tech today fall07
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Put an ice cube on your kitchen counter and it will melt. But how does it
melt? What is happening at the microscopic level? When it is melting,
is it liquid or solid or something in between? Figuring out how atomsbehave in a chunk of ice may not seem the makings of high science, but it is. Especially if
you think about ice and basically all materials in a broader, fundamental way: What hap-
pens to a materials structure as it changes its form? And what conditions bring about these
changes? These are the same principles that govern everything from catalyst reactivity to
superconductivity.
Fundamental questions intrigue Mohammad Islam, an engineer who turns to science
for inspiration. This year, the young researchers penchant for wanting to understand how
things work earned him both an NSF CAREER Award and an Alfred P. Sloan Award.
Islam, a professor in chemical engineering and materials science and engineering,
explains that when alloying elements are added to iron to make steel, making it very strong,
changes have occurred to the materials structure at the sub-micron level.
There must be reasons why the structure changes and gives rise to new properties
that we want. Wouldnt it be great if we could understand this phenomena and tailor it?
asks Islam. To this end, he and his research group synthesize colloids, which can be thoughtof as micron-sized atoms, and use them as building blocks to make structures generally
formed by atoms. By working with colloids instead of fast-moving Angstrom-sized atoms, he
can view the colloids behavior within a three-dimensional material in real time with an optical
microscope. These experiments are not possible in structures formed by atoms because
visualizing the atoms would be extremely difficult.
From Nanomaterials to Macro-Applications
Presently, Islam is working with carbon nanotubes, which
are a micron in length and a nanometer in diameter. They
are rigid and strong, much stronger than steel. They con-
duct heat better than diamond, yet their density is close
to that of air. Impressed with these attributes, Islam has
set out to make macroscopic composite materials that
incorporate the same properties of tiny carbon nanotubes.
Then the question becomes: Can we put carbon nano-
tubes into polymers and make the composite material
very strong with high heat conductivity but maintain the
polymeric malleability? he said. Polymers are generally
nonconducting and lack strength.
The applications go on: If carbon nanotubes can
increase the conductivity of polymers, can they dissipate
heat from electronic chips? This would allow a more
compact circuitry with higher performance for smaller,
more powerful computers. Also, if Islam and his team can
quickly and cheaply produce exceptionally strong and light
THE NSFRECOGNIZESGREAT TALENT
THE BEST OF
BOTH WORLDS
Mohammad Islam and his research
group synthesize colloids and use them
as building blocks to make structures
generally formed by atoms.
This year, three CIT faculty membersFred Higgs, Mohammad Islam, and Ken Maiearnedthe National Science Foundations Faculty Early Career Development (CAREER) Award. These
important awards, along with sizable funding, are given to young professors who are doing an
exemplary job integrating education and research. We have no doubt that these individuals
will make significant contributions to engineering and inspire students to follow their leads.
B Y S H E R R Y S T O K E S
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Whether you are fabricating arti-
ficial hip joints or computer chips,
you have particles in between rub-
bing surfaces that cause wear. We
are developing computer models to
predict this general problem, and
were doing state-of-the-art experi-
ments to validate the models.
carbon nanotube composites, they could be used in aircrafts or cars. He says, If we can
make a car that weighs a hundred pounds and its body is strong like steel, wouldnt that be
better for the environment?
These materials can be used for biological applications, too. He explains that carbon
nanotubes can be coated with biological polymers and used to deliver drugs or genes inside
human cells. So, then the question becomes, what is the effect of having this foreign
material inside your cell? Is it toxic? Can you use these materials for drug delivery without
having a negative impact on your health? These are some of the questions we are asking,
and we are doing experiments that explore this, concludes Islam.
Tribology. You may not know
the word, but engineers are
certainly familiar with the
concepts that comprise this highly specialized area of
study: friction, lubrication, and wear.Many engineers do not understand what tribol-
ogy is because it is such a broad and diffuse topic. It
usually shows up as friction-related problems. Or with
mechanical engineering and materials science devices,
the great showstopper is adhesion, where surfaces
stick together, and thats a tribology problem, too,
says C. Fred Higgs III.
Joining Carnegie Mellon in 2003, Higgs is
the first professor to teach tribology in mechanical
engineering, and he is earning impressive accolades,
including the NSFs Early Career Development Award.
