Wetting properties of thin liquid polyethylene propylene films

Instability and morphology of thin liquid films on chemically heterogeneous substrates

A new mechanism for the surface instability and dewetting of thin films on chemically heterogeneous substrates is identified and simulated. The time scale for instability varies inversely with the potential difference due to the heterogeneity. Heterogeneities can even destabilize spinodally stable films, reduce the time of rupture substantially for thicker films, and produce complex and locally ordered morphological features (e.g., ripples and castle-moat structures, lack of undulations before hole formation) that are not predicted by the spinodal mechanism.

Pattern Formation in Spontaneous Dewetting of Thin Apolar Films

Various stages of evolution of surface instability leading to dewetting are investigated for thin (<100 nm) fluid films subjected to the long range van der Waals interactions on a nonwettable solid. The problems of pattern selection and complete three-dimensional morphology are resolved based on numerical solutions of the nonlinear two-dimensional thin film equation. The initial small scale random nonhomogeneities are quickly reorganized into a large scale coherent bicontinuous structure consisting of "hills" and "valleys," which is reminiscent of the classical picture of the spinodal decomposition in the linear approximation. On the level of a "unit-cell," the bicontinuous structure slowly evolves into an increasingly axisymmetric circular pattern, and eventually a growing circular hole (dry spot) is formed. Scaling arguments, as well as the simulations give the characteristic mean area of a unit-cell containing a single hole to be proportional to (h04gamma/|S|), where h0 is mean thickness, gamma is surface tension, and S is the spreading coefficient. Copyright 1997 Academic Press. Copyright 1997Academic Press