Lensless Miniature Portable Fluorometer for Measurement of Chlorophyll and CDOM in Water Using Fluorescence Contact Imaging

We report on the design, fabrication, and verification of a proof-of-concept miniature fluorometer, which is designed to measure chlorophyll and colored dissolved organic matter (CDOM) concentration in aquatic environment. The system utilizes light emitting diodes (LEDs) for fluorescence excitation and absorption filters for excitation light attenuation. The excitation LED for chlorophyll has peak emission at 465 nm, and the excitation LED for CDOM has peak emission at 341 nm. Our device demonstrates the concept of attaching two different absorption filters on a single sensor array for measuring the fluorescence signal from two different fluorescent dyes. We have tested the system's ability to detect fluorescence from various concentrations of fluorescein as a close simulant and the calibration standard for chlorophyll, and quinine sulfate dihydrate (QSD) as a simulant and calibration standard for CDOM. We have successfully acquired the fluorescent signal for fluorescein between 0.7 and 1000 nM and for QSD between 2.6 and 638 nM.