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Molecular memory for
computers
The molecular switch
consists of two interlocked rings of atoms. When a voltage bias is
applied, the one molecule does a half-turn, the red and the green
molecules shown in the diagram are reversed, and the switch is
"closed."
‘A molecular computer will
enable us to do things we cannot even imagine now.’
—
JAMES
HEATH
UCLA
WASHINGTON,
Researchers say they
have developed microscopic chemical switches that could form the
basis of tiny, fast and cheap computers that will “do things we
cannot even imagine
now.”
THE HAIR-THICK switches can be turned on and off time after time,
offering the possibility of random-access memory — a key facility of
computers that allows users to store and manipulate information.
The team at the University of California at Los
Angeles hope they have taken a big step toward making a “molecular
computer” that will replace the big, unwieldy and power-hungry silicon
computers of today.
“With molecules comes
the message that we are working as small as we possibly can,” Fraser
Stoddart, a UCLA chemistry professor who designed the switches, said in a
telephone interview.
UNIMAGINABLE
POWER
Researchers predict that molecular computers will someday replace
those based on silicon chips and could ultimately make it possible to have
a computer so small it could be woven into clothing, for instance. They
should be able to hold vast amounts of data safely, with less fear of
crashes and other glitches.
“A molecular
computer will enable us to do things we cannot even imagine now,” UCLA’s
James Heath, who led the study, said in a statement. It would be a million
times more efficient, he said, than a silicon-based machine.
The basis of the tiny switch is a molecule called a
catenane. As described in Friday’s issue of the journal Science, it
consist of two tiny, interlocked rings made up of atoms linked in a
circle.
“Imagine two interlocked rings as
part of a chain,” Stoddart said. Each has two structures on it, called
recognition sites, that will interact electrochemically.
A pulse of electricity will remove one electron, causing one
ring to flip or rotate around the other. This turns the switch on. Putting
an electron back turns the switch off.
Last
year, the same team made a less efficient switch made out of a molecule
called a rotaxane that could work only once.
“It was a bit like a fuse — you could use it for as long as you
wanted to and then you lit it and blew it,” Stoddart said. “It gave us the
basis for read-only memory.”
ROOM-TEMPERATURE
RAM
The new switch can be open
and closed over and over again — like the difference between a CD-ROM that
can be recorded on once, and a disk that can be erased and used over and
over.
“It is very robust. You can do this at
room temperature,” said
Stoddart, whose team is cooperating with a group
at Hewlett-Packard.
It is also easy to see
whether the catenane is working. “It is green in the starting state ...
and then it switches to being maroon,” Stoddart said. “You can use your
eyes to detect it.”
At first the switch worked in solution — not very practical for a
computer — but Stoddart’s team managed to get the molecules to form a
film. They will sit in place just like a thin film of oil, Stoddart
said.
Having switches is one thing, but the
scientists now need wires to hook them together and the overall
architecture to make the components into a computer.
“There is still a problem with wires — if you can get them
down to about a millionth of their present size, then these can be very,
very small devices,” Stoddart said.
His
group is working with buckytubes with this aim in mind. The long, thin
buckytubes, also known as
nanotubes, are made of pure carbon.
Stoddart, whose work is being funded by the U.S.
Defense Advanced Research Projects Agency, says he has already designed a
switch that may be even faster. It has a dumbbell design and may be more
efficient than the linked rings.
source:
REUTERS
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