Using Biology To Create Electronics: DNA Used To Create Self-assembling Nano Transistor...

 Source:   American Society For Technion - Israel Institute Of
Technology

Date:2003-11-21

Using Biology To Create Electronics: DNA Used To Create Self-assembling Nano
Transistor

NEW YORK, N.Y., and HAIFA, Israel, November 17, 2003 - Scientists at the
Technion-Israel Institute of Technology have harnessed the power of DNA to
create a self-assembling nanoscale transistor, the building block of
electronics. The research, published in the Nov. 21, 2003 issue of Science,
is a crucial step in the development of nanoscale devices.

Erez Braun, lead scientist on the project and associate professor in the
Faculty Physics at the Technion, says science has been intrigued with the
idea of using biology to build electronic transistors that assemble without
human manipulation. However, until now, demonstrating it in the lab has
remained elusive. "This paper shows you can start with DNA proteins and
molecular biology and construct an electronic device," he said.

"Erez Braun and his colleague Uri Sivan are some of the few pioneers in this
field," said Horst Stormer, professor in Columbia University's Departments
of Physics and Applied Physics and scientific director of the Nano Science
and Engineering Centers. "This is outstanding research in the area that
matters most in nano technology: self-assembly."

To get the transistors to self assemble, the Technion research team attached
a carbon nanotube -- known for its extraordinary electronic properties -- 
onto a specific site on a DNA strand, and then made metal nanowires out of
DNA molecules at each end of the nanotube. The device is a transistor that
can be switched on and off by applying voltage to it.

The carbon nanotubes used in the experiment are only one nanometer, or a
billionth of a meter, across. In computing technology, as scientists reach
the limits of working with silicon, carbon nanotubes are widely recognized
as the next step in squeezing an increasing number of transistors onto a
chip, vastly increasing computer speed and memory. Braun emphasized that
computers are only one application; these transistors may, for example,
enable the creation of any number of devices in future applications, such as
tiny sensors to perform diagnostic tests in healthcare.

Though transistors made from carbon nanotubes have already been built, those
required labor-intensive fabrication. The goal is to have these nanocircuits
self-assemble, enabling large-scale manufacturing of nanoscale electronics.

DNA, according to Braun, is a natural place to look for a tool to create
these circuits. "But while DNA by itself is a very good self-assembling
building block, it doesn't conduct electrical current," he noted.

To overcome these challenges, the researchers manipulated strands of DNA to
add bacteria protein to a segment of the DNA. They then added certain
protein molecules to the test tube, along with protein-coated carbon
nanotubes. These proteins naturally bond together, causing the carbon
nanotube to bind to the DNA strand at the bacteria protein.

Finally, they created tiny metal nanowires by coating DNA molecules with
gold. In this step, the bacteria protein served another purpose: it
prevented the metal from coating the bacteria-coated DNA segment, creating
extending gold nanowires only at the ends of the DNA strand.

The goal, Braun explained, was to create a circuit. However, "at this point,
the carbon nanotube is located on a segment of DNA, with metal nanowires at
either end. Theoretically, one challenge here would be to encourage the
nanotube to line up parallel to the DNA strand, meet the nanowires at either
end, and thus make a circuit.

"There are some points where nature smiles upon you, and this was one of
those points," Braun continued. "Carbon nanotubes are naturally rigid
structures, and the protein coating makes the DNA strand rigid as well. The
two rigid rods will align parallel to each other, thus making an ideal
DNA-nanotube construct."

"In a nutshell, what this does is create a self-assembling carbon nanotube c
ircuit," he concluded.

Scientists controlled the creation of transistors by regulating voltage to
the substrate. Out of 45 nanoscale devices created in three batches, almost
a third emerged as self-assembled transistors.

Braun added, however, that while this research demonstrates the feasibility
of harnessing biology as a framework to construct electronics, creating
working electronics from self-assembling carbon nanotube transistors is
still in the future.

Braun conducted the research with colleagues Kinneret Keren, Rotem S.
Berman, Evgeny Buchstab, and Uri Sivan.

-- 
Ken

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