Nanotubes filmed in moving liquid for the first time

All it takes is an optical microscope and a video camera to film carbon nanotubes being jostled by water molecules, researchers have found.

The discovery could provide biologists with a relatively cheap and simple way to study how nanotubes interact with living cells and DNA.

Doctoral student Rajat Duggal of the Carbon Nanotechnology Laboratory at Rice University in Texas, US, came up with the idea while studying DNA fragments under an optical microscope. He realised the technique could be applied to carbon nanotubes.

Matteo Pasquali, also at Rice University, told New Scientist: “The diameter of DNA molecules and nanotubes is similar, so if you can see one in this way then you should be able to see the other.”

Ultrasound bombardment

Nanotubes tend to clump together, so to film them individually, Pasquali and Duggal first put clumps of the tubes into a mixture of water and a surfactant called sodium dodecyl sulphate (SPS).

They bombarded the clumps with ultrasound waves to break them apart, allowing the SDS to surround and encase each tube.

The researchers then added a red fluorescent dye, which attached itself to the SDS coating and glowed under an optical microscope, making the nanotubes clearly visible.

Without the SDS molecules, the nanotubes are 3000 to 5000 nanometres long and about 1 nanometre in diameter, and 7 nanometres in diameter with the SDS. Watch a video of the moving nanotubes here (4.5MB wmv).

Full Article, New Scientist

Ants use pedometers to find home

    Desert ants have an internal system - like a pedometer - that keeps track of how many steps they take, according to a new study. The insects seem to rely on this system to find their way back to the nest after foraging. Other insects may also possess this pedometer-like system.

Some types of ant appear to use visual cues or leave scent trails to find their way home. But desert ants have a remarkable ability to retrace their steps from their nesting site even though they travel on flat terrain that is devoid of landmarks, and any odours quickly fade in the hot temperatures.

Previously, researchers have found evidence that ants use the position of the sun as a compass (see Nature, DOI: 10.1038/293731a0). But, as Harald Wolf at the University of Ulm, Germany, and his colleagues point out, for such a compass to be of use desert ants would need a way to track distance.

Wolf and his colleagues became interested in the mystery while studying Saharan desert ants (Cataglyphis fortis). When the researchers shortened the ants' legs the insects had trouble finding home.

Full Article, New Scientist