Soliton-like propagation of dipole reorientation in confined single-file water chains

Water molecules confined in a narrow nanotube channel orient themselves into a uniformly ordered single-file chain. Here, we report by means of comprehensive molecular dynamics simulations and soliton-model-based theoretical analysis that the reorientation (i.e., rotation) of a single water molecule in this dipole chain, triggered for example by an external charge, can induce successive reorientation of the rest of the water molecules, which propagates in a soliton-like manner. The resulting local potential energy peak separating the reoriented and the pending reorientation subsections moves with an unweakened peak intensity at a constant velocity in the ambient environment, and particularly, can penetrate or make a turn through a crossed nanotube junction. The propagation velocity depends on the strength of the external charge, in agreement with our sine-Gordon soliton-based theoretical analysis. We further show that this unidirectional propagation originates from the partially inhibited fluctuation in dipole orientation of reoriented water with respect to that of original ones. These findings may be helpful in the development of high-efficiency information transmitting, processing and storage devices and the understanding of functioning of biological water channels.