Forming antifouling organic multilayers on porous silicon rugate filters towards in Vivo/Ex vivo biophotonic devices

We describe the development and optimization of porous silicon photonic crystal surface chemistry towards implantable optical devices. Porous silicon rugate filters were prepared to obtain a narrow linewidth reflectivity peak in the near-infrared (7001000 nm) with low background reflectivity elsewhere. The morphology of the mesoporous structures (pore diameter < 50 nm) was such that only small proteins could infiltrate the pores whereas larger proteins were excluded. To provide stability in biological media, we established an approach to build organic multilayers containing hexa(ethylene oxide) moieties in porous silicon. The optical changes associated with organic derivatization were monitored concurrently with FTIR characterization. Furthermore, the antifouling capability of our chemical strategy is assessed and the penetration of different sized proteins into the structure was determined. The structural stability in biological environments was evaluated by incubation in human blood plasma over time while monitoring the optical signature of the photonic crystal.