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 Molecular
Computers
Considering the
challenges that confront the development of a computer
technology on the molecular scale, the idea of logic gates or
memory cells on an atomic scale seems pure fantasy. Believe it
or not, such a proposal was put forth by none other than
Richard Feynman when he said in 1959 that "the principles
of physics do not speak against the possibility of maneuvering
things atom by atom. It would be possible for a physicist to
synthesize any substance that the chemist writes down."
Feynman saw the manipulation of individual atoms as an
inevitable extension of technology. He pointed out that the
first large and crude machines were used to build smaller and
finer machines, which in turn were used to construct still
smaller devices, until it would shrink to a microscopic scale.
This would continue until the limits of matter are reached.
Feynman's proposal of machines building ever-smaller machines
became known as the top-down approach.
With the emergence of several new revolutionary concepts
lately in the field of computers, each claiming to herald in
an era of tiny, super fast computers in a scale undreamt of,
Feynman's hypothesis is becoming a reality. Time can
attest whether these developments, still at an embryonic
stage, would really usher in a new era of extremely minute,
super fast processors altering existing methodology of basic
computational techniques using silicon chip technology.
Recently computer scientists claimed to have achieved great
progress towards constructing a tiny, super-fast computer,
which they are calling as Molecular Computers. They say that
such computers built on a crystalline structure, will soon
replace those based on silicon chips and ultimately make it
possible to have a computer so small as a grain of salt.
What more are these scientists claiming? They say that these
will require far less power than current computers, and will
be able to store voluminous data permanently. They will do
away with the need to erase files, and also be immune to
attacks from computer viruses, crashes and other forms of
destruction. A team from Hewlett Packard and the University of
California at Los Angeles says its work could ultimately lead
to computers 100 billion times faster than today's most
powerful PCs. Their findings have been published in Science
magazine.
As of now, computers are based on silicon chips. The
information they carry is etched onto them with beams of
light, and it is becoming increasingly difficult to do this
precisely on chips getting smaller by the day. The ability to
shrink these ICs (Integrated Circuits) - the on-off switches
that are the basis of computing is limited by the wavelength
of light.
Researchers claim they have devised a way to construct
circuits using a chemical process. This should make them as
small as a molecule. They believe the process would lead to
components infinitely smaller than today's smallest
transistor. Smaller transistors consume less power and
generally switch on and off more quickly. They can also be
produced in greater quantities without raising costs of
production.
Phil Kuekes, a computer scientist at Hewlett Packard in Palo
Alto claims " we have actually built the very simplest
gates used in computers - logic gates - and they work."
James Heath, a UCLA chemistry Prof. who has worked on the
project, said his team created molecular logic gates that
switches "on" and "off" by changing
electrical voltage that represent "bits" of
information. They have achieved this by creating a new
compound, called rotaxane, which grows in a crystalline
structure.
The team of Heath and Kuekes, who wrote in the journal SCIENCE
recently, said that rotaxane molecules, sandwiched between
metal electrodes, functioned as logic gates. A crystal can
absorb information in the form of an electrical charge, and
organize it more efficiently. The chips made using this
molecular technology can be as small as a grain of sand.
However, it can have additional capabilities, like switching
the TV to your favorite channel, and eliminating the necessity
for input device like the mouse.
The next step would be to structure the chip. Instead of
etching the structure onto the surface, as is currently done
with silicon chip technology, it will de downloaded
electrically. The team claimed that they could download all
the complexity by wire attached to a bigger computer. But
there're a few hurdles yet. Currently available wires are too
big - much bigger than the rotaxane molecules - to do this.
Efforts are being made to shrink the wires until they're the
same diameter as the molecules, and then the miniaturized
technology will become a reality.
They also said that it might be possible to use carbon
nanotubes - long thin tubes made of pure carbon. Also known as
"Bucky tubes," they are no thicker than most
molecules.
This same team has recently announced that they made the
largest "defect tolerant" computer ever and called
it the Teramac.
– Subhajit Ghosh
May 3, 2000
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