Mysterious nanobubble burst?

December 2, 2008
Mysterious nanobubble burst?
A bubble on the surface (radius R, contact angle θ); at the edges gas flows inwards and achieves an equilibrium with the outflow of gas. This results in a bubble that can remain intact for a long time.

( -- The nanobubbles that develop on submerged surfaces should not really be able to exist. Because of the enormous internal pressure, they should disappear within a short time. Nevertheless, they sometimes last for hours: an unexplained phenomenon.

Professor Detlef Lohse of the University of Twente and his colleague Professor Michael Brenner of Harvard have, however, revealed something of interest. They demonstrated that an equilibrium can develop between the gas that leaves the bubble and the gas that flows into it. It is even possible to calculate the dimensions of a bubble in which this happens. The researchers’ work is being published in Physical Review Letters at the end of November.

The fact that bubbles can develop on a water-repellent surface, submerged in water, had already been demonstrated: these are the round ‘caps’ (see figure) with a diameter of about 100 nanometres and a height of 10 nanometres. The reason they develop is still a mystery but they are nevertheless useful: for example, liquids flow more easily, more rapidly and with less energy consumption along surfaces covered with bubbles. The first techniques for stimulating bubble formation have already been developed as well.


Nevertheless, it is frustrating that there is still no explanation of how nanobubbles exist. Why should they develop? Small gas bubbles should dissolve rapidly because of the immense internal pressure, the gas flowing out of the bubble. They should disappear within microseconds, whereas measurements have shown that they can last for hours. Lohse and Brenner are searching for the reason why gas flows out of the bubble and, at the same time, inwards. When the two forces are in equilibrium, the bubble can remain intact for much longer than was first thought possible.

According to their theory, the inward flow takes place at the edge of the bubble; in other words, where the edge of a bubble comes in contact with a hydrophobic surface. It is known that, close to a hydrophobic surface, there is a higher concentration of gas molecules: these are then attracted by the surface. If these molecules now flow in via the edge of a bubble, they can reach a state of equilibrium with the molecules that are coming out of the bubble. This equilibrium is actually unstable: according to the second law of thermodynamics, this should only be a transitional phase, implying that the bubbles will dissolve within hours or perhaps days.

The theory, presented in Physical Review Letters, explains the long life of the bubbles. However, the researchers would like to look further into the long-term behaviour of these bubbles. Is the equilibrium unstable after all? Besides this, the new insights help with artificial stimulation of bubbles at the surface, for example, by means of electrolysis.

More information:

Provided by University of Twente, Netherlands

Explore further: Researchers in Northwestern Hawaiian Islands finds highest rates of unique marine species

Related Stories

Methane observatories successfully deployed in the Arctic

September 22, 2015

It is not only the space agencies that launch landers with sensors to far away places . Marine science institutions have a lot of unknown ground to cover in their quest for knowledge. Also they are depending on groundbreaking ...

The sun

September 28, 2015

The sun is the center of the Solar System and the source of all life and energy here on Earth. It accounts for more than 99.86% of the mass of the Solar System and it's gravity dominates all the planets and objects that orbit ...

Enzymatic micromotor-driven CO2 sequestration in water

September 17, 2015

Rapid decontamination of an aqueous solution by a freely moving microscrubber: this scenario has been realized by American scientists for the sequestration of CO2 from water. In the journal Angewandte Chemie, they introduce ...

Visual details released of recently discovered methane seep

September 10, 2015

Researchers at Scripps Institution of Oceanography at UC San Diego have released details of a deep-sea site roughly 48 kilometers (30 miles) west of Del Mar (just north of San Diego, Calif.) where methane is seeping out of ...

Recommended for you

Touchless displays superseding touchscreens?

October 2, 2015

While touchscreens are practical, touchless displays would be even more so. That's because, despite touchscreens having enabled the smartphone's advance into our lives and being essential for us to be able to use cash dispensers ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Dec 04, 2008
You know what I'm thinking; what does this mean for those hydrophobic materials used for immersion lithography?

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.