A vibration-charge-induced unidirectional transport of water molecules in confined nanochannels

We propose a novel nanoscale design for unidirectional transport of water molecules through a single-walled carbon nanotube (SWCNT). This is achieved by using a vibration charge and a composite SWCNT with asymmetrical surface energy. With the proposed system, we demonstrated, using molecular dynamics simulations, that a continuous unidirectional water flow can be driven by a vibration charge without osmotic pressure or a drop in hydrostatic pressure. It is shown that the net flux of continuous unidirectional water flow can be controlled by adjusting the parameters of periodic vibration charge, temperature, and the degree of heterogeneity in surface energy. The remarkable net flux was the combined effect of the kinetic energy provided by the vibration charge, and the water density gradient resulted from the heterogeneous surface energy of the SWCNT. The present nanoscale design can efficiently convert the energy of vibration charges to the transport of water molecules. It may find applications in liquid circulation without a pressure gradient, lab-on-a-chip technology, desalination of sea water, filtration of polluted water, etc. © The Royal Society of Chemistry 2012.