Future Industries Institute, University of South Australia , Mawson Lakes Campus, Adelaide, South Australia 5095, Australia.
School of Chemistry and Australian Institute for Nanoscale Science and Technology, The University of Sydney , Sydney, New South Wales 2006, Australia.
Langmuir. 2017 Nov 7;33(44):12602-12608. doi: 10.1021/acs.langmuir.7b03100. Epub 2017 Oct 24.
Surface properties such as topography and chemistry affect the motion of the three-phase contact line (solid/liquid/air), which in turn affects the contact angle of a liquid moving on a solid surface. In this work, the motion of the receding water contact line was studied on chemically and topographically patterned surfaces obtained from the dewetting of thin polymer films. The patterned surfaces consisted of hydrophilic poly(4-vinylpyridine) (P4VP) bumps, which were either microsized and sparse or nanosized and dense, on top of a hydrophobic polystyrene (PS) background layer. These patterns are designed for atmospheric water capture, for which the easy roll off of water droplets is crucial to their efficient performance. The dynamic receding water contact angle and contact line height of the patterned surfaces were measured by vertically withdrawing the surfaces from a water bath and compared to those of a flat P4VP substrate. For both the micropatterned and nanopatterned surfaces, the height of the dynamic contact lines normalized by the capillary length was characterized by the equilibrium limit that was predicted from static states. The nanopatterned surface had a faster increase in the normalized height as the capillary number increased. The dynamic receding contact angles on all surfaces studied decreased with increasing withdrawing velocity. Surprisingly, even for these patterned surfaces with high hysteresis, the dynamic receding contact angle followed the Cox-Voinov relation at capillary numbers of between 1 × 10 and 5 × 10.
表面特性（如形貌和化学性质）会影响三相接触线（固/液/气）的运动，而接触线的运动会影响液体在固体表面上的前进接触角。在这项工作中，通过研究从薄聚合物薄膜去湿过程中获得的化学和形貌图案化表面上后退水接触线的运动，来研究前进接触角。图案化表面由亲水聚（4-乙烯基吡啶）（P4VP）凸起组成，这些凸起要么是微尺寸稀疏的，要么是纳米尺寸密集的，位于疏水性聚苯乙烯（PS）基底层之上。这些图案是为大气水捕获设计的，对于这种捕获，水滴的易滚落对于其高效性能至关重要。通过将表面从水浴中垂直抽出，测量图案化表面的动态后退水接触角和接触线高度，并将其与平坦的 P4VP 基底的接触角和接触线高度进行比较。对于微图案化和纳米图案化表面，通过静态状态预测的平衡极限来描述归一化毛细长度的动态接触线高度。随着毛细数的增加，纳米图案化表面的归一化高度增加更快。所有研究表面的动态后退接触角都随着抽出速度的增加而减小。令人惊讶的是，即使对于这些具有高滞后性的图案化表面，在 1×10 到 5×10 的毛细数范围内，动态后退接触角也遵循 Cox-Voinov 关系。
