Changes in microbubble dynamics near a boundary revealed by combined optical micromanipulation and high-speed imaging

The authors report optical observations of the change in the dynamics of one and the same ultrasound contrast agent microbubble due to the influence of interfaces and neighboring bubbles. The bubble is excited by a 2.25 MHz ultrasound burst and its oscillations are recorded with an ultrahigh-speed camera at 15 million frames per second. The position of an individual bubble relative to a rigid wall or second bubble is precisely controlled using optical tweezers based on Laguerre-Gaussian laser beams [P. Prentice , Opt. Express 12, 593 (2004); V. Garbin , Jpn. J. Appl. Phys. 44, 5773 (2005)]. This allows for repeated experiments on the very same bubble and for a quantitative comparison of the effect of boundaries on bubble behavior. (c) 2007 American Institute of Physics.