Low-friction nanoscale linear bearing realized from multiwall carbon nanotubes

We demonstrate the controlled and reversible telescopic extension of multiwall carbon nanotubes, thus realizing ultralow-friction nanoscale linear bearings and constant-force nanosprings. Measurements performed in situ on individual custom-engineered nanotubes inside a high-resolution transmission electron microscope demonstrated the anticipated van der Waals energy-based retraction force and enabled us to place quantitative limits on the static and dynamic interwall frictional forces between nested nanotubes. Repeated extension and retraction of telescoping nanotube segments revealed no wear or fatigue on the atomic scale. Hence, these nanotubes may constitute near perfect, wear-free surfaces.