The blueprints for most nanomachines assume that the nuts and bolts of these structures will work in much the same way as the normal-sized versions, with carbon nanotubes acting as atomic-scale pipes, and so on. Similarly, it is hoped that other carbon-based components, such as fullerene (C60) molecules, will offer the same lubricating properties as graphite. Now, Tonya Coffey and Jacqueline Krim of North Carolina State University in the US have checked whether fullerenes can act as low-friction ball bearings by measuring the friction acting on a gas as it flows over a bed of C60 molecules.

The C60 molecules on a surface can either rotate rapidly or remain fixed, depending on the nature of the surface and the number of monolayers. To measure the friction, Coffey and Krim grew layers of C60 on quartz crystal oscillators and then passed methanol or krypton gas over the surface. Shifts in the amplitude of the crystal oscillations gave a direct measure of the frictional force between the flowing gas and the C60.

If the ball-bearing analogy is indeed correct, the frictional forces should be smaller for the rotating C60 molecules. However, the opposite is true, which confirms that many of our ideas about the macroscopic world may have to be completely revised for the nanoworld.