Effective factors on water transport through connections of carbon nanotubes

Recent studies have demonstrated the ultrafast water flow through smooth carbon nanotubes. Several reasons have been suggested for this phenomena, one of the most important of which is the smoothening of the potential energy landscape felt by water molecules. In practice, carbon nanotubes may not have a perfectly simple smooth geometry. This feature can be cuased by any kind of defects during practical construction or deliberately created to provide nanochannels with specific applications. Molecular dynamics simulation method has been employed to study the effect of wall roughness and the rate of wettability of nanochannel’s wall on the transport of water in carbon nanotubes. We start with a (10,10) carbon nanotube (CNT) as our reference channel and generate nano-junctions by attaching other CNTs with larger radius but same length to it. This pattern is repeated alternately and as many as time desired. In adittion to the effect of wall roughness, another effective parameter is the wettability of nanochannel’s wall that can be adjusted by varying the interaction strength between tube wall and water molecules. Our results show that the fluid-wall friction coefficient increases compared to smooth nanotubes and also friction coefficient increases with increasing roughness in nanotubes (increasing the amplitude or decreasing the wavelength of roughness), while the slip legth decreases. In addition, we observed that by reducing the interaction parameters the friction coefficient decreases compared to the hydrophilic case. Finally, from the analysis of our simulations we obtain a useful insight into the equilibrium structure of water and the dependance of quantities such as friction coefficient, viscosity and slip length on wettability and roughness of carbon nanotubes. While the results of first stage, i.e the filling of nanotube with water, aid in improving our previous knowledge about the capillary effect in rough carbon nanotubes.