Water transport performance of inhomgenous nanoconfined systems

Abstract

Graphene nanochannels have attracted extensive attention in the fields of physics, biology, mechanics and materials due to their super long slip length and unique fluid transport properties. Up to now, research on confined liquid transport of carbon-based materials relies primarily on homogeneous nanoconfinement. Here, we investigate the transport behavior of confined water between inhomogeneous graphene channels by means of molecular dynamics simulations. Our results show that the confined water in the channel transforms into different lamellar structures in different areas. With the increase of water density, the water structure will gradually change from liquid to regular square-like solid. Besides, the speed of water decreases first, then increases and then decreases again with the increase of water density. This is because under low density (0.8–0.9 g/cm3), the interface friction increases with the increase of density, causing the speed of water to decrease. When the density reaches phase transition density (1.0 g/cm3), the friction coefficient will reduce sharply. With the continuing increase of density (1.0–1.4 g/cm3), interface friction increases, leading to speed drop of water again. Our results provide theoretical support for understanding the phase state and transport characteristics of water in confined systems, and have some guiding significance for material transport in biological channels and seawater desalination.