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Fluorescence spectroscopy on a moving particle


An optical lab-on-a-chip system is presented that enables fluorescence spectroscopy to be performed on moving analytes. The analytes are continuously excited within a novel optical waveguide structure. Fluorescence spectra are recorded as the analyte traverses the detection area of a chip-size spectrometer that is integrated onto a microfluidic platform. To achieve a strong interaction between the excitation light and analyte we use an anti-resonant waveguide: the light is guided within the target-containing medium, thereby enabling a continuous excitation of a large volume. Guiding the excitation light within the lower-refractive-index fluid is achieved by coupling the light into the waveguide at a specific angle of incidence. A compact spectrometer is integrated along the fluidic channel. The spectrometer consists of a detector array that is coated with a linear variable band-pass filter. The filter converts the spectral fluorescence information into a spatially dependent signal that is analyzed by the detector array. Such chip-size spectrometers are especially applicable for characterizing moving analytes. The operational system will be demonstrated by characterizing polystyrene beads coated with a fluorescent dye. The fluorescence was excited with a 533 nm green laser at a flow speed of 2 mm/s and recorded during flow with a spectral resolution of 5 nm. Experiments are in progress to measure native fluorescence spectra of bacteria in solution with UV excitation light.


Schmidt, O. ; Bassler, M. ; Kiesel, P. ; Johnson, N. M. Fluorescence spectroscopy on a moving particle. 2007 MRS Spring Meeting; 2007 April 09-13; San Francisco; CA; USA.