Miniaturized and integrated fluorescence detectors for microfluidic capillary electrophoresis devices

Microfluidic devices are revolutionary in their ability to use very small quantities of liquid samples and to perform biochemical analyses with unprecedented speed. Toward the goal of a lab-on-a-chip that integrates a series of analysis steps and analytical components into a single microfluidic device, one of the most critical aspects of size reduction is miniaturizing and integrating the fluorescence detection system. We present here details of a new integrated fluorescence detection system. A microfluidic biochemical analysis device is mounted on a compact detection platform that comprises a fluorescence-collecting microlens and micromachined fluorescence detector in which a multilayer optical interference filter is monolithically integrated and patterned on a hydrogenated amorphous silicon (a-Si:H) photodiode. A central aperture in the micromachined a-Si:H fluorescence detector allows semiconductor laser light to pass up through the detector and to irradiate a microchannel of the microfluidic analysis device. Such an optical configuration enables a detachable, reusable, compact module to be constructed for the excitation source and detector. The micromachined a-Si:H fluorescence detector exhibits high sensitivity for practical fluorescent labeling dye, making it ideal for application to portable point-of-care microfluidic biochemical analysis devices.