(Invited) A Frequency Domain Optofluidics Dissolved Oxygen Sensor

Concentration of Dissolved oxygen (DO) is an important indicator of water quality. Fluorescence quenching is a commonly used optical method to measure DO. Steady-state fluorescence intensity measurements are easy to be influenced by acquisition artifacts, which makes determination of absolution DO values difficult. We developed a miniaturized, optofluidics frequency-domain DO sensor that measures fluorescence quenching using fluorescence lifetime changes of Ruthenium (Ru(dpp)3Cl2) rather than intensity. Dissolved oxygen is quantified by the phase shift between excitation modulation and emission modulation through process. Compact, low cost components such as diode lasers and photodiodes have been used for the potential of scalable distributed sensing applications. The sensor is evaluated using water samples with different oxygen concentrations. Experimental results show that the lifetime measured in frequency domain corresponds well to dissolved oxygen concentration. Long-term experimental demonstrates that the proposed sensor remains stable in the presence of photobleaching; since the measured phase shift is not affected by reduction of the fluorescence intensity. The sensitivity of the DO measurement is also enhanced through the total internal reflection design.

(Invited) A Frequency Domain Optofluidics Dissolved Oxygen Sensor Journal Articles