For the next five years, Higgs will receive a
total of $400,000 from the NSF to develop computer
models that will predict how surfaces will wear whenthey are under a load and rub together. Complicating
the matter is the fact that debris or foreign particles
will affect wear, too. Higgs says that many industries,
ranging from data storage to biotechnology, deal with
friction and surface-wear problems caused by abrasive
nanoparticles that are sandwiched between rubbing
surfaces.
Illustrating his point, Higgs explains how artificial hips deteriorate over time. In the
human hip, the femur (the top of the leg bone) moves around in the cup-like acetabulum,
forming the hip joint. In the hip joint, a thick liquid called synovial fluid keeps the femur
lubricated, reducing friction and easing movement.
But in an artificial hip, we are not able to create the same conditions. While there
are some fluids in the joint, they are unable to give complete separation of the surfaces.
Because of that contact, you get wear on the artificial hip, and nanoparticles begin toaccelerate the wear. After 10 or 15 years, the hip needs replaced again, says Higgs.
Whether you are fabricating artificial hip joints or computer chips, you have particles in
between rubbing surfaces that cause wear. We are developing computer models to predict
this general problem, and were doing state-of-the-art experiments to validate the models,
he says. For example, Higgs developed a sophisticated algorithm on particle augmented
mixed lubrication (PAML), which can predict wear in hip joints and in fabricating computer
chips. Consequently, Carnegie Mellon, along with Higgs and his recently graduated Ph.D.
student, Elon Terrell, filed for a patent on the PAML algorithm, which is the engine behind
these computer models. The algorithm enables Higgs to develop what he calls in silico
modeling simulations, where the actual engineering process, such as the polishing of
computer chips or the wear of artificial hip joints, is simulated on a computer without
TRIBOLOGY GAINS
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omitting the complex physics involved. By doing in silicomodeling (a termed coined by Higgs
colleague at the University of Florida), he can run computer experiments that very closely
mimic the actual physical experiments that his group is conducting in the lab to validate their
models. Some of the companies interested in testing the PAML model on their devices are
Hitachi, Seagate, and the Data Storage Institute in Singapore.
The work that Higgs and his students are involved in will affect a variety of technolo-
gies, including integrated circuits and data storage nanotechnology, coal flow energy systems,
dental tribology, and, of course, total joint replacements.
If you look at the way computing machines are built, they fall
into two broad groups: hardwired systems that have fixed
hardware functionality and reconfigurable systems that enable
people to define what their systems will do at the hardware level.
You really havent seen very much of the reconfigurable world creeping into the hard-
wired microprocessor world, says
Ken Mai, a professor in electrical and
computer engineering. He explains
that reconfigurable logic has lower
performance and efficiency than logic
hardwired for the same function.
But, then again, reconfigurability has
its prosuser-defined functionality,
fast time to market, and the ability to
fix bugs and upgrade hardware if
necessary.
Early in his career, Mai began
exploring the notion of transferring
some aspects of reconfigurability onto
the hardwired side, and he focused
his attention on the memory system.
The memory system is fairly ame-
nable to adding configurability to it be-
cause there arent that many different
things you want to do with memory,
says Mai. He believes that making the
memory reconfigurable will have small
impact on performance and that users
could gain a lot in performance and
efficiency.
This year, Mai received an NSF
Early Career Development Award,
along with $400,000, to explore
options for adding reconfigurability to memory systems at various levels of their design,
including the circuit, microarchitecture, and architecture levels.
One of the more compelling reasons for enhancing the memory system, says Mai, is
that if you look at the way computers are designed, we are at an inflection pointwe are not
really sure what we need to do next.
He explains that in terms of microprocessor design we have hit two walls. One prob-
lem that limits how applications perform is that we cant pull data from the memory system as
quickly as we run calculations. The memory has not scaled the same way as microprocessor
cores have, says Mai.The second wall deals with processor speed. For a number of years, people have been
increasing the clock frequency or the processor rate, says Mai. Today, processing speed
isnt growing as it once had. If you look now, companies arent trying to sell their processors
based on clock frequency, he says. At this point, trying to increase performance by scaling up
the clock rate unacceptably increases the power. Eventually we get to the point where the
microprocessors can no longer be cooled sufficiently in a normal desktop system. With these
fundamental constraints identified, the question becomes, how do we build computing sys-
tems that are robust, easy to operate, reliable, and economically feasible? This question fuels
a large portion of Mais research, and his NSF-funded project will reveal the role reconfigurable
memory systems may play in advancing microprocessor design.
A TALE OF POWER AND
PERFORMANCE
Ken Mai
You really havent seen very much of
the reconfigurable world creeping into
the hardwired microprocessor world.
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