Integrated Nanoscale Silicon Membranes for Separation Collection and
Integrated Nanoscale Silicon Membranes for Separation, Collection, and Preconcentration of Biomolecules Electrical and Computer Engineering Biomedical Engineering Christopher C. Striemer David Z. Fang Philippe M. Fauchet Thomas R. Gaborski Jessica Snyder James L. Mc. Grath University of Rochester, NY, USA Funding Support Johnson & Johnson/URMC Discovery Fund
Pnc-Si Membranes Porous nanocrystalline Si: • Ultrathin: 3 nm - 25 nm thickness transport rate 1 thickness • minimal surface area – low loss • Nanopores: <5 nm to 50 nm diameter • Low complexity fabrication: Si integration • Stable: temperature / pressure • Known/controllable pore size distribution thickness = 15 nm
Membrane fabrication – part I
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
Pore size control cutoff • Pore morphology - strong function of RTP temperature. • Increasing temperature: • larger pores • higher porosity cutoff
Membrane fabrication – part II
Anisotropic EDP etching • (111) planes form etch-stops – well defined edges/corners • Very slow Si. O 2 etch rate – enables membrane formation (111)
Pnc-Si membranes • Buffered oxide etch – complementary high-contrast etch pnc-Si/Si. O 2 sandwich 7 nm pnc-Si
Membrane stability 0 PSI 3 PSI 6 PSI 12 PSI 15 PSI 200 mm 9 PSI 15 nm thickness Elastic deformation without rupture
Molecular separations
Molecular separation demo Time lapse movie – 6. 5 minutes Pnc-Si membranes are highly effective in separating small molecules from proteins
Dye transport rate comparison porosity = 0. 2% The diffusion rate of dye through pnc-Si is > 9 X that of a commercial dialysis membrane with 50 k. Da cutoff
Transport rate comparison porosity = 7. 8% porosity = 0. 2% • Pnc-Si membranes differing by nearly 40 X in porosity have dye rates within 10%. • Bulk diffusion is rate-limiting.
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 9 X increase in molecular transport rate relative to commercial membranes. Contact: Christopher Striemer <striemer@ece. rochester. edu>
- Slides: 14