Numerical analysis of electrokinetic transport in micro-nanofluidic interconnect preconcentrator in hydrodynamic flow

The phenomenon of enrichment of charged analytes due to the presence of an electric field barrier at the micro-nanofluidic interconnect can be harnessed to enhance sensitivity and limit-of-detection in sensor instruments. We present a numerical analysis framework to investigate two critical electrokinetic phenomena underlying the experimental observation in Plecis et al. (Micro Total Analysis Systems, pp 1038–1041, 2005b): (1) ion transport of background electrolytes (BGE) and (2) enrichment of analytes in the micro-nanofluidic devices that operate under hydrodynamic flow. The analysis is based on the full, coupled solution of the Poisson–Nernst–Planck (PNP) and Naviér–Stokes equations, and the results are validated against analytical models of simple canonical geometry. Parametric simulation is performed to capture the critical effects of pressure head and BGE ion concentration on the electrokinetics and ion transport. Key findings obtained from the numerical analysis indicate that the hydrodynamic flow and overlapped electrical double layer induce concentration–polarization at the interfaces; significant electric field barrier arising from the Donnan potential forms at the micro–nano interfaces; and streaming potential and overall potential are effectively established across the micro-nanofluidic device. The simulation to examine analyte enrichment and its dependence on the hydrodynamic flow and analyte properties, demonstrates that order-of-magnitude enrichment can be achieved using properly configured hydrodynamic flow. The results can be used to guide practical design and operational protocol development of novel micro-nanofluidic interconnect-based analyte preconcentrators.