Forming acoustic attraction force to concentrate microbubbles in flow using a matrix array transducer

We have reported our attempts for active path selection of microbubbles by acoustic radiation forces, where we have investigated to control microbubbles by forming multiple focal points of continuous wave using a matrix array transducer. However, because those focal points were located to sweep microbubbles along the slope of sound pressure, it was difficult to concentrate microbubbles against the direction of flow. To produce attractive force to concentrate microbubbles in flow, we formed time-shared acoustic field of two focal points with phase variation. We have succeeded to concentrate microbubbles in water flow utilizing two focal points with opposite phase, where streamline of microbubbles was clearly confirmed in a thin channel. Also we confirmed induction performance using an artificial blood vessel with Y-form bifurcation, where induction rate to a desired path was calculated and varied according to the emission pattern of the focal points in time-shared acoustic fields.