Researchers use high-speed cameras to reveal bubbles that burst like blooming flowers

The oil industry, pharmaceutical companies and bioreactor manufacturers all face a common enemy: bubbles. Bubbles can form during the manufacture or transport of various liquids, and their formation and rupture can cause significant product quality problems.

Inspired by these questions and the puzzling physics behind bubbles, an international scientific collaboration was born. Gerald Fuller, chemical engineer from Stanford University, with his doctorate. students Aadithya Kannan and Vinny Chandran Suja, as well as visiting doctoral students. University of Naples student Daniele Tammaro has teamed up to study how different types of bubbles burst.

The researchers were particularly interested in bubbles containing proteins embedded on their surface, which is common in the pharmaceutical industry and in bioreactors used for cell culture. In an unexpected result, the researchers found that the protein bubbles they were studying opened like flowers when they burst with a needle. Their results are detailed in a study published in the journal of the Proceedings of the National Academy of Sciences July 19.

“What really strikes me is that even after all these years of research, bubble physics continues to surprise us with phenomena of unexpected beauty,” said Suja.

Burst the bubble

Bubbles can burst in different ways, depending on their physical and chemical properties. One important property is called viscoelasticity.

“Most of the materials around us aren’t actually perfectly liquid like water or olive oil. Nor are they perfectly elastic, like a pencil eraser. They fall somewhere in between. explained Fuller, who is Professor Fletcher Jones II in the School of Engineering and co-led the study with Professor Pier Luca Maffettone of the University of Naples.

This “intermediate” state is called viscoelasticity, and researchers have found that unlike conventional soap bubbles, viscoelastic bubbles that have both liquid and solid properties deform and take on shapes that mimic a blooming flower.

But as Tammaro notes, “With our eyes it is not possible to see how the hole opens when a bubble bursts, so we just see a bubble disappearing.”

The researchers therefore used high-speed cameras operating at 20,000 images per second, more than 300 times faster than a human eye, to capture and study the phenomenon.

“While I was working on my thesis on bubble coalescence in biologic drug formulations, I decided to examine bubble rupture using a high speed camera that we had in our lab”, Kannan said. “When we did that, we saw that this bubble, which had proteins on its surface, actually exhibited a very different disruption mechanism than what we traditionally expected.”

In the laboratory, the researchers soaked a metal ring in a solution of proteins with viscoelastic properties. They then carefully inflated bubbles on this ring using a highly controlled airflow. Once the bubbles were large enough, they came in contact with a hanging needle and burst.

As the video shows, when the bubbles hit the needle, the surface peels off like petals. This peeling occurs because the viscoelastic properties on the surface allow the solution to have stronger characteristics than common soap bubbles. Kannan compared this special bursting bubble to a bursting balloon, which also peels off like a flower.

Investigate the physics of bubbles

Once the flowering phenomenon was sufficiently observed, the researchers began to develop analytical models of the burst. Using current knowledge of bubble dynamics and mathematical models, the team presented a set of promising computer reproductions of blooming bubbles in their paper.

By studying the formation and bursting of bubbles, the team hopes to eventually learn how to reduce the generation and bursting of bubbles in real-world applications. They predict that their findings will have applications in fields ranging from the production of drugs and vaccines to the transportation of oil.

“It’s really important to see how generalizable this is and how flowering is different for other systems,” Kannan concluded.