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Here we present optical tweezers as a micromanipulation tool for the study of ultrasound contrast agent (UCA) microbubbles. Optical trapping and the resulting manipulation of individual and multiple microbubbles enables the study of their dynamics with controlled boundary conditions. The bubble response to ultrasound is recorded optically using the ultra high-speed Brandaris 128 camera. In our experiments, the amplitude of bubble oscillations was found to be strongly influenced by the vicinity of the sample chamber wall. Experiments with two trapped bubbles also showed a considerable influence of the neighboring bubble on the amplitude of oscillations of the other one.

We present time-resolved optical measurements of the coupled dynamics of two UCA microbubbles in ultrasound. We isolate microbubble pairs using optical tweezers to move them away from confining walls and study purely the bubble-bubble interaction. The dynamics in ultrasound is recorded optically using the ultra-high speed camera Brandaris 128. Our measurements indicate that the viscous drag on a translating and oscillating microbubble is not accounted for with enough accuracy by existing models using the elementary form of Stokes drag.