物理化学学报 >> 2010, Vol. 26 >> Issue (11): 2989-2996.doi: 10.3866/PKU.WHXB20101025

胶体及界面化学 上一篇    下一篇

超疏水表面微纳二级结构对冷凝液滴最终状态的影响

刘天庆, 孙玮, 孙相彧, 艾宏儒   

  1. 大连理工大学化工学院, 辽宁大连116024
  • 收稿日期:2010-04-29 修回日期:2010-07-06 发布日期:2010-10-29
  • 通讯作者: 刘天庆 E-mail:liutq@dlut.edu.cn
  • 基金资助:

    国家自然科学基金(50876015)资助项目

Effect of Hierarchical Architecture of Super-Hydrophobic Surface on the Condensed Drop's Final State

LIU Tian-Qing, SUN Wei, SUN Xiang-Yu, AI Hong-Ru   

  1. School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning Province, P. R. China
  • Received:2010-04-29 Revised:2010-07-06 Published:2010-10-29
  • Contact: LIU Tian-Qing E-mail:liutq@dlut.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (50876015).

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摘要：

从超疏水表面(SHS)上初始冷凝液核长大、合并、形成初始液斑开始, 分析计算了冷凝液斑变形成为Wenzel 或Cassie 液滴过程中界面能量的变化, 并以界面能曲线降低、是否取最小值为判据, 确定冷凝液滴的最终稳定状态. 计算结果表明: 在只有微米尺度的粗糙结构表面上, 冷凝液滴的界面能曲线一般都是先降低再升高,呈现Wenzel 状态;而当表面具有微纳米二级粗糙结构,且纳米结构的表面空气面积分率较高时, 冷凝液滴的能量曲线持续降低, 直至界面能最小的Cassie 状态, 因此可以自发地形成Cassie 液滴. 还计算了文献中具有不同结构参数的SHS 上冷凝液滴的状态和接触角, 并与实验结果进行了比较, 结果表明, 计算的冷凝液滴状态与实验观察结果完全吻合. 因此, 微纳二级结构是保持冷凝液滴在SHS上呈现Cassie 状态的重要因素.

 

关键词: 超疏水表面, 微纳结构, 表面, 界面, 自由能, 冷凝

Abstract:

The interface free energy of a local condensate from the growth and combination of numerous initial condensation nuclei was calculated during its shape changes from an early flat shape to a Wenzel or Cassie state on the super-hydrophobic surface (SHS). The final state of the condensed drop was determined according to whether the interface free energy continuously decreased or it had a minimum value. Our calculations indicate that condensation drops on a surface only with micro roughness display Wenzel state because the interface free energy curve of a condensed drop first decreases and then increases, existing a minimum value corresponding to Wenzel drop. On a surface with appropriate hierarchical roughness, however, the interface energy curve of a condensed drop will constantly decline until it reaches the Cassie state. Therefore, a condensed drop on a hierarchical roughness surface can spontaneously reach the Cassie state. In addition, the states and apparent contact angles of condensed drops on a SHS with different structural parameters were calculated and compared with experimental observations. Results show that the calculated condensed drop states agree well with the experimental results. It can be concluded that micro and nano hierarchical roughness is the key structural factor responsible for sustaining condensed drops in the Cassie state on a SHS.

 

Key words: Super-hydrophobic surface, Micro and nano hierarchical structure, Surface, Interface, Free energy, Condensation