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Trends in porous silicon biomedical devices: tuning microstructure and performance trade-offs in optical biosensors

High surface area mesoporous silicon microcavities are investigated for direct detect optical biosensor applications. Device quality is reported as a function of fabrication parameters. A dilute KOH etch process is utilized to modify the intrinsic 3D microstructure to enable enhanced pore infiltration of large biomolecules. Results suggest that the KOH etch mechanism is a two step process consisting of a fast step where high surface area nanostructures are rapidly removed. This is followed by a slower step where silicon is removed from the pore channel walls. The enzyme, Glutathione-S-Transferase (50kDa), is utilized to probe pore infiltration. Results from a solid phase immobilized enzyme assay support our conclusions on the impact the KOH etch step has on modifying the porous silicon microstructure. Preliminary findings point to trade-offs that exists between optimizing microstructure with microcavity operation mode and device sensitivity.