Nanoelectrokinetic Selective Preconcentration of Charged Molecules and Its Dynamics

Abstract

A multilayer micro/nanofluidic device was presented for the selective preconcentration and online collection of charged molecules with different physicochemical properties based on ion concentration polarization phenomena (ICP). With a balance of electroosmotic drag force and electrophoretic force on the molecules, a sample mixture of sulforhodamine B and Alexa Fluor 488 could be highly preconcentrated and separated simultaneously. A repeated microchamber structure was employed to capture each dye at a desirable position. For subsequent on-chip or off-chip application, pneumatic microvalves were integrated and selectively collected the target dyes with cyclic valve operations. Using the integrated system, Alexa Fluor 488 was solely collected (with a separation resolution of 1.75) out of the mixture at a 30-fold preconcentration ratio. Furthermore, investigating the mechanism of preconcentration under ICP revealed that molecular interactions affected the location of preconcentrated plugs for satisfying local electroneutrality depending on their mobility. This integrated device would be a key component for lab on a chip applications.