Micro flow modules with combined fluid flow channel and optical detection waveguide - hyper Rayleigh scattering as a case study

Micro flow modules with optical detection have been fabricated in a way which enables optical waveguiding inside and a defined interaction length along the fluid channel. Because of the usually lower refractive index of the solution compared with that of the substrate, so-called "leaky" optical wave-guiding must be employed. The combination of the fluid flow channel function with that of the optical waveguide has advantages for all miniaturized optical detection cells. It has been shown for hyper Rayleigh scattering (HRS) that improvement of the analytical principle is inherent in the miniaturization. The detection limit can be enhanced by at least a factor of 20. The applied HRS measurement procedure also enables simultaneous detection of two photon absorption (TPA) fluorescence. The severe boundary conditions of capillary electrophoresis were used as micro flow module design constraints to enable the transfer of the approach to other types of analysis.