At IBM scientists are investigating the possibility of using structures made of DNA strings as buildings blocks for future microchip designs. The structures, dubbed “DNA origami”, self assemble onto lithographic templates which can lead to manufacturing of circuit features down to 22 nanometers.
The utility of this approach lies in the fact that the positioned DNA nanostructures can serve as scaffolds, or miniature circuit boards, for the precise assembly of components – such as carbon nanotubes, nanowires and nanoparticles – at dimensions significantly smaller than possible with conventional semiconductor fabrication techniques. This opens up the possibility of creating functional devices that can be integrated into larger structures, as well as enabling studies of arrays of nanostructures with known coordinates.
The techniques for preparing DNA origami, developed at Caltech, cause single DNA molecules to self assemble in solution via a reaction between a long single strand of viral DNA and a mixture of different short synthetic oligonucleotide strands. These short segments act as staples – effectively folding the viral DNA into the desired 2D shape through complementary base pair binding. The short staples can be modified to provide attachment sites for nanoscale components at resolutions (separation between sites) as small as 6 nanometers (nm). In this way, DNA nanostructures such as squares, triangles and stars can be prepared with dimensions of 100 – 150 nm on an edge and a thickness of the width of the DNA double helix.
The lithographic templates were fabricated at IBM using traditional semiconductor techniques, the same used to make the chips found in today’s computers, to etch out patterns. Either electron beam or optical lithography were used to create arrays of binding sites of the proper size and shape to match those of individual origami structures. Key to the process were the discovery of the template material and deposition conditions to afford high selectivity so that origami binds only to the patterns of "sticky patches" and nowhere else.
Press release: IBM Scientists Use DNA Scaffolding To Build Tiny Circuit Boards …
Images: Low concentrations of triangular DNA origami are binding to wide lines on a lithographically patterned surface.
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