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THROUGH THE SALLYPORT
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Bacteria Power
Introducing the World’s First Motorized Nanocar
The U.S. Air Force has long been interested in microscale air vehicles—
In follow-up work to last year’s groundbreaking invention of the
some as small as insects—to serve as spy drones, but it has been stymied
world’s fi rst single-molecule car, chemists at Rice University have
by the lack of a suitable, compact power source. But a diverse team of
produced the fi rst motorized version of their tiny nanocar.
researchers from Rice and the University of Southern California (USC)
thinks it has discovered a power source small enough: bacteria.
Rice geochemist Andreas Lüt- cade-long collaboration with
tge will spearhead the team principal investigator Ken-
of microbiologists, engineers, neth Nealson, a USC profes-
and geochemists as they join sor who helped pioneer the
forces to create bacteria fuel fi eld of modern geobiology
y
ersit
cells that could power palm- and the investigation of the
size spy drones and other genetic pathways that some
electronic devices. Fueled microbes rely on to maintain
by a $4.4 million grant from their respiratory metabolism
the Department of Defense’s in oxygen-poor environments.
Y
asuhiro Shirai, Rice Univ
Multidisciplinary University Shewanella oneidensis uses
y
Research Initiative, the Rice– metals instead of oxygen to
USC research team hopes to fully metabolize its food.
Graphic b
prove its concept valid within “Since this organism is ca-
“We want to construct things from the bottom up, one molecule at
fi ve years by producing a self- pable of passing electrons di-
a time, in much the same way that biological cells use enzymes to
propelled prototype. rectly to solid metal oxides,”
assemble proteins and other supermolecules,” says James Tour, the
The key is understanding Nealson explains, “it is not
Chao Professor of Chemistry, professor of mechanical engineering and how the bacteria Shewanella particularly surprising that it
materials science, and professor of computer science. “Everything oneidensis attach to can do the same to
that’s produced through biology—from the tallest redwood to the
and interact with the anode of the
largest whale—is built one molecule at a time. Nanocars and other
anode surfaces in- fuel cell. It seems
synthetic transporters may prove to be a suitable alternative for
side the fuel cell. a reasonable step
bottom-up systems where biological methods aren’t practical.”
Anodes are the to apply the same
The nanocar consists of a rigid chassis and four alkyne axles that
parts of fuel cells approaches to un-
and batteries that derstanding cur-
spin freely and swivel independently of one another. It measures just
gather excess elec- rent production.
3-by-4 nanometers and is about the same width as a strand of DNA,
trons for harvest- What is new here
but much shorter. Approximately 20,000 of them could be parked
ing. To optimize is the incorpora-
side by side across the diameter of a human hair. They are the fi rst
its design, the team tion of colleagues
nanoscale vehicles with an internal motor.
must understand in chemistry, geol-
The motorized model of the nanocar is powered by light. Its rotating how bacteria trans- ogy, engineering,
motor, a molecular framework that was developed by Ben Feringa fer electrons to an- and evolutionary
at the University of Groningen in the Netherlands, was modifi ed by
ode surfaces under Rice geochemist Andreas biology to opti-
Tour’s group so it would attach in line with the nanocar’s chassis.
a variety of condi-
Lüttge will spearhead the
mize the entire
When light strikes the motor, it rotates in one direction, pushing the
tions. system, not just
team of microbiologists,
car along like a paddlewheel. The four buckyball wheels that were
“There are three the bacteria.”
primary compo-
engineers, and geochemists
used in the original version of the nanocar drained energy from the
The research-
nents in the sys- as they join forces to cre- ers still have a lot
motor and were replaced with spherical molecules of carbon, hydro-
tem: the bacteria, to learn about the
gen, and boron called p-carborane.
ate bacteria fuel cells that
the surface, and chemical cues that
Initial tests carried out in a bath of toluene solvent found that the
could power palm-size spy
the solution that the Shewanella
motor rotates as designed. Follow-up tests are under way to determine
the bacteria are di-
drones and other electronic
use—both individ-
whether the motorized car can be driven across a fl at surface.
gesting,” says Lüt- devices. ually and in colo-
The research appeared in the April 13 issue of Organic Letters. tge. “Any change nies—but they are
Other members of the research team include postdoctoral associ- in one variable will incredibly effi cient
ate Jean-François Morin and doctoral student Yasuhiro Shirai. The
affect the other at converting or-
research was funded by the National Science Foundation, the Welch
two, and what we want to do ganic inputs to electricity. “We
Foundation, Honda, the Natural Sciences and Engineering Research
is fi nd out how to tweak each are confi dent,” Lüttge says,
Council of Canada, and Le Fonds Québécois de la Recherche sur la
one to optimize the perfor- “that they’ll be great candi-
Nature et les Technologies.
mance of the whole system.” dates for our fuel cells.”
Lüttge’s participation in
—Jade Boyd
—Jade Boyd
the program grew out of a de-
10 Rice Sallyport
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