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自然界中的微纳复合结构超疏水表面由于其独特的润湿性质引起了人们的广泛关注, 大量实验研究表明了仿生人工微纳复合结构表面润湿性能的优越性, 然而液滴在微纳复合结构表面的润湿状态和转型过程的理论研究还并不完善. 本文首先用热力学方法分析了液滴在微纳复合结构表面可能存在的所有状态(四种稳定润湿状态和五种亚稳态到稳定态转型中的过渡态), 推导出了相应的能量表达式及表观接触角方程; 基于最小能量原理, 确定液滴在微纳复合结构表面的稳定状态, 较以往模型相比, 能够更好的预测已有的实验结果; 其次研究了微纳结构尺寸对稳定润湿状态和亚稳态到稳定态转型过程的影响; 最后提出了微纳复合结构表面设计原则, 即确定“超疏水稳定区”尺寸范围, 为超疏水表面的制备提供理论依据.Superhydrophobicity of biological surfaces with micro/nanoscale hierarchical roughness has recently been given great attention and widely reported in many experimental studies due to the unique wettability. For example, the dual-scale structure of the lotus leaf not only shows high contact angle and low contact angle hysteresis but also presents good stability and mechanical properties. Though lots of experimental studies on the wettability of artificial hierarchical rough surface have been carried out, a thorough analysis on the contribution of micro- and nano-scaled roughness to the metastable wetting states and their transition is still lack. In this paper, a thermodynamic approach is applied to analyze all the wetting states (including four stable wetting states and five transition states) of a water droplet on a surface with micro/nanoscale hierarchical roughness, and the corresponding free energy expressions and apparent contact angle equations are deduced. The stable wetting states are confirmed by the principle of minimum free energy. And the calculated results by these state equations can fit well with the experimental results reported in the literature when compared with the previous models. Meanwhile, the influence of micro/nanoscale roughness on the stable wetting states and metastable-stable transition has been analyzed thermodynamically. It is found that there is a synergistic effect of micro and nanoscale roughness on wettability, which nlay result in many different wetting states. There are four wetting states during increasing relative pitch of a microscaled structure at a given nanoscaled structure, but two wetting states can be obtained as increasing relative pitch of nanoscaled structure at a given microscaled structure. The change of nondimensional energy and nondimensional energy barrier in the metastable-stable transition process of water droplet wetting micro and nanoscaled structure is quantitatively analyzed. Results indicate that the micro-scaled structure is never wetted in a special size range of the nanoscaled structure, and the special size range is of great significance to enhance superhydrophobic stability of the microscaled structure. Furthermore, the existence of microscaled structure decreases the transition energy barrier of water droplet wetting nanoscaled structure, which is helpful for understanding the experimental results reported in the literature. Finally, all possible stable wetting states of water droplet no a surface with micro/nanoscale hierarchical roughness are discribed in a wetting map. A design principle of superhydrophobic surface with micro/nanoscale hierarchical roughness is put forward, which is helpful to ensure the size of micro/nanoscale structure in the “stable superhydrophobic region” and to provide a theoretical guidance in the preparation of superhydrophobic surface.
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Keywords:
- micro/nanoscale structured surface /
- wetting state /
- energy barrier /
- superhydrophobic stability
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[8] Young T 1805 Philos. Trans. R. Soc. London 95 65
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[20] Cha T G, Yi J W, Moon M W, Lee K R, Kim H Y 2010 Langmuir 26 8319
[21] Wang S T, Jiang L 2007 Adv. Mater. 19 3423
[22] Hejazi V, Nosonovsky M 2013 Colloid. Polym. Sci. 291 329
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[24] Boreyko J B, Baker C H, Poley C R, Chen C H 2011 Langmuir 27 7502
