Nature445, 749-753 (15 February 2007) | doi:10.1038/nature05532; Received 23 March 2006; Accepted 20 November 2006
Charge- and size-based separation of macromolecules using ultrathin silicon membranes
Christopher C. Striemer1, Thomas R. Gaborski2, James L. McGrath2 and Philippe M. Fauchet1
Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA
Department of Biomedical Engineering, University of Rochester, Rochester, New York 14620, USA
Correspondence to: Christopher C. Striemer1 Correspondence and requests for materials should be addressed to C.C.S. (Email: striemer@ece.rochester.edu).
Commercial ultrafiltration and dialysis membranes have broad pore size distributions and are over 1,000 times thicker than the molecules they are designed to separate, leading to poor size cut-off properties, filtrate loss within the membranes, and low transport rates1, 2. Nanofabricated membranes have great potential in molecular separation applications by offering more precise structural control3, 4, yet transport is also limited by micrometre-scale thicknesses5. This limitation can be addressed by a new class of ultrathin nanostructured membranes where the membrane is roughly as thick (10 nm) as the molecules being separated, but membrane fragility and complex fabrication have prevented the use of ultrathin membranes for molecular separations1. Here we report the development of an ultrathin porous nanocrystalline silicon (pnc-Si) membrane using straightforward silicon fabrication techniques that provide control over average pore sizes from approximately 5 nm to 25 nm. Our pnc-Si membranes can retain proteins while permitting the transport of small molecules at rates an order of magnitude faster than existing materials, separate differently sized proteins under physiological conditions, and separate similarly sized molecules carrying different charges. Despite being only 15 nm thick, pnc-Si membranes that are free-standing over 40,000 m2 can support a full atmosphere of differential pressure without plastic deformation or fracture. By providing efficient, low-loss macromolecule separations, pnc-Si membranes are expected to enable a variety of new devices, including membrane-based chromatography systems and both analytical and preparative microfluidic systems that require highly efficient separations.
10 nm) as the molecules being separated, but membrane fragility and complex fabrication have prevented the use of ultrathin membranes for molecular separations
m2 can support a full atmosphere of differential pressure without plastic deformation or fracture. By providing efficient, low-loss macromolecule separations, pnc-Si membranes are expected to enable a variety of new devices, including membrane-based chromatography systems and both analytical and preparative microfluidic systems that require highly efficient separations.
