Dynamics of Capillary-Viscous Dewetting

Abstract

In this work the kinetics of partial dewetting was investigated for the case where dewetting, driven by capillary forces, is resisted by viscous effects. Both axisymmetric and unidirectional dewetting cases were considered. The analysis extended previous investigations using the Brochard-Wyart and de Gennes (1992) relation, having a cut off of molecular size beyond which the continuum approach is no longer valid, to obtain the dynamic contact angle condition at the receding contact line, and an analogous relation at the advancing contact line at the constant liquid film thickness side. The dynamic contact angle conditions at both sides of the ridge along with the viscous dissipation in the system were considered. A general formulation that can be used for different dynamic contact angle relations was developed. Simplification led to an analytical solution for the dynamic contact angle, size of the dry zone, and width of the ridge. The validity of the approximation was considered. The dynamics of dewetting for the simplified formulation was found to be consistent with the one developed by de Gennes et al. (2010). The dewetting dynamics based on Hoffman, and Brochard-Wyart and de Gennes contact angle relations were together found to yield results in good agreement with available experimental data over the whole viscosity range. The use of the receding contact angle in the model was found to be of primary importance for the case involving contact angle hysteresis.