Theory of the force of Friction Acting on Water Chains Flowing through Carbon Nanotubes

TL;DR

This paper develops a theoretical model to explain the frictional forces on water chains flowing through carbon nanotubes, highlighting differences between metallic and insulating nanotubes and their impact on flow velocities.

Contribution

It introduces a perturbation theory-based model for water flow friction in nanotubes, accounting for phonon and electron excitations, and predicts flow velocity variations based on nanotube conductivity.

Findings

Flow velocities of water chains are consistent with experiments if nanotubes are metallic.

Insulating nanotubes could allow much higher water flow velocities under the same pressure.

The model explains the role of electronic excitations in water transport through nanotubes.

Abstract

A simple model for the friction experienced by the one dimensional water chains that flow through subnanometer diameter carbon nanotubes is studied. The model is based on a lowest order perturbation theory treatment of the friction experienced by the water chains due to the excitation of phonon and electron excitations in both the nanotube and the water chain, as a result of the motion of the chain. On the basis of this model, we are able to demonstrate that the observed flow velocities of water chains through carbon nanotubes of the order of cm/s can be accounted for, if the nanotube is metallic. If it is insulating, however, our calculations imply that the flow velocity of the water could be much larger for the pressure gradient in experimental studies of water flow through subnanometer diameter nanotubes.