Fabrication of encoded rugate porous silicon interferometer for biosensor

Multi-encoded rugate porous silicon (PSi)-based optical biosensor was developed to specify the biomolecules. Multi-encoded rugate PSi was generated by an electrochemical etching of silicon wafer using an electrode configuration in aqueous ethanolic HF solution. Multi-encoded rugate PSi displayed three very sharp reflection bands whose reflection maxima varied spatially across the PSi. The sensor system studied consisted of a multilayer of PSi modified with biotin. The system was probed with various fragments of an aqueous protein analyte. The sensor operates by measurement of the reflection peaks in the white light reflection spectrum from the PSi layer. When the biotin-derivatized rugate PSi was exposed to protein in phosphate buffer solution (PBS), the molecular binding caused a change of its refractive index is detected as a shift in wavelength of these reflection peaks. A red-shift of reflective spectra were observed, when the biotin-modified rugate PSi was exposed to a flow of protein.