Liquid Waveguide-Based Evanescent Wave Sensor That Uses Two Light Sources with Different Wavelengths

摘要

We demonstrate a prototypic optofluidic evanescent wavensensor made of poly(dimethylsiloxane) (PDMS) elastomernin which two light sources with different wavelengths arencoupled into an optofluidic liquid-core/liquid-claddingn(L2) waveguide. The exponentially decaying evanescentnwave interacts with analyte molecules dissolved in thencladding fluids or products formed by in situ reactionsnat the core cladding interface. The analyte moleculesnexhibit distinctly different light absorbance at the twonwavelengths during the light analyte interaction. There-nfore, by using the normalized absorbance calculatednfrom the intensity ratio of the two wavelengths insteadnof the absolute magnitude of either signal, unwantedneffects from omnipresent external noise sources cannbe reduced. In addition, the differential absorption ofnthe two beams by the analyte solutions can be used tonenhance the resolution of sample analysis. The eva-nnescent wave sensor based on a liquid waveguide cannalso be used for real-time monitoring of chemicalnreactions, because the core and cladding fluids in thenL2 waveguide are slightly miscible at the core claddingninterface due to the diffusional mixing.