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"Smart Dust" Sensors to Be Used for Eco Detection

Mason Inman
for National Geographic News
November 14, 2006
 
Part of the Digital Places Special News Series
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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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