An Ohmic model for electrokinetic flows of binary asymmetric electrolytes. (August 2016)

• Record Type: Journal Article
• Authors: Persat, Alexandre; Santiago, Juan G.
• Is Part Of: Current opinion in colloid & interface science. Volume 24(2016)
• Page Start: 52
• Page End: 63
• Publication Date: 2016-08
• Subjects: Electroosmotic flow -- AC electrokinetics -- Induced-charge electroosmosis -- Electrokinetic instabilities -- Leaky dielectric model -- Ohmic model; Surface chemistry -- Periodicals; Colloids -- Periodicals; 541.33
• DOI: 10.1016/j.cocis.2016.06.001
• Languages: English
• ISSNs: 1359-0294

Abstract

Abstract: The transport of electrolytes in electric fields is a ubiquitous phenomenon commonly harnessed in microfluidics. A classic leaky dielectric model for flow generated by electric fields accurately predicts electrohydrodynamic transport phenomenon but is valid for millimeter-scale and larger flows and at relatively low ionic strength. Here, we derive and use a modified version of this model to sub-millimeter scales more relevant to microfluidics, where diffusive transport of charged species becomes non-negligible. We formulate a general equation set, the modified Ohmic model, applicable to the transport of binary, asymmetric electrolytes. We leverage this model to describe a variety of microfluidic electrokinetic systems, including DC electroosmosis, alternating current electrokinetics (ACEK) and induced-charge electroosmosis (ICEO), thus highlighting some unifying principles of these flows. Graphical abstract: Highlights: We derive a general model for electrokinetic flows including diffusive currents. We review free charge dynamics and distribution in electric double layers. Our model describes a variety of common electrokinetic flows. We discuss the effects of electrolyte asymmetry in electrokinetic flows.