Microlens systems for fluorescence detection in chemical microsystems

Abstract

Abstract. Micro-optical systems based on refractive microlenses are investigated. These systems are integrated on a chemical chip. They focus an excitation beam into the detection volume (microliter or even submicroliter scale) and collect 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 measurement of three illumination systems. The measurements show that an adroit placement and combination of microfabricated lenses and stops can increase the separation between the excitation light and the fluorescence light. Moreover we present the successful detection of a 20 nM Cy5™ (Amersham Life Science Ltd.) solution in a 100-m-wide and 50-m-deep microchannel (excitation volume Ϸ250 pL) using one of these illumination systems. The microchemical chip with the micro-optical system has a thickness of less than 2 mm.

Space- and time-resolved spectrophotometry in microsystems

“…Because these systems often require separation (5), mixing (6,7), and reaction (8) of components with distinct optical profiles, they would benefit from a method that allows the components to be characterized optically in space and time. Advances in miniaturization of components used in spectrophotometric systems have produced a number of useful microsystems: these systems typically work at a single wavelength at any one time (9,10) or perform measurements at a single spatial location (11)(12)(13)(14)(15), and most cannot be easily interfaced with microfluidic systems (16)(17)(18). Miniaturized systems for integrating microspectrometers and microfluidics have been proposed but not demonstrated (19,20).…”

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

“…These are the reasons why we take advantage of microfabrication technology to directly integrate the detection system onto the chemical chip. This solution enables the fabrication of small and closely spaced optical elements, their precise alignment with respect to the microfluidics, and the realization of original detection system configurations [17], [18]. A chemical chip with partially integrated optical elements was previously realized [19].…”

Noise analysis and measurement of integrator-based sensor interface circuits for fluorescence detection in lab-on-a-chip applications

“…As Roulet et al explained, in a "typical" FD situation the fluorescent signal is 250,000 times weaker than the baseline excitation light [40]. A measurement of the combined excitation and fluorescent signal would require an 18-bit analog-to-digital converter (ADC), and only a single bit would represent the signal.…”