Controlling nanoslot overlimiting current with the depth of a connecting microchamber

¹ Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion - Israel Institute of Technology - Technion City 32000, Israel
² Department of Chemical and Biomolecular Engineering, Center for Microfluidics and Medical Diagnostics, University of Notre Dame - Notre Dame, IN 46556, USA

yossifon@tx.technion.ac.il

Received: 30 March 2010
Accepted: 9 June 2010

Abstract

The overlimiting ion flux, in excess of the limiting-value stipulated by diffusion, across a wide nanoslot (of fixed depth) is shown to be sensitively dependent on the depth of the connecting microchamber at one end of the nanoslot, which controls the onset of a vortex instability that specifies the dimension of the concentration polarization layer responsible for overlimiting behavior. Simple scaling arguments relating the microchamber depth to the effective fluid viscosity produce experimentally verified scaling dependence of the polarization layer length, the onset voltage for overlimiting behavior and the overlimiting current on the microchamber depth.