Sol-gel planar waveguides for improved fluorescence microarrays

The real-time monitoring of the hybridization signal, giving access to the reaction kinetics, can widen the results of a microarray experiment. Nevertheless, the presence of a strong fluorescent mix often degrade the experimental sensitivity, limiting the interest of this technique: the implementation of an evanescent wave excitation scheme can represent in this case a real advantage. In this paper, we propose high refractive index waveguides fabricated by sol-gel process for evanescent wave microarray applications. The influence of the sol composition and annealing parameters on materials microstructure are carefully studied to obtain good optical properties and high refractive index (n = 1.8-2.1) using thermal treatments below 250 °C. Monomode TiO₂ planar waveguides chelated by acetic acid are used as substrates for waveguide-based microarray in real-time experiments, demonstrating a significant increase of the signal to noise ratio.