You know those rainbow-colored patterns that slide and swirl on the surface of soap bubbles? Yeah, well, researchers at Stanford University have figured out a way to stop that. This may seem a little underwhelming, breakthrough-wise, but history has taught us that it's important to keep Stanford grad students busy.
Actually, as Trace Dominguez reports in today's DNews dispatch, the new research has plenty of potentially useful applications for industry, medicine and food science.
About those swirls: They're called eddies, technically, and they're an optical phenomenon generated by Marangoni Effect. This refers to the tendency of molecules to move from areas of low surface tension to high surface tension. When you see colors swirling on a soap bubble, it's actually molecules called surfactants rushing around and rearranging themselves. The idea is to send reinforcements to parts of the bubble that are getting too thinned out.
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The Stanford team figured out a way essentially pause this swirling, which allows for closer examination of the fluid dynamics involved. They did this by creating an air bubble underwater then slowly raising it to the surface of a water solution. The experiment produced some very beautiful kaleidoscope patterns -- you can check out the video here. But it also provided an unexpectedly useful technique for understanding fluid dynamics on the molecular level.
"Those patterns contain information on the thickness of the film as a function of space and time," explains Gerald Fuller, professor of chemical engineering, in the demo video. "So you create a movie that reveals the dynamics of that soapy liquid as it drains away from the apex of the bubble."
As to the practical elements of the experiment, the scientists hope to find way to create more stable bubbles. This could improve techniques for separating crude oil from water, for instance, or make for better drug formulations. Perhaps most importantly of all, they're studying how the structure of bubbles can improve the quality of beer foam.
-- Glenn McDonald
Stanford News: Stanford Engineers Stop Soap Bubbles From Swirling
NASA: The Marangoni Effect: A Fluid Phenom