The transportation properties of water in nanochannels have been widely studied by molecular dynamics (MD) simulations. In the environments of electric fields, the behaviors of water, such as molecular dipole orientations, flux, diffusion rate, water filling/empty equilibriums and phase-transition processes, etc., are much influenced. This review surveys the methods of introducing electric fields in MD simulations, including assigning charges near tubes, adding ions or charged amino acids to the water phases on both sides of nanotubes, and directly applying electric fields through the whole nanotubes. Besides, the relevant applications using electric fields, such as flow switch, signal transmission, water pump, stable storage, etc., are also included. Finally, some issues in the relevant MD studies are presented.

Contents
1 Introduction
2 Methods of introducing electric fields in MD simulations and the relevant applications
2.1 Assigning charges on or near nanotubes
2.2 Introducing ions or charged amino acids to water phases on both sides of nanotubes
2.3 Directly applying electric fields through nanotubes
3 Influences of electric fields on the behaviors of water in nanotubes
3.1 Effects on water filling/empty equilibriums and phase-transition processes
3.2 Effects on water dipole orientations in nanotubes
3.3 Effects on water flux in nanotubes
3.4 Diffusion and permeation of water inside nanotubes under electric fields
4 Some issues in the relevant MD studies
5 Research prospects