A polymeric waveguide resonant mirror (RM) device for detection in microfluidic flow cells

Abstract

A novel resonant mirror (RM) device, which consisted of silica sol–gel spacer and polystyrene waveguide layers on a standard microscope slide glass substrate, was developed in this work. The device was successfully used to measure the absorption spectrum of methylene blue with a limit of detection (LOD) of at most 20.8 μM at 635 nm and a minimum detectable absorption coefficient of 0.94 cm⁻¹. A RM device consisting of dye-doped polystyrene waveguide layer was then demonstrated to be suitable to monitor antibody–antigen (in this case, anti-IgG and IgG) binding and was shown to be capable of detecting at least 100 nM IgG. The sensitivity of the device was estimated to be 17.27° per refractive index unit (RIU), which corresponds to a resolution of 1.45 × 10⁻⁴ RIU for the set-up used. The RM device developed in this work can be easily integrated with microfluidic devices to identify and quantify (bio) chemical species by either absorption spectroscopy or measurement of effective optical thickness or both. In addition, the device was fabricated using a simple and low cost fabrication technique, spin coating. Hence, it can be easily mass produced.