Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, United States.
Langmuir. 2011 Apr 5;27(7):3693-7. doi: 10.1021/la2001893. Epub 2011 Mar 7.
Two series of experiments, both involving contact line pinning, are reported that were designed using the contact line perspective of wetting and require this perspective to explain the observed results. Perspectives based on contact areas, for example, Wenzel's and Cassie's, are not useful in either of these experimental situations. In the first type of experiment described, sessile water drops were pinned on low contact angle hysteresis surfaces using 40 different shape/size lithographed hydrophilic features. Hydrophilic arcs (sections of circles), short wedges (pointed to the center of the circle), long wedges (pointed to the opposite side of the circle), and the upper outlines of the short and long wedges were prepared and studied. These features were based on circles with diameters of 4 and 6 mm and arcs of 30°, 60°, 90°, and 120°. The volume of water that could be pinned depends on the linear shape of the portion of the feature that interacts with the receding contact line and not on the feature area. In the second type of experiment, thin hydrophilic contact lines were used to support films of water (puddles and kinetically trapped thin films) on water-repellent surfaces and used to control the shape (both 2D and 3D) of these thin films and puddles. Elongated water puddles, 60 mm long and 4 mm wide, were prepared using contact line patterns with line widths of 500, 250, and 100 μm. Curved puddles, geometric shapes, letters of the English alphabet, and puddles with variable liquid thicknesses (heights) were also prepared.
报告了两项涉及接触线钉扎的实验系列，这些实验是基于润湿的接触线视角设计的，需要从这个视角来解释观察到的结果。基于接触面积的视角，例如 Wenzel 和 Cassie 的视角，在这两种实验情况下都没有用。在描述的第一种实验类型中，使用 40 种不同形状/尺寸的光刻亲水特征将静止的水滴固定在低接触角滞后表面上。亲水弧（圆的一部分）、短楔形（指向圆心）、长楔形（指向圆的对面）以及短楔形和长楔形的上轮廓被制备和研究。这些特征基于直径为 4 和 6 毫米的圆以及 30°、60°、90°和 120°的圆弧。可以固定的水体积取决于与后退接触线相互作用的特征部分的线性形状，而不是特征面积。在第二种实验类型中，使用薄的亲水接触线来支撑水膜（水坑和动力学捕获的薄膜）在疏水性表面上，并用于控制这些薄膜和水坑的形状（二维和三维）。使用线宽为 500、250 和 100 μm 的接触线图案制备了 60 毫米长、4 毫米宽的拉长水坑。还制备了弯曲水坑、几何形状、英文字母和具有可变液体厚度（高度）的水坑。
