An Integrated Young Interferometer Based on UV-Imprinted Polymer Waveguides for Label-Free Biosensing Applications

Abstract

We demonstrate a polymer-rib waveguide Young interferometer sensor fabricated by UV imprinting. 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 glucose-water solution was used to characterize the sensor response against bulk refractive index changes. Recorded sensing responses show a linear correspondence with the refractive index changes of glucose solutions with a detection limit of about 10−5. To verify the polymer sensor’s biosensing capability, an immunoassay was performed with c-reactive proteins (CRP) and human CRP-specific antibodies adsorbed on the waveguide surface. 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/mm2 was determined for 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.