The first thing that often springs to mind when you mention bubbles are those pots of soapy liquid with a bubble-blower toy you had as a kid (or as an adult – you’re never too old for these things).
But bubbles also play a key role in many areas of science, from scanning for tumours to potentially delivering drugs around the body to target specific areas, and making champagne taste that little bit better.
At the Royal Society’s Summer Science Exhibition recently, one of the stands was devoted to bubble science, exploring the interesting properties of bubbles, such as the fact that the temperature inside a rapidly collapsing bubble is greater than the surface of the sun.
Bubbles, defined as spheres filled with air, are everywhere, from volcanoes to boiling water and inkjet printers. And champagne lovers, take note – bubbles account for 30 per cent of its taste, said Dr Gianluca Memoli, senior research scientist at the National Physical Laboratory and one of the researchers manning the POP! The Sound of Bubbles exhibit.
“They thought it was the grape affecting the taste, but actually it was the bubbles,” Dr Memoli told me, referring to a French study on champagne – I bet the researchers had fun doing that one.
A mouthful of bubbles – why Italian ice cream beats McFlurry
The same goes for ice cream, Dr Memoli explained. “If you think about ice cream, Italian ice cream has smaller holes [bubbles] than the ice cream you get in McDonalds – that is why it tastes better.”
But it is the special connection between gas bubbles and sound waves that makes them so useful. When a bubble is subjected to a sound wave, the ‘ring’ or sound they produce varies according to their properties and their surroundings. It is this quality that means they can be used as cost-effective medical sensors to detect cancer in the human body.
|Dr Gianluca Memoli next to the musical ‘bubble organ’|
By injecting a patient with microbubbles, tumours show up much more clearly on an ultrasound scan, meaning doctors can improve the accuracy of their cancer diagnosis from 60 per cent to 95 per cent.
“The fact that bubbles are used to detect, and are so successful, is pushing people to look more at what they can do,” said Dr Memoli. He explained that researchers are now looking at ways to ‘load’ bubbles with drugs designed to target tumours, and to then move those bubbles round the body before releasing the drug in the target area.
Dr Memoli’s fascination for bubbles first began when he studied them for the European Space Agency during his PhD.
Setting the scene, he said: “Imagine you are in your space shuttle and you are going towards Mars. At some point you start seeing lights switch on and off on your control panel.
“The problem there is that bubbles are blocking the fuel to the engine. Normally you don’t need to think about that because gravity takes the bubbles up to the surface, but if there’s no gravity, the bubbles stay there. So in space, you cannot get rid of it.
“So we were studying artifical gravity to get the bubbles away. After that, I got fascinated.”
Photo of Dr Gianluca Memoli taken by me at the Royal Society’s Summer Science Exhibition.