CMOS-based phase fluorometric oxygen sensor system

The design and development of a phase fluorometric oxygen (O-2) sensor system using single-chip CMOS detection and processing integrated circuit (DPIC) and sol-gel derived xerogel thin-film sensor elements is described. The sensor system determines analyte concentrations using the excited state lifetime measurements of an O-2-sensitive luminophore (tris(4,7-diphenyl-1,10-phenathroline)ruthenium (II)) embedded in the xerogel matrix. A light emitting diode (LED) is used as the excitation source, and the fluorescence is detected by the DPIC using a 16 x 16 phototransistor array on-chip. The DPIC also consists of a current mirror, current-to-voltage converter, amplifier, bandpass filter, and phase detector. The DPIC output is a dc voltage that corresponds to the detected fluorescence phase shift. With a 14-kHz modulation frequency, the entire system including driving the LED consumes 80 mW of average power. The sensor system provides stable, reproducible, analytically reliable, and fast response (similar to 20 s) to changes in the gaseous oxygen concentrations and establishes the viability for low cost, low power and miniaturized biochemical sensor systems.