Department of Physics, University of Ioannina, Greece.
Max Planck Institute for Polymer Research, Mainz, Germany.
Soft Matter. 2018 Sep 19;14(36):7429-7434. doi: 10.1039/c8sm01333k.
Superhydrophobic surfaces are usually assumed to be rigid so that liquids do not deform them. Here we analyze how the relation between microstructure and wetting changes when the surface is flexible. Therefore we deposited liquid drops on arrays of flexible micropillars. We imaged the drop's surface and the bending of micropillars with confocal microscopy and analyzed the deflection of micropillars while the contact line advanced and receded. The deflection is directly proportional to the horizontal component of the capillary force acting on that particular micropillar. In the Cassie or "fakir" state, drops advance by touching down on the next top faces of micropillars, much like on rigid arrays. In contrast, on the receding side the micropillars deform. The main force hindering the slide of a drop is due to pinning at the receding side, while the force on the advancing side is negligible. In the Wenzel state, micropillars were deflected in both receding and advancing states.
超疏水表面通常被认为是刚性的，以至于液体不会使它们变形。在这里，我们分析当表面具有弹性时，微观结构和润湿性之间的关系如何变化。因此，我们在柔性微柱阵列上沉积液滴。我们使用共聚焦显微镜对液滴的表面和微柱的弯曲进行成像，并分析接触线前进和后退时微柱的挠度。挠度与作用在特定微柱上的毛细力的水平分量成正比。在 Cassie 或“ Fakir”状态下，液滴通过触及其下一个微柱的顶面来前进，这与在刚性阵列上的情况非常相似。相比之下，在后退侧，微柱会发生变形。阻碍液滴滑动的主要力是由于在后退侧的固定，而在前进侧的力可以忽略不计。在 Wenzel 状态下，微柱在后退和前进状态下都发生了偏转。
