Simanaitis Says

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SCIENCE DUO

IT’S GREAT being a science dilettante, learning just enough about a topic to be fascinated without having to roll up one’s intellectual sleeves and actually do the science.

AAASClose

The weekly Science magazine, published by the American Association for the Advancement of Science, continues to be my primary source for this. Here are two items from Science, 4 January 2013.

Stomp for power. Quite coincidentally, a friend recently pondered whether it was possible to extract power from the impacts of pedestrians using walkways. I didn’t know, but Science reports that researchers at Georgia Tech are working on just such a thing.

At its heart is piezoelectrics, in which certain materials interchange mechanical strain and electrical behavior. Deform the material, and it gives off an electric charge; apply a voltage, and it deforms. A current shortcoming (ha! an electrical pun) is that piezoelectric devices typically generate mere microwatts of power.

Auto engine knock sensors are piezoelectric devices; so are fuel injection pressure sensors. But, thus far, efforts to generate significant power haven’t been as successful.

That is, until researchers at Georgia Tech happened to protect the top of a piezoelectric device with PMMA, one type of plastic, and mount the device on Kapton, a different plastic material. Inexplicably, the gizmo generated significantly more electricity.

After considerable investigation, the researchers concluded that the two dissimilar plastics were rubbing against each other and generating static electricity. This is the sort of thing that happens when you walk around a supermarket, then touch a can on the shelf—and feel a shock.

Initially, the plastic-encased device was generating a maximum potential of 5 volts. By arranging the materials to optimize friction between the electron-rich Kapton and electron-poor PMMA, researchers measured a potential as much as 1000 volts, albeit at a meager current density of around 1 watt per cubic inch.

According to Science, a 6-cm x 6-cm (about 2.4-in. square) device powered by nothing more than foot tapping could recharge a cell phone battery or illuminate a bank of 600 LEDs.

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An advanced piezoelectric generator powers 600 LED bulbs through foot tapping. Image from Science, 4 January 2013.

The researchers are considering packaging this technology in 200 layers, the goal being to harvest ocean power. Large-scale power sources are envisioned producing as much as 10 kilowatts per cubic foot—just, in a sense, by tapping another kind of foot.

A Crocodile’s cracked face. Crocodiles have body, facial and jaw scales of keratinized skin (think human calluses). Patterns of these scales are formed during embryo development. However, specialists in areas as varied as genetics and evolution, computer graphics and crocodile farming have teamed up to study the matter. They propose that two decidedly different mechanisms give rise to the patterns.

The researchers agree with conventional wisdom that a crocodile’s body patterns are genetic. However, they claim that face and jaw scales have less to do with heredity; these scales are random polygon domains rather than genetically controlled elements.

Image

A corn snake, left column, has head scales that are left/right symmetric. A crocodile, center, shows no such symmetry. In fact, right, crocs display different distributions of scale size and pattern. Images from Science, 4 January 2013.

The work used high-resolution 3D geometry to analyze scale size and pattern. Researchers observed a combination of order and chaos akin to an assemblage of soap foam.

They hypothesize that rapid growth of the embryo’s face and jaw causes random cracking that characterizes these scale patterns.

Ain’t science—and Science—neat? ds

© Dennis Simanaitis, SimanaitisSays.com, 2013

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This entry was posted on January 22, 2013 by in Sci-Tech and tagged , , , .
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