Monolithically Integrated Optical Microfluidic Chip by Single Step Lithography and Etching for Detection of Fluorophore Tagged Recombinant Bovine Somatotropin (rbST)

Abstract

An optical microfluidic sensor is developed on silica-on-silicon planar waveguide by using a novel single step lithography and etching of silicon dioxide layers deposited on silicon wafer. The proposed sensor consists of a multiple waveguide system designed with optical couplers of S-bends integrated with microfluidic channel on silicon-on-silicon. The microfluidics channel is bonded with PDMS having the refractive index lower than the core of the waveguide, hence the PDMS layer acts both as the sealing layer and top cladding of the silica-on-silicon waveguide. The fluorescence detection efficiency of the device is demonstrated with laser induced fluorescence detection of Alexa-647 tagged recombinant bovine somatotropin (rbST). The lowest concentration of rbST that could be detected by the proposed lab-on-a-chip is as low as 120 ng/ml. Further, the sensitivity of the monolithically integrated single waveguide and multiple waveguides are compared for the fluorescence detection of the rbST.