An SU-8 based fluidic immuno-spectroscopic lab-on-a-chip for rapid quantitative detection of biomolecules

A 30mm-long multimode waveguide, 40 mu m wide and 40 mu m high, is fabricated on a silicon wafer using polymer SU-8 as the core and liquid buffer as the cladding. Antibodies are successfully immobilized on the SU-8 is surface designated for binding target antigens disperse in the buffer solution. Evanescent-wave spectroscopy is performed by exciting the fluorescently-labeled antigens, bound to the waveguide surface within its evanescence field, and measuring emission fight intensity. This evanescent-wave biosensor detects specific molecular interaction; its output depends on antigen concentration with a sensitivity of 40 light counts per 1 mu g/ml.