PALO ALTO, Calif., Sept. 13 (UPI) -- Researchers at Stanford University have found a way to halt the kaleidoscopic swirl of colors on the surface of a soap bubble -- a first.
A soap bubble's rainbow appearance is at least partially explained by the Marangoni effect. The Marangoni effect is the name for the movement of surfactant molecules from areas of lesser surface tension to areas of higher surface tension. The effect ensures an equal distribution of surface tension, stabilizing the bubble.
In a recent experiment, scientists successfully paused the Marangoni effect in soap bubbles, freezing the colorful displays in place.
"We were able to actually stop the Marangoni flows. Arrest them," Gerald Fuller, a professor of chemical engineering at Stanford, said in a news release. "It was a remarkable phenomenon and with very delicate control of these flows and these patterns."
Fuller and his colleagues achieved the feat by slowly bringing an air bubble to the surface in a soapy solution -- raising it and pausing it, raising it and pausing it. With each bump towards the surface, a new Marangoni flow was created, halting and encapsulating the flow beneath it. The researchers were able to create a bubble with seven distinct Marangoni flows.
"The colors on the bubbles indicate the thickness of the film, so you have these valleys and hills that are in a geometrical frustrated state on a surface that itself is ephemeral," explained researcher Saad Bhamla.
Bhamla, now a postdoctoral scholar in bioengineering, previously worked in Fuller's lab as a graduate student. He is the lead author of a new paper on the Marangoni effect in soap bubbles.
Though the bubble experiment may seem like a one-off trick, scientists in a variety of fields are keen to understand how and why surfactants behave as they do. And the bubble -- especially a manipulable one -- is an ideal scientific model for future surfactant experiments.
Researchers say their new work -- detailed in the journal Physical Review Letters -- could help scientists produce higher quality, longer lasting of beer foam, or separate crude oil from water. The findings could even help doctors find a substitute for lung surfactants, a breakthrough that could prevent collapsed lungs in newborns and put an end to neonatal respiratory distress syndrome.
"As you appreciate prevalence of surfactant foams in food products and in personal products, you realize that there is a need to understand the lifetime of these systems," Fuller said.