Tech Today Fall07

7/27/2019 Tech Today Fall07

1/5

10

ENGINEERING

NE

W

S

T E C H T O D A Y

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


2/5

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

FOOTHOLD IN CIT


3/5

12

ENGINEERING

NE

W

S

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.


4/5


5/5

Documents

Tech Today Fall07