[25] Barbieri L, Wagner E, Hoffmann P 2007 Langmuir 23 1723
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[29] 2008 Eur. Phys. J. B 64 493
[30] Liu S S, Zhang C H, Zhang H B, Zhou J, He J G, Yin H Y 2013 Chin. Phys. B 22 106801
[31] Nosonovsky M, Bhushan B 2007 Microelectron. Eng. 84 382
[32] Xue Y H, Chu S G, Lv P Y, Duan H L 2012 Langmuir 28 9440
[33] Whyman G, Bormashenko B 2011 Langmuir 27 8171
[34] Jeong H E, Lee S H, Kim J K, Suh K Y 2006 Langmuir 22 1640
[35] Pompe T, Herminghaus S 2000 Phys. Rev. Lett. 85 1930
[36] Guo J H, Dai S Q, Dai Q 2010 Acta Phys. Sin. 59 2601 (in Chinese) [郭加宏, 戴世强, 代钦 2010 物理学报 59 2601]
[37] Chen X, Ma R, Li J, Hao C, Guo W, Luk B L, Li S C, Yao S, Wang Z 2012 Phys. Rev. Lett. 109 116101
[38] Öner D, McCarthy T J 2000 Langmuir 16 7777
[39] Zheng Q S, Yu Y, Zhao Z H 2005 Langmuir 21 12207
[40] Yao C W, Garvin T P, Alvarado J L, Jacobi A M, Jones B G, Marsh C P 2012 Appl. Phys. Lett. 101 111605
[41] Li W, Amirfazli A 2005 J. Colloid Interface Sci. 292 195
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[1] Neinhuis C, Barthlott W 1997 Ann. Bot. 79 667
[2] Ensikat H J, Ditsche-Kuru P, Neinhuis C, Barthlott W 2011 Beilstein J. Nanotechnol. 2 152
[3] Bhushan B, Her E K 2010 Langmuir 26 8207
[4] Gao H, Wang X, Yao H, Gorb S, Arzt E 2005 Mech. Mater. 37 275
[5] Liu J L, Feng X Q, Xia R, Zhao H P 2007 J. Phys. D: Appl. Phys. 40 5564
[6] Yang Z, Wu Y Z, Ye Y F, Gong M G, Xu X L 2012 Chin. Phys. B 21 126801
[7] Bhushan B, Nosonovsky M 2010 Phil. Trans. R. Soc. A 368 4713
[8] Young T 1805 Philos. Trans. R. Soc. London 95 65
[9] Wenzel R N 1936 Ind. Eng. Chem. 28 988
[10] Cassie A B D, Baxter S 1944 Trans. Faraday Soc. 40 546
[11] McHale G 2009 Langmuir 25 7185
[12] Xia F, Jiang L 2008 Adv. Mater. 20 2842
[13] Gong M G, Xu X L, Yang Z, Liu Y S, Liu L 2010 Chin. Phys. B 19 56701
[14] Yu J, Wang H J, Shao W J, Xu X L 2014 Chin. Phys. B 23 16803
[15] Shirtcliffe N J, McHale G, Newton M I, Chabrol G, Perry C C 2004 Adv. Mater. 16 1929
[16] Gao L, McCarthy T J 2006 Langmuir 22 2966
[17] Patankar N A 2004 Langmuir 20 8209
[18] Jeong H E, Lee S H, Kim J K, Suh K Y 2006 Langmuir 22 1640
[19] Sajadinia S H, Sharif F 2010 J. Colloid Interface Sci. 344 575
[20] Cha T G, Yi J W, Moon M W, Lee K R, Kim H Y 2010 Langmuir 26 8319
[21] Wang S T, Jiang L 2007 Adv. Mater. 19 3423
[22] Hejazi V, Nosonovsky M 2013 Colloid. Polym. Sci. 291 329
[23] Bormashenko E, Starov V 2013 Colloid. Polym. Sci. 291 343
[24] Boreyko J B, Baker C H, Poley C R, Chen C H 2011 Langmuir 27 7502
[25] Barbieri L, Wagner E, Hoffmann P 2007 Langmuir 23 1723
[26] Extrand C W 2004 Langmuir 205013
[27] Zhao X W, Jiang P, Gao Y, Wang J X, Song L, Liu D F, Liu L F, Dou XY, Luo S D, Zhang Z X, Xiang Y J, Zhou W Y and Wang G 2005 Chin.Phys. 14 1471
[28] Wang B, Nian J Y 2013 Acta Phys. Sin. 62 146801 (in Chinese) [王奔, 念敬妍 2013 物理学报 62 146801]
[29] 2008 Eur. Phys. J. B 64 493
[30] Liu S S, Zhang C H, Zhang H B, Zhou J, He J G, Yin H Y 2013 Chin. Phys. B 22 106801
[31] Nosonovsky M, Bhushan B 2007 Microelectron. Eng. 84 382
[32] Xue Y H, Chu S G, Lv P Y, Duan H L 2012 Langmuir 28 9440
[33] Whyman G, Bormashenko B 2011 Langmuir 27 8171
[34] Jeong H E, Lee S H, Kim J K, Suh K Y 2006 Langmuir 22 1640
[35] Pompe T, Herminghaus S 2000 Phys. Rev. Lett. 85 1930
[36] Guo J H, Dai S Q, Dai Q 2010 Acta Phys. Sin. 59 2601 (in Chinese) [郭加宏, 戴世强, 代钦 2010 物理学报 59 2601]
[37] Chen X, Ma R, Li J, Hao C, Guo W, Luk B L, Li S C, Yao S, Wang Z 2012 Phys. Rev. Lett. 109 116101
[38] Öner D, McCarthy T J 2000 Langmuir 16 7777
[39] Zheng Q S, Yu Y, Zhao Z H 2005 Langmuir 21 12207
[40] Yao C W, Garvin T P, Alvarado J L, Jacobi A M, Jones B G, Marsh C P 2012 Appl. Phys. Lett. 101 111605
[41] Li W, Amirfazli A 2005 J. Colloid Interface Sci. 292 195
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