The physics of nanoshelled microbubbles
Résumé
Nanoshelled microbubbles are suitable markers for perfused areas in ultrasonic imaging, and have potential applications in therapy. With radii up to 5 microns, their resonance frequencies are in the lower megahertz range. We explored the physics of nanoshelled microbubbles, with special attention to the influence of the nanoshell on the oscillation offset with respect to the driving phase. Microbubbles above resonance size oscillate π rad out of phase with respect to microbubbles under resonance size. As the damping becomes less, this transition in offset becomes more abrupt. Therefore, the damping due to the friction of the nanoshell can be derived from this abruptness. We support our results with some high-speed optical observations of oscillating microbubbles in an ultrasonic field.
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