Active induction of microbubbles in flow at T-form bifurcation through acoustic focal points with phase variation

We have ever reported the method to produce three-dimensional acoustic force field to prevent microbubbles dispersing in flow. However, because produced acoustic force worked only to propel microbubbles in the direction of propagation of ultrasound, there was a limitation in direction to affect the behavior of microbubbles. In this research we examined to produce attractive force toward the transducer by considering phase variation of acoustic field. We used a flat matrix array transducer including 64 PZT elements, which was specially developed to produce a continuous wave. We prepared a T-form bifurcation model as artificial blood vessel, which was difficult to control the course of microbubbles. We produced an acoustic field of two focal points with opposite phase, where the middle of the points covers the bifurcation. As the results, when microbubbles suspension (average diameter of 4 um, density of 2.35 μl/ml) was injected with velocity of 40 mm/s, we confirmed that microbubbles aggregations were produced before reaching the bifurcation point and entered the bifurcation to be propelled to the desired path, where the course of microbubbles corresponded to the middle of the two focal points.