Just
as the printing press revolutionized the creation
of reading matter, a "nano-printing" technique developed
at MIT could enable the mass production of nano-devices
currently built one at a time.
The most immediate candidate for this innovation
is the DNA microarray, a nano-device used to diagnose
and understand genetic illnesses such as Alzheimer's,
viral illnesses such as AIDS, and certain types of
cancer. The ability to mass produce these complex
devices would make DNA analysis as common and inexpensive
as blood testing, and thus greatly accelerate efforts
to discover the origins of disease.
The
demand for ever-shrinking devices of ever-increasing
complexity in areas from biomedicine to information
technology has spurred several research efforts
toward high-resolution, high-throughput nano-printing
techniques. Professor Francesco Stellacci and graduate
student Arum Amy Yu, both in the Department of
Materials Science and Engineering, have developed
a printing method that is unmatched in both information
content per printing cycle and resolution. They
achieved the latter using what Yu calls "nature's
most efficient printing technique: the DNA/RNA
information transfer."
In the new printing method, called Supramolecular
Nano-Stamping (SuNS), single strands of DNA essentially
self-assemble upon a surface to duplicate a nano-scale
pattern made of their complementary DNA strands.
The duplicates are identical to the master and can
thus be used as masters themselves. This increases
print output exponentially while enabling the reproduction
of very complex nano-scale patterns.
One such pattern is found on a DNA microarray, a
silicon or glass chip printed with up to 500,000
tiny dots. Each dot comprises multiple DNA molecules
of known sequence, i.e. a piece of an individual's
genetic code. Scientists use DNA microarrays to discover
and analyze a person's DNA or messenger-RNA genetic
code. This allows for, say, the early diagnosis of
liver cancer, or the prediction of the chances that
a couple will produce a child with a genetic disease.
Frequent, widespread use of these devices is hindered
by the fact that producing them is a painstaking
process that involves at least 400 printing steps
and costs approximately $500 per microarray.
MIT's
nano-printing method requires only three steps
and could reduce the cost of each microarray to
under $50. "This would completely revolutionize diagnostics," said
Stellacci. With the ability to mass produce these
devices and thus make DNA analysis routine, "we could
know years in advance of cancer, hepatitis, or Alzheimer's."
Another
benefit would be large-scale diagnostics that could
provide useful information about disease. Take
diabetes. "We don't know if it's genetic. The
only way to find out is to test a lot of people," said
Stellacci. "The more we test with microarrays, the
more we know about illnesses, and the more we can
detect them."
SuNS has applications beyond DNA microarrays. Materials
both organic and inorganic (metal nanoparticles,
for example) can be made to assemble along a pattern
composed of DNA strands. This makes SuNS a versatile
technology that could be used to produce other complex
nano-devices currently manufactured slowly and expensively:
micro- and nano-fluidics channels, single-electron
transistors, optical biosensors and metallic wires,
to name a few.
Stellacci recently received renewed funding from
the Deshpande Center for Technological Innovation
to continue work on SuNS. The work is also funded
by the National Science Foundation.
A version of this article appeared in the May 18,
2005 issue of MIT
Tech Talk (Volume 49, Number 28).
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