Molecular filter-nanosieve

Abstract

Demonstrated in this paper is a molecular sieve. The focus of this work is making a "smart" filter. This filter has electrochemical and electromechanical properties that would allow both sorting and filtering of solutions. Prior sifters and sieving structures have been at the mercy of a static material structure, whereas the convention proposed here allows dynamic control of filtering size during an assay. The filter mechanism simply relies on a sandwiched layer of oxide, grown in a RF Sputtering system. This allows for almost Angstrom level control of the thickness. An oxide layer is sandwiched between two layers of silicon with e-beam written holes 100nm in diameter, one offset from the other. Dry etching is used to carve these holes in the silicon layers, and wet oxide etching defines a void in the sandwiched layer. The distance that the two silicon layers are separated dictates the smallest filtering size. Analysis is available through several methods. Mechanically, a fluid can be passed through the holes carrying along with it the particles or molecules that are small enough to make it through the oxide layer. Electrochemically, a charged particle can be placed on one side of a container and separated by the filter, while having the tendency to get to the other side, with different concentration, by passing through the filter [1].

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