Asymmetric nanochannels for efficient saltwater transport diodes

Abstract

Surprising results in water transport through asymmetric nanochannels are observed due to symmetry breaking. However, these nanochannels are typically filled with solvent molecules, which leads to the absence of mass entrance behavior. In this study, we investigate saltwater transport through uncompletely filled asymmetric nanochannels under positive and negative pressure differences. We observe the emergence of a saltwater transport diode effect in large asymmetric nanochannels. Additionally, the water occupancy, transfer rate, velocity, and order parameters exhibit distinct behaviors under positive and negative pressure differences. The results can be attributed to the size-dependent barrier present in the asymmetric nanochannels under positive pressure, while no barrier exists under negative pressure. The pressure difference tunes both the gap of the water occupancy in the large asymmetric nanochannels and the gap of the water transfer rate through the large asymmetric nanochannels between positive and negative pressure difference. These findings enhance our understanding of saltwater transport in complex asymmetric nanochannels and aid in the design of novel fluidic devices.