Fabrication of multilayer systems combining microfluidic and microoptical elements for fluorescence detection

This paper presents the fabrication of a microchemical chip for the detecti on of fluorescence species in microfluidics. The microfluidic network is we t-etched in a Borofloat 33 (Pyrex) glass wafer and sealed by means of a sec ond wafer. Unlike other similar chemical systems, the detection system is r ealized with the help of microfabrication techniques and directly deposited on both sides of the microchemical chip. The detection system is composed of the combination of refractive microlens arrays and chromium aperture arr ays. The microfluidic channels are 60 mum wide and 25 mum deep. The utiliza tion of elliptical microlens arrays to reduce aberration effects and the in tegration of an intermediate (between the two bonded wafers) aluminum apert ure array are also presented. The elliptical microlenses have a major axis of 400 mum and a minor axis of 350 mum. The circular microlens diameters ra nge from 280 to 300 mum. The apertures deposited on the outer chip surfaces are etched in a 3000-Angstrom -thick chromium layer, whereas the intermedi ate aperture layer is etched in a 1000-Angstrom -thick aluminum layer. The overall thickness of this microchemical system is less than 1.6 mm. The wet -etching process and new bonding procedures are discussed. Moreover, we pre sent the successful detection of a 10-nM Cy5 solution with a signal-to-nois e ratio (SNR) of 21 dB by means of this system.