A Thermodynamic Analysis of the Validity of Wenzel and Cassie's Equations
TAN Shuai-Xia1,2, LU Xiao-Ying1,2, LI Wen3, ZHAO Ning1, ZHANG Xiao-Li1, XU Jian1
1State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 1001902Graduate University of the Chinese Academy of Sciences, Beijing 1001903Key Laboratory of Low Dimensional Materials and Application Technology (Ministry of Education) and Faculty of Materials and Optoelectronic Physics, Xiangtan University, Xiangtan 411105
A Thermodynamic Analysis of the Validity of Wenzel and Cassie's Equations
TAN Shuai-Xia1,2, LU Xiao-Ying1,2, LI Wen3, ZHAO Ning1, ZHANG Xiao-Li1, XU Jian1
1State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 1001902Graduate University of the Chinese Academy of Sciences, Beijing 1001903Key Laboratory of Low Dimensional Materials and Application Technology (Ministry of Education) and Faculty of Materials and Optoelectronic Physics, Xiangtan University, Xiangtan 411105
Wettable properties of a considered solid on its contact angle (CA) can be analyzed theoretically using the classical Wenzel and Cassie's equations. However, recent strong interest in superhydrophobic surfaces has demanded a re-examination of the applicability of the two equations. We report a thermodynamic analysis to determine the universality, in particular, the limitations of the two equations. Using some special surfaces, we demonstrate that the two equations are valid for micro-scale heterogeneous structures, however they are invalid for macro-scale heterogeneous surfaces. Furthermore, the present calculations suggest that fundamental thermodynamic analysis is the most powerful and reliable approach to determine the comprehensive wettability for various structurally patterned surfaces.
Wettable properties of a considered solid on its contact angle (CA) can be analyzed theoretically using the classical Wenzel and Cassie's equations. However, recent strong interest in superhydrophobic surfaces has demanded a re-examination of the applicability of the two equations. We report a thermodynamic analysis to determine the universality, in particular, the limitations of the two equations. Using some special surfaces, we demonstrate that the two equations are valid for micro-scale heterogeneous structures, however they are invalid for macro-scale heterogeneous surfaces. Furthermore, the present calculations suggest that fundamental thermodynamic analysis is the most powerful and reliable approach to determine the comprehensive wettability for various structurally patterned surfaces.
TAN Shuai-Xia;LU Xiao-Ying;LI Wen;ZHAO Ning;ZHANG Xiao-Li;XU Jian. A Thermodynamic Analysis of the Validity of Wenzel and Cassie's Equations[J]. 中国物理快报, 2009, 26(8): 80502-080502.
TAN Shuai-Xia, LU Xiao-Ying, LI Wen, ZHAO Ning, ZHANG Xiao-Li, XU Jian. A Thermodynamic Analysis of the Validity of Wenzel and Cassie's Equations. Chin. Phys. Lett., 2009, 26(8): 80502-080502.
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2009, Vol. 26 
