NANOTECH: Wiring Up Molecular Switches

From: J. R. Molloy (
Date: Mon Oct 29 2001 - 11:09:17 MST

A team of researchers at the University of California, Los Angeles, has moved
an important step closer to building a computer from the bottom up: They have
attached molecular switches on a grid as small as 50 nanometers.

The breakthrough is new ground in molecular memory and logic, said James
Heath, UCLA chemistry and biochemistry professor as well as co-scientific
director of the California NanoSystems Institute. The team has developed
a 16-bit memory circuit that uses molecular switches that "work pretty well"
on traditional wiring, Heath said. The process uses chemical assembly and
fluidics to mount the switches on a crossbar-type structure.

The research has yet to be published, but Heath gave a glimpse of the next
step toward molecular computers this week at UCLA. His presentation was part
of a statewide series of events to celebrate the 100th anniversary of the
Nobel Prizes. The audience included Nobel laureates and Crown Princess
Victoria of Sweden.

One of the reasons California is widely touting the Nobel Prize Centennial is
that the state has the largest concentration of Nobel laureates anywhere in
the world. Of the 700 recipients of the Nobel Prize, more than 100 have been
Californians. Since World War II, California has averaged two Nobel Prize
winners per year.

While honoring past contributions to science, the event focused on showing the
best of present research at UCLA and the University of California, Santa
Barbara. That included Heath's discoveries on the path to ultimately building
an energy-efficient computer made of nanowires and organic molecules.

"The goal is to reach a realistic limit to create a computer that requires
very little energy to operate," Heath said. "It's a problem of trying to make
this very efficient computing machine." Circuitry is one of the next steps.

"Learning how to use that circuit is really learning how to grab that
molecular signature at a specific junction. That's a big challenge," Heath
said. "If you look at the nanoliterature, you'll find a lot of device stuff,
but you very rarely will find anything on circuits, because they are just that
much harder."

By devices, Heath meant molecular switches, which are now working well enough
in his lab to go to the next step -- to place and connect the molecular
switches on a lithographic grid. The molecular switches change their
conductivity as electricity passes through.

Heath's team already has demonstrated a reconfigurable molecular switch that
works in a solid state at room temperature -- a breakthrough that solves one
of the obstacles toward the creation of molecular computers.

Work on the switches, now in their fifth generation, was in conjunction with
UCLA chemist J. Fraiser Stoddart. Stoddart came to UCLA a few years ago from
England's University of Birmingham.

"There's a long way to go," Heath said. "Right now we have circuits with
molecules on a grid on normal lithographic wires." The goal is that one day
the grid would be assembled with carbon nanotubes.

Describing the computer architecture as a road map, Heath said the system was
at the neighborhood level. "We are getting the logic and memory circuitry at
the link scales that are molecular or scalable to molecular. That's where we
are," he said. "We don't have them talking to each other yet."

For now, the switches are put together as a single molecular layer on top of
the wires and line up through chemical assembly. "The wires are done more or
less using traditional approaches all at room temperature," Heath said.

Specifically, Heath's team is working on building a Boolean logic,
non-reversible computing machine from the bottom up. "It's complicated enough
that if you do it, you are going to learn something," Heath said.

"One of the challenges but one of the real hopes is that you can somehow take
advantage of this wonderful beauty at the molecular scale and be able to
utilize that for things like information technology," Heath said. "The real
difficult problem we went after was not just to try to make a computer, but to
try to make a computer that operated at what we think is the appropriate
method for computation."

Heath is "making large progress on small problems," said Paul Boyer, a 1997
Nobel Prize-winning chemist at UCLA. "Jim and I share, in one sense, a study
in nanosystems," Boyer said. "In my instance, I was lucky to work with a
particular enzyme -- a biologic nanosystem that turned out to be a little
molecular motor that worked in cells to make some of the compounds we need for
life. Now Jim, instead of looking at something that's already there, is trying
to assemble these nanocircuits from the bottom up."

It was another California Nobel Prize winner, the late quantum physicist
Richard Feynman, who predicted the age of nanotechnology when he gave his
now-famous 1959 lecture at California Institute of Technology in Pasadena. His
talk, "There's Plenty of Room at the Bottom," outlined the theoretical concept
of manipulating individual atoms to build molecules.

In his presentation before the Nobel laureates, Heath acknowledged Feynman's
legacy. How to run a molecular computer using a very small amount of energy is
one of the problems Feynman thought about in the years before he died in 1988,
Heath said. "The ones and zeroes are going to cost you energy to switch them
back and forth," he said.

--- --- --- --- ---

Useless hypotheses, etc.:
 consciousness, phlogiston, philosophy, vitalism, mind, free will, qualia,
analog computing, cultural relativism, GAC, Cyc, Eliza, cryonics, individual
uniqueness, ego, human values, scientific relinquishment, malevolent AI

We move into a better future in proportion as science displaces superstition.

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