Friction law for water flowing in carbon nanotubes

Previous molecular dynamics (MD) studies have suggested relationships that fail to predict the measurements of water flow through membranes of carbon nanotubes (CNTs). Through MD simulations of water transport over a flow rate range much wider than ever reported (0.002-1,400m/s) and use of flexible boundary condition, we discover a universal phenomenological logarithmic relationship between the CNT-water friction stress and flow rate, which is independent on tube chiralities, size and wetting properties. This logarithmic relationship is quantitatively in good agreement with the experimental observations. It thus provides a new basis for understanding the mechanisms of liquid slip at atomically smooth surfaces.