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

• Main Authors: Nam, Sungmin (Author), Cho, Inhee (Author), Heo, Joonseong (Author), Lim, Geunbae (Author), Bazant, Martin Z. (Contributor), Moon, Dustin Jaesuk (Author), Sung, Gun Yong (Author), Kim, Sung Jae (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Chemical Engineering (Contributor)
• Format: Article
• Language: English
• Published: American Physical Society, 2015-03-24T16:04:59Z.
• Subjects: Article
• Online Access: Get fulltext

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[superscript −1] for SC and d[superscript 4 over 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.
Basic Science Research Program (Grant 2013R1A1A1008125)
Global Frontier Project (Center for Integrated Smart Sensor. Grant CISS-2011-0031870)
Future Based Technology Development Program (Nano Fields) (Grant 2012-0001033)
Korea. Ministry of Health and Welfare (Grant HI13C1468)
Korea. Ministry of Health and Welfare (Grant HI14C0559)
Korea (South). Ministry of Science, ICT and Future Planning (Korean Health Technology RND Project)