  Using molecular dynamics simulations, we propose a novel nanoscale watermill
for unidirectional transport of water molecules through a curved single-walled
carbon nanotube (SWNT). In this nanoscale system, a revolving charge is
introduced to drive water chain confined inside the SWNT, which is served as
nano waterwheel and nano engine. A resonance-like phenomenon is found that the
revolving frequency of the charge plays a key role in pumping water chain. The
water flux across the SWNT increases with respect to the revolving frequency of
the external charge and reaches the maximum when the frequency is 4 THz.
Correspondingly, the number of the hydrogen bonds of water chain inside the
SWNT decreases dramatically with the frequency ranging from 4 THz to 25 THz.
The mechanism behind the resonant phenomenon has been investigated
systematically. Our findings are helpful for designing nanoscale fluidic
devices and energy converters.
