Adjustable diffusion enhancement of water molecules in a nanoscale water bridge

Abstract

The emergence of nanofluidics in the last few decades has led to the development of various applications such as water desalination, ultrafiltration, osmotic energy conversion, etc. In particular, understanding water molecule transport in nanotubes is of importance for designing novel ultrafiltration and filtering devices. In this paper, we use an electric field to form a nanoscale water bridge as an artificial water channel to connect two separate disjoint nanotubes by molecular dynamics simulations. The extended length of the water bridge under different electric field strengths could adjust the diffusion process of the water molecules crossing the two disjoint nanotubes and the diffusion coefficients could be remarkably enhanced up to 4 times larger than the value in bulk water. By analyzing the structure of the water bridge, it is found that the diffusion enhancement originates from the strengthened interactions and the increase of hydrogen bonds between the water molecules due to the restrained reorientation from the external electric field. Our result provides a promising insight for realizing an efficient mass transport between various disjoint nanochannels.