Pei Junxian, Liao Yutian, Li Qian, Shi Kui, Fu Jia, Hu Xuejiao, Huang Zhi, Xue Longjian, Xiao Xu, Liu Kang
MOE Key Laboratory of Hydraulic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China; State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065, China.
MOE Key Laboratory of Hydraulic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China.
J Colloid Interface Sci. 2022 Jun;615:302-308. doi: 10.1016/j.jcis.2022.01.157. Epub 2022 Jan 29.
Structured hydrophobic surfaces often suffer from Cassie-wetting failure due to trapped water in structure gaps for a long-term operation. Sustainable Cassie-wetting on such surface could be achieved by coating an atom-thick and moisture-impermeable graphene on it.
Water contact angles were measured to clarify the effect of graphene on wetting, and water impermeability was verified by moisture deposition and evaporation. Sliding angle measurements and vapor condensation were carried out to demonstrate the stable Cassie-state wetting and application.
Interestingly we found the graphene does not significantly disrupt the wetting behavior of the structured hydrophobic surface, showing a wettability transparency. Moreover, the impermeability of graphene keeps moisture away from the structure gaps. Owning to the combination of these two properties, droplets on the graphene-coated structured surface exhibit a stable Cassie-state hydrophobic wetting, even under the situation of moisture deposition and evaporation. Using the modified surface, we also found a 40-100% increase in condensation efficiency for a 5-hour vapor condensation at a subcooling of 40 °C. These results suggest an effective strategy to prevent Cassie-wetting failure of structured hydrophobic surface and are expected to promote its further application in more complex conditions.
由于在长期运行过程中结构间隙中会截留水分，结构化疏水表面常常会出现 Cassie 浸润失效。在这种表面上通过涂覆一层原子厚度且不透湿的石墨烯可实现可持续的 Cassie 浸润。
测量水接触角以阐明石墨烯对浸润的影响，并通过水分沉积和蒸发验证不透湿性。进行滑动角测量和蒸汽冷凝实验以证明稳定的 Cassie 态浸润及其应用。
有趣的是，我们发现石墨烯不会显著扰乱结构化疏水表面的浸润行为，呈现出浸润透明性。此外，石墨烯的不透湿性使水分远离结构间隙。由于这两种特性的结合，即使在有水分沉积和蒸发的情况下，涂覆石墨烯的结构化表面上的液滴也表现出稳定的 Cassie 态疏水浸润。使用这种改性表面，我们还发现在 40℃过冷度下进行 5 小时蒸汽冷凝时，冷凝效率提高了 40 - 100%。这些结果表明了一种防止结构化疏水表面出现 Cassie 浸润失效的有效策略，并有望促进其在更复杂条件下的进一步应用。
