Research press release


Nature Communications

Physics: Turning drops back into bubbles



今回、Duyang Zangたちは、こうした過去の研究で観測された数々の効果を組み合わせて、制御された液泡形成を実現した。今回の研究では、まず音響放射力を用いて液滴を薄膜に変形させた後、超音波音場を用いて、この薄膜をお椀形に曲げ、その内部に共振空洞を形成させた。そして、共振によって空洞が大きくなり、その周囲に液体界面が曲面状に形成し、閉じた液泡が生じることが判明した。


Although bubbles normally burst into droplets, a method to achieve the reverse phenomenon, that is, forming bubbles from droplets, is described in Nature Communications this week. The findings help identify strategies for the manipulation of fluid-fluid interfaces with potential applications in the fabrication of soft materials.

Acoustic levitation is a common technique used to study droplet dynamics by which a droplet can be made to hover in the air under the effect of sound waves. Acoustic pressure has previously been exploited to deform liquid drops by flattening them into a thin film and by inducing buckling.

Duyang Zang and colleagues combine these previously observed effects to achieve controlled bubble formation. They show that a droplet is first deformed into a thin film by acoustic radiation force. Next, the ultrasonic field causes the film to buckle into a bowl shape, which encloses a resonant cavity. The resonance causes the cavity to grow and the liquid interface to curve around it, creating a closed bubble, the authors find.

The observed process might offer an alternative route to bubble formation, which could have applications in foam preparations in the food, cosmetics and pharmaceutical industries.

doi: 10.1038/s41467-018-05949-0

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