Enhanced water transport through short nanochannels by regulating the direction of hydrostatic pressure

Molecular dynamics simulations are carried out to study the transport properties of water molecules across 1.34 nm long single-walled carbon nanotubes (SWCNTs) under hydrostatic pressure with different directions. It is found that when the deflection angle φ between the hydrostatic pressure and the tube-axis direction changes from 0 ° to 90 °, the net flux shows significant differences. It is interesting to note that the maximum flux is counter-intuitively obtained at φ=45°, which is about three times that of at φ=0°. This enhancement is mainly attributed to the excellent intermolecular structure, the orientation distribution, and the filling rate of in-tube water at φ=45°. Yet, it is worth noting that with the increase of the length of the SWCNT, the anomalous effect will gradually weaken until it almost disappears. Our work is of great significance for the practical application of high-efficiency nanofiltration membranes under pressure gradients.