Despite their remarkable effect on printing accuracy and uniformity, charge migrations that dominate the deformation of ink droplets during electrohydrodynamic jet printing have not been widely investigated. In this work, the large deformation mechanisms of a conductive nanodroplet under a strong electric field are examined from the point of view of charge migrations. It is found that the charge migrations include the charge relaxation in the bulk of the droplet and surface charge convection at the fluid interface. A conductive nanodroplet first evolves into an ellipsoid through charge relaxation. Then, the ellipsoid is deformed by the convection of the surface charges in four modes, namely, tip streaming (mode 1), lobe formation (mode 2), finger stretching (mode 3), and dumbbell stretching (mode 4). Finally, the stretched nanodroplet is broken into secondary droplets. Modes 1, 2, and 4 are in agreement with the experimental observations. Furthermore, it is found that over 20% of the charges are distributed inside the bulk nanodroplet and the other charges are distributed at the surface, causing the four deformation modes. Analysis based on the electric Reynolds number (the ratio of electric field force to viscous force) and the Coulombic capillary number (the ratio of surface tension to Coulombic force) shows that the nanodroplet is prolate if the electric field force is dominant. When the Coulombic force plays a crucial role, the nanodroplet deforms into an ellipsoid with wide cones. By contrast, the nanodroplet will generate hemispherical ends if the deformation is dominated by the effect of surface tension.Despite their remarkable effect on printing accuracy and uniformity, charge migrations that dominate the deformation of ink droplets during electrohydrodynamic jet printing have not been widely investigated. In this work, the large deformation mechanisms of a conductive nanodroplet under a strong electric field are examined from the point of view of charge migrations. It is found that the charge migrations include the charge relaxation in the bulk of the droplet and surface charge convection at the fluid interface. A conductive nanodroplet first evolves into an ellipsoid through charge relaxation. Then, the ellipsoid is deformed by the convection of the surface charges in four modes, namely, tip streaming (mode 1), lobe formation (mode 2), finger stretching (mode 3), and dumbbell stretching (mode 4). Finally, the stretched nanodroplet is broken into secondary droplets. Modes 1, 2, and 4 are in agreement with the experimental observations. Furthermore, it is found that over 20% of the charges are distribut...

中文翻译：

---

强电场下导电纳米液滴的大变形

尽管它们对打印精度和均匀性有显着影响，但在电流体动力喷射打印过程中主导墨滴变形的电荷迁移尚未得到广泛研究。在这项工作中，从电荷迁移的角度研究了导电纳米液滴在强电场下的大变形机制。发现电荷迁移包括液滴本体中的电荷弛豫和流体界面处的表面电荷对流。导电纳米液滴首先通过电荷弛豫演变成椭圆体。然后，椭圆体通过四种模式的表面电荷对流变形，即尖端流（模式 1）、叶形成（模式 2）、手指拉伸（模式 3）和哑铃拉伸（模式 4）。最后，拉伸的纳米液滴被分解成二次液滴。模式 1、2 和 4 与实验观察一致。此外，发现超过 20% 的电荷分布在体纳米液滴内部，其他电荷分布在表面，导致四种变形模式。基于雷诺数（电场力与粘性力的比值）和库仑毛细管数（表面张力与库仑力的比值）的分析表明，如果电场力占主导地位，纳米液滴是扁长的。当库仑力起关键作用时，纳米液滴变形为具有宽锥体的椭圆体。相比之下，如果变形受表面张力的影响，纳米液滴将产生半球形末端。尽管它们对打印精度和均匀性有显着影响，但在电流体动力喷射打印过程中主导墨滴变形的电荷迁移尚未得到广泛研究。在这项工作中，从电荷迁移的角度研究了导电纳米液滴在强电场下的大变形机制。发现电荷迁移包括液滴本体中的电荷弛豫和流体界面处的表面电荷对流。导电纳米液滴首先通过电荷弛豫演变成椭圆体。然后，椭圆体通过四种模式的表面电荷对流变形，即尖端流（模式 1）、叶形成（模式 2）、手指拉伸（模式 3）和哑铃拉伸（模式 4）。最后，拉伸的纳米液滴被分解成二次液滴。模式 1、2 和 4 与实验观察一致。此外，发现超过 20% 的费用是分配给...