(209c) Integration of Microfluidic and Planar Waveguide for Spectroscopic Monitoring of Chemical Reactions

Spectroscopy is a powerful analytical tool in studying and detecting chemical bindings on surface. We perform evanescent wave spectroscopy using a waveguide with a solid core and a liquid cladding layer to probe chemical reactions on the waveguide core-cladding interface. Unlike the conventional luminescence detection principles based on confocal microscopy, where light is focused onto the sample, evanescent field excitation utilizes exponentially decaying fields, within a distance of wavelength of the guided modes on the surface of a waveguide. The signal-to-noise ratio is improved by probing only the labeled analyte molecules bound to recognition elements, such as antibodies, oligonucleotides and bioreceptors on the waveguide surface, without background signals from impurity and unbound fluorophores outside the evanescent field. The geometry of the evanescent field waveguide provides good discrimination between bound and unbounded analyte in a molecular level and allows the analysis of both scattering and absorbing samples such as blood, serum or cell extracts, which would otherwise strongly attenuate the excitation light beam and build up spurious signals. In our experiments, both absorption and photoluminescence spectrum are measured, allowing spectroscopic monitoring of antibodies-antigen binding activities. Our device integrates multimode waveguide and microfluidic channel on a silicon substrate. Results from interaction of Cy3-conjugated antigens and anti-mouse IgG interactions will be presented.