煎饼在超疏水表面上弹跳
Pancake bouncing on superhydrophobic surfaces
摘要：
促进液滴快速分离的工程表面对于广泛的应用（包括防冰、滴状冷凝6和自清洁）具有重要意义。在这里，我们展示了用纳米纹理装饰的亚毫米级柱晶格图案化的超疏水表面如何产生一种反直觉的弹跳机制：液滴在撞击时扩散，然后使表面呈扁平的煎饼形状而不会缩回。与传统的完全回弹相比，这允许接触时间减少四倍。我们表明，煎饼弹跳的结果从整流的毛细能量存储在穿透液体到向上运动足以解除下降。此外，横向液滴在表面上传播的时间尺度和垂直运动的时间尺度必须是可比的。特别是，通过设计具有锥形微/纳米纹理的表面，其表现为谐波弹簧，时间尺度变得与冲击速度无关，从而允许在宽范围的冲击速度上发生煎饼弹跳和快速液滴脱离。
英文摘要：
Engineering surfaces that promote rapid drop detachment is of importance to a wide range of applications including anti-icing, dropwise condensation6, and self-cleaning. Here we show how superhydrophobic surfaces patterned with lattices of submillimetre-scale posts decorated with nano-textures can generate a counter-intuitive bouncing regime: drops spread on impact and then leave the surface in a flattened, pancake shape without retracting. This allows for a four-fold reduction in contact time compared to conventional complete rebound. We demonstrate that the pancake bouncing results from the rectification of capillary energy stored in the penetrated liquid into upward motion adequate to lift the drop. Moreover, the timescales for lateral drop spreading over the surface and for vertical motion must be comparable. In particular, by designing surfaces with tapered micro/nanotextures which behave as harmonic springs, the timescales become independent of the impact velocity, allowing the occurrence of pancake bouncing and rapid drop detachment over a wide range of impact velocities.
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