CMOS Fluorometer for Oxygen Sensing
This letter presents an integrated complementary metal-oxide semiconductor fluorometer that utilizes frequency-domain fluorescence lifetime imaging spectroscopy for oxygen-sensing applications. The implemented fluorometer chip consists of a p+/n-well/p-substrate photodiode, a phase readout circuit with integrated zero-crossing detection to extract the frequency-domain phase shift into a time-domain delay, and a high-resolution time-to-digital converter for digital quantization of the converted time delay. The fabricated fluorometer consumes less than 8.3 mW power and has a temporal resolution of 110 ps. During oxygen-sensing experiments, a ruthenium complex was used as an oxygen-sensitive dye whose lifetime was measured as a function of the of the oxygen concentration in water.