High-throughput Non-linear Electrokinetic Separations

This presentation focuses on the development of methods for scalable non-linear electrokinetic separations for bioanalytical sample preparation and water purification. Non-linear electrokinetic separations facilitated by ion concentration polarization (ICP), when scaled, suffer from the formation of convective vortices that lead to unwanted remixing. This fluidic instability is driven by steep gradients in electrolyte concentration and electric field strength at the separation interface. Strategies to address this challenge include geometric confinement of vortices, creation of microstructured sites for vortex nucleation, facilitation of surface conduction of ions through ion depleted zones, and reduction of current density at ion permselective structures and electrodes. Our research group has reported an approach that combines these four strategies. In this approach, packed beds of microspheres are employed to construct 3D electrodes, ion permselective structures, and sensing interfaces. The resulting device architectures are readily scaleable from nanoliters to milliliters per minute. We further discuss the impact of tunable experimental parameters such as device dimensions, sample composition, volume throughput, and microsphere properties on critical performance measures including separation efficiency, enrichment factor, and power consumption.