Quantum-mechanical water-flow enhancement through a sub-nanometer carbon nanotube

Abstract

Experimental observations unambiguously reveal quasi-frictionless water flow through nanometer-scale carbon nanotubes (CNTs). Classical fluid mechanics is deemed unfit to describe this enhanced flow, and recent investigations indicated that quantum mechanics is required to interpret the extremely weak water–CNT friction. In fact, by quantum scattering, water can only release discrete energy upon excitation of electronic and phononic modes in the CNT. Here, we analyze in detail how a traveling water molecule couples to both plasmon and phonon excitations within a sub-nanometer, periodic CNT. We find that the water molecule needs to exceed a minimum speed threshold of ∼50 m/s in order to scatter against CNT electronic and vibrational modes. Below this threshold, scattering is suppressed, as in standard superfluidity mechanisms. The scattering rates, relevant for faster water molecules, are also estimated.

Estimating water transport in carbon nanotubes: a critical review and inclusion of scale effects

“…3 Meanwhile, Ambrosetti et al reported a critical value of 50 m s −1 , which is described as a requirement to be surpassed with a view to scattering water against CNTs. 60 Concurrently, Ambrosetti et al also pointed towards the straightforward transfer of Landau's criterion of superfluidity, 61 wherein they mentioned the interaction with the quasilinear dispersion of the plasmon and phonon modes and a solid-state analog of the superfluid to be embodied by the (5,5) carbon nanotube. A generalized superfluidity mechanism was also considered for the observed friction suppression over the higher complexity of water.…”