Sensing Using Fluorescent-Core Microcapillaries

Abstract

This thesis covers microfluidic sensing using whispering gallery modes supportedin silica microcapillaries coated with a fluorescent film, hereby calledfluorescent core microcapillaries (FCMs). We give an introduction to this classof device, and describe how it can be built and used effectively in microfluidicsensing. We then discuss the theory and experimental observations of thesemodes, including their shape, origin, wavelength, efficiency, and refractometricsensitivity. The thickness of the fluorescent film is a key factor in optimizingFCM-based detection, as is the polarization and order of the mode analyzed.Next, the effect of thermal fluctuations within a WGM is discussed. Filmthickness, film composition, and analyte solvent play key roles in the thermalresponse of this device, and complete thermal stability is theoretically shownand approximately demonstrated. We developed a method for functionalizationof the channel surface using a polyelectrolyte strategy, and subsequentlydemonstrate nanomolar detection of neutravidin. We conclude with a discussionof outstanding obstacles and potential avenues for further research. Theappendix contains initial research on an organic lasing chromophore that maybe a future component of the fluorescent film.