Foam bubbles finally brought to order

The first fabrication of the Weaire-Phelan foam which is the natural formation of bubbles in soap lather has been created in a laboratory for the first time in Trinity College Dublin by the Foams andComplex Systems Research Group in the School of Physics with help from CRANN, a nanoscience research facility based in the Naughton Institute. The ideal foam, which has bubbles of equal size- making it low energy, had been hypothesized in ’93 by Prof. Denis Weaire and his student Robert Phelan in TCD but it was unable to be made until now. This hypothetical structure became infamous with the building of the Water Cube Aquatic Centre for the Beijing Olympics, which based its outer walls on the Weaire-Phelan structure.

Lord Kelvin, in 1887, begun the discussion on “What is the ideal or lowest energy structure of a liquid foam?” He came to the conclusion that it took the form of a simple crystal structure. Although just a guess, this was backed up by the discovery of another foam structure of lower energy by Prof. Weaire and Robert Phelan through use of computer software created by Prof Kenneth Brakke of Susquehanna University. The Weaire-Phelan structure uses two different types of bubble shapes, both of which have equal size and volume, the dodecahedron with pentagonal faces and the tetrakaidecahedron with two hexagonal and twelve pentagonal faces.

Now it exists in reality, thanks to the work of the Foams & Complex Systems Research Group in Trinity College. Dr. Ruggero Gabbrielli, an SFI funded, visiting Post Doc from the University of Trento was the driving force behind the team. He recognized that previous failures to produce the foam could be put down to the shape of the containers used, therefore he designed the Brakke, a receptacle whose walls intricate form accommodate the Weaire-Phelan bubbles. This discovery was made in CRANN and proved an instant success when bubbles of the right size were introduced into it.

Could the new foam be of any practical use? “Not immediately”, says Dr Stefan Hutzler, head of the research group in the School of Physics, “Let’s just admire its extraordinary beauty first. In solidified form and on various scales, such exotic ordered foams could find applications as chemical filters, heat exchangers and optical components.” Prof Weaire, commenting on the discovery stated that it’s “Wonderful, it opens up a lot of further possibilities.”

The paper reporting the fabrication of the Weaire Phelan structure was accepted for publication in the time honoured Philosophical Magazine Letters last week, on the 25th of November. Incidentally, this is the same journal in which both Kelvin, in 1887 and Weaire and Phelan, in 1993, published their work on the structure of ideal foam.

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