Electrophoresis system with integrated on-chip fluorescence detection

A monolithic capillary electrophoresis system with integrated on-chip fluorescence detection has been microfabricated on a silicon substrate. Photodiodes in the silicon substrate measure fluorescence emitted from eluting molecules. An on-chip thin film interference filter prevents excitation light from inhibiting the fluorescence detection. A transparent conducting ground plane prevents the high electric fields from interfering with the photodiode response. A truly monolithic device has been fabricated using surface micromachining methods eliminating elaborate bonding procedures. Separations of DNA restriction fragments have been performed in these devices with femtogram detection limits using SYBR Green I intercalating dye.