Yi Taeil, Wong Harris
Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA.
J Colloid Interface Sci. 2007 Sep 15;313(2):579-91. doi: 10.1016/j.jcis.2007.05.015. Epub 2007 May 13.
A liquid film of thickness h<100 nm is subject to additional intermolecular forces, which are collectively called disjoining pressure Pi. Since Pi dominates at small film thicknesses, it determines the stability and wettability of thin films. Current theory derived for uniform films gives Pi=Pi(h). This solution has been applied recently to non-uniform films and becomes unbounded near a contact line as h-->0. Consequently, many different effects have been considered to eliminate or circumvent this singularity. We present a mean-field theory of Pi that depends on the slope h(x) as well as the height h of the film. When this theory is implemented for Lennard-Jones liquid films, the new Pi=Pi(h,h(x)) is bounded near a contact line as h-->0. Thus, the singularity in Pi(h) is artificial because it results from extending a theory beyond its range of validity. We also show that the new Pi can capture all three regimes of drop behavior (complete wetting, partial wetting, and pseudo-partial wetting) without altering the signs of the long and short-range interactions. We find that a drop with a precursor film is linearly stable.
厚度h<100 nm的液膜受到额外的分子间力作用，这些力统称为附加压力Πi。由于Πi在小液膜厚度时起主导作用，它决定了薄膜的稳定性和润湿性。针对均匀薄膜推导的现有理论给出了Πi = Πi(h)。该解最近已应用于非均匀薄膜，并且当h→0时在接触线附近变得无界。因此，人们考虑了许多不同的效应来消除或规避这种奇异性。我们提出了一种附加压力Πi的平均场理论，它取决于薄膜的斜率h(x)以及高度h。当将该理论应用于 Lennard-Jones 液膜时，新的Πi = Πi(h, h(x))在h→0时在接触线附近是有界的。因此，Πi(h)中的奇异性是人为的，因为它是将一种理论扩展到其有效范围之外导致的。我们还表明，新的Πi可以捕捉液滴行为的所有三种状态（完全润湿、部分润湿和伪部分润湿），而不会改变长程和短程相互作用的符号。我们发现带有前驱膜 的液滴是线性稳定的。
