A 'micro-windmill' designed
by researchers with the University of Texas at Arlington is shown on top of
a penny. The device's designers say the windmills could be used in the
future to charge cellphones or power homes. (University of Texas at
Arlington)Researchers in Texas have created a windmill so
small it appears as a speck on the surface of a penny. But they say a
multitude of the micro-machines, linked together, could someday generate
enough energy to charge up a cellphone or a house.
"Imagine your
phone is out of battery, so you take out a sleeve that has 1,000 windmills
on it and wave it in the air for a few minutes," said Jung-chih Chiao, an
electrical engineering professor at the University of Texas at Arlington.
"That could give you enough power to get by and send a message."
The
micro-windmill is only 1.8 millimetres at its widest point. As many as 10 of
the tiny devices could fit on one grain of rice.
Chiao, who designed
the micro-windmill prototype with research associate Smitha Rao, said it was
fabricated using nickel alloy components that are flexible and
durable.
The device was built using a subset of the micro-fabrication
process for the tiny semiconductors used in everyday electronic
circuits.
Origami principles usedThe windmills are
then constructed from ultra-thin slices of semiconductor material known as a
wafers.
"A windmill is a three-dimensional structure, but the
semiconductor fabrication technique is two-dimensional," Chiao told CBC News
from Arlington.
"So how do you do it? A simple way of thinking about
this is like origami."
Assembling windmills using tweezers and
constructing them like gingerbread houses would be too difficult due to the
micro-scale of the assembly, he said.
"But with origami, sometimes
you fold one side and the other side will stand up. We're using that kind of
principle," Chiao said, adding that producing one micro-windmill would cost
the same as making 1,000 because they would be on the same
wafer.
While the University of Texas team has not been able to
disclose how much electricity was generated with the micro-windmill, because
of a patent application that's still being filed, Chiao said the use of
thousands of the windmills together could eventually provide enough power to
run a household's security, communication and lighting
systems.
Dust friction a challenge"We got the idea
because I didn't want to put a big wind turbine in my backyard, but I have a
lot of wind there because I live near an airport," Chiao said. "I thought,
'Can I just set something up so I can power a sensor or light at
night?'"
A flat panel of 10,000 micro-windmills mounted on a six-foot
by six-foot window might be able to do the trick, he says.
Similarly,
a smartphone case studded with windmills could be useful in emergency
situations after the sun has set and a person needs to contact the outside
world but has run out of battery. Even holding the phone out for several
minutes during a windy day could power up the battery, Chiao
says.
"Sometimes there's not enough solar energy and sometimes you
don't have the connector available that can plug into the power outlet," he
said.
Chiao and Rao, who works with micro-robotic devices, are now in
talks with the Taiwanese fabrication foundry WinMEMS Technologies Co., about
commercializing their invention.
The researchers are still exploring
potential physics challenges that might limit the design, such as friction
problems that might occur if a piece of dust jams the mini-rotor
blades.
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