Physicists have created “everlasting bubbles”

The shell of a water/glycerol gas marble is spherical and liquid after 101 days. Human-made bubbles could be used to make foams.

It is possible that soap bubbles are ephemeral, bursting after just a few minutes. French physicists have created bubbles out of plastic particles, water, and glycerol, according to a new paper published in the journal Physical Review Fluids. The longest bubble was built for 465 days.

Physicists have been fascinated by bubbles. Physicists in France created a theoretical model for how soap bubbles form when air hits a soapy film. The researchers found that bubbles formed above a certain speed, which is dependent on the width of the jet of air.

The mathematicians at New York University's Applied Math Lab fine-tuned the method for blowing the perfect bubble after conducting a series of experiments with thin, soapy films. It's best to use a circular wand with a 1.5 inch perimeter and blow it at a consistent rate of 6.9 cm/s, according to the mathematicians. The bubble will burst if you blow at higher speeds. The same thing will happen if you use a larger wand.

Physicists determined in 2020 that a key ingredient for creating giant bubbles is mixing in different strand lengths of soap film. The soap film can reach a'sweet spot' that's stretchy but not so stretchy that it's torn apart. The strands in the soap film were different lengths.

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Extending the lifespan of bubbles is something scientists are interested in. A bubble is a volume of air encased in a thin liquid skin and isolated from its neighbors. The force that arises from the attraction of atoms is called surface tension. The bubbles want to assume the shape with the least surface area because the more surface area the more energy is required to maintain it.

The lifetimes of three types of bubbles are compared.

In a standard atmosphere, most bubbles burst within minutes. At the same time, the liquid component slowly evaporates, because of the pull of gravity. As the amount of liquid decreases, the "walls" of the bubbles become thinner, and small bubbles in a foam combine into larger ones. Coarsening is a combination of these two effects. The thin liquid film walls that separate bubbles are strengthened by adding some kind of surfactant. The inevitable always occurs.

Physicists in France found that a spherical shell made of plastic can hold pressurized gas. The objects were called "gas marbles." Liquid marbles are droplets of liquid coated with tiny liquid-repelling beads that can roll around on a solid surface without breaking apart. The mechanical properties of gas marbles have been studied, but no experiments have been conducted to explore their longevity.

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Several colleagues, including Aymeric Roux of the University of Lille, decided to fill that gap. Standard soap bubbles, gas marbles made using water, and gas marbles made with water and glycerol were all used in the experiment. The plastic particles were spread on the surface of the water bath to form a raft. The researchers used a spoon to push the bubbles over the raft until the entire surface of each bubble was covered with plastic particles.

Lifetime of liquid films attached to a metallic frame. The frames are horizontal and pyramidal.

The soap bubbles burst quickly. The plastic particle coating mitigated the drainage process for the water-based gas marbles, which collapsed between six and 60 minutes. To extend the lifetime even further, the researchers needed to neutralize the evaporation.

glycerol was added to the water. According to the authors, glycerol has a high concentration of hydroxyl groups, which in turn have a strong affinity with water molecule, creating strong hydrogen bonds. glycerol is better able to absorb water from the air. The researchers were able to determine the best ratio of water-to-glycerol for long-lived gas marbles, which lasted from five weeks to 465 days.

The researchers' work goes beyond bubbles. They were able to create robust liquid films and shape them into different objects by dipping a metallic frame below a liquid surface covered with a layer of jammed plastic particles. The frame was slowly lifted back up to the surface. They were able to make a 3D pyramid shape out of water andglycerol liquid film. The pyramid has been around for over 300 days.

Physical review fluids are in the book. About DOIs can be found in the 10.103/physRevFluids.7.L.

A listing image by A. Roux et al.