Department of Mechanical and Aerospace Engineering, University of Texas at Arlington 500 West First Street, Woolf Hall 226, Arlington, TX, 76019, United States of America.
Sci Rep. 2017 Aug 29;7(1):9717. doi: 10.1038/s41598-017-10036-3.
It has been reported that, in a foggy environment, water drops with either barrel or clam-shell shapes are capable of self-running on conical wire-like structures, such as cactus spines, spider silk, and water striders' legs. On the other hand, the corresponding moving mechanisms are still not quite understood. For instance, it is unclear under what conditions clam-shell drops would move from the tip towards the root on a conical wire. In this work, based on the balance of forces, we derive conditions for a drop to self-transport towards or away from the root. We find that, although barrel and clam-shell drops have different shapes, these conditions are applicable to both of them, which thus provide good guidelines for developing artificial fog collectors. Furthermore, based on the derived conditions, we interpret drop movements on both hydrophilic and hydrophobic wires, with the support of experimental results on cactus spines. Finally, our results indicate that not all the cacti are able to harvest water from fog.
据报道，在雾环境中，具有桶状或蛤壳状的水滴能够在类似仙人掌刺、蜘蛛丝和水黾腿的锥形线状结构上自行滚动。另一方面，相应的移动机制仍不完全清楚。例如，在什么条件下蛤壳状的水滴会从锥形丝的尖端向根部移动还不清楚。在这项工作中，我们基于力的平衡，推导出了水滴自行向根部或远离根部移动的条件。我们发现，尽管桶状和蛤壳状的水滴形状不同，但这些条件适用于两者，这为开发人工雾收集器提供了很好的指导。此外，基于推导的条件，我们解释了在亲水和疏水丝上的水滴运动，并用仙人掌刺上的实验结果支持。最后，我们的结果表明，并非所有的仙人掌都能够从雾中收集水。
