"Prominent scientists, including Sir David Attenborough and Richard Dawkins, have called on the government to toughen its guidance on the promotion of creationism in classrooms, accusing "religious fundamentalists" of portraying it as scientific theory in publicly funded schools.

Today's wireless-sensor networks can do everything from supervising factory machinery to tracking environmental pollution to measuring the movement of buildings and bridges. Working together, distributed sensors can monitor activity along an oil pipeline or throughout a forest, keeping track of multiple variables at a time.

While uses for wireless sensors are seemingly endless, there is one limiting factor to the technology — power. Even though improvements have brought their energy consumption down, wireless sensors’ batteries still need changing periodically. Especially for networks in remote locales, replacing batteries in thousands of sensors is a staggering task.

To get around the power constraint, researchers are harnessing electricity from low-power sources in the environment, such as vibrations from swaying bridges, humming machinery and rumbling foot traffic. Such natural energy sources could do away with the need for batteries, powering wireless sensors indefinitely.

Now researchers at MIT have designed a device the size of a U.S. quarter that harvests energy from low-frequency vibrations, such as those that might be felt along a pipeline or bridge. The tiny energy harvester — known technically as a microelectromechanical system, or MEMS — picks up a wider range of vibrations than current designs, and is able to generate 100 times the power of devices of similar size. The team published its results in the Aug. 23 online edition of Applied Physics Letters.

“There are wireless sensors widely available, but there is no supportive power package,” says Sang-Gook Kim, a professor of mechanical engineering at MIT and co-author of the paper. “I think our vibrational-energy harvesters are a solution for that.”

Putting the squeeze on

To harvest electricity from environmental vibrations, researchers have typically looked to piezoelectric materials such as quartz and other crystals. Such materials naturally accumulate electric charge in response to mechanical stress (piezo, in Greek, means to squeeze or press). In the past few years, researchers have exploited piezoelectric material, or PZT, at the microscale, engineering MEMS devices that generate small amounts of power..."

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