TechKnowledgey 2004
by Jeff Eckert
TechKnowledgey
2004
Events, Advances, and News
From the Electronics World
Advanced
Technologies
New Cooling Technique for
Electronic Devices
Close-up of a prototype synthetic jet
(SynJet).Vibrating diaphragms (on right)
produce trains of turbulent air puffs that
flow out of the white tubes and into the
cooling fins of the electronic device. Photo
by Gary Meek, courtesy of Georgia Tech.
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NUTS & VOLTS
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You have probably noticed that
today's microprocessors and
other devices have presented designers with thermal management problems in recent years.
The traditional approach has
been to simply employ larger
heatsinks and more powerful fans.
However, heatsinks can take up a lot
of space, and cooling fans have
mechanical limitations.
For example, much of the circulated air bypasses the heatsinks and
does not mix well with the thermal
boundary layer that forms on the
fins. Fans placed directly above
heatsinks have "dead areas" where
their motor assemblies block air
flow.
E
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And, as designers boost air flow
to increase cooling, fans use more
energy, create more noise, and take
up more space. Researchers at the
Georgia Institute of Technology
( www.gatech.edu) have concluded
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that conventional fan-driven cooling
is incompatible with future high-density, low-power systems and
therefore have been working on alternative solutions. A concept that
seems to have great potential is their
patented synthetic jet (SynJet)
device. The operating principle is
simple. Perhaps you have demonstrated the amazing power of your
stereo system by letting the "woofer"
blow out a lighted match.
In much the same manner, the
SynJet uses an electromagnetic or
piezoelectric driver, vibrating at a
rate of 100 to 200 Hz, to suck in and
then expel air from a cavity.
This creates pulsating jets that
are directed to precise locations
where cooling is needed. According
to the inventors, the device is better
than a fan in that it has no friction
parts to wear out, uses less energy,
and creates less noise. They point
out that, although the jets move 70
percent less air than fans of comparable size, "the air flow they produce
contains tiny vortices which make
the flow turbulent, encouraging efficient mixing with ambient air and
breaking up thermal boundary layers. You get a much higher heat
transfer coefficient with synthetic
jets, so you do away with the major
cooling bottleneck seen in conventional systems." Furthermore, "The
ability to scale the jet modules to suit
specific applications and to integrate
them into electronic equipment
could provide cooling solutions over
a broad range of electronic hardware
ranging from desktop computers to
mobile phones, and other portable
devices that are now too small
or have too little power for active
cooling."
Plastic Memories May Offer
High-Density Storage
Engineers at Princeton University
( www.princeton.edu) and
Hewlett-Packard ( www.hp.com)
have discovered a combination of
materials that could lead to cheap
and super-compact electronic memory devices for archiving digital
images or other data. The invention
could result in a single-use memory
card that permanently stores data
and is faster and easier to use than a
compact disk. The device could be
very small, because it would not
involve moving parts such as the
laser and motor drive required by
CDs. The concept is based on poly-ethylenedioxythiophene (PEDOT), a
polymer material that is clear and
electrically conductive. It has been
used for years as an antistatic coating on photographic film, and more
recently as an electrical contact on
video displays that require light to
pass through the circuitry. PEDOT
conducts electricity at low voltages
but permanently loses its conductivity when exposed to higher voltages
(and thus higher currents), making it
act like a fuse or circuit breaker. This
led the researchers to think about
using PEDOT as a way of storing digital information. As we all know, digital images and computer data are
stored as long strings of ones and
zeroes. A PEDOT-based memory
device would have a grid of circuits
in which all the connections contain
a PEDOT fuse. A high voltage could
be applied to any of the contact
points, blowing that particular fuse
and leaving a mix of working and
nonworking circuits. These open or
closed connections would represent
FEBRUARY 2004
