Electrokinetic Instabilities and Sample Stacking

摘要

Electrokinetic instabilities occur in electrokinetic microchannel flows with heterogeneous electrolytes. These instabilities can be leveraged in providing rapid mixing, but are often unwanted in microfluidic applications which use heterogeneous electrolytes to achieve high resolution and new functionality. One important application of heterogeneous electrolytes is field-amplified sample stacking methods which use conductivity gradients to achieve sample preconcentration prior to electrophoretic separation. In this work, we analyze the flow physics of electrokinetic flows with conductivity gradients using theoretical analyses, numerical computations, and experimental observations. Various models including two-dimensional and depth-averaged formulations have been developed, and modeling results compare well with experimental observations. Based on this understanding, we have developed novel sample stacking methods with sample preconcentrations exceeding 1,000 fold. The work also provides guidelines for the design and optimization of on-chip chemical and bio-analytical assays.