(Almost) Stationary Isotachophoretic Concentration Boundary in a Nanofluidic Channel Using Charge Inversion.

The present work is an experimental study of a new means to induce a quasi-stationary boundary for concentration or separation in a nanochannel induced by charge inversion. Instead of using pressure-driven counter-flow to keep the front stationary, we exploit charge inversion by a highly charged electrolyte, Ru(bpy)3Cl2, that changes the sign of the zeta potential in part of the channel from negative to positive. Having a non-charge inverting electrolyte (MgCl2) in the other part of the channel and applying an electric field can create a standing front at the interface between them without added dispersion due to an externally applied pressure-driven counterflow.