The transport direction of water droplets on a functionalized surface is of great significance due to its wide applications in microfluidics technology. The prevailing view is that a water droplet on a wedge-shaped groove always moves towards the wider end. In this paper, however, molecular dynamics simulations show that a water droplet can move towards the narrower end if placed at specific positions. It is found that the direction of water droplet transport on a grooved surface is related to its initial position. The water droplet moves towards the wider end only when it is placed near the wider end initially. If the water droplet is placed near the narrower end, it will move in the opposite direction. The novel phenomenon is attributed to the opposite interactions of the groove substrate and the groove upper layers with water droplets. Two effective models are proposed to exploit the physical origin of different transport directions of water droplets on a wedge-shaped groove surface. The study provides an insight into the design of nanostructured surfaces to effectively control the droplet motion.

中文翻译：

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楔形槽上水滴的初始位置驱动的反向传输

由于其在微流体技​​术中的广泛应用，水滴在功能化表面上的传输方向具有重要意义。流行的观点是楔形凹槽上的水滴总是向较宽的一端移动。然而，在本文中，分子动力学模拟表明，如果放置在特定位置，水滴可以向较窄的一端移动。研究发现，水滴在凹槽表面的传输方向与其初始位置有关。仅当最初将水滴放置在较宽端附近时，水滴才会向较宽端移动。如果水滴放置在较窄的一端附近，它将向相反的方向移动。这种新现象归因于凹槽基底和凹槽上层与水滴的相反相互作用。提出了两种有效模型来利用楔形凹槽表面上水滴不同传输方向的物理起源。该研究提供了对纳米结构表面设计的深入了解，以有效控制液滴运动。