Wang Meng, Shi Yanzhao, Wang Shun, Xu Huanlin, Zhang Hui, Wei Min, Wang Xiaopeng, Peng Wanxi, Ding Hang, Song Meirong
College of Science and College of Forestry, Henan Agricultural University, Zhengzhou, Henan 450002, P. R. China.
Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230022, P. R. China.
iScience. 2023 Mar 11;26(4):106389. doi: 10.1016/j.isci.2023.106389. eCollection 2023 Apr 21.
Droplets directionally bouncing off moving superhydrophobic solid surfaces are universal in nature and are crucial in many biological, sustainable, environmental, and engineering applications. However, their underlying physics and regulation strategies remain relatively unknown. This paper demonstrates that the maximum directional acceleration of a post-impact droplet mainly occurs in the spreading stage and that the orientational velocity of the droplet mainly originates in the early impingement process. Furthermore, it clarifies the underlying physics based on momentum transfer process imposed by the boundary layer of impacts and proposes a strategy for regulating the directional droplet velocity using a comprehensive formula. Finally, it shows that directional bouncing reduces the flight momentum of a small flying device by 10%-22%, and the experimental values agree closely with the predicted values. This study reveals the droplet bounce orientation mechanism imposed by moving substrates, provides manipulation methods, and makes positive and meaningful discussions of practical applications.
液滴从移动的超疏水固体表面定向反弹在自然界中普遍存在，并且在许多生物、可持续、环境和工程应用中至关重要。然而，其潜在的物理原理和调控策略仍然相对未知。本文表明，撞击后液滴的最大定向加速度主要发生在铺展阶段，并且液滴的定向速度主要起源于早期撞击过程。此外，基于撞击边界层施加的动量传递过程阐明了潜在的物理原理，并提出了使用综合公式调控液滴定向速度的策略。最后，结果表明定向反弹使小型飞行装置的飞行动量降低了10%-22%，实验值与预测值非常吻合。本研究揭示了移动基底施加的液滴反弹定向机制，提供了操控方法，并对实际应用进行了积极且有意义的讨论。
