Vibrating-Charge-Driven Water Pump Controlled by the Deformation of the Carbon Nanotube

The directed transport of water molecules in a single-walled carbon nanotube (SWNT) based on a ratchet effect is investigated by molecular dynamics simulations The system is driven far away from thermal equilibrium by an additional deterministic perturbation of a,vibrating charge, and the spatial inversion symmetry is broken by the continuous deformations of the SWNT. It is well-known that the water flux across a circular channel decreases when the channel is narrowed or deformed. However, our simulation results show that the water flux almost increases linearly within a deformation of 1.9 angstrom. There exists an optimized value of deformation at which the pumping capacity takes its maximum, value. Moreover, the direction of transport even exhibits a change of sign with narrowing the carbon nanotube.