Abstract
A new route will be presented for an all-parallel fabrication of highly flexible, freestanding membranes with well-defined porosity. This fabrication is based on arrays of well-defined Au nanoparticles (NPs) exhibiting a high degree of hexagonal order as obtained in a first step by a proven micellar approach. These NP arrays serve as masks in a second reactive ion etching (RIE) step optimized for etching Si and some important Si compounds (silicon oxide, silicon nitride) on the nanoscale. Application to commercially available silicon nitride membranes of well-defined thickness, delivers a diaphragm with millions of nanopores of intended and controlled size, shape, and areal density with narrow distributions of these parameters. Electrophoretic transport measurements indicated a very low flow resistance of these porous membranes in ionic solutions as expected theoretically. Size-selective separation of protein molecules was demonstrated by real-time fluorescence microscopy.
Highlights
Various types of excellent freestanding nanoporous membranes for applications such as charge- and size-based separation of molecules have been reported during the last decade
These NP arrays serve as masks in a second reactive ion etching (RIE) step optimized for etching Si and some important Si compounds on the nanoscale
The allparallel nanoengineering process starts with a commercial silicon nitride (SN) membrane, typically with a size of 500 μm × 500 μm and a thickness of 75 nm supported by a 5 mm × 10 mm Si carrier with a chemically etched pyramidal opening at the back side (Silson Ltd, Northampton, England)
Summary
Various types of excellent freestanding nanoporous membranes for applications such as charge- and size-based separation of molecules have been reported during the last decade. Molecular filtering as a direct application of our nanoporous membranes is demonstrated: Successful size-selective separation of dye molecules and labeled proteins is observed by real-time fluorescence microscopy.
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