Experimental Verification of Overlimiting Current by Surface Conduction and Electro-Osmotic Flow in Microchannels

Sungmin Nam, Inhee Cho, Joonseong Heo, Geunbae Lim, Martin Z. Bazant, Dustin Jaesuk Moon, Gun Yong Sung, and Sung Jae Kim

Phys. Rev. Lett. 114, 114501 – Published 16 March 2015

Abstract

Direct evidence is provided for the transition from surface conduction (SC) to electro-osmotic flow (EOF) above a critical channel depth ( $d$ ) of a nanofluidic device. The dependence of the overlimiting conductance (OLC) on $d$ is consistent with theoretical predictions, scaling as $d^{- 1}$ for SC and $d^{4 / 5}$ for EOF with a minimum around $d = 8 μ m$ . The propagation of transient deionization shocks is also visualized, revealing complex patterns of EOF vortices and unstable convection with increasing $d$ . This unified picture of surface-driven OLC can guide further advances in electrokinetic theory, as well as engineering applications of ion concentration polarization in microfluidics and porous media.

Received 16 July 2013

DOI:https://doi.org/10.1103/PhysRevLett.114.114501

Authors & Affiliations

Sungmin Nam^1,‡, Inhee Cho¹, Joonseong Heo², Geunbae Lim², Martin Z. Bazant³, Dustin Jaesuk Moon¹, Gun Yong Sung^4,*, and Sung Jae Kim^1,5,†

¹Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-744, Republic of Korea
²Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
³Department of Chemical Engineering and Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
⁴Department of Material Science and Engineering, Hallym University, Chunchon 200-702, Republic of Korea
⁵Big Data Institute and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea

^*Corresponding author. gysung@hallym.ac.kr
^†Corresponding author. gates@snu.ac.kr
^‡Present address: Department of Mechanical Engineering, Stanford University, Stanford, California 94305, USA.

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Issue

Vol. 114, Iss. 11 — 20 March 2015

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