High-Sensitivity MEMS Based On-Chip Fluorescence Detection System: Measurement and Analysis of Ultimate Sensitivity Limits

This paper discusses the concentration to detected photocurrent relationship of a high-sensitivity MEMS based on-chip fluorescence detection system consisting of a light source, sample chamber, and detector all integrated into a set of 3"xl" glass slides. A green organic light-emitting diode (OLED) has been used as the excitation source and organic photodiode (OPD) has been used as the fluorescence detector. A novel integrated cross-polarization scheme was used to filter out excitation light from the fluorescent dye emission spectrum. Two commonly used dyes in biotechnology applications, Rhodamine 6G and Fluorescein, have been detected down to ten's of nanomole which is several order of magnitude improvement in detection limits over existing literature using OPD. A theoretical model has been developed to study fluorescence signal variation with dye concentration for this particular system. A theoretical curve fitting has been performed based on the model. The theoretical fit matches closely with experimental data. Future modifications of the detection system have been suggested based upon results obtained from modeling.