Lee Choongyeop, Kim Hyunsik, Nam Youngsuk
School of Aerospace and Mechanical Engineering, Korea Aerospace University , Goyang 412-791, Korea.
Langmuir. 2014 Jul 22;30(28):8400-7. doi: 10.1021/la501341x. Epub 2014 Jul 9.
We experimentally investigated the impact dynamics of a water drop on oil-infused nanostructured surfaces using high-speed microscopy and scalable metal oxide nano surfaces. The effects of physical properties of the oil and impact velocity on complex fluid dynamics during drop impact were investigated. We show that the oil viscosity does not have significant effects on the maximal spreading radius of the water drop, while it moderately affects the retraction dynamics. The oil viscosity also determines the stability of the infused lubricant oil during the drop impact; i.e., the low viscosity oil layer is easily displaced by the impacting drop, which is manifested by a residual mark on the impact region and earlier initiation of prompt splashing. Also, because of the liquid (water)-liquid (oil) interaction on oil-infused surfaces, various instabilities are developed at the rim during impact under certain conditions, resulting in the flower-like pattern during retraction or elongated filaments during spreading. We believe that our findings will contribute to the rational design of oil-infused surfaces under drop impact conditions by illuminating the complex fluid phenomena on oil-infused surfaces during drop impact.
我们使用高速显微镜和可扩展的金属氧化物纳米表面，通过实验研究了水滴在注油纳米结构表面上的冲击动力学。研究了油的物理性质和冲击速度对液滴冲击过程中复杂流体动力学的影响。我们发现，油的粘度对水滴的最大铺展半径没有显著影响，但对回缩动力学有一定程度的影响。油的粘度还决定了液滴冲击过程中注入的润滑油的稳定性；即，低粘度油层很容易被冲击的液滴置换，这表现为冲击区域上的残留痕迹以及较早开始的快速飞溅。此外，由于注油表面上的液（水）-液（油）相互作用，在某些条件下，冲击过程中边缘会出现各种不稳定性，导致回缩过程中出现花状图案或铺展过程中出现细长的细丝。我们相信，我们的研究结果将有助于在液滴冲击条件下合理设计注油表面，通过阐明液滴冲击过程中注油表面上复杂的流体现象。
