Modification of the optical properties of polydimethylsiloxane (PDMS) for photonic crystal biosensor application

The sensitivity of a photonic crystal optical biosensor device can be enhanced through the difference in effective refractive index of dielectric materials. In this work, we report the optical modification of refractive index of PDMS from 1.41 to above, by incorporating the additive materials to enhance the sensitivity of photonic crystal optical biosensor devices. The refractive index of mixed-PDMS materials are measured by ellipsometry technique. The surface and cross section morphologies are characterized by Field-Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM). The grating structure of 800 nm period PDMS with low refractive index was fabricated by Nano-Imprinting Lithography (NIL) then the mixed-PDMS with high refractive index was spun on the periodic PDMS as photonic crystal device. The sensitivity of devices is characterized and demonstrated by reflection spectra intensity of fluids on surface of the devices.