Recently, microbubbles attract attention as ultrasound contrast agents in the medical field because of their excellent ultrasound scattering including superharmonic response. Such superharmonic signals obtained by detecting ultrasound waves can be used for distinguish responses of contrast agents from those of surrounding tissues. Therefore, nonlinear oscillation of insonified microbubbles has been studied actively. However, most of such studies focus on dynamics of single microbubble. This research investigates how interaction between a pair of microbubbles affects their oscillation. Our numerical simulation shows that I to 2 natural frequency ratio of the two microbubbles can result in their superharmonic resonance. Its mechanism was discussed on the basis of their equations of motion coupled through nonlinear terms.
