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The eBearing News
November 10, 2000
U.S. Researchers Create Frictionless Nanobearings
copyright © 2000 eBearing Inc.
Physicists at the University of California, Berkeley, have created ultra-tiny bearings
and springs, with near-frictionless characteristics.
The researchers manipulated hollow tubes of carbon atoms called nanotubes. A
scanning-tunnelling microscope and transmission electron microscope (TEM) at Lawerence
Berkeley National Laboratory were used to peel the tips off of nanotubes, creating a
telescope-like arrangement of an inner and outer nanotube.
Nanotubes are hollow cages of carbon atoms several nanometers (1 nanometer = 1 billionth
of a meter) thick and up to several thousand nanometers long.
It would take a pile of 10,000 nanotubes to stretch across the diameter of a human hair.
When turning round and round, the inner nanotube works like a bearing inner race, the
outer nanotube like an outer race. However, when the inner nanotube is pulled out of the
outer nanotube and then released, the device acts like a spring, with the inner
nanotube going back into place extremely quickly, in just 1-10 nanoseconds.
To make a bearing, the researchers first attached one end of a multi-wall nanotube
to a gold wire, then used the TEM to snag the top. They then peeled the top off to reveal
the inner tubes. A typical experiment converted a nine-walled nanotube with an outer
diameter of eight nanometers (about 100 atoms wide) into two telescoped tubes, the inner
one having four walls and a diameter of four nanometers.
Both the springs and bearings appear to act with no wear and tear, so they could
be important components of the microscopic and nanoscale machines under development
around the world. Friction is a big problem with MEMS, but the nanotubes appear to
slide as if there is no friction acting on them. After 20 cycles of pushing and pulling,
the nanotube structures showed no change in molecular structure, indicating that there
is essentially no friction between the two sliding nanotubes.
The researchers believe that miniscule intermolecular forces, called Van der Waals
forces, serve to lubricate the nanotube bearings.
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- by Bruce A. Carr
from individual research,
tips and commercial sources.
Bruce Carr edited this content.
Copyrighted material; unauthorized reproduction prohibited.
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eBearing.com ... for everything that moves™
Entire contents Copyright © 1999-2011, eBearing Inc. All rights reserved.
eBearing.com and "... for everything that moves" are registered trademarks of eBearing Inc.
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