| The Human Genome Project has revealed a vast amount of genetic and genomic data. The daunting task that remains is to decipher the function of the thousands of genes that make up the human genome and to understand how genetic variation leads to predisposition to disease. Molecular and cellular assays have enabled this investigation.; Microarrays are growing in popularity as a technology used to implement molecular and cellular assays. They are analyzed, primarily, using fluorescent markers and either a confocal laser scanner or a CCD imager. Both optical detection systems provide sensitive, rapid, and high-resolution imaging capabilities. However, neither can be integrated into the microarray platform. In addition, most microarray-based assays use fluorescence intensity to provide experimental data. Unfortunately, fluorescence intensity can be misinterpreted due to its dependence on factors other than those being measured. Fluorescence lifetime, on the other hand, is independent of intensity. Furthermore, it can provide more biologically significant information.; The research described here was undertaken to develop a new optical detection system that can be integrated within the platform of a microarray and can be used to measure fluorescence lifetime. The system uses silicon photodiodes for optical detection, as these are readily available in standard CMOS fabrication processes, thus facilitating cost reduction, and system integration and miniaturization. A differential architecture has been developed that eliminates the need for external optical filters, as required by the aforementioned optical detection systems, further facilitating integration and miniaturization. The silicon photodiodes have been integrated directly below the microarray sites, eliminating the need for detection lenses. Finally, analog circuits have been designed to accurately detect and sample the fluorescence emission. The data sampled by this circuit is used in conjunction with the Rapid Lifetime Determination method to reliably measure the lifetime of the detected fluorescence.; Ultimately, this fluorescence lifetime measurement system is to be integrated with a microfluidic solution delivery system to realize a "lab-on-a-chip". In so doing, a cost-effective and efficient miniaturized hand-held system for clinical diagnostics and research can be realized. |
