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Integrated Nanoscale Silicon Membranes for Separation, Collection, and Preconcentration of Biomolecules Thomas R. Gaborski Jessica Snyder James L. McGrath University of Rochester, Rochester, NY, USA Funding Support Johnson & Johnson/URMC Discovery Fund Electrical and Computer Engineering Biomedical Engineering Christopher C. Striemer David Z. Fang Philippe M. Fauchet

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Pnc-Si Membranes Ultrathin: 3 nm - 25 nm thickness Porous nanocrystalline Si: thickness = 15 nm minimal surface area low loss Nanopores:

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Membrane fabrication part I

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Pore formation Form spontaneously during crystallization phase change volume contraction dynamic strain during anneal Critical process variables anneal temperature film thickness deposition conditions Novel result not previously reported

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Pore size control Pore morphology - strong function of RTP temperature. Increasing temperature: larger pores higher porosity cutoff

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Membrane fabrication part II

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Anisotropic EDP etching (111) planes form etch-stops well defined edges/corners Very slow SiO 2 etch rate enables membrane formation (111)

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Pnc-Si membranes Buffered oxide etch complementary high-contrast etch pnc-Si/SiO 2 sandwich 7 nm pnc-Si

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Membrane stability 15 PSI 9 PSI 6 PSI 3 PSI 0 PSI 12 PSI Elastic deformation without rupture 200 m 15 nm thickness

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Molecular separations

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Molecular separation demo Pnc-Si membranes are highly effective in separating small molecules from proteins Time lapse movie 6.5 minutes

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Dye transport rate comparison The diffusion rate of dye through pnc-Si is > 9X that of a commercial dialysis membrane with 50 kDa cutoff porosity = 0.2%

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Transport rate comparison Pnc-Si membranes differing by nearly 40X in porosity have dye rates within 10%. Bulk diffusion is rate-limiting. porosity = 0.2% porosity = 7.8%

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Summary Ultrathin porous nanocrystalline silicon membranes are a newly discovered material with interesting properties. Pnc-Si membranes are robust and practical for laboratory applications. For dialysis applications, pnc-Si exhibits a 9X increase in molecular transport rate relative to commercial membranes. Contact: Christopher Striemer