A single molecule has been made to walk on two
legs. Ludwig Bartels and his colleagues at the University of
California at Riverside, guided by theorist Talat Rahman of Kansas
State University, created a molecule -- called 9,10-dithioanthracene
(DTA) -- with two "feet" configured in such a way that only one foot at a
time can rest on the substrate.
Activated by heat or the nudge of a
scanning tunneling microscope tip, DTA will pull up one foot, put
down the other, and thus walk in a straight line across a flat
surface. The planted foot not only supplies support but also keeps
the body of the molecule from veering or stumbling off course.
In tests on a standard copper surface, such as the kind used to
manufacture microchips, the molecule has taken 10,000 steps without
faltering. According to Bartels (email@example.com,
951-827-2041), possible uses of an atomic-sized walker include
guidance of molecular motion for molecule-based information storage
or even computation.
DTA moves along a straight line as if placed onto
railroad tracks without the need to fabricate any nano-tracks; the
naturally occurring copper surface is sufficient. The researchers
now aim at developing a DTA-based molecule that can convert thermal
energy into directed motion like a molecular-sized ratchet.
Kwon et al.,
Physical Review Letters, upcoming article