A molecular "human" to drive the molecular car.
http://www.newsroom.ucr.edu/cgi-bin/display.cgi?id=1166
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 next month in 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.
--
"Facts are meaningless. You could use facts to prove anything that's even
remotely true!" -- Homer J. Simpson
