Zhu Shengya, Ren Hongru, Li Xuhao, Xiao Ye, Li Chun
School of Mechanics, Civil Engineering and Architecture, Northwestern Polytechnical University, Xi'an 710072, China.
School of Science, Chang'an University, Xi'an 710064, China.
Phys Chem Chem Phys. 2023 Feb 8;25(6):4969-4979. doi: 10.1039/d2cp04608c.
The impact behaviors of droplets on nanostructure-arrayed surfaces are ubiquitous in nature and engineering applications. And the influence of the impact position of a droplet on its bouncing dynamics is of great significance since there is inevitable randomness in the impact position of droplets on the surface of nanostructured arrays, but the difference in the dynamics process caused by this randomness has not been recognized. Here, by using molecular dynamics simulations, the effect of impact position on the bouncing dynamics of a water droplet on nanopillar-arrayed surfaces is systematically investigated. The simulation results highlight that the impact position plays an important role in droplet dynamics after impact, especially at the retraction stage, and the effect of impact position on the bouncing behavior is highly sensitive to the impact velocity. Importantly, from the point of energy conversion, the droplet deformation and contact state jointly determine whether the droplet can bounce back or not, which reveals the mechanism of impact position effects on the bouncing behavior of the droplet. Interestingly, the effect of impact position would be weakened with an increase in the size ratio of the droplet diameter to nanopillar spacing, and this effect becomes negligible when the size ratio is greater than 5.2. These findings demonstrate the key role played by the impact position and may provide new insights into the practical application of nanostructure-arrayed surfaces.
液滴在纳米结构阵列表面的撞击行为在自然界和工程应用中普遍存在。由于液滴在纳米结构阵列表面的撞击位置不可避免地存在随机性，而这种随机性所导致的动力学过程差异尚未得到认识，因此液滴撞击位置对其弹跳动力学的影响具有重要意义。在此，通过分子动力学模拟，系统地研究了撞击位置对纳米柱阵列表面上水滴弹跳动力学的影响。模拟结果表明，撞击位置在撞击后液滴动力学中起着重要作用，尤其是在回缩阶段，并且撞击位置对弹跳行为的影响对撞击速度高度敏感。重要的是，从能量转换的角度来看，液滴变形和接触状态共同决定了液滴是否能够反弹，这揭示了撞击位置对液滴弹跳行为产生影响的机制。有趣的是，随着液滴直径与纳米柱间距尺寸比的增加，撞击位置的影响会减弱，当尺寸比大于5.2时，这种影响可以忽略不计。这些发现证明了撞击位置所起的关键作用，并可能为纳米结构阵列表面的实际应用提供新的见解。
