Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Langmuir. 2013 Jul 30;29(30):9516-24. doi: 10.1021/la401282c. Epub 2013 Jul 16.
Water suspended on chilled superhydrophobic surfaces exhibits delayed freezing; however, the interdrop growth of frost through subcooled condensate forming on the surface seems unavoidable in humid environments. It is therefore of great practical importance to determine whether facile defrosting is possible on superhydrophobic surfaces. Here, we report that nanostructured superhydrophobic surfaces promote the growth of frost in a suspended Cassie state, enabling its dynamic removal upon partial melting at low tilt angles (<15°). The dynamic removal of the melting frost occurred in two stages: spontaneous dewetting followed by gravitational mobilization. This dynamic defrosting phenomenon is driven by the low contact angle hysteresis of the defrosted meltwater relative to frost on microstructured superhydrophobic surfaces, which forms in the impaled Wenzel state. Dynamic defrosting on nanostructured superhydrophobic surfaces minimizes the time, heat, and gravitational energy required to remove frost from the surface, and is of interest for a variety of systems in cold and humid environments.
水在冷却的超疏水表面上呈悬停状态时会延迟冻结；然而，在潮湿环境中，通过在表面上形成过冷冷凝物，似乎不可避免地会出现霜的跨滴生长。因此，确定在超疏水表面上是否可以方便地除霜具有重要的实际意义。在这里，我们报告说，纳米结构的超疏水表面促进了悬停 Cassie 状态下的霜生长，从而使其能够在低倾斜角度（<15°）下部分融化时动态去除。融化的霜的动态去除分为两个阶段：自发去湿和随后的重力移动。这种动态除霜现象是由相对于微结构超疏水表面上形成的刺穿 Wenzel 状态的霜的解冻后水的低接触角滞后驱动的。在纳米结构超疏水表面上进行的动态除霜可最大程度地减少从表面去除霜所需的时间、热量和重力能，这对于寒冷和潮湿环境中的各种系统都很有意义。
