A VCSEL-based micro-optical fluorescence detection system for capillary electrochromatography

Summary form only given. We are currently exploring the use of vertical-cavity surface-emitting lasers (VCSELs) and planar diffractive optics for miniaturized chemical analysis systems that combine capillary separation techniques with optical fluorescence detection. Chemical analysis based on capillary separations, such as capillary gel electrophoresis and capillary electrochromatography, combined with optical detection is a powerful tool for analyzing complex liquid mixtures. High voltage is used to drive samples through the capillary channels by a combination of electrophoresis (the motion of charged species in a liquid under the influence of an external electric field) for ions and electrokinetic flow (the bulk flow of an ionic solution in a capillary due to an applied electric field) for the neutral species in the solution. Both ionic and neutral molecules undergo separation as the solution flows through the capillary. The capillary can be a micromachined channel in a flat substrate. As the separated components pass a point near the end of the column, identification by fluorescence under optical excitation provides an extremely sensitive detection method. Since the wavelengths of VCSELs are suitable for direct fluorescence in most materials, these systems use dyes as either tags or for indirect fluorescence. These chemical analysis systems benefit greatly from miniaturization. Sample volumes, driving voltages and the analysis time are all significantly reduced. The resulting devices can be field portable and inexpensive.