Ballistic and non-ballistic gas flow through ultrathin nanopores. Nanotechnology 23:145706

Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY 14627, USA.
Nanotechnology (Impact Factor: 3.82). 04/2012; 23(14):145706. DOI: 10.1088/0957-4484/23/14/145706
Source: PubMed


We show that ultrathin porous nanocrystalline silicon membranes exhibit gas permeance that is several orders of magnitude higher than other membranes. Using these membranes, gas flow obeying Knudsen diffusion has been studied in pores with lengths and diameters in the tens of nanometers regime. The components of the flow due to ballistic transport and transport after reflection from the pore walls were separated and quantified as a function of pore diameter. These results were obtained in pores made in silicon. We demonstrate that changing the pore interior to carbon leads to flow enhancement resulting from a change in the nature of molecule-pore wall interactions. This result confirms previously published flow enhancement results obtained in carbon nanotubes.

25 Reads
  • Source
    • "Experimental observations of biomolecule diffusion through porous membranes showed good agreement with theoretical predictions [8]. The negligible thickness ($5–60 nm) of pnc-Si membranes affords remarkably high hydraulic and gas permeability [7] [9]. These fundamental properties make pnc-Si a unique nanomaterial for chemical, biomolecule and nanoparticle separations. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Assays for initiating, controlling and studying endothelial cell behavior and blood vessel formation have applications in developmental biology, cancer and tissue engineering. In vitro vasculogenesis models typically combine complex three-dimensional gels of extracellular matrix proteins with other stimuli like growth factor supplements. Biomaterials with unique micro- and nanoscale features may provide simpler substrates to study endothelial cell morphogenesis. In this work, patterns of nanoporous, nanothin silicon membranes (porous nanocrystalline silicon, or pnc-Si) are fabricated to control the permeability of an endothelial cell culture substrate. Permeability on the basal surface of primary and immortalized endothelial cells causes vacuole formation and endothelial organization into capillary-like structures. This phenomenon is repeatable, robust and controlled entirely by patterns of free-standing, highly-permeable pnc-Si membranes. Pnc-Si is a new biomaterial with precisely defined micro- and nanoscale features that can be used as a unique in vitro platform to study endothelial cell behavior and vasculogenesis.
    Acta Biomaterialia 11/2014; 10(11). DOI:10.1016/j.actbio.2014.07.022 · 6.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ultrathin porous nanocrystalline silicon (pnc-Si) membranes metallized with gold are used as flexible conductive electrodes in chemical capacitive vapor sensor. This use of a porous electrode simplifies the conventional parallel-plate design of typical sensors. pnc-Si is a 15 nm thick membrane material with pore sizes ranging from 5 to 50 nm and porosities from <0.1 to 15% fabricated using standard silicon semiconductor processing techniques. We experimentally test the mechanical stability and elasticity of pnc-Si. The very thin porous membrane allows fast analyte vapor permeation to the underlying polymer material that serves as receptor which is tested using an optical profiler. Electrical techniques are used to determine the degree of swelling and the reversibility of the polymer/pnc-Si membrane system when exposed to analyte-containing vapors.
    Sensors and Actuators B Chemical 02/2012; 162(1):22–26. DOI:10.1016/j.snb.2011.11.076 · 4.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The development of wearable or implantable technologies that replace center-based hemodialysis (HD) hold promise to im-prove outcomes and quality of life for patients with ESRD. A prerequisite for these technologies is the development of highly efficient membranes that can achieve high toxin clearance in small-device formats. Here we examine the application of the po-rous nanocrystalline silicon (pnc-Si) to HD. pnc-Si is a molecularly thin nanoporous membrane material that is orders of mag-nitude more permeable than conventional HD membranes. Material developments have allowed us to dramatically increase the amount of active membrane available for dialysis on pnc-Si chips. By controlling pore sizes during manufacturing, pnc-Si mem-branes can be engineered to pass middle-molecular-weight protein toxins while retaining albumin, mimicking the healthy kid-ney. A microfluidic dialysis device developed with pnc-Si achieves urea clearance rates that confirm that the membrane offers no resistance to urea passage. Finally, surface modifications with thin hydrophilic coatings are shown to block cell and protein adhesion.
    Advances in Chronic Kidney Disease 01/2013; 20(6):508-515. · 2.05 Impact Factor
Show more