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

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.

Femtosecond laser microstructuring: an enabling tool for optofluidic lab‐on‐chips

“…The sensing arm of the MZI orthogonally crosses the channel, while the reference arm passes over it (see layout in Fig. 13) [100]. The device is capable of refractive index sensing with a spatial resolution of the order of the waveguide mode diameter (10-15 μm).…”

“…This system provides waveguides with refractive index contrast Δn % 5 ¢ 10 3 , which is sufficient REVIEW ARTICLE 455 Figure 13 (online color at: www.lpr-journal.org) Schematic of the femtosecond-laser-fabricated microfluidic channel and integrated MZI. The sensing arm crosses orthogonally the channel, while the reference one passes over it [100].…”

Progress in ultrafast laser processing and future prospects

“…Figure 13(a) shows a 3D schematic illustration of an optofluidics system fabricated by femtosecond laser 3D processing, which is used to perform label-free spatially selective sensing of liquid samples [107]. In this optofluidics system, an unbalanced MZI was constructed with optical waveguides by femtosecond laser refractive index modification after fabrication of a straight microfluidic channel embedded in fused silica by FLAE.…”

Ship-in-a-Bottle Biomicrochips Fabricated by Hybrid Femtosecond Laser Processing

“…Femtosecond laser processing is a promising technique for fabrication of biomicrochip since it can be used to modify the interior of glass in a spatially selective manner due to multiphoton absorption and thereby to directly form 3D microfluidic structures inside substrates [1][2][3][4]. We developed a technique fabricating true three-dimensional (3D) microfluidic structures inside photosensitive glass by femtosecond laser direct writing followed by thermal treatment and successive chemical wet etching.…”