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 "Smart dust" particles self-assemble on drops of oil in water. The
microscopic particles are flakes of porous silicon manufactured on the
nanometer (one billionth of a meter) scale. The sensors can
spontaneously assemble, orient, sense, and report on their local
environment.
Researchers hope to use such tiny, cheap sensors to
measure all manner of ecological variables, from chemicals in the soil
to scents in the air.
Photograph by Jamie Link, UCSD
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November 14, 2006
Part of the Digital Places Special News Series
More Digital Places Stories>>
Dust is usually a nuisance. But "smart dust" could revolutionize how we monitor and understand the world around us.
Smart dust is the name researchers have given to the idea of having
handfuls of tiny, cheap sensors called motes that can be scattered
around to measure all manner of things in the environment, from
chemicals in the soil to scents in the air.
So far, the motes that are the size of dust particles aren't
that smart, and the smart ones are far bigger than dust, as Michael
Sailor puts it.
But Sailor, a chemist at the University of California, San
Diego, and many other researchers are working on making the smallest
motes smarter.
Sailor's group develops sensors less than a hair's breadth
across. But each small device can do only one simple job: detect a
certain chemical.
Other researchers are working at the problem from the opposite
direction, with complex sets of sensors assembled in a box about the
size of a cell phone.
Along with the sensors, the boxes contain equipment such as cameras,
computer chips, and wireless communications technology for linking the
sensors together to form a network. (Related news: "GPS-Equipped Pigeons Enlisted as Pollution Bloggers" [October 31, 2006].)
As high-tech gadgets get smaller and cheaper, these two research
avenues are bringing the "smart" side and the "dust" side ever closer
together.
"If we tried to build these [sensors] 15 years ago, they would have
cost millions of dollars" a piece, said Michael Hamilton, director of
the James San Jacinto Mountains Reserve, run by the University of
California.
"Today they cost hundreds of dollars. And we expect in ten years, they'll be just a few dollars."
"Technology Playground"
At the James Reserve, nestled in the mountains of southern California,
Hamilton oversees a pioneering project in which arrays of larger but
smarter sensors watch the minutiae of life, revolutionizing ecological
studies.
"The James Reserve is this wonderful technology playground now," Hamilton said.
The reserve is collaborating with the Center for Embedded Network
Sensing at the University of California, Los Angeles, where center
researchers build all sorts of experimental equipment.
"We get to try out everything from very small wireless devices
for measuring microclimate, [to] development of miniature camera
systems … that can detect patterns in animal behavior or … color
changes that might relate to flowering," Hamilton said.
They also have inconspicuous cameras watching birds' nests to monitor how many eggs hatch.
Birds' reproductive success is closely tied to climate, since
the temperature has to be in the right range for eggs to develop
properly and for the birds to find enough food to feed their
hatchlings.
(Related news: "Early Birds: Is Warming Changing U.K. Breeding Season?" [June 3, 2003].)
The system has revealed that "there's a lot more nest failure
than we expected," Hamilton said. Before, the team simply couldn't keep
track of how many eggs failed to hatch, and "we didn't know why they
failed."
Now the researchers can answer such questions, and hope to someday use
their fine details to put together answers to big issues in ecology.
"The holy grail of all this is: Can we forecast change?" Hamilton said.
Smart Sand
Meanwhile, Sailor, the UCSD chemist, is striving to create
cheaper, smaller, cleverer motes that would also address environmental
problems.
One of his group's main projects could be called smart sand.
His team's sensors are engineered at the nanoscale—the size of
molecules—and are cheap because they're etched out of flakes of
silicon, the stuff of computer chips and beaches.
"They're basically made of sand," Sailor said.
Sailor's smart sand reflects a specific color of light because it's
made in extremely thin layers. The same effect gives beetles and
butterflies their iridescent colors.
But unlike insects' bodies, Sailor's sand-size sensors change colors when they come in contact with certain chemicals.
"We've made sarin-gas detectors," Sailor said, referring to the
nerve gas that the Aum Shinrikyo cult used in a set of subway attacks
in Japan in 1995, and Sailor's group is working on many more.
Sailor envisions using such particles to test water for bacterial contamination.
The devices could also be injected into people to find tiny
cancerous tumors before they're large enough to show up on other tests.
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http://news.nationalgeographic.com/news/
2006/11/061114-smart-dust.html
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