Industry News
DNA circuit boards
SCIENTISTS at the California Institute of little like taking a deck of playing cards
Technology (Caltech) and IBM’s and throwing it on the floor; they are
Almaden Research Center have scattered willy-nilly all over the place.
developed a new technique to orient Such random arrangements of DNA
and position self-assembled DNA origami are not very useful. If they carry
shapes and patterns—or “DNA electronic circuits, for example, they are
origami”—on surfaces that are difficult to find and wire up into larger
compatible with today’s semiconductor circuits.”
manufacturing equipment. These To eliminate these problems,
precisely positioned DNA Rothemund and his colleagues at the
nanostructures, each no more than one Almaden Research Center developed a This opens up the possibility of creating
one-thousandth the width of a human way to precisely position DNA origami functional devices that can be
hair, can serve as scaffolds or miniature nanostructures on a surface, “to line integrated into larger structures as well
Issue VI 2009
circuit boards for the precise assembly them up like little ducks in a row,” as enabling studies of arrays of
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of computer-chip components. Rothemund says. “This knocks down nanostructures with known coordinates.
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The advance, described in the one of the major roadblocks for the use “The spacing between the
current issue of the journal Nature of DNA origami in technology,” he components can be 6 nanometers, so
Nanotechnology, could allow the adds. the resolution of the process is roughly
semiconductor industry to pack more In a process developed by IBM 10 times higher than the process we
power and speed into tiny computer scientists, electron-beam lithography currently use to make computer chips,”
chips, while making them more energy and oxygen plasma etching are used to Rothemund says. “Then, if you want to
efficient and less expensive to make patterns on silicon wafers, design a really small electronic device,
oasiasemiconductor
manufacture than is possible today. creating lithographic templates of the say, you just design DNA strands to
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DNA origami structures have been proper size and shape to match those create the pattern you want, attach little
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heralded as a potential breakthrough of individual triangular DNA origami chemical ‘fastening posts’ to those DNA
for the creation of nanoscale circuits structures created by Rothemund. The strands, assemble the pattern, and then
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and devices. In a process created by etched patches are negatively charged, assemble the components onto the
Caltech senior research associate Paul as are DNA origami structures, and are pattern,” he explains.
W. K. Rothemund and his colleagues, therefore “sticky.” The process isn’t limited to
DNA molecules self-assemble in To connect the origami to the organizing things that are of interest to
solution via a reaction between a long templates, magnesium ions are added physical scientists and engineers, like
single strand of viral DNA and a mixture to the saltwater solution containing the electronic components, Rothemund
of different short synthetic DNA origami. The positively charged adds. For example, he says, “Biologists
strands. These short segments act as magnesium ions can stick to both the studying how proteins interact can
staples that effectively fold the viral DNA origami and the negatively place them in patterns on top of DNA
DNA into desired two-dimensional charged patches on the template. Thus, origami. This may be useful in the case
shapes through complementary base- when the solution is poured over the of motor proteins, the little machines
pair binding. template, a negative-positive-negative that power our muscles. They work in
In this way, DNA nanostructures “sandwich” is formed, with the gangs, with multiple motors pulling
such as squares, triangles, and stars can magnesium atoms acting as a glue to together. To study how different
be prepared that measure 100 to 150 hold the origami to the sticky patches. configurations of motors cooperate,
nanometers on an edge and are as thick “The triangles bind strongly to the scientists may use DNA origami to
as the DNA double helix is wide. sticky patches, but also they can wiggle organize the gangs.”
One roadblock to the use of DNA a bit, so they line up with the outline of “Rothemund and his colleagues
origami, however, is that the structures the sticky patch. So not only can we put have removed a key barrier to the
are made in saltwater solution— origami where we want them, but they improvement and advancement of
whereas electronic circuits are created can be oriented in the direction we future computer chips. They
on surfaces, like a silicon wafer, so they want them,” Rothemund says. accomplished this through the
can be integrated with other The positioned DNA nanostructures revolutionary approach of combining
technologies. can then serve as scaffolds or miniature the building blocks for life with the
DNA origami structures also adhere circuit boards for the precise assembly building blocks for computing,” says
randomly to surfaces, which means that of components such as carbon Ares Rosakis, Theodore von Kármán
“if you just pour DNA origami over a nanotubes, nanowires, and Professor of Aeronautics and
surface to which they stick, they attach nanoparticles at dimensions significantly Mechanical Engineering and chair of
everywhere,” explains Rothemund, who smaller than possible with conventional Caltech’s Division of Engineering and
jointly led the project with IBM. “It’s a semiconductor fabrication techniques. Applied Science.
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