’Gas marbles’ surprise with their strength.
Robust bubbles of gas encapsulated in a microsphere–liquid shell could trap gases Extremely strong and stable bubbles have been created by trapping a small amount of gas in a liquid film surround by polymer microparticles.1 The researchers have dubbed the new bubbles ‘gas marbles’ and say that they could be used as tiny chemical reactors, to stabilise foams or to capture toxic gases.
Such materials have already been used to manipulate small quantities of liquids or as microreactors and water pollution sensors.
Similar to their liquid relatives, the new gas marbles can roll on surfaces and withstand external forces, but while liquid marbles maintain their shape thanks to the properties of the liquid inside them, there is only air inside the gas marbles.
‘At first glance, [their strength] is surprising, but these materials contain two fluid–fluid interfaces, inner gas–water and water–outer gas, whereas liquid marbles contain only one, water–gas or oil–gas,’ says Bernard Binks, a physical chemist at the University of Hull, UK, ‘Gas marbles were first generated by accident while we were studying particulate films,’ says co-author Yousra Timounay at the University of Syracuse in the US.
The new material consists of a volume of air enclosed in a shell of polystyrene beads connected by an aqueous surfactant solution.
During the process, the particle film detaches from the frame and closes over itself to form a bubble.
To test the stability of the gas marbles, the researchers varied the pressure inside them by injecting or removing gas with a syringe until they burst or collapsed.
This remarkable strength is due to cohesion between neighbouring particles induced by the liquid film between them.
‘However, they may be of use as controlled release vehicles, say, of volatile perfumes from inner to outer gas phases upon application of a suitable trigger like temperature,’ Binks adds.