Physicists Just Broke a Record by Keeping a Bubble Intact for 465 Days

When you think of the word “fleeting”, many people will immediately conjure up the image of a soap bubble: delicate, beautiful, and gone in an instant (or maybe a few). Now a team of physicists led by Aymeric Roux from the University of Lille in France has defied this cliché and created a bubble that retained its shape for a record 465 days. While perhaps not as beautiful as the soap bubbles’ sparkling, shifting iris, the team’s creation, made using glycerin (also known as glycerol), could help scientists develop new materials, such as foam and film.


“We show that covering a bubble water shell with microparticles inhibits gravity-induced drainage, and that further addition of glycerol leads to a stable state where the evaporation of water is matched by the hygroscopicity of glycerol, which absorbs water molecules contained in the ambient air. ” they write in their paper. “This results in bubbles that can hold their integrity in a standard atmosphere for more than a year, without any significant development of their radius.”


In general, there are three things that contribute to the short life of a bubble in an atmospheric environment. Gravity can drain material from the bubble membrane; evaporation can reduce the amount of liquid present; and the very presence of small nuclei in the air can destabilize the whole thing. To see if they could extend the life of the bubble, the team turned to a recent invention called “gas balls”. These are gas bubbles whose shells are made of liquid and partially moistening particles, surrounded by ambient gas.


The particles, usually a kind of polymer or plastic, allow the spheres to retain their structural integrity even when touched. Roux and colleagues wanted to see if they could make a gas ball stay intact for a long time, so they experimented with different kinds of bubbles. Soap bubbles were included as a point of comparison, and the team also constructed gas spheres of nylon particles and water, nylon particles, and a mixture of water and glycerol.


Of course, the soap bubbles did not last long at all – no longer than a minute. The water-based gas spheres performed better and survived for durations of between 6 and 60 minutes. The glycerol water spheres, on the other hand, survived spectacularly long, longer than 101 days, with the longest-lasting a full 465 days. This, the team notes, is the result of the addition of glycerol. This substance is a hygroscopic material – that is, it easily and readily absorbs moisture from the surrounding environment or atmosphere.


The nylon particles prevent the bubble membrane from draining away gravity; glycerol, which absorbs moisture from the atmosphere, rebuilds what evaporates away. As these two phenomena are neutralized, the bubble also becomes impenetrable to be burst by the annoying gas nuclei that kick around in the air. This is what allowed the bubble to retain its structure for such long periods of time.


“We have shown that air bubbles that hold their integrity for more than a year can be manufactured in a simple way by replacing surfactants with partially wetting particles and water with a water / glycerol mixture,” the researchers write.


The team also constructed a detailed model of the material’s properties and used this model to create other structures, such as a pyramid stretched over a metal frame, by dipping it into the material and slowly lifting it out. At least one of the pyramids the team created survived for 378 days when they wrote the newspaper. These remarkable results suggest that a whole new class of objects could be created from this mixture of materials, the researchers note – with physical and chemical properties that we have not yet discovered.


The research is published in Physical review fluids.

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