The sensing system has six excitation light sources for stimulating different fluorophore microbeads in a solution. Each fluorophore bead has different peak absorption and excitation spectra enabling particle differentiation by measuring fluorescent responses under different excitation lights. A PDMS microfluidic chip technology was used to load an aliquot volume of the sample. A highly sensitive silicon photomultiplier tube (SiPM), MicroFC (SensL Inc., Cork, Ireland), was used to detect corresponding fluorescence signals from each fluorophore microbead. A filter wheel containing 12 different bandpass filters controlled by microprocessor was deployed above SiPM to selectively measure corresponding fluorescent signals, as illustrated in the figure.
In summary, we have developed an LED-based portable fluorescent sensing system that is capable of differentiating multiple fluorophore microbeads. Future work includes full characterization of the sensor system and fabrication of integrated electronic circuitry for a standalone and field-deployable fluorometer.
 Dai, C. et al. American Journal of Infection Control43, (2015), 78-81.
 Wu, S., Duan, N., Shi, Z., Fang, C. and Wang, Z. Analytical chemistry86, (2014), 3100-3107.