A high-speed camera was used to observe the motion of the three-phase contact (TPC) line for a small rising bubble ruptured by a submerged horizontal glass plate. The experimental data for the radial position of the TPC line as a function of time were used to examine both hydrodynamic and molecular-kinetic models previously developed for wetting/dewetting processes. It was found that both models were not able to describe the experimental data using the physically consistent values of parameters. A better fit could be obtained if the equilibrium contact angle, obtained from the TPC versus time measurements, was used in place of the thermodynamic contact angle determined by the Wilhelmy plate technique; however, the parameters obtained by this fitting could not be physically justified. Importantly, the equilibrium contact angle was found to be a function of the bubble radius and was significantly different from the Young contact angle. This radius dependence of contact angles and other curvature-dependent effects, which are not considered in the hydrodynamic and molecular-kinetic models, may be the cause of the deviations from the experimental results.
Langmuir: the ACS Journal of Surfaces and Colloids Vol. 19, Issue 17, p. 6796-6801