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Monday, August 21, 2000

One Step Closer to Molecular Computing

WASHINGTON: Researchers said on Thursday they had 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 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.

Researchers predict that molecular computers will some day 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.

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 last week'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.''

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,'' Stoddart, whose team is cooperating with a group at Hewlett-Packard Co, said.

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 carbon buckytubes with this aim in mind. These are long, thin tubes made of pure carbon that are also known as carbon nanotubes.

Stoddart, whose work is being funded by the US 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.--Reuters

http://thestar.com.my/tech/story.asp?file=/2000/8/21/technology/21smallpc&sec=technology

-- (Dee360degree@aol.com), August 21, 2000