When you burst a bubble, it rapidly disintegrates into liquid droplets before your eyes, disappearing almost instantaneously. While this process may seem relatively unimportant, scientists have long been interested in the underlying physics and chemistry of it as bubble formation plays a key role in a wide range of industries.
Now a team of researchers, led by Duyang Zang from Northwestern Polytechnical University, China, has managed to achieve the reverse phenomenon: turning liquid droplets into bubbles.
To do this, they used a technique known as “acoustic levitation,” which is commonly used to study the dynamics of liquid droplets. It enables scientists to levitate droplets in the air using sound waves and manipulate their shape by adjusting either the sound intensity or the distribution of the sound field.
Previously, researchers have used acoustic levitation to deform liquid droplets either by flattening them into a thin film or inducing buckling in their shape.
In a paper published in the journal Nature Communications, the researchers outlined how they combined these two approaches in order to achieve a controlled bubble formation.
First, they levitated a liquid droplet and deformed it into a thin film using sound waves. They then adjusted the sound field to buckle the flattened droplet into a bowl shape, manipulating it further until it grew into a sphere with an air cavity inside—in other words, a bubble. You can see this process at work in the video above.
“Similar phenomena have been observed before, but this is the first time the underlying mechanism was uncovered,” Duyang Zang, lead author of the study from the Department of Applied Physics at Northwestern, told Newsweek.
“Moreover, this is the first time the bubble can be formed in a controlled manner via this mechanism, he added. “We can adjust the volume of the air cavity through external dragging to triggering the transition.”
The latest findings could have implications for a number of different fields, according to the researchers, as bubble formation is a critical process in the preparation of foams, which are used extensively in industries concerned with food, cosmetics, pharmaceuticals and ultra-light materials, among others.
According to Zang, some possible applications of their technique could be encapsulating medicines in tiny bubbles for the purpose of drug delivery, or using levitated bubbles as templates for the assembly of nanomaterials.