What’s 100 times stronger than steel, weighs one-sixth as much and can be snapped like a twig by a tiny air bubble? The answer is a carbon nanotube--and a new study by Rice University scientists details exactly how the much-studied nanomaterials snap when subjected to ultrasonic vibrations in a liquid.

“We find that the old saying ‘I will break but not bend’ does not hold at the micro- and nanoscale,” said Rice engineering researcher Matteo Pasquali, the lead scientist on the study, which appears this month in the Proceedings of the National Academy of Sciences.

The mechanism by which carbon nanotubes break or bend under the influence of bubbles during sonication is the topic of a new paper led by researchers at Rice University. The team found that short nanotubes are drawn end-first into collapsing bubbles, stretching them, while longer ones are more prone to breakage.

Carbon nanotubes, hollow tubes of pure carbon about as wide as a strand of DNA, are one of the most-studied materials in nanotechnology. For well over a decade, scientists have used ultrasonic vibrations to separate and prepare nanotubes in the lab. In the new study, Pasquali and colleagues show how this process works--and why it’s a detriment to long nanotubes. That’s important for researchers who want to make and study long nanotubes.

“We found that long and short nanotubes behave very differently when they are sonicated,” said Pasquali, professor of chemical and biomolecular engineering and of chemistry at Rice. “Shorter nanotubes get stretched while longer nanotubes bend. Both mechanisms can lead to breaking.”

Discovered more than 20 years ago, carbon nanotubes are one of the original wonder materials of nanotechnology. They are close cousins of the buckyball, the particle whose 1985 discovery at Rice helped kick off the nanotechnology revolution.