Physics of Fluids Group, Faculty of Science and Technology, Impact and MESA.
Langmuir. 2009 Oct 20;25(20):12293-8. doi: 10.1021/la900330q.
We experimentally investigate drop impact dynamics onto different superhydrophobic surfaces, consisting of regular polymeric micropatterns and rough carbon nanofibers, with similar static contact angles. The main control parameters are the Weber number We and the roughness of the surface. At small We, i.e., small impact velocity, the impact evolutions are similar for both types of substrates, exhibiting Fakir state, complete bouncing, partial rebouncing, trapping of an air bubble, jetting, and sticky vibrating water balls. At large We, splashing impacts emerge forming several satellite droplets, which are more pronounced for the multiscale rough carbon nanofiber jungles. The results imply that the multiscale surface roughness at nanoscale plays a minor role in the impact events for small We less than or approximately equal 120 but an important one for large We greater than or approximately equal 120. Finally, we find the effect of ambient air pressure to be negligible in the explored parameter regime We less than or approximately equal 150.
我们通过实验研究了液滴冲击不同超疏水表面的动力学行为，这些表面由规则的聚合物微图案和粗糙的碳纤维组成，具有相似的静态接触角。主要的控制参数是韦伯数 We 和表面的粗糙度。在小 We 的情况下，即小的冲击速度，两种类型的基底的冲击演化是相似的，表现出 Fakir 状态、完全反弹、部分反弹、气泡捕获、射流和粘性振动水球。在大 We 的情况下，出现了飞溅冲击，形成了几个卫星液滴，对于多尺度粗糙碳纤维丛林来说，这种情况更为明显。结果表明，在小 We（小于或约等于 120）的冲击事件中，纳米尺度的多尺度表面粗糙度的作用较小，但在大 We（大于或约等于 120）的冲击事件中作用较大。最后，我们发现，在所研究的参数范围内，环境气压的影响可以忽略不计（We 小于或约等于 150）。
