RIVERSIDE,
Calif. – A research team, led by UC Riverside's Ludwig
Bartels , is the first to design a molecule that can move in a straight
line on a flat surface. It achieves this by closely mimicking human walking.
The “nano-walker” offers a new approach for storing large amounts of information
on a tiny chip and demonstrates that concepts from the world we live in can
be duplicated at the nanometer scale – the scale of atoms and molecules.
The molecule – 9,10-dithioanthracene or “DTA” – has two linkers that act as feet.
Obtaining its energy from heat supplied to it, the molecule moves such that only
one of the linkers is lifted from the surface; the remaining linker guides the
motion of the molecule and keeps it on course. Alternating the motions of its
two “feet,” DTA is able to walk in a straight line without the assistance of
nano-rails or nano-grooves for guidance.
The researchers will publish their work in next month's issue of Physical Review
Letters.
“Similar to a human walking, where one foot is kept on the ground while the other
moves forward and propels the body, our molecule always has one linker on a flat
surface, which prevents the molecule from stumbling to the side or veering off
course,” said Bartels, assistant professor of chemistry and a member of UCR's
Center for Nanoscale Science and Engineering. “In tests, DTA took more than 10,000
steps without losing its balance once. Our work proves that molecules can be
designed deliberately to perform certain dynamic tasks on surfaces.”
Bartels explained that, ordinarily, molecules move in every unpredictable direction
when supplied with thermal energy. “DTA only moves along one line, however, and
retains this property even if pushed or pulled aside with a fine probe.” Bartels
said. “This offers an easy realization of a concept for molecular computing proposed
by IBM in the 1990s, in which every number is encoded by the position of molecules
along a line similar to an abacus, but about 10 million times smaller. IBM abandoned
this concept, partly because there was no way to manufacture the bars of the
abacus at molecule-sized spacing.
“DTA does not need any bars to move in a straight line and, hence, would allow
a much simpler way of creating such molecular memory, which would be more than
1000 times more compact than current devices.”
The UCR research team is now trying to build a molecular ratchet, which would
convert random thermal oscillation into directed motion. “It would be similar
to an automatic watch that rewinds itself on the arm of the bearer – except that
it would be just one nanometer in diameter,” Bartels said.
A nanometer is one billionth of a meter. A nanometer is to a meter what an inch
is to 15,783 miles, more than half the distance around the Earth's equator.
Bartels was assisted in the study by Ki-Young Kwon, Kin L. Wong and Greg Pawin
of UCR; and Sergey Stolbov and Talat S. Rahman of Kansas State University. The
US Department of Energy funded the research. Additional support came from the
Petroleum Research Fund and the Air Force Office of Scientific Research. The
San Diego Supercomputer Center provided computational resources.
Related Links:
- UCR Department
of Chemistry
- Center
for Nanoscale Science & Engineering Additional
Contacts:
- Ludwig
Bartels The University of California, Riverside
is a major research institution and a national
center for the humanities. Key areas of research
include nanotechnology, genomics, environmental
studies, digital arts and sustainable growth
and development. With a current undergraduate
and graduate enrollment of nearly 17,000, the
campus is projected to grow to 21,000 students
by 2010. Located in the heart of inland Southern
California, the nearly 1,200-acre, park-like
campus is at the center of the region's economic
development.
Visit www.ucr.edu or
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