A NEW REFLECTION IN THE MIRROR; insulating tiny batteries
Posted on Wednesday, January 10, 2007 @ 20:45:19 UTC by vlad
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A NEW REFLECTION IN THE MIRROR, January 10
A research group has devised a
new type of mirror that reverses the magnetic field of a light wave upon
reflection, rather than its electric field, as regular mirrors do. Seems like a
minor difference? It's not.
Full story at http://www.physorg.com/news87647182.html
A HOT IDEA FOR INSULATING TINY BATTERIES, January 10
Engineering physics
researchers are devising a unique "blanket" that will enable them to squeeze as
much electricity as possible from nuclear-powered batteries the size of a grain
of coarse salt.
Such batteries, which exploit the natural decay of
radioisotopes to generate electricity, could provide virtually
indefinite power for micro-technologies like fly-sized robots for
military applications or sensors that monitor a building's health.
Other technologies such as fuel cells, chemical batteries or
turbine generators also might work in micro-scale applications, says
Professor James Blanchard. "But all of them are short-lived," he says.
"They either need to be recharged or refueled. Our niche is things that
need to be placed and ignored, and just keep running for years."
Nuclear microbatteries convert heat or energy to electricity more
efficiently when they are hot, so it makes sense to insulate them, says
Blanchard. "The better the insulation, the hotter the source gets, so
the more efficient the battery can be," he says.
However, insulating a millimeter-square battery in a way that
minimizes heat loss is no easy task. Multifoil insulation is an
effective macro-level insulator that combines several thin layers of
foil each separated by a vacuum. "They work because they're radiating
heat from one layer to another, as opposed to conducting heat through a
solid," says Blanchard.
For the microscale, however, multifoil insulation is far too thick.
So, capitalizing on the layered concept, which reduces heat
radiation for a fixed temperature drop, Blanchard and graduate student
Rui Yao decided to sandwich semicircular silicon oxide pillars-poor
conductors-between very thin silicon sheets.
"You want as little conduction through these pillars as possible," says Blanchard.
They developed elaborate computer models to study the heat
radiation and conduction of their microscale insulaton. And, using
Wisconsin Center for Applied Microelectronics clean room facilities,
Yao constructed silicon prototypes.
He now is experimentally verifying what his computer models
suggest-that heat is radiating through the silicon layers without much
heat loss. "The prototypes he built are a little thicker than the ones
we ultimately want to get, but they're consistent with his models,"
says Blanchard.
Funded by a three-year, $300,000 Department of Energy grant and
inspired by an earlier collaboration with Sandia National Laboratory
researchers, Blanchard and Yao are still testing and refining the
insulation. Implementation for this promising technology, they say, is
a couple of years down the road.
"It looks like we'll have an effective insulator that's better than
any solid-and better, even, than some of the multi-foil insulations
that you can buy commercially," says Blanchard.
Source: University of Wisconsin
Link: http://www.physorg.com/news87664837.html
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