Abstract:
Direct injection of a submicroliter ethanol solution of insoluble surfactant onto the surface of levitated or pendant bubbles in water facilitates the spreading of a known monolayer coverage on the surface of a bubble. As the bubble dissolves, its surface area decreases and the monolayer is compressed. This method has facilitated the measurement of the evolution of the damping of capillary oscillations [Asaki et al., Phys. Rev. Lett. 75, 2686--2689 (1995); 75, 4336(E) (1995)]. It has also been used to obtain direct measurements of the film pressure as a function of coverage for pendant bubbles. To investigate the effect on radial pulsations, new methods of monitoring the radial response of a bubble would be desirable. A novel method of exciting the radial pulsations of bubbles in oil will be described [Marston et al., J. Acoust. Soc. Am. 99, 2560(A) (1996)] based on dielectrophoretic levitation and modulation of the Maxwell stress of an applied electric field. [Work supported by the Office of Naval Research.]