Figure 2: Visualization of local contact line pinning.
From: High-resolution liquid patterns via three-dimensional droplet shape control
(a) A scanning electron micrograph (SEM) of a square array of cylindrical micropillar array with diameter D=7 μm, pitch L=20 μm and height H=13 μm. (b) Time-lapse images of the local microscopic contact line dynamics of a Wenzel droplet. The line-of-sight for the acquisition of these images is shown in a. (c) Schematic illustrating the contact line dynamics that result in local energy barriers and contact line pinning responsible for the formation of wetting droplets with contact angles exceeding 90°. As a result, the classical Wenzel equation, which relies on global surface energy minimization, is invalid. Scale bar, 20 μm.
