title: Microbubble shape oscillations excited through ultrasonic parametric driving.
abstract: An air bubble driven by ultrasound can become shape-unstable through a parametric instability. We report time-resolved optical observations of shape oscillations (mode n=2 to 6) of micron-sized single air bubbles. The observed mode number n was found to be linearly related to the ambient radius of the bubble. Above the critical driving pressure threshold for shape oscillations, which is minimal at the resonance of the volumetric radial mode, the observed mode number n is independent of the forcing pressure amplitude. The microbubble shape oscillations were also analyzed numerically by introducing a small nonspherical linear perturbation to a Rayleigh-Plesset-type equation, capturing the experimental observations in detail.
authors.affiliation: Department of Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands.
authors.forename: Michel
authors.initials: M
authors.lastname: Versluis
authors.forename: David E
authors.initials: DE
authors.lastname: Goertz
authors.forename: Peggy
authors.initials: P
authors.lastname: Palanchon
authors.forename: Ivo L
authors.initials: IL
authors.lastname: Heitman
authors.forename: Sander M
authors.initials: SM
authors.lastname: van der Meer
authors.forename: Benjamin
authors.initials: B
authors.lastname: Dollet
authors.forename: Nico
authors.initials: N
authors.lastname: de Jong
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse