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ABSTRACT:
John Cummings, Alex Zettl, Steven Louie and Marvin
Cohen have shown, through controlled and reversible
telescopic extension, that multiwall nanotubes can perform
as extremely low friction nanoscale linear bearings
and constant force nanosprings. Measurements of individual
custom engineered nanotubes — performed in situ
inside a high resolution transmission electron microscope
— have explicitly demonstrated the anticipated
van der Waals energy-based retraction force. These measurements
have also placed quantitative limits on the static and
dynamic nanotube/nanotube interwall frictional forces,
and shown that the nanotubes behave as constant force
springs that do not follow Hooke's law.
On the atomic scale, no wear and fatigue were observed
after observation of repeated extension and retraction
of telescoping nanotube segments. This indicates that
Berkeley Lab's new multiwall nanotubes may constitute
near-perfect, wear-free surfaces.
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