A droplet impacting on a superhydrophobic surface exhibits complete bouncing. The impacting process usually consists of spreading and retracting stages, during which the droplet contacts the underlying substrate. Recent research has been devoted to reducing the contact time using textured surfaces with different morphologies or flexibilities. Here, we design submillimeter superhydrophobic ridges and show that impacting droplets bounce off the surface immediately after capillary emptying in a petal-like shape at a certain Weber number range. The absence of a horizontal retraction process in two directions leads to ∼70% reduction in contact time. We demonstrate that the petal bouncing is attributed to the synergistic cooperation of the hierarchical structures and anisotropic property, which endows effective energy storage and release. When touching the bottom of the grooves, obvious flying wings appear along the ridges with a velocity component in the vertical direction, which help the energy releasing process in achieving fast droplet detachment. At higher Weber numbers, the anisotropic surface distorts the mass distribution and promotes uniform fragmentation of the droplet, and therefore the overall contact time is dramatically reduced. Simple analyses are proposed to explain these phenomena, showing a good agreement with the experimental results. The contact time reduction on anisotropic superhydrophobic surfaces is expected to have a great influence on the design and fabrication of anti-icing and self-cleaning surfaces.

中文翻译：

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液滴对各向异性超疏水表面的影响

撞击超疏水表面的液滴表现出完全的弹跳。冲击过程通常由展开和缩回阶段组成，在此阶段，液滴与下面的基材接触。最近的研究致力于使用具有不同形态或柔韧性的纹理表面来减少接触时间。在这里，我们设计了亚毫米级的超疏水性脊，并表明，在一定的韦伯数范围内，毛细管以花瓣状排空后，撞击液滴会立即从表面反弹。在两个方向上都没有水平回缩过程，可减少约70％的接触时间。我们证明花瓣的弹跳归因于分层结构和各向异性特性的协同配合，赋予了有效的能量存储和释放。当接触凹槽的底部时，沿脊部会出现明显的飞翼，在垂直方向上具有速度分量，这有助于能量释放过程实现快速的液滴分离。在较高的韦伯数下，各向异性表面会扭曲质量分布并促进液滴的均匀破碎，因此，总的接触时间将大大减少。提出了简单的分析来解释这些现象，与实验结果显示出很好的一致性。各向异性超疏水表面上接触时间的减少预计将对防冰和自清洁表面的设计和制造产生重大影响。这有助于能量释放过程实现快速的液滴分离。在较高的韦伯数下，各向异性表面会扭曲质量分布并促进液滴的均匀破碎，因此，总的接触时间将大大减少。提出了简单的分析来解释这些现象，与实验结果显示出很好的一致性。各向异性超疏水表面上接触时间的减少预计将对防冰和自清洁表面的设计和制造产生重大影响。这有助于能量释放过程实现快速的液滴分离。在较高的韦伯数下，各向异性表面会扭曲质量分布并促进液滴的均匀破碎，因此，总的接触时间将大大减少。提出了简单的分析来解释这些现象，与实验结果显示出很好的一致性。减少各向异性超疏水表面上的接触时间预计将对防冰和自清洁表面的设计和制造产生重大影响。与实验结果吻合良好。各向异性超疏水表面上接触时间的减少预计将对防冰和自清洁表面的设计和制造产生重大影响。与实验结果吻合良好。各向异性超疏水表面上接触时间的减少预计将对防冰和自清洁表面的设计和制造产生重大影响。