CMOS-based phase fluorometric oxygen sensor system

The design and development of a phase fluorometric oxygen O₂ 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 O₂-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 × 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 ∼ 20 s to changes in the gaseous oxygen concentrations and establishes the viability for low cost, low power and miniaturized biochemical sensor systems.