BU engineers find why some particles—like microplastics—get concentrated and aerosolized by bursting bubbles, while others don’t

By Andrew Thurston

Bubbles are fun for everyone. But, it turns out, they can also be little menaces.

When a bubble pops, it can concentrate and aerosolize any particles stuck on it. Not a big deal when it’s a store-bought soapy bubble bursting in the yard or on your hand. But it’s a major concern when the particles it carries are potentially hazardous: bubbles caught in a crashing wave can send vaporized microplastics into the air where they might mess with the Earth’s atmosphere; bubbles burst by a flushing toilet can fling bacteria meters and onto nearby surfaces; a frothing cruise ship hot tub was once shown to be a Legionnaires’ disease super-spreader.

Now, a new study by Associate Professor James Bird (ME) and other Boston University engineers illustrates why bubbles fire some contaminants into the air, while allowing others to sink harmlessly. After taking a close-up look at what happens when bubbles pop, the researchers found a new way to predict which particles are flung high—and which ones fall—overhauling a 40-year-old theory of fluid dynamics. Their results, which were published in Physical Review Letters, could help scientists track marine pollution or more accurately predict the transmissibility of a virus.

“With this new theory, we can better model potential ocean sources of pollutants or how other particles in the ocean can get into the atmosphere and act as cloud condensation nuclei, altering the climate,” says Lena Dubitsky (ENG’23), a doctoral student in the BU Fluid Lab and joint lead author on the paper. “In terms of public health, this model helps predict what drop size might contain the most pathogens.” And that can be crucial in determining how easily a disease might spread or whether a small drop can sneak a virus through the defenses protecting our lower respiratory tract.

Read the full article at BU’s The Brink.


Banner photo: Doctoral student Lena Dubitsky (center) with her coauthors Oliver McRae (left), an ENG postdoctoral associate, and James Bird, an ENG associate professor of mechanical engineering. They used the high-speed camera to watch bubbles bursting in the small box at left. Photo by Jake Belcher