Unidirectional Transport of Water through an Asymmetrically Charged Rotating Carbon Nanotube

Achieving a high speed, unidirectional water flow through carbon nanotubes (CNTs) is a key factor in designing novel nanofluidic devices. In this study, utilizing molecular dynamics (MD) simulations, we propose a novel nanoscale water pump for directed water transportation using charged rotating CNTs. Two basic conditions for stable water flow, including thermodynamic nonequilibrium and spatial asymmetry, are provided by introducing partial charges on carbon atoms of the channel with asymmetric patterns and its rotation, respectively. We demonstrate that the performance of the water pump is proportional to the gradient of a linear charge distribution and angular velocity of the rotation. Our results indicate that, in a constant total charge, there is a linear relationship between water flux and charge difference of the nanotube ends. In addition there is a logarithmic relationship between the water flux and the nanotube angular velocity. In fact, there is no considerable flux when the nanotube is rotating with low angular velocities. However, increasing the angular velocity first increases the flux rate and then leads to its saturation. Furthermore, the relationship between the water flux and charge density is investigated. The results can be used in designing future CNT-based pumps and high-flux nanoscale systems for practical applications.