In fluid transport across nanopores, there is a fundamental dissipation thatarises from the connection between the pore and the macroscopic reservoirs.This entrance effect can hinder the whole transport in certain situations, forshort pores and/or highly slipping channels. In this paper, we explore thehydrodynamic permeability of hourglass shape nanopores using molecular dynamics(MD) simulations, with the central pore size ranging from several nanometersdown to a few Angstr{\"o}ms. Surprisingly, we find a very good agreementbetween MD results and continuum hydrodynamic predictions, even for thesmallest systems undergoing single file transport of water. An optimum ofpermeability is found for an opening angle around 5 degree, in agreement withcontinuum predictions, yielding a permeability five times larger than for astraight nanotube. Moreover, we find that the permeability of hourglass shapenanopores is even larger than single nanopores pierced in a molecular thingraphene sheet. This suggests that designing the geometry of nanopores may helpconsiderably increasing the macroscopic permeability of membranes.
展开▼
