Bubble science

Posted on Jun 4, 2013

Bubble science

In the news today is an interesting story about how researchers at the University of Sheffield have used hot microbubbles to develop a new technique that will allow manufacturers to make food products more efficiently. Whether because they’re fun or because everyone knows what one is, science stories involving bubbles (of all shapes and sizes) always attract plenty of media attention. BBC Four even produced a one hour documentary about the science of bubbles called ‘POP!”

In 2003, I wrote a story for the Institute of Physics about antibubbles based on a paper by Stephane Dorbolo (and colleagues) from the University of Liège in Belgium. The research, published in the New Journal of Physics, revealed for the first time how antibubbles form and move through a liquid.

Antibubbles are the exact opposite of bubbles and move down instead of up. Whereas a bubble is a thin flim of liquid in air which encloses a pocket of air, an antibubble is a thin film of air made inside a liquid, enclosing a pocket of that liquid. Scientists have known about them for almost a century but why and how they form was a mystery until this paper was published.

rise_of_antibubbles_01
Prompted by their claim that they could create antibubbles in a variety of liquids, I asked whether it would be possible (in theory) to do this with Belgium’s most famous export – beer. Little did I know this was actually a very interesting scientific proposition.

The researchers didn’t think it would be possible because you can’t create antibubbles (or bubbles) in pure water, alcohol or oil. However, they found that you can make antibubbles in beer. This is because beer contains protein which makes it a surfactant just like dishwashing liquid – demonstrating what British real-ale drinkers have claimed for a long time: that Belgian beer actually is a lot like dish-water! Dr Stephane Dorbolo said:

“Antibubbles are mysterious phenomena but we now understand them much better. We have come up with a good model describing how they form and move and have also learnt more about the type of liquids you can create them in. We tried to create them in beer for fun, and didn’t think it would be possible, but were amazed when we magaged to create giant antibubbles which lasted for almost two minutes and that moved around a glass of beer before bursting.”

 

“You can’t create antibubbles in pure water, alcohol or oil. But beer is a special case because it is very similar to dishwashing liquid and contains what we call surfactants which is what you need to be able to produce anti bubbles. We also found that when they die, or burst, they morph into a form of structure which we have nicknamed the jellyfish form because it looks very like a jellyfish swimming through water. It slowly moves and fades away until it disappears altogether.”

 

 

The BBC covered the story and even included a guide on how to make antibubbles at home. The images the team produced of bursting antibubbles were strange and beautiful (if you subscribe to New Scientist you can see them here).  The Guardian’s Tim Radford poked gentle fun at the piece saying it was “yet another demonstration of very domestic science: in the past few years physicists have examined why biscuits crumble . . . how to make the perfect cup of tea . . . and only last week the equation for making the perfect roast turkey.”

The pictures of antibubbles in a glass of Belgian beer appeared in most national media the day after we released the story and continued to be featured in magazines all around the world. Domestic, yes. Fun, certainly. But also very interesting science.

You can read the original IOP press release in our archives here and, if you’re interested in the life and death of antibubbles, Physics World magazine has more details on the research here.

Posted by David Reid.