Spori Doris M, Drobek Tanja, Zürcher Stefan, Ochsner Mirjam, Sprecher Christoph, Mühlebach Andreas, Spencer Nicholas D
Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Zürich, Switzerland.
Langmuir. 2008 May 20;24(10):5411-7. doi: 10.1021/la800215r. Epub 2008 Apr 29.
To enhance our understanding of liquids in contact with rough surfaces, a systematic study has been carried out in which water contact angle measurements were performed on a wide variety of rough surfaces with precisely controlled surface chemistry. Surface morphologies consisted of sandblasted glass slides as well as replicas of acid-etched, sandblasted titanium, lotus leaves, and photolithographically manufactured golf-tee shaped micropillars (GTMs). The GTMs display an extraordinarily stable, Cassie-type hydrophobicity, even in the presence of hydrophilic surface chemistry. Due to pinning effects, contact angles on hydrophilic rough surfaces are shifted to more hydrophobic values, unless roughness or surface energy are such that capillary forces become significant, leading to complete wetting. The observed hydrophobicity is thus not consistent with the well-known Wenzel equation. We have shown that the pinning strength of a surface is independent of the surface chemistry, provided that neither capillary forces nor air enclosure are involved. In addition, pinning strength can be described by the axis intercept of the cosine-cosine plot of contact angles for rough versus flat surfaces with the same surface chemistries.
为了加深我们对与粗糙表面接触的液体的理解，我们进行了一项系统研究，在这项研究中，我们在具有精确控制表面化学性质的各种粗糙表面上进行了水接触角测量。表面形态包括喷砂玻璃载玻片以及酸蚀、喷砂钛、荷叶和光刻制造的高尔夫球座形微柱（GTM）的复制品。即使在存在亲水性表面化学性质的情况下，GTM也表现出异常稳定的卡西型疏水性。由于钉扎效应，亲水性粗糙表面上的接触角会向更疏水的值偏移，除非粗糙度或表面能使得毛细力变得显著，从而导致完全润湿。因此，观察到的疏水性与著名的文泽尔方程不一致。我们已经表明，只要不涉及毛细力和空气封闭，表面的钉扎强度就与表面化学性质无关。此外，钉扎强度可以通过具有相同表面化学性质的粗糙表面与平坦表面的接触角的余弦 - 余弦图的轴截距来描述。
