from the good dr... very interesting technology...
By JUDY SIEGEL
JERUSALEM (February 19) - Israeli scientists have become the first to "coax"
individual biological
molecules into forming an electric circuit.
This marriage of biotechnology and electronics will eventually make possible the
production of a
transistor sized 1/100,000th of the width of a human hair, 100th or less of the space
required today.
The breakthrough was accomplished by Prof. Uri Sivan, Dr. Erez Braun and Dr. Yoav
Eichen of the
Technion.
"In conventional micro-electronics, you start trying to reduce size as much as possible,
from the top
down. In a biological system, you begin with information in the DNA and build from
bottom to top,"
Sivan explained yesterday on the eve of publication of their discovery in Nature. "No
one can
manually arrange molecules of this size - which can be viewed only via an atomic force
microscope -
so we had to use molecules in which all chemical information is coded, allowing
self-assembly into
structures based on chemical selectivity."
He added that the basic problem that had to be overcome is that "if you look for a
system that builds
itself, the molecules are insulated and don't transfer electricity; metals, which do pass
electrons, don't
self-assemble. We therefore decided to integrate biological and electronic materials to
take
advantage of both properties."
The Technion team produced a preliminary demonstration of an enabling technology
that uses
processes of molecular recognition unique to biological molecules and place miniature
electronic
components in molecular sites to form a complete electronic circuit.
They placed conducting electrodes on an insulating substrate while connecting the outer
parts of the
electrodes externally to a computer, for example, while the internal part was coated
with short DNA
molecules.
Each of the DNA molecules had a defined and different "genetic" code for each
electrode.
Then long-stranded DNA molecules with complementary sequences were stretched
between the
electrodes, based on molecular recognition, so a complete DNA network was created.
This
network didn't conduct electrons, but it served as an "intelligent" template for the
assembly of the
electronic circuit by coating it with a conducting metal.
In a series of experiments, the scientists demonstrated their concept by producing a
conducting
metal wire connecting two gold electrodes 12 microns apart. The diameter of the wire
was 100
nanometers (each of these is 1/100,000th of the width of a human hair).
"The applications could take 20 years, but they are virtually infinite," explained Sivan.
"Using
transistors of this size, you could store all knowledge printed in every book in the
world inside a
cube 1/5 of a millimeter in each direction. Our work was basic science, and
applications in
nanoelectronics are still far off, but this alternative technology to micro-electronics will
allow the
production of devices that are 100-300 times smaller, with higher complexity, at a
lower cost.
Beyond the miniaturization, the innovation will make possible entirely new logic based
on extensive
connectivity." |
