Daughter bubbles generation via bubble bursting induced by ultrasonic radiation

Bubble bursting at the air–liquid interface is known to result in mass transfer from the aqueous phase to surrounding air, influencing global climate and human health. Here, we document an intriguing phenomenon that when primary bubbles burst at the air–liquid interface exposed to ultrasonic radiation, daughter bubbles of 0.1–10 μm are efficiently dispersed from the air into the lower aqueous phase. It is clarified that the formation of daughter bubbles is attributed to primary bubble bursting induced by ultrasonic radiation. A ring of smaller daughter bubbles was obtained when the primary bubble was placed under the acoustic probe and several smaller daughter bubbles were trapped by the bubble film folded toward the acoustic probe when the primary bubble was horizontally offset. Our results not only give insight into the interaction between ultrasound and the air–liquid surface but also offer a micro–nano bubble generation method with high efficiency of hundreds of times than natural bubble bursting, which can be widely used in microbial culture and medical imaging.