High-speed footage shows transient ultrasonic nucleation of different hydrophobic particles in suspension

In this study, we investigated if hydrophobic particles of the materials carbon black and zinc oxide act as cavitation nuclei, using high-speed photography during 1 MHz, low-amplitude sonication. Carbon black particles were observed to lose their gaseous shells and become acoustically inactive, whilst zinc oxide particles were observed to generate bubbles without becoming acoustically inactive. Zinc oxide might be a suitable candidate for an ultrasound contrast agent. Carbon black might be a suitable candidate for ultrasound-guided drug delivery.