New research by Marcel Lucas of the Georgia Institute of Technology in Atlanta and colleagues shows dramatic variations in the friction of carbon nanotubes depending on whether they are stroked along or perpendicular to their axes. The transverse coefficient of friction turns out to be higher.
The researchers explain this frictional asymmetry by a "hindered rolling" effect, which they also find is reduced in chiral nanotubes. As well as helping to sort nanotubes, this could lead to anisotropic adhesives with far-reaching applications.
Further reading
M Lucas et al. 2009 Nature Materials. Published online doi:10.1038/nmat2529.