Self-induced spontaneous transport of water molecules through a symmetrical nanochannel by ratchetlike mechanism

Water molecules, confined in a carbon nanotube, were monitored using molecular dynamics simulation. Spontaneous directional transportation during a long timescale was observed in the symmetrical nanochannel by a ratchet-like mechanism. This ratchet-like system was without any asymmetrical structure or external field, while the asymmetric ratchet-like potential solely resulted from the transported water molecules that formed hydrogen-bonded chains. Remarkably, the resulting net water fluxes reached the level of the biological channel and the average duration for spontaneous directional transportation reached the timescale of many biomolecular functions. This is the first report that heat energy from the surroundings can be used to drive molecules uni-directionally during a long timescale in a nanochannel system. This effect is ascribed to the unique structure of the water molecule.