In this paper, we present a system for fluorescent monitoring of multiple gas concentrations using a simple and robust
single detector setup. Two gas-sensitive fluorescent films are illuminated by two separate excitation sources modulated
at different frequencies. Cross-polarization is used to shield the excitation light from the detector, allowing fluorescent
signals from both films to be simultaneously monitored and quantified using a microprocessor and lock-in detection.
Simultaneous detection of O2 and CO2 in a mixture of gases is done as a proof-of-concept of this frequency
discrimination technique. The detection of oxygen is based on the fluorescence quenching of platinum octaethylporphine
(PtOEP) lumiphore in presence of O2. The detection of CO2 is based on fluorescence quenching of hydroxypyrene
trisulfonic acid trisodium salt (HPTS) in presence of CO2. A single microprocessor is used to drive the excitation source
(different color LEDs), and sample and analyze the detector response at the two different frequencies. The device
demonstrated minimal crosstalk between the O2 and CO2 signals. The O2 concentration was measured in the useful
range between 20 and 0%, and CO2 demonstrated a useful range between 5% and 0%. The polarization filtering is
color-independent and can be readily extended to systems with more than two colors; due to the frequency
discrimination, it is immune to cross-talk in which one dye excites another. The whole arrangement is a compact, lowcost,
simultaneous multi-color fluorescent sensor system suitable for many biological, chemical, and gas-monitoring
We report on the development of a portable fluorescence detection system. By combining a CMOS sensor and crosspolarization
scheme, we achieved multiplexed detection with a single white emission LED excitation. We demonstrated
fluorescence detection of Fluorescein and Rhodamine B in PDMS channels and achieved 1μM limit of detection (LOD).
Microparticles with green and red fluorescence were detected simultaneously without changing the light sources or
filters. We were able to clearly resolve microparticles, even if aggregated. The compact microfluorescence approach
offers high spatial and spectral resolution, and is suitable for multiplexed detection in point-of-care applications.