Jia Huiru, Li Xuhao, Chen Kang, Yang Fan, Ren Hongru, Li Huan, Li Chun
Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China.
School of Urban Planning and Municipal Engineering, Xi'an Polytechnic University, Xi'an 710048, China.
Langmuir. 2024 Sep 11. doi: 10.1021/acs.langmuir.4c02642.
The phenomenon of spontaneous droplet transport has a wide range of implications in water collection, microfluidic manipulation, oil-water separation, and various other fields. Achieving efficient and controllable spontaneous droplet transport is therefore of paramount importance. This study investigates the potential of surface charge manipulation to enhance spontaneous droplet transport through comprehensive molecular dynamics simulations. Our findings reveal that the surface charge of the substrate significantly influences its wettability, reducing the contact angle of the droplet and increasing both the contact area and interaction energy. Moreover, we introduce a novel approach to enhance droplet mobility by creating a surface charge gradient on the substrate. By introducing bands with varying charges along a specific direction of the substrate, the droplet experiences a force directed toward regions of increasing charge, thereby facilitating its movement. Importantly, the driving mechanism of droplet motion is well explained by combining classical electrowetting theory with the analysis of the droplet's advancing and receding contact angles, which demonstrates that a more pronounced surface charge gradient generates greater force and enhances droplet mobility. These findings offer valuable insights into the design of microfluidic systems and related applications based on electrowetting.
自发液滴传输现象在集水、微流体操控、油水分离及其他诸多领域有着广泛的影响。因此，实现高效且可控的自发液滴传输至关重要。本研究通过全面的分子动力学模拟，探究了表面电荷操控对增强自发液滴传输的潜力。我们的研究结果表明，基底的表面电荷显著影响其润湿性，减小了液滴的接触角，增加了接触面积和相互作用能。此外，我们引入了一种新颖的方法，通过在基底上创建表面电荷梯度来增强液滴的迁移率。沿着基底的特定方向引入具有不同电荷的条带，液滴会受到指向电荷增加区域的力，从而促进其移动。重要的是，通过将经典的电润湿理论与液滴前进和后退接触角的分析相结合，很好地解释了液滴运动的驱动机制，这表明更明显的表面电荷梯度会产生更大的力并增强液滴的迁移率。这些发现为基于电润湿的微流体系统及相关应用的设计提供了有价值的见解。
