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The last paper Bartels and his team published on
this subject generated a great deal of interest. It was included in
the American Institute of Physics "Top 25 Physics Stories for 2005."
The new molecule carrier runs on a copper surface. It can pick up and
release up to two carbon dioxide (CO2) molecules and carry
them along its straight path.
"Carrying a load slows the molecule down" explained
Bartels. "Attachment of one CO2 molecule makes the carrier
need twice as much energy for a step, and a carrier with two CO2s
requires roughly three times the energy. This is not unlike a human
being carrying heavy loads in one or both hands." Bartels explained
that using machines at the scale of single molecules will ultimate be
the most efficient way to build objects or to deliver material.
"It resembles the way nature does it: the molecule
carrier transports carbon dioxide across a surface," he said. "In the
human body, the molecule hemoglobin carries oxygen from and carbon
dioxide to the lungs, thereby allowing us to breathe – and to live."
Bartels cautions, however, that this research is
still in its infancy. "In 2005 we invented the molecular walker, which
moves in a straight line rather than hopping around in all directions
as a normal molecule would do. Now it can carry a load."
Bartels said the continuing evolutionary process
will take some time.
"Ten years ago, a cell phone could just place calls,
nothing else. Now it plays mp3-files, organizes your day, lets you
send emails and browse the web." He said his team will be pursuing the
next step for this molecule carrier. "Next, we would like to be able
to make one go around corners, rotate its cargo or send out photons to
tell us where it is."
The molecule carrier is anthraquinone, which
consists of three fused benzene rings with one oxygen atom on each
side. An organic compound, anthraquinone is widely used in the pulp
industry for turning cellulose from wood into paper. It is also the
parent substance of a large class of dyes and pigments. Its chemical
formula is C14H8O2.
The UCR study used a scanning tunneling microscope
in Bartels's laboratory that gives a precise picture of individual
molecules. Experiments took place on a highly polished copper surface,
cleaned so that only the desired molecules were present on it. An
individual anthraquinone molecule appears in Bartels' microscope as an
almost rectangular feature with slightly rounded edges. |
