Polymer on Quartz Waveguide Sensing Platform for Enhanced Evanescent Fluorescence Spectroscopy

Abstract

This paper presents the study of the performance of a novel SU-8 waveguide on a quartz substrate for evanescent fluorescence spectroscopy. The sensitivity of the sensing platform (SU-8/quartz) was compared to an SU-8 waveguide on silica fabricated with the standard protocol. The physical properties of the SU-8/quartz waveguide resulting from a novel fabrication process allowed for a higher fluorescence coupling and lower optical losses than the SU-8/silica waveguide. The impact of the different indices of refraction of both waveguides on the fluorescence collection efficiency was calculated with three-dimensional finite-difference time-domain simulations by simulating randomly oriented and phased dimensionless current dipoles in the vicinity of their sensing layers. An evanescent fluorescence spectroscopy experiment was performed with different concentrations of Alexa-647 labeled-BSA proteins immobilized on the two polymer waveguides to compare the sensitivity of both sensing platforms. The SU-8/quartz waveguide revealed to have a higher calculated fluorescence collection efficiency and also a greater measured fluorescence light output compared to the SU-8/silica waveguide.

Integrated fluorescence excitation, collection, and filtering on a GaN waveguide chip

“…Ozhikandathil et al have proposed an evanescent cascaded waveguide coupler for fluorescence detection, and the detection limit of recombinant bovine somatotropin (rbST) in milk was 25 ng/mL [12] . Abdul-Hadi et al have utilized a novel SU-8 waveguide-on-quartz substrate for evanescent fluorescence spectroscopy, with collection efficiency of 10.3% at the top of the waveguide [13] . Since most of the energy is confined inside the waveguide, the mode distribution of the evanescent wave around the waveguide is very weak, and the fluorescence excitation efficiency is limited.…”

High-Aspect-Ratio SU-8-Based Optofluidic Device for Ammonia Detection in Cell Culture Media

“…The fabrication process for SU-8 is more facile and allows high control over the resulting thickness, optical transparency, and enables the fabrication of the device with high rigidity. Therefore, SU-8 has been used for the fabrication of integrated photonic devices − and microfluidic components. − Due to the fact that SU-8 has 80% optical transmittance at 380 nm wavelength, plateauing at ∼98% transmittance for wavelengths over 520 nm, it is an ideal material for devices used for particularly colorimetric sensing. However, it has not been used to develop a complete optofluidic system containing both optical and fluidic components in one single manufacturing step, as reported in this paper.…”