Interlayer forces in telescoping nanotubes

The ability to fabricate low-friction surfaces and lubricants is one of the key requirements for the miniaturization of mechanical systems, especially on the nanoscale where friction and surface adhesion often dominate over gravity and even electrostatic attraction. In this context, multiwalled carbon nanotubes (MWNT) have been proposed as the ideal nanobearing because of their inert, ultra-smooth surfaces and the narrow separation between their neighboring shells that prevents the accumulation of contaminant particles between sliding parts. In analogy with graphite, the weak van der Waals interaction between nanotube shells could provide the equivalent of lubrication, allowing easy relative sliding of nanotube layers. We have externally induced telescoping motion in MWNTs while measuring the force acting between the two layers involved in this motion. The restoring van der Waals force is comparable with theoretically predicted values. Defects are found to modulate this force and can lead to jamming.