Effect of nanoroughness on highly hydrophobic and superhydrophobic coatings.
Effect of nanoroughness on highly hydrophobic and superhydrophobic coatings.
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DOI：
10.1021/la302127y
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
Lena Mammen;Xu Deng;Maria B. Untch;Dandapani Vijayshankar;P. Papadopoulos;R. Berger;E. Riccardi;F. Leroy;D. Vollmer
中科院分区：
文献类型：
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作者：
Lena Mammen;Xu Deng;Maria B. Untch;Dandapani Vijayshankar;P. Papadopoulos;R. Berger;E. Riccardi;F. Leroy;D. Vollmer
针对低能表面，通过实验和数值研究了纳米粗糙度对接触角和钉扎的影响。纳米粗糙度是通过四乙氧基硅烷的化学气相沉积引入的，并通过扫描力显微镜进行量化。在平坦表面上增加 2 nm 的均方根粗糙度可将半氟化硅烷氟化后的接触角增加多达 30°。另一方面，纳米粗糙度可以改善或削弱由组装的覆盆子颗粒制成的超疏水表面的拒液性。进行分子动力学模拟是为了从微观上了解半氟化硅烷的长度和表面涂层密度如何影响疏水性。固液表面自由能计算表明，润湿行为很大程度上取决于半氟化硅烷的密度和排列。在实验值范围内的涂层密度下，一些水分子可以渗透到半氟化链之间，从而增加表面能。结合实验和数值数据表明，粗糙度引起的接触角增加与液体渗透到纳米孔中或相邻半氟化分子之间引起的钉扎增加相竞争。
The effect of nanoroughness on contact angles and pinning is investigated experimentally and numerically for low-energy surfaces. Nanoroughness is introduced by chemical vapor deposition of tetraethoxysilane and was quantified by scanning force microscopy. Addition of a root-mean-square roughness of 2 nm on a flat surface can increase the contact angle after fluorination by a semifluorinated silane by up to 30°. On the other hand, nanoroughness can improve or impair the liquid repellency of superhydrophobic surfaces that were made from assembled raspberry particles. Molecular dynamics simulations are performed in order to gain a microscopic understanding on how the length and the surface coating density of semifluorinated silanes influence the hydrophobicity. Solid-liquid surface free energy computations reveal that the wetting behavior strongly depends on the density and alignment of the semifluorinated silane. At coating densities in the range of experimental values, some water molecules can penetrate between the semifluorinated chains, thus increasing the surface energy. Combining the experimental and numerical data exhibits that a roughness-induced increase of the contact angle competes with increased pinning caused by penetration of liquid into nanopores or between neighboring semifluorinated molecules.