Capillary waveguide sensors

Capillary waveguide sensors (CWSs) consist of a capillary with a chemically sensitive inner coating. They are multifunctional devices in being optical waveguides, sample cavities, sampling devices, flow-through cells, mechanical support for sensor coatings and wavelength discriminators. The optical properties of the inner coating vary with the analyte to be measured, and can be detected by methods including measurement of refractive index, absorption, reflection, luminescence and luminescence lifetime. In many cases, this is accomplished by evanescent wave spectroscopy. Numerous optical configurations are discussed. Specifically, sensors are described which measure carbon dioxide, oxygen, and pH in addition to environmental contaminants such as gasoline. The ease and low costs of fabrication render CWSs ideally suited for both clinical sampling and testing.