A SU-8 microfluidic total analysis system integrating silicon photodiodes and buried waveguides

This work describes the monolithic integration of several optical structures that are needed for optical absorption or scattering measurements. The main objective is the development of a fabrication method to allow maximum integration through the use of a photosensitive polymer called SU8. A sealed microfluidic circuitry plus an optical one has been integrated monolithically on a silicon substrate with micro fabricated photodiodes. This work gives only a brief overview of the fabrication process. Further details are described elsewhere (F. J. Blanco (2003), J. M. Ruano (2004), M. Aguirregabiria). The microsystem proposed here contains a pair of silicon mesa photodiodes for light intensity measurement purposes, SU8 buried waveguides to confine light, a y-branch splitter to couple light to both photodiodes, a connector for input fibre coupling and a microfluidic circuit with an analytical chamber to allow propagation of light through the substance under analysis.