Sommers A D, Jacobi A M
Department of Mechanical and Manufacturing Engineering, Miami University, 56 Engineering Building, Oxford, OH 45056, USA.
J Colloid Interface Sci. 2008 Dec 15;328(2):402-11. doi: 10.1016/j.jcis.2008.09.023. Epub 2008 Sep 17.
The behavior of water droplets on aluminum surfaces with parallel grooves tens of microns in width and depth is considered, and a mechanistic model is developed for predicting the critical droplet size-droplets at incipient sliding due to gravity. The critical droplet size is nearly 50% smaller on micro-grooved surfaces than on the same surface without micro-grooves. The application of existing models fails to predict this behavior, and a new model based on empiricism is developed. The new model provides reasonable predictions of the critical droplet size for a given inclination angle, advancing contact angle, and maximum contact angle. When the grooves are aligned parallel to gravity, the maximum apparent contact angle does not occur at the advancing front but rather along the side of the droplet because of contact-line pinning. Droplets on these surfaces are elongated and possess a parallel-sided base contour shape. Novel data are provided for droplets in a Wenzel state, a Cassie-Baxter state, and combined state on micro-grooved surfaces, and the ability of the empirical model to handle these variations is explored. These findings may be important to a broad range of engineering applications.
研究了宽度和深度为几十微米的平行沟槽铝表面上水滴的行为，并建立了一个机理模型来预测临界液滴尺寸——即由于重力开始滑动时的液滴尺寸。微沟槽表面上的临界液滴尺寸比无微沟槽的相同表面上的临界液滴尺寸小近50%。现有模型的应用无法预测这种行为，因此开发了一种基于经验主义的新模型。新模型针对给定的倾斜角、前进接触角和最大接触角，对临界液滴尺寸提供了合理的预测。当沟槽与重力方向平行排列时，由于接触线钉扎，最大表观接触角并非出现在前进前沿，而是出现在液滴的侧面。这些表面上的液滴呈细长形，底部轮廓形状为平行边。提供了微沟槽表面上文泽尔状态、卡西-巴克斯特状态和组合状态下液滴的新数据，并探讨了经验模型处理这些变化的能力。这些发现可能对广泛的工程应用具有重要意义。
