Charge- and size-based separation of macromolecules using novel ultrathin silicon membranes

Summary form only given.Commercial ultrafiltration and dialysis membranes have broad pore size distributions and are several orders of magnitude thicker than the molecules they are designed to separate, leading to poor size cutoff properties, filtrate loss within the membranes, and low transport rates. Nanofabricated membranes have great potential in molecular separation applications by offering more precise structural control, but either they are fragile and their preparation is cumbersome and expensive, or transport through them is still limited by mum-scale thicknesses. In this presentation, we describe a novel ultrathin porous nanocrystalline silicon membrane manufactured using straightforward silicon fabrication techniques and providing control over average pore sizes from <5 nm to >25 nm. These novel membranes can retain proteins while permitting the transport of small molecules at rates one order of magnitude or more faster than existing materials, separate differently sized proteins under physiological conditions, and separate similarly sized molecules carrying different charges. Despite being only several nm thick, such large-area, free-standing membranes can support a full atmosphere of differential pressure without plastic deformation or fracture. By providing efficient, low-loss macromolecule separations, these 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, including optical biosensors. In this presentation, the manufacture and physical properties of the membranes will be presented, several examples of their use for molecular separation will be discussed, and future applications in research and development as well as in the commercial sector will be outlined.