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Molecular Understanding of Osmosis in Semipermeable Membranes A. V. Raghunathan and N. R. Aluru*

Summary: Molecular Understanding of Osmosis in Semipermeable Membranes
A. V. Raghunathan and N. R. Aluru*
Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology,
University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
(Received 12 December 2005; published 10 July 2006)
We investigate single-file osmosis of water through a semipermeable membrane with an uncharged, a
positively and a negatively charged nanopore. Molecular dynamics simulations indicate that the osmotic
flux through a negatively charged pore (J) is higher compared to the osmotic flux in a positively charged
pore (J) followed by the osmotic flux in the uncharged pore (J0), i.e., J > J > J0. The molecular
mechanisms governing osmosis, steady state osmosis, and the observed osmotic flux dependence on the
nanopore charge are explained by computing all the molecular interactions involved and identifying the
molecular interactions that play an important role during and after osmosis. This study helps in a
fundamental understanding of osmosis and in the design of advanced nanoporous membranes for various
applications of osmosis.
DOI: 10.1103/PhysRevLett.97.024501 PACS numbers: 82.39.Wj, 47.56.+r, 47.61.k
In all living matter, osmosis is a primary passive mode of
``pumping'' water, which is an essential ingredient to life.
Osmosis is a complex phenomenon in which a solvent is
driven by its free energy gradient through a semipermeable
membrane towards a solute-rich reservoir. Osmosis has


Source: Aluru, Narayana R. - Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign


Collections: Engineering; Materials Science