Coupled dynamics of an isolated UCA microbubble pair

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.