First-cycle oscillation excursions of Pickering-stabilised microbubbles subjected to a high-amplitude ultrasound pulse

Pickering stabilisation is a manufacturing process involving the adsorption of colloidal particles at gas-liquid interfaces. It is used to create the shells of stable, long-lived ultrasound contrast agent microbubbles. The purpose of the present study is to determine whether high-amplitude sonication influences the integrity of Pickering-stabilised shells. To this purpose, Pickering-stabilised microbubbles were subjected to high-speed photography at 10 million frames per second during 1-MHz, 1-MPa sonication. In addition, radial excursions as a function of time were simulated using the Rayleigh-Plesset equation for free gas microbubbles and microbubbles encapsulated by Pickering-stabilised shells of 7.6-Nm stiffness. The maximum expansions observed from camera recordings were either agreeing with those computed for Pickering-stabilised microbubbles or corresponding to greater values. The results indicate that optically identical microbubbles may undergo shell disruption of different severity. We conclude that the disruption occurs during sonication and not prior to it. These findings may aid in the development of Pickering-stabilised agents that facilitate ultrasoundtriggered release.