Monolithically integrated semiconductor fluorescence sensor for microfluidic applications

This article presents a monolithically-integrated semiconductor sensor for fluorescence detection on a microfluidic platform. Vertical-cavity surface-emitting lasers (VCSELs) for 773 nm excitation, PIN photodetectors and optical emission filters have been integrated on one GaAs substrate. These optoelectronic components are optically coupled to a glass microfluidic channel (100 μm width and 45 μm depth) through the use of a discrete micro-lens to form a complete sensor. The experimental limit of detection was 250 nM of IRDye 800 Phosphoramidite. Based on an S/N = 3, the theoretical limit of detection was determined to be 40 nM. Laser background levels currently limit the sensor sensitivity. Large gains in sensitivity are possible through the systematic reduction of laser background by increasing spectral and spatial filtration. The low-cost, compact and parallel architecture makes this sensor a candidate for fluorescence-based sensing applications.