Department of Chemical and Biological Engineering, State University of New York at Buffalo, Buffalo, NY 14260, USA.
J Colloid Interface Sci. 2011 Jul 1;359(1):304-10. doi: 10.1016/j.jcis.2011.03.037. Epub 2011 Mar 16.
A two-dimensional nanodrop on a hydrophilic solid surface decorated with nanopillars is examined using a nonlocal density functional theory. It is shown that, in contrast to the commonly used Wenzel formula, even an extremely small roughness can considerably increase the contact angle. The contact angle depends on the distance between pillars, their height and width, as well as their composition. It was found that for all selected pillar heights and compositions, the largest contact angle is obtained when the distance between pillars acquires a size at which the liquid molecules can no longer penetrate between them. The further decrease in the interpillar distance decreases the contact angle, in qualitative agreement with the Cassie-Baxter formula. Considering pillars of various compositions, the role of the gradient of the fluid-solid interaction potential is examined. The presence of such a gradient does not allow the formation of a stable nanodrop on the surface. However, asymmetrical metastable nanodrops can be formed.
使用非局部密度泛函理论研究了在纳米柱修饰的亲水固体表面上的二维纳米液滴。结果表明，与常用的 Wenzel 公式相反，即使是非常小的粗糙度也可以显著增加接触角。接触角取决于柱之间的距离、它们的高度和宽度以及它们的组成。结果发现，对于所有选定的柱高和组成，当柱之间的距离达到液体分子不再能够穿透它们之间的尺寸时，获得最大接触角。进一步减小柱间距离会降低接触角，这与 Cassie-Baxter 公式定性一致。考虑到各种组成的柱子，研究了流体-固体相互作用势梯度的作用。这种梯度的存在不允许在表面上形成稳定的纳米液滴。然而，可以形成不对称的亚稳纳米液滴。
