Wu Chenyang, Qin Xuezhi, Zheng Huanxi, Xu Zhenyu, Song Yuxin, Jin Yuankai, Zhang Huanhuan, Mo Jiaying, Li Wanbo, Lu Jian, Wang Zuankai
Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, China.
Hong Kong Center for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, 999077, China.
Small. 2023 Oct 2:e2304635. doi: 10.1002/smll.202304635.
Rapid detachment of impacting droplets from underlying substrate is highly preferred for mass, momentum, and energy exchange in many practical applications. Driven by this, the past several years have witnessed a surge in engineering macrotexture to reduce solid-liquid contact time. Despite these advances, these strategies in reducing contact time necessitate the elegant control of either the spatial location for droplet contact or the range of impacting velocity. Here, this work circumvents these limitations by designing a dual gradient surface consisting of a vertical spacing gradient made of tapered pillar arrays and a lateral curvature gradient characterized as macroscopic convex. This design enables the impacting droplets to self-adapt to asymmetric or pancake bouncing mode accordingly, which renders significant contact time reduction (up to ≈70%) for a broad range of impacting velocities (≈0.4-1.4 m s ) irrespective of the spatial impacting location. This new design provides a new insight for designing liquid-repellent surfaces, and offers opportunities for applications including dropwise condensation, energy conversion, and anti-icing.
在许多实际应用中，为了实现质量、动量和能量交换，非常希望撞击液滴能迅速从下层基底分离。受此驱动，在过去几年中，为减少固液接触时间而进行的工程宏观纹理设计激增。尽管取得了这些进展，但这些减少接触时间的策略需要精确控制液滴接触的空间位置或撞击速度范围。在此，这项工作通过设计一种双梯度表面来规避这些限制，该表面由锥形柱阵列构成的垂直间距梯度和宏观凸起的横向曲率梯度组成。这种设计使撞击液滴能够相应地自适应不对称或薄饼状弹跳模式，从而在很宽的撞击速度范围（约0.4 - 1.4米/秒）内，无论空间撞击位置如何，都能显著减少接触时间（高达约70%）。这种新设计为设计疏水表面提供了新的思路，并为包括滴状冷凝、能量转换和防冰在内的应用提供了机会。
