Impeded Mass Transportation Due to Defects in Thermally Driven Nanotube Nanomotor

A thermally driven nanotube nanomotor provides linear mass transportation controlled by a temperature gradient. However, the underlying mechanism is still unclear, as the mass transportation velocity in experiment is much lower than that resulting from simulations. Considering that defects are common in fabricated nanotubes, we use molecular dynamics simulations to show that the mass transportation would be considerably impeded by defects. The outer tube of a double-walled carbon nanotube transports along the coaxial inner tube subject to a temperature gradient. While encountering the defects in the inner tube, the outer tube might be bounced back or trapped at some specific sites due to the potential barriers or wells induced by the defects. The stagnation phenomenon provides a probable picture to understand the low transportation velocity at the microscopic level. We also show that a similar stagnation phenomenon holds in mass transportation of a fullerene encapsulated in a defective carbon nanotube. Our result is expected to be helpful in designing nanotube nanomotors.