Soap bubbles' secrets go pop

February 23, 2016
Soap bubbles' secrets go pop
(a) Typical progression in the cavity created in a film when the gas flow rate Vg increases and is below the minimum value for creating bubbles Vc. (b) Bubbles form when Vg is greater than Vc. L. Salkin et al., Phys. Rev. Lett. (2016). Credit: Institut de Physique de Rennes (CNRS/Université Rennes)

Some phenomena that appear to be well understood are much more mysterious than it seems. In spite of the numerous applications that rely on the presence or absence of bubbles, no advanced scientific studies had been carried out so far into how bubbles form. A team of researchers in the Matière Molle Department at the Institut de Physique de Rennes (CNRS/Université Rennes) tackled this question and developed a self-sustaining bubble machine in the laboratory. The researchers have managed to determine the minimum speed at which air must be blown on a soap film to form bubbles, under various experimental conditions. This work, which would allow optimization of various industrial processes, was published on February 19, 2016 in Physical Review Letters.

Many natural phenomena and industrial processes, such as foam production, require the formation of thin liquid films, while others require the opposite: preventing bubbles from forming. The latter include glass making and depositing liquid coatings onto plates or fibers. To study soap in the laboratory, researchers developed an experimental bubble machine that can produce long-lived thin liquid films.

A tank placed above the setup lets a soap solution flow between two stretched nylon wires. The liquid flows under gravity, and is then pumped back to the tank. When the two wires, each about one meter long, are separated, they form a rectangular . An "artificial mouth" made of a needle connected to a pressure regulator mimics human breathing. At low speed, the gas jet deforms the film and creates a cavity that becomes thinner as the gas rate increases, until the rate reaches the threshold for bubble formation. These rapid phenomena, which are difficult to see with the naked eye, are revealed when filming the experiments with a high-speed camera.

The researchers thus modeled the results as a function of the different experimental configurations. They have identified the key physical factors that control the minimum breathing speed for generating bubbles on a soap film. The team also characterized the influence of the distance separating the "mouth" from the film on bubble formation, then observed that the velocity and thickness of the soap film did not impact bubble production under the conditions studied.

So this work produces excellent data for bubble size and formation frequency measurement. This may help to optimize diverse .

Explore further: Researchers find soap film micro-channel size tunable with electric charge

More information: Louis Salkin et al. Generating Soap Bubbles by Blowing on Soap Films, Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.077801

Related Stories

Soap bubbles for predicting cyclone intensity?

January 8, 2014

Could soap bubbles be used to predict the strength of hurricanes and typhoons? However unexpected it may sound, this question prompted physicists at the Laboratoire Ondes et Matière d'Aquitaine (CNRS, France) to perform ...

Liquid crystal bubble OASIS in space

April 27, 2015

No matter how beautiful or crystal clear the bubbling waters of an oasis may be, they seldom lead to technology breakthroughs. Yet, NASA's OASIS investigation's bubbles may lead to an ocean of new improvements in our technology ...

Cavitation bubbles bursting with cleaning power

January 12, 2016

It's easy to think of soap suds when one thinks of bubbles, but these bubbles can clean without chemicals. These are cavitation bubbles, which are created when air is churned up in water. And what researchers are learning ...

Recommended for you

Electrons at the speed limit

August 26, 2016

Electronic components have become faster and faster over the years, thus making powerful computers and other technologies possible. Researchers at ETH Zurich have now investigated how fast electrons can ultimately be controlled ...

Understanding nature's patterns with plasmas

August 23, 2016

Patterns abound in nature, from zebra stripes and leopard spots to honeycombs and bands of clouds. Somehow, these patterns form and organize all by themselves. To better understand how, researchers have now created a new ...

Measuring tiny forces with light

August 25, 2016

Photons are bizarre: They have no mass, but they do have momentum. And that allows researchers to do counterintuitive things with photons, such as using light to push matter around.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.