Water wettability in nanoconfined environment

Water confined in nanoscale space behaves quite differently from that in the bulk. For example, in biological aquaporins and in carbon nanotubes, the traversing water molecules form a single file configuration. Water would stay in vapor state in extremely hydrophobic narrow nanopores owing to the physicochemical interactions between the water molecules and the surface of the nanopore. A spontaneous wet-dry transition has been identified in both biological and artificial nanopores. The nanopore is either fulfilled with liquid water or completely empty. Based on this mechanism, the wetting and dewetting processes inside nanopores have been further developed into highly efficient nanofluidic gates that can be switched by external stimuli, such as light irradiation, electric potential, temperature, and mechanical pressure. This review briefly covers the recent progress in the special wettability in nanoconfined environment, water transportation through biological or artificial nanochannels, as well as the smart nanofluidic gating system controlled by the water wettability.