Acoustic pulsation of a microbubble confined between elastic walls.

This paper reports an experimental and theoretical study of the dynamics of microbubbles flattened between the two walls of a microfluidic channel. Using a micropit, a single bubble is trapped by capillarity at a specific position in the channel and its oscillation under ultrasound is observed by stroboscopy. It is shown that the bubble dynamics can be described by a two-dimensional Rayleigh-Plesset equation including the deformation of the walls of the channel and that the bubble behaves as a secondary source of Rayleigh waves at the wall interface. Above a critical pressure threshold, the bubble exhibits a two-dimensional shape oscillation around its periphery with a period doubling characteristic of a parametric instability. We report how each shape mode appears, varying the bubble radius and the amplitude of excitation, and demonstrate that the wall deformation has no significant effect on their dynamics. [ABSTRACT FROM AUTHOR]