Department of Mechanical Engineering and Applied Mechanics, North Dakota State University, Fargo, ND 58108-6050, USA.
J Colloid Interface Sci. 2010 Jan 15;341(2):326-32. doi: 10.1016/j.jcis.2009.09.019. Epub 2009 Sep 27.
The morphology of liquid droplets wetting on filaments depends on the filament configuration, droplet volume, and contact angle. A stable morphology is the one that minimizes the potential energy of the droplet-filament system, while morphology transition may happen when an intermediate state exists which corresponds to a higher potential energy. This paper aims to explore such morphology transition of droplet wetting on filament rails made of two parallel identical microfilaments. Detailed numerical simulations were performed to extract the surface energy of the droplet-filament system at varying filament spacings, droplet volumes, and contact angles. Critical conditions of the morphology transition between two symmetrical wetting morphologies (i.e., liquid droplet bridge and barrel-shaped droplet) were determined. A family of characteristic curves in terms of the dimensionless droplet volume vs the filament spacing at varying contact angles was obtained, which can be used as a universal law to govern the morphology transition for such droplet-filament rail systems. The results and concepts presented in this work can be extended to broad wetting systems and utilized for the analysis and design of microfluidic devices and testers based on droplet-filament systems.
液滴在纤维上的润湿形态取决于纤维构型、液滴体积和接触角。稳定的形态是使液滴-纤维系统势能最小化的形态，而当存在对应于更高势能的中间状态时，形态可能会发生转变。本文旨在探索由两根平行相同微纤维制成的纤维轨道上液滴润湿的这种形态转变。通过详细的数值模拟，提取了在不同纤维间距、液滴体积和接触角下的液滴-纤维系统的表面能。确定了两种对称润湿形态（即液桥和桶形液滴）之间形态转变的临界条件。获得了一系列特征曲线，这些曲线以无量纲液滴体积与接触角变化的纤维间距为参数，可以用作此类液滴-纤维轨道系统形态转变的通用规律。本文的结果和概念可以扩展到广泛的润湿系统，并用于基于液滴-纤维系统的微流控器件和测试器的分析和设计。
