Production and active control of microbubbles aggregations in artificial capillary with multiple sound sources

We have previously reported our attempts for active control of microbubble aggregations, by making use of acoustic force, which acts to propel microbubbles and to adjust the size of aggregations. However, because we have used simple shape of artificial blood vessels, the behavior of aggregations in a capillary, e.g., probability to obstruct in bloodstream, possibility of embolization, has not been predicted. Thus we designed and fabricated a capillary-mimicking artificial blood vessel to apply to production and active control of microbubble aggregations with multiple sound sources. Then we have set two kinds of transducers to produce aggregations and to propel aggregations, respectively. First we measured the size of aggregation, which increases according to the exposure time of ultrasound emission. When ultrasound was stopped, the aggregation suddenly flaked off the vessel wall and flew to downstream, propelled to the desired path and finally caught at a narrower path. We verified the same experiment under similar parameters to calculate the probability of path block. When the flow velocity was 20 mm/s, almost 50% of aggregations were induced to the desired path and 80% of them blocked the narrowest path in downstream.