Three-dimensional Mach-Zehnder interferometer in a microfluidic chip for spatially-resolved label-free detection.

Crespi, Andrea; Gu, Yu; Ngamsom, Bongkot; Hoekstra, Hugo J W M; Dongre, Chaitanya; Pollnau, Markus; Ramponi, Roberta; van den Vlekkert, Hans H et al. · Lab Chip · 2010

basic_science · Level V

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Abstract

Ultrafast laser writing of waveguides in glasses is a very flexible and simple method for direct on-chip integration of photonic devices. In this work we present a monolithic optofluidic device in fused silica providing label-free and spatially-resolved sensing in a microfluidic channel. A Mach-Zehnder interferometer is inscribed with the sensing arm orthogonally crossing the microfluidic channel and the reference arm passing over it. The interferometer is integrated either with a microchannel fabricated by femtosecond laser technology or into a commercial lab-on-chip for capillary electrophoresis. The device layout, made possible by the unique three-dimensional capabilities of the technique, enables label-free sensing of samples flowing in the microchannel with spatial resolution of about 10 microm and limit of detection down to 10(-4) RIU.