High speed observation of microbubble cavitation with single and multi-trap holographic spatial control: Progress and Prospects

Unger and Marston presented their seminal approach for studying cavitation processes at the single bubble level in 1988: demonstrating that laser-based optical trapping could be used to oppose the buoyancy force of bubbles in solution, and so afford a level of stable spatial control [1]. Since then, the exploitation of that valuable conceptual methodology has been subdued, with sparing use in observing bespoke cavitation arrangements occurring much later (circa 2003-2008) in the context of sonoporation. Here, the development of microbubbles containing a thin outer shell offering longevity as ultrasound contrast agents, together with the recognition that their presence during insonation could be used to enhance the uptake of exogenous species [i.e. drugs and genetic material] into cells and tissues led to a comparatively brief flurry of activity aimed at assessing the microscopic, and microsecond, mechanism whereby sonopores could be formed. Since then, a few insights have emerged using the methodology of optically trapped microbubbles, however it is probably fair to say that progress has been much slower than expected. This paper will examine and review the interim progress as well as assessing which new experiments might be worth trying as laser technology and dynamic holography evolve.