A number of nanoscale mechanical devices have been proposed.
One of our interests is to explore the properteis of carbon
nanotube based gears via realistic computer simulations. Our
preliminary molecular dynamics (MD) simulation studies (Nanotechnology,
Vol.8, No.3, 95, 1997 ), have demonstrated that the
molecular gears work well if the gear temperature is below 1000K
in a vacuum. In the current work, we study molecular dynamics of
the gears in atomspheres.
Simulations show that the gear works well in a 200K He and Ne
at <0.5 atm. Gear temperature reaches a maximum of ~400K at
first ~500 ps and then decrease to near the gas temperature of
200K. However, the gas impede the gear rotation and reduce
rotaion rate from 0.1 to 0.05 revolution per picosecond. At
higher gas densities or pressures, these molecular gears do not
work as the gear teeth slip.
To our knowledge, it is the first time MD simulations have
been used to study heat and momentum transfer on the nanoscale.
More importantly, this study reveals the flow and surface
phenomena involved. We observe that gear cooling is driven not
only by gas flow around the molecular gears but also, possibly,
by liquid-like capillary flow of gas atoms inside the carbon
Dr. Jie Han, NASA Ames Research Center, Moffett Field, CA 94035,
ph: 415-604-4799 fax: 415-604-3957 email: email@example.com