Microfabrication technology enables the application of electrokinetics as a method of performing chemical analyses and achieving liquid pumping in electronically-controlled microchip systems with no moving parts. As electrokinetic microfluidic systems grow in complexity, the understanding of flow physics of heterogeneous electrolyte systems such as sample concentration schemes and fluidic nanochannels becomes more important. This talk reviews studies of isotachophoretic sample preconcentration and nanochannel electrophoresis at Stanford. We have used isotachophoretic stacking methods that leverage leading-to-sample ion concentration ratios of order 1015 and local electric fields of 4 kV/cm to effect millionfold sample stacking in less than 120 sec. We can detect 100 attomolar sample concentrations. We are also studying and leveraging the unique separation mo-dalities offered by nanoscale electrokinetic channels. We have used 40 and 100 nm deep channels etched in fused silica to independently measure mobility and valence of small ions. We also use these devices to separate 10 to 100 base pair DNA in the absence of a gel separation matrix. The goal of our work is to explore and exploit electrokinetic flow regimes with extreme scales of length and charge density.
Audio (MP3 File, Podcast Ready)
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