Abstract
We demonstrate a polymer rib waveguide Young interferometer sensor fabricated by UV-imprinting. An inverted rib waveguide structure was utilized in order to simplify the fabrication process. In this configuration grooves are formed on the under cladding layer by UV-imprinting and core material is spin coated on top to fill the grooves. Glucose water solution was used to characterize the sensor response against ambient refractive index changes. The sensing responses correspond linearly with the refractive index change of glucose solutions with a detection limit of about 10-5. To verify the capability of the polymer sensor for biosensing, an immunoassay was performed with c-reactive protein (CRP) and human CRP specific antibody adsorbed on the waveguide surface as a receptor. The CRP solution in PBS (phosphate buffered saline) buffer with a concentration of 2 µg/ml (16 nM) resulted in an obvious response which was over a couple hundred times of the noise level. Based on these values, a detection limit of about 2.4 pg/mm2 was found for the surface sensing of molecular adsorption. With the proposed waveguide configuration, the fabrication of polymer sensors can be ultimately transferred to roll-to-roll mass production to produce low-cost disposable sensors.
Highlights
Applying optical methods to label-free detection of biomolecular binding interactions has become increasingly popular
Many label-free optical biosensor configurations are built on the platform of planar waveguides, including surface plasma resonance (SPR) [3, 4], ring resonators [5]–[7], grating coupler sensors [8, 9] and interferometers [10]–[13]
Fabrication of the inverted-rib waveguide-based interferometer is an etch-free process. Both eff the imprinted mould and the inverted-rib waveguide are patterned without involving a reactive ion etching (RIE) procedure which might cause additional surface roughness leading to increased scattering loss
Summary
Optoelectronics and Measurement Techniques Laboratory, University of Oulu, Finland VTT Technical Research Center of Finland, Oulu, Finland VTT Technical Research Center of Finland, Oulu, Finland VTT Technical Research Center of Finland, Oulu, Finland Optoelectronics and Measurement Techniques Laboratory, University of Oulu, Finland. An inverted-rib waveguide structure was utilized to simplify the fabrication process. In this configuration, grooves were formed on the undercladding layer by UV imprinting and the core material was spin coated on top to fill the grooves. A CRP solution in a PBS (phosphate buffered saline) buffer with a concentration of 2 μg/ml (16 nM) produced a marked response, exceeding the noise level over two hundred times. Based on these values, a detection limit of about 2.4 pg/mm was determined for surface sensing of molecular adsorption.
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