Pathak Shakul, Chakraborty Monojit, DasGupta Sunando
Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
Langmuir. 2022 Mar 29;38(12):3656-3665. doi: 10.1021/acs.langmuir.1c03037. Epub 2022 Mar 14.
It is well known that the wettability of a droplet on a solid substrate can be modified by the application of an electric field. The phenomenon of electrowetting along with the associated physics of droplet shape change and dynamics has traditionally been studied at the micro-scale leading to exciting applications. The present work is undertaken to explore the physics of electrowetting actuation of droplet movement at the molecular level. Molecular simulations are performed to obtain the dynamic spreading of the droplet under the action of a radially symmetric electric field on a silica substrate. The dynamic behavior of the contact diameter is found to be qualitatively similar to that observed at the laboratory scale. Further simulations of droplet actuation across an array of electrodes illustrated the dynamics of the center of mass, which is then used to estimate the contact line friction and compared with the predictions from a reduced-order model. A scaling analysis is used to probe the physics of the problem correlating the contact line friction coefficient and the droplet velocity after actuation. The results and understanding elicited from the fundamental approach have the potential to guide the development of quick and precise control of nano-sized droplets and may prove to be pivotal in the development of future nanofluidic systems, nanomanufacturing methodologies, and high-resolution optoelectronic devices.
众所周知，通过施加电场可以改变液滴在固体基底上的润湿性。传统上，电润湿现象以及相关的液滴形状变化和动力学物理过程是在微观尺度上进行研究的，从而带来了令人兴奋的应用。目前的工作旨在探索液滴在分子水平上的电润湿驱动物理过程。进行分子模拟以获得在二氧化硅基底上径向对称电场作用下液滴的动态铺展情况。发现接触直径的动态行为在定性上与在实验室尺度上观察到的相似。对液滴在一系列电极上的驱动进行的进一步模拟说明了质心的动力学，然后用它来估计接触线摩擦力，并与降阶模型的预测结果进行比较。使用标度分析来探究该问题的物理过程，将接触线摩擦系数与驱动后的液滴速度联系起来。从这种基本方法中得出的结果和认识有可能指导纳米级液滴快速精确控制的发展，并且可能在未来纳米流体系统、纳米制造方法和高分辨率光电器件的发展中起到关键作用。
