Fast Mass Transport Through Sub-2-Nanometer Carbon Nanotubes

TLDR

These membranes enable fundamental studies of mass transport in confined environments and offer more energy‑efficient nanoscale filtration. We measured gas and water flow through microfabricated membranes containing aligned carbon nanotubes with diameters below 2 nm. The flows exceed Knudsen and continuum predictions by more than an order of magnitude for gas and three orders for water, and are several orders higher than commercial polycarbonate membranes, matching molecular‑dynamics extrapolations.

Abstract

We report gas and water flow measurements through microfabricated membranes in which aligned carbon nanotubes with diameters of less than 2 nanometers serve as pores. The measured gas flow exceeds predictions of the Knudsen diffusion model by more than an order of magnitude. The measured water flow exceeds values calculated from continuum hydrodynamics models by more than three orders of magnitude and is comparable to flow rates extrapolated from molecular dynamics simulations. The gas and water permeabilities of these nanotube-based membranes are several orders of magnitude higher than those of commercial polycarbonate membranes, despite having pore sizes an order of magnitude smaller. These membranes enable fundamental studies of mass transport in confined environments, as well as more energy-efficient nanoscale filtration.