An important area of our research is the development of microfluidic and nanofluidic systems for comprehensive proteome analysis. The crude protein sample, which is a complex mixture of thousands of proteins, is separated and prepared for mass spectrometric (MS) analysis on the microfluidic chip before introduction into the MS by electrospray ionization (ESI). Once fully developed these systems will increase the number of proteins identified providing a more complete description of the proteome while increasing the speed and reproducibility. One functional element of this system are nanofluidic/microfluidic interfaces (NMIs) that provide rapid enrichment of protein samples that ultimately makes detection of ultra-trace components possible. A unique aspect of our NMI concentrators is that they enrich samples based on electrophoresis and are therefore are compatible with microchannel coatings that reduce surface charge and deleterious protein adsorption. In the images on the right, the enrichment of a sample that is not detectable at its initial concentration is shown in a microchannel terminated with a nanocapillary membrane. The negatively charged sample is enriched by electrophoresis, and an enriched band is eluted by switching the direction of the electric field.