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Charge Inversion and Flow Reversal in a Nanochannel Electro-osmotic Flow R. Qiao and N. R. Aluru*
 

Summary: Charge Inversion and Flow Reversal in a Nanochannel Electro-osmotic Flow
R. Qiao and N. R. Aluru*
Department of Mechanical and Industrial Engineering, Beckman Institute for Advanced Science and Technology,
University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
(Received 6 August 2003; published 10 May 2004)
Ion distribution and velocity profiles for electro-osmotic flow in a 3.49 nm wide slit channel with a
surface charge density of 0:285 C=m2 are studied using molecular dynamics simulations. Simulation
results indicate that the concentration of the co-ion exceeds that of the counterion in the region 0.53 nm
away from the channel wall, and the electro-osmotic flow is in the opposite direction to that predicted
by the classical continuum theory. The charge inversion is mainly caused by the molecular nature of
water and ions. The flow reversal is caused by the immobilization of counterions adsorbed on the
channel wall and due to the charge inversion phenomena.
DOI: 10.1103/PhysRevLett.92.198301 PACS numbers: 82.39.Wj, 47.11.+j, 47.15.Gf, 82.45.h
When an ionic solution is in contact with a charged
surface, an electrical double layer (EDL) with a net posi-
tive or negative charge develops near the surface. If an
external electrical field is applied in the direction tangen-
tial to the surface, the fluid will be dragged by the moving
ions in the EDL and an electro-osmotic transport is
generated. Because of its scalability and ease of control,

  

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

 

Collections: Engineering; Materials Science