We studied the changes in the dynamics of an ultrasound contrast agent microbubble due to the vicinity of an interface or a neighboring bubble. The bubble was excited by a 2.25 MHz ultrasound burst, and its oscillations were recorded optically with an ultra-high speed camera at 15 million frames per second. The position of the bubble relative to a wall or a second bubble was precisely controlled using optical tweezers based on Laguerre-Gaussian laser beams. This allowed for repeated experiments on the very same bubble, and for a quantitative comparison of the effect of boundaries on bubble behavior.

V. Garbin, D. Cojoc, E. Ferrari, E. Di Fabrizio, M. Overvelde, S. M. van der Meer, N. de Jong, D. Lohse and M. Versluis, Applied Physics Letters 90, 114103 (2007)