Are Superhydrophobic Surfaces Best for Icephobicity?
Are Superhydrophobic Surfaces Best for Icephobicity?
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DOI：
10.1021/la104762g
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发表时间：
2011-03-15
期刊：
影响因子：
3.9
通讯作者：
Poulikakos, Dimos
中科院分区：
文献类型：
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作者：
Jung, Stefan;Dorrestijn, Marko;Poulikakos, Dimos
结冰可能会对地面和空中的人类活动造成灾难性后果。在这里，我们研究了未经处理和涂层表面（从亲水到超疏水）的水结冰延迟，并利用这些延迟来评估疏冰性。过冷水微滴被喷墨沉积并聚结，直到聚集的质量发生自发冻结。具有纳米级粗糙度和较高润湿性的表面表现出出乎意料的长冻结延迟，比具有较大分级粗糙度和低润湿性的典型表面粗糙度超疏水表面至少长一个数量级。与对过冷水滴的异质成核和冻结延迟的主要关注直接相关，观察到的随后的结晶过程由两个不同的阶段组成：一个非常快速的再辉部分凝固阶段和随后的较慢阶段。对用于连续液体质量积累直至形成冰点的液滴碰撞过程的观察揭示了以前未见过的大气压、低于冰点温度的液体对液体弹跳的情况。基于固体表面附近水的熵减，我们对经典异质成核理论进行了修正，预测了观察到的冻结延迟趋势。我们的研究结果对最近强调延迟冰形成的超防水表面配方提出了质疑，并表明防冰设计必须优化润湿性和粗糙度的竞争影响。
Ice formation can have catastrophic consequences for human activity on the ground and in the air. Here we investigate water freezing delays on untreated and coated surfaces ranging from hydrophilic to superhydrophobic and use these delays to evaluate icephobicity. Supercooled water microdroplets are inkjet-deposited and coalesce until spontaneous freezing of the accumulated mass occurs. Surfaces with nanometer-scale roughness and higher wettability display unexpectedly long freezing delays, at least I order of magnitude longer than typical Surface roughness superhydrophobic surfaces with larger hierarchical roughness and low wettability. Directly related to the main focus on heterogeneous nucleation and freezing delay of supercooled water droplets, the observed ensuing crystallization process consisted of two distinct phases: one very rapid recalescent partial solidification phase and a subsequent slower phase. Observations of the droplet collision process employed for the continuous liquid mass accumulation up to the point of ice formation reveal a previously unseen atmospheric-pressure, subfreezing-temperature regime for liquid-on-liquid bounce. On the basis of the entropy reduction of water near a solid surface, we formulate a modification to the classical heterogeneous nucleation theory, which predicts the observed freezing delay trends. Our results bring to question recent emphasis on super water-repellent surface formulations for ice formation retardation and suggest that anti-icing design must optimize the competing influences of both wettability and roughness.