title: Experimental verification of overlimiting current by surface conduction and electro-osmotic flow in microchannels.
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  μm. 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.
authors.affiliation: Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-744, Republic of Korea.
authors.forename: Sungmin
authors.initials: S
authors.lastname: Nam
authors.affiliation: Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-744, Republic of Korea.
authors.forename: Inhee
authors.initials: I
authors.lastname: Cho
authors.affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
authors.forename: Joonseong
authors.initials: J
authors.lastname: Heo
authors.affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
authors.forename: Geunbae
authors.initials: G
authors.lastname: Lim
authors.affiliation: Department of Chemical Engineering and Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Martin Z
authors.initials: MZ
authors.lastname: Bazant
authors.affiliation: Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-744, Republic of Korea.
authors.forename: Dustin Jaesuk
authors.initials: DJ
authors.lastname: Moon
authors.affiliation: Department of Material Science and Engineering, Hallym University, Chunchon 200-702, Republic of Korea.
authors.forename: Gun Yong
authors.initials: GY
authors.lastname: Sung
authors.affiliation: Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-744, Republic of Korea.|Big Data Institute and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors.forename: Sung Jae
authors.initials: SJ
authors.lastname: Kim
mesh_terms: D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D008962:Models, Theoretical; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods; D009997:Osmotic Pressure; D013499:Surface Properties