We describe interlayer force measurements during prolonged, cyclic telescoping motion of a multiwalled carbon nanotube. The force acting between the core and the outer casing is modulated by the presence of stable defects and generally exhibits ultralow friction, below the measurement limit of $1.4\times {10}^{-15}\mathrm{N}/\mathrm{\text{atom}}$ and total dissipation per cycle lower than $0.4\mathrm{meV}/\mathrm{\text{atom}}$. Defects intentionally introduced in the form of dangling bonds lead to temporary mechanical dissipation, but the innate ability of nanotubes to self heal rapidly optimizes the atomic structure and restores smooth motion.

• Received 30 March 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.025501