Hypothesis

Recently, it has been shown that the contact time of impacting water droplets on a superhydrophobic cylindrical surface decreases when its radius becomes comparable to that of the droplet, yet the correlation of this reduction with the impact velocity is unclear. Moreover, on a flat surface, experiments involving the addition of a single macrotexture, along with covering the surface with macroscopic cylindrical ridges (ribbed pattern), have been reported to shorten the contact time. Hence, a ribbed-curved surface with an additional macrotexture may logically lead to a very short contact time.

Experiments

Such a surface was obtained by utilizing an extruder-type 3D printer and a copper wire was used as the additional macrotexture. The bouncing of water droplets of three different volumes on curved and ribbed-curved samples with two different diameters was investigated for varied impact velocities.

Findings

For the curved surfaces, a scaling model for the contact time reduction with respect to the impact velocity was found. Our data show that adding a wire to the peak of a cylinder containing both micro- and macro-scale roughness (wired ribbed-curved surfaces) yields the contact time even shorter than the inertial-capillary time scale, an unprecedented phenomenon.

中文翻译：

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尽可能缩短接触时间：液滴对具有宏观特征的圆柱形超疏水表面的冲击

假设

近来，已经表明，当水滴的半径变得与水滴的半径相当时，撞击水滴在超疏水圆柱表面上的接触时间减少，但是这种减少与撞击速度的相关性尚不清楚。此外，据报道，在平坦表面上进行的实验包括添加单一的宏观纹理，并用宏观的圆柱形凸脊（肋状图案）覆盖表面，从而缩短了接触时间。因此，具有附加宏观纹理的肋状弯曲表面在逻辑上可能会导致非常短的接触时间。

实验

这种表面是通过使用挤出机式3D打印机获得的，铜线被用作附加的宏观纹理。研究了三种不同体积的水滴在具有两个不同直径的弯曲和带肋弯曲样品上的弹跳，以了解不同的冲击速度。

发现

对于弯曲表面，找到了相对于冲击速度减少接触时间的比例模型。我们的数据表明，将导线添加到同时包含微观和宏观粗糙度（有线有肋弯曲表面）的圆柱体的峰顶上，产生的接触时间甚至比惯性毛细管时标短，这是前所未有的现象。