http://www.ibm.com/News/1998/07/24.phtml
IBM scientists help discover "molecular
wheels" -- a breakthrough for designing
nanoscale devices
On July 24, IBM scientists
and a team of international
collaborators reported the
discovery of "molecular
wheels": propeller-shaped
molecules that rotate rapidly
in a bearing-like structure
formed by surrounding
molecules. The scientists
believe this unexpected
phenomenon shows great
promise for the development of molecular mechanical devices
and further demonstrates the validity of using single molecules to
perform the various functions required in such devices.
In a paper published in Science, IBM's Zurich Research
Laboratory, together with colleagues at the French National
Center for Scientific Research (CNRS) in Toulouse, and the Riso
National Laboratory in Roskilde, Denmark, report their design of
the propeller-shaped molecules which can switch between two
states -- rotating and immobilized, and the high-speed molecular
rotation which they observed by using a scanning tunneling
microscope (STM).
"Our discovery of the molecular wheel came about from recent
molecular switch experiments in which we were investigating a
reversible change in the shape of specifically designed molecules
triggered by a voltage pulse from the STM tip," said James
Gimzweski, who leads the nano-engineering effort at IBM's Zurich
Research Laboratory. "We believe that compared to other
proposed or synthetic molecular mechanisms, the molecular
wheel, which works in a dry state and appears to be wearless, is
advantageous for creating gears and motors at the nanoscale
level."
In viewing the
STM images, the
researchers
found a ring-like
object instead of
the molecule that
had been there.
The object, now
in a slightly
different position,
shifted by just
one-fourth of a
nanometer. It evidently jumped into a tiny space left vacant by an
irregularity in the molecular layer and thus escaped the
immobilizing grip of four molecules that surrounded it closely on
one side. An adjacent molecule on the other side confined its
further lateral motion and, in effect, contributed to forming a
bearing for rotation of the central molecule. This rotation was
responsible for the blurred, ring-like appearance of the molecule
in the STM image. Researchers at CNRS calculated the behavior
of the molecular wheel. Such wheels may someday become the
smallest conceivable components of molecular engines.
-------------------------------------------------------------------
Alexander Chislenko <http://www.lucifer.com/~sasha/home.html>
Extropy Online <http://www.extropy.org/eo/index.htm>
-------------------------------------------------------------------