically driven evolution of silicone oil drops laden with TiO2 particles also revealed a significant drop stretching in the inter-electrode direction in qualitative agreement with the experimental data. Still, numerical simulations predict an unbounded stretching with two tongues developing at the two drop sides. This prediction disagrees with the experiments where the dielectrophoretically driven stretching ceases and steady-state drop configurations without tongues are attained. This disagreement is probably related to the fact that in the experiments, [Formula: see text] particles settle onto the substrate and are subjected to significant additional friction forces, which could ultimately arrest them.