When one bubble in a group pops, the others rearrange themselves to balance out the cluster. Studies of soap foam may shed light on solidified foams of metal and plastic. (FROM ROBERT SAYE AND JAMES SETHIANUC BERKELEY/LBNL)
Pop! Unlocking the mystery of bubbles

Although scientists have long understood the behavior of a single soap bubble, they have not been able to mathematically describe the behavior of clusters of bubbles, otherwise known as foams. When one bubble in a group pops, the other bubbles quickly rearrange themselves to balance out the cluster — but because the forces behind all that shape-shifting are different from the forces determining when each bubble pops, it’s difficult to make a computer model that can incorporate all phases of a foam’s life.

Now, scientists have solved the problem by creating a model that splits a foam’s life into three phases, researchers reported last week in Science: rearrangement, in which the bubbles slide around each other to achieve stability; drainage, in which gravity draws the fluid inside a bubble’s membrane toward the earth; and rupture, in which a bubble’s membrane becomes so uneven that it finally pops, forcing the remaining bubbles to rearrange themselves and allowing the cycle to begin again.

While the researchers tested their model using soap bubbles, they hope their work will help materials scientists better understand and control the properties of solidified foams made of metal and plastic. Those foams are vital for applications requiring materials that are both light and strong, such as prosthetic limbs.

— ScienceNow , the daily online news service of the journal Science.