title: Bubble rubbing on solid surface: experimental study.
abstract: This is the first interferometric study in the literature on wetting film entrapped between bubble and moving solid substrate. Unique experimental setup was specially designed for monitoring the thickness profiles of wetting film, intercalated between the bubble and moving solid surface. For this reason, special procedure developed for this study was applied for determination of 3D film thickness profiles. This allowed us to determine 3D profiles of the disjoining, the lift pressures as well as the viscous stress tensor as a function of the velocity of the solid surface. Thus, one can see that a strong linear dependence between the average film thickness and the speed of motion of the solid surface exists until a certain critical speed of motion, beyond which the dependence becomes weaker but keeps its linear trend. Similar is the propensity with the average lift pressure. Moreover, one can observe how the inhomogeinity of the film surfaces changes upon increasing the speed of motion of the solid surface. The proposed technique reveals new possibilities for investigation of bubbles and solid surfaces on deeper level when they are in relative motion towards each other. Thus, one can conduct detailed tribological studies on bubbles moving in close proximity to solid surfaces.
authors.affiliation: Department of Physical Chemistry, Sofia University, 1164 Sofia, Bulgaria. Electronic address: fhsk@chem.uni-sofia.bg.
authors.forename: Stoyan I
authors.initials: SI
authors.lastname: Karakashev
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Stöckelhuber
authors.forename: Roumen
authors.initials: R
authors.lastname: Tsekov
authors.forename: Gert
authors.initials: G
authors.lastname: Heinrich
keywords: Bubble; Friction; Interferometry; Lift force; Thin wetting films; Tribology