Flexible Opto-Fluidic Fluorescence Sensors Based on Heterogeneously Integrated Micro-VCSELs and Silicon Photodiodes

We present mechanically flexible opto-fluidic fluorescence sensors based on heterogeneously integrated microscale vertical cavity surface emitting lasers (micro-VCSELs) and silicon photodiodes (Si-PDs). Micro- and millimeters-scale, printable forms of 850 nm-emitting micro-VCSELs and Si-PDs are coassembled into integrated fluorescence sensor arrays over large area in flexible, liquid-proof constructions on a polyethylene terephthalate (PET) substrate, where lithographically defined optical isolation trenches and multilayer-based wavelength- and angle-selective spectral filters are incorporated to effectively block the wave-guided and reflected excitation light to the Si-PD and, thus, significantly enhance the signal-to-noise ratio and detection limit. The resulting optoelectronic fluorescence sensors integrated with elastomeric fluidic channels on plastics also enable mechanically bendable operation at a bending radius of down to ∼50 mm, as well as multiplexed, real-time monitoring of fluorescent analytes flown through the opto-fluidic channels, with minimum detectable luminophore concentration of 5 × 10 –5 wt %.