| In this dissertation, a low-cost, portable and user-friendly optical detection system was developed for microfluidic based lab-on-a-chip (LOC) devices. The conventional analytical methods of measuring these devices require expensive benchtop instruments that are not suitable for point-of-care (POC) applications. The optical detection system developed in this work consists of three major components: a broadband emission white LED to excite multiple fluorephores, a wavelength-independent cross-polarization signal isolation scheme, and a CMOS image sensor for signal detection. The combination of the setup enables simultaneous detection of multiple fluorescent samples. As a proof of concept, the system was applied for optical oxygen detection. The oxygen concentration was indicated by the red luminescence emission intensity of platinum octaethylporphyrin (PtOEP). The sensitivity of the oxygen sensor reached ~41, comparable to the ~50 values reported by others using an external spectrometer. To achieve multi-color analysis, CIE 1931 color space based signal conversion technique was developed, being intuitive and user-friendly. This technique was used for analyzing images of pH and urine glucose colorimetric test strips taken by a camera phone. The linear response ranges are 1-12 and 0-60mM for pH and urine glucose, respectively. Finally, the optical detection system was applied for fluorescent micro-particle detection, achieving ~3microm special resolution. In the particle counting test, 98% and 85% accuracy were achieved in static and dynamic conditions, respectively. With further development and optimization, the optical detection system can be integrated into microfluidic LOC systems for POC applications. |
