Cavitation nucleation in acoustic vaporization of superheated droplets

Acoustic Droplet Vaporization (ADV) is the phase-change process of superheated droplets into bubbles induced by ultrasound waves. The increase in liquid/vapor system volume together with the strong pressure and flow fields created by the rapid vaporization can be exploited in biomedical applications such as embolotherapy and targeted drug delivery. In the effort to elucidate the underlying physics and to improve the precision and safety of ADV, we conduct experiments to characterize micron-sized perfluorocarbon droplet/bubble system dynamics by means of ultra-high-speed videomicroscopy and ultrasound imaging. We also aim at reducing the negative pressure amplitude needed to induce the phase-change by engineering the droplet composition and by tuning the acoustic driving. Experimental observations of cavitation nucleation spots are compared with theoretical models combining nucleation theory and acoustic propagation inside the droplet core in a probabilistic framework, and the influence of their number and positions on the subsequent dynamics of the interface is examined.