Electrokinetic Microflow Instability With Conductivity Gradients

We have experimentally identified and quantified an electrokinetic flow instability that occurs in DC-electric-field driven microfluidic channels with significant conductivity gradients. We have, for the first time, developed a physical model for this instability which captures the interactions between bulk charge accumulation, electromigration, convection, and diffusion. A linear stability analysis based on this model captures key physics of this convective instability with a threshold electric field. The model and experiments show conductivity gradients and their associated bulk charge accumulation are crucial for such instabilities.