Development and characterisation of integrated microfluidics on waveguide-based photonic platforms fabricated from hybrid materials

This article reports on a detailed investigation of sol-gel processed hybrid organic-inorganic materials for use in lab-on-a-chip (LoC) applications. A particular focus on this research was the implementation of integrated microfluidic circuitry in waveguide-based photonic sensing platforms. This objective is not possible using other fabrication technologies that are typically used for microfluidic platforms. Significant results on the surface characterisation of hybrid sol-gel processed materials have been obtained which highlight the ability to tune the hydrophilicity of the materials by careful adjustment of material constituents and processing conditions. A proof-of-principle microfluidic platform was designed and a fabrication process was established which addressed requirements for refractive index tuning (essential for waveguiding), bonding of a transparent cover layer to the device, optimized sol-gel deposition process, and a photolithography process to form the microchannels. Characterisation of fluid flow in the resulting microchannels revealed volumetric flowrates between 0.012 and 0.018 μl/min which is characteristic of capillary-driven fluid flow. As proof of the integration of optical and microfluidic functionality, a microchannel was fabricated crossing an optical waveguide which demonstrated that the presence of optical waveguides does not significantly disrupt capillary- driven fluid flow. These results represent the first comprehensive evaluation of photocurable hybrid sol-gel materials for use in waveguide-based photonic platforms for lab-on-a-chip applications.