Droplet Growth Dynamics during Atmospheric Condensation on Nanopillar Surfaces
Droplet Growth Dynamics during Atmospheric Condensation on Nanopillar Surfaces
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DOI：
10.1080/15567265.2018.1495282
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发表时间：
2018-07
影响因子：
4.1
通讯作者：
M. R. Haque;C. Qu;E. Kinzel;A. Betz
中科院分区：
文献类型：
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作者：
M. R. Haque;C. Qu;E. Kinzel;A. Betz
凝聚液滴在粗糙表面上异相成核的吉布斯自由能垒随凝结环境中湿度的变化而显著变化。环境因素(环境温度和相对湿度)和基质特性(拓扑结构、表面化学和基质温度)对大气凝结现象的影响对于阐明凝结液滴的润湿状态和凝结液的收集应用是非常重要的。据报道，从潮湿的空气中凝结出来的纯硅和制成的纳米管状表面有助于凝析油的收集。记录了90min的液滴生长和尺寸分布。由于柱子的钉扎效应，在硅表面凝聚了球形液滴，在纳米柱表面观察到了不规则形状的液滴。根据凝聚液滴的能量平衡，描述了液滴钉扎对聚结事件的影响。数学模型表明，纳米管几何形状的某些尺寸组合(柱间距、柱直径和柱高度)需要显示凝聚液滴的钉扎机制。在聚结事件产生的空隙中观察到液滴的再生。从成核开始，在多个时间和长度尺度上跟踪单个液滴的生长，以进一步了解直接生长和合并的机制。缩写：ESM：环境扫描电子显微镜；HCP：六方密排；MPL：微球光刻；RH：相对湿度
ABSTRACT The Gibbs free energy barrier for heterogeneous nucleation of a condensed droplet on a rough surface changes significantly with changes of humidity content in the condensing environment. The influence of environmental factors (ambient temperature and relative humidity) and substrate characteristics (topology, surface chemistry, and substrate temperature) on atmospheric condensation phenomenon is very important to elucidate the condensed droplet wetting state and condensate harvesting applications. Condensation from the humid air has been reported for plain silicon and fabricated nanopillar surfaces to facilitate condensate harvesting. Droplet growth and size distributions were recorded for 90 min. Spherical droplets condensed on the silicon surfaces and irregular-shaped droplets were observed on the nanopillar surfaces due to the pinning effect of the pillars. The effect of droplet pinning on coalescence events has been described based on the energy balance for the condensed droplets. A mathematical model reveals that certain dimensional combinations (pillar pitch, pillar diameter, and pillar height) of the nanopillar geometry are required to exhibit the pinning mechanism for condensed droplets. Regeneration of droplets was observed at void spaces generated from coalescence events. The growth of individual droplets was tracked over multiple time and length scales, starting from nucleation to get further insight into the direct growth and coalescence mechanisms. Abbreviation: ESEM: Environmental Scanning Electron Microscope; HCP: Hexagonal Closed-Packed; MPL: Microsphere Photolithography; RH: Relative Humidity