Abstract
By analogy to unit operations (e.g., mixers, reactors, etc.) used in conventional chemical engineering, the concept of microunit operations permits the integration of complicated chemical systems onto a small microchip. A protocol for fabrication of such microchips is described, and its use is illustrated in several examples. In addition, the thermal lens microscope, which determines nonfluorescent species at the single-molecule level, is indispensable as an ultrasensitive detector for general use. Applications of microchip technology are given for chemical analysis, immunoassay, and full bioassay. Microchip analysis can provide very large enhancements in sensitivity and substantial reductions in measurement time as compared with conventional analytical methods.