Fast Mass Transport through Sub-2nm Carbon Nanotubes*

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