<title>Integrated microfluidic-optical detection system on a chip</title>

Abstract

In this paper the fabrication and test of a microfluidic system integrated with optical waveguide and photodiode circuits on the same silicon chip are presented. A chemical reaction taking place in the miniature flow channels, which form a simple chemical distribution system on chip is detected by the photodiodes receiving light transmitted via the optical waveguide circuit. Reactions which cause either a change in absorbance or luminescence have been employed in the studies made. The mesa photodiode structures are butt coupled to the multilayer glass optical waveguides and have integral quantum efficiencies of approximately 80%, responsivities of about 0.5 and a broad spectral response. Anisotropic etching of the {100} silicon in a KOH solution is used to form these highly efficient mesa photodiodes. The buried optical waveguide structures, which are formed in low loss (0.5 dB/cm) germanium doped core glass, couple very effectively to the mesa diodes. Light is coupled to the waveguides via an optical fiber which is fastened to the chip by means of a simple connector etched into the silicon. Fluids are transported to and from the chip by means of quartz capillaries similarly fastened to the chip by means of integrated connectors.