Institute of Condensed Matter Physics, Zhejiang Provincial Key Laboratory of Solid State Optoelectronic Devicces, and Zhejiang Institute of Photonelectronics, Zhejiang Normal University, Jinhua321004, China.
Institute of Theoretical Physics, State Key Laboratory of Quantum Optics and Quantum Optics Devices, Shanxi University, Taiyuan030006, China.
ACS Nano. 2023 Feb 14;17(3):2182-2189. doi: 10.1021/acsnano.2c08383. Epub 2023 Feb 2.
The spontaneous directional movement of water droplets on a wedge-shaped groove has gained extensive attention due to the advantage of not requiring energy input and its potential wide applications. However, manipulating the direction of movement of water droplets on a wedge-shaped groove has been not fully achieved, and the fundamental understanding of its underlying mechanism remains unclear. Here, molecular dynamics simulations and theoretical analyses are combined to reveal the mechanism of movement in opposite directions of a water droplet at the same position on the wedge-shaped groove interface. It is shown that the moving direction of the water droplet is related to its wetting state on the surface, i.e., the Wenzel and the Cassie states. A water droplet initially in the Wenzel and Cassie states will move toward the diverging and the converging ends, respectively. This phenomenon is attributed to the opposite roles played by the groove substrate and the upper layers in the two wetting states. Moreover, it is found that the water droplet is likely to move faster on a surface with a higher groove, larger opening angle and stronger hydrophobicity. These findings are expected to be of benefit for fully understanding droplet movement and shedding light on the regulation of the direction of movement of the droplets on the groove surface.
由于无需能量输入且具有广泛的潜在应用，楔形槽上水滴滴的自发定向运动引起了广泛关注。然而，在楔形槽上操纵水滴的运动方向尚未完全实现，其潜在机制的基本理解仍不清楚。在这里，通过分子动力学模拟和理论分析，揭示了在楔形槽界面同一位置处水滴向相反方向运动的机制。结果表明，水滴的运动方向与其在表面上的润湿状态有关，即 Wenzel 和 Cassie 状态。最初处于 Wenzel 和 Cassie 状态的水滴将分别向发散和汇聚端移动。这种现象归因于在这两种润湿状态下，槽基底和上层的相反作用。此外，还发现水滴在具有较高凹槽、较大开口角和较强疏水性的表面上更有可能更快地移动。这些发现有望有助于全面理解液滴运动，并为调控液滴在槽表面上的运动方向提供启示。
