Yao Lu, Sharifi-Mood Nima, Liu Iris B, Stebe Kathleen J
Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, United States.
Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, United States.
J Colloid Interface Sci. 2015 Jul 1;449:436-42. doi: 10.1016/j.jcis.2014.12.070. Epub 2014 Dec 31.
The capillary energy landscape for particles on curved fluid interfaces is strongly influenced by the particle wetting conditions. Contact line pinning has now been widely reported for colloidal particles, but its implications in capillary interactions have not been addressed. Here, we present experiment and analysis for disks with pinned contact lines on curved fluid interfaces. In experiment, we study microdisk migration on a host interface with zero mean curvature; the microdisks have contact lines pinned at their sharp edges and are sufficiently small that gravitational effects are negligible. The disks migrate away from planar regions toward regions of steep curvature with capillary energies inferred from the dissipation along particle trajectories which are linear in the deviatoric curvature. We derive the curvature capillary energy for an interface with arbitrary curvature, and discuss each contribution to the expression. By adsorbing to a curved interface, a particle eliminates a patch of fluid interface and perturbs the surrounding interface shape. Analysis predicts that perfectly smooth, circular disks do not migrate, and that nanometric deviations from a planar circular, contact line, like those around a weakly roughened planar disk, will drive migration with linear dependence on deviatoric curvature, in agreement with experiment.
弯曲流体界面上粒子的毛细管能量景观受到粒子润湿性条件的强烈影响。接触线钉扎现象现已在胶体粒子中被广泛报道，但其在毛细管相互作用中的影响尚未得到探讨。在此，我们展示了关于弯曲流体界面上具有钉扎接触线的圆盘的实验与分析。在实验中，我们研究了零平均曲率主界面上微盘的迁移；微盘的接触线在其尖锐边缘处被钉扎，且尺寸足够小，以至于重力影响可忽略不计。圆盘从平面区域向曲率陡峭的区域迁移，其毛细管能量可根据沿粒子轨迹的耗散推断得出，该耗散在偏斜曲率中呈线性关系。我们推导了具有任意曲率的界面的曲率毛细管能量，并讨论了表达式中的各项贡献。通过吸附到弯曲界面上，粒子消除了一块流体界面并扰动了周围的界面形状。分析预测，完全光滑的圆形圆盘不会迁移，而与弱粗糙化平面圆盘周围类似的平面圆形接触线的纳米级偏差将驱动迁移，且与偏斜曲率呈线性相关，这与实验结果一致。
