Measurement of dynamics of laser-induced cavitation around nanoparticle with high-speed digital holographic microscopy

Micro/nano bubble formation on the surface of laser-irradiated nanoparticles has been widely studied in various industrial applications. The elucidation of the mechanism underlying cavitation induced by irradiating nanoparticles with laser is imperative. In this work, high-speed digital holographic microscopy is applied to visualize the in-situ dynamics of laser-induced bubbles generated on nanoparticles randomly dispersed in liquids. The growth and collapse of a bubble along its 3D trajectory are quantified. Experimental results show two patterns of bubble formation. One is that the maximum bubble wall speeds occur during either expansion or contraction. The other is that the maximum speeds are similar in both periods. It is found that the durations of growth and collapse are not equal, and their difference increases with the bubble maximum diameter, which is caused by altered heat transfer processes in bubbles. It implies large bubbles expand relatively quickly and shrink relatively slowly. This work will help understand the interaction among laser, nanoparticles and surrounding medium.