CONTACT-ANGLE, FILM AND LINE TENSION OF FOAM FILMS .2. FILM AND LINE TENSION MEASUREMENTS

New experiments with air bubbles floating at the surface of aqueous solutions of sodium dodecyl sulfate have been carried out. At a given size the spontaneous shrinking of such a bubble has been stopped by regulating the pressure inside the cell. The relaxation of the contact line radius with time has been recorded by taking photographs. The film curvature was measured by utilizing a precise differential interferometric technique. The data allows independent calculation of the film and line tensions, γ and κ. For a "stopped" bubble both γ and κ relax with time: κ tends to zero and γ tends to its equilibrium value known from other experiments. The results suggest that for this system one can introduce the concept of dynamic line tension, which arises because of the motion of the contact line. This effect can be important in all cases when the interactions between fluid colloid particles and/or biological cells are accompanied with formation of a three-phase contact line. © 1992.