Microlens systems for fluorescence detection in chemical microsystems

Micro-optical systems based on refractive microlenses are investigated. The se systems are integrated on a chemical chip. They focus an excitation beam into the detection volume (microliter or even submicroliter scale) and col lect the emitted light from fluorescent molecules. The fluorescence must be carefully separated by spatial and spectral filtering from the excitation. This paper presents the ray tracing simulation, fabrication, and measureme nt of three illumination systems. The measurements show that an adroit plac ement and combination of microfabricated lenses and stops can increase the separation between the excitation light and the fluorescence light. Moreove r we present the successful detection of a 20 nM Cy5 (TM) (Amersham Lire Sc ience Ltd.) solution in a 100-mum-wide and 50-mum-deep microchannel (excita tion volume approximate to 250 pL) using one of these illumination systems. The microchemical chip with the micro-optical system has a thickness of le ss than 2 mm. (C) 2001 Society of Photo-Optical Instrumentation Engineers.