Vol. 38, No. 18

3-14-2006
By: Pam Frost Gorder

Materials society honors young theorist

Li's work reveals the secret life of atoms, molecules

The image of a single red blood cell filled the screen of Ju Li's computer. He pressed a button, and the cell started to move. A fine web of protein molecules — a kind of supportive exoskeleton for the cell — shimmered as the cell stretched and contorted.

"This protein cytoskeleton is very important to the function of the cell," Li said. "It behaves like a solid over a short period and can withstand a lot of stress, but if you watch it for a long time, you can see that it actually flows like a glass." (A little background: scientists consider glass to be a hybrid state between liquid and solid, because even after it looks as if it's solidified, glass is still flowing — just very slowly.)

Such revelations are commonplace for anyone who views the microscopic universe with Li's "AtomEye" program.  He created it in large part himself, along with a suite of physics-based materials simulation programs. The goal, he said, was for researchers to be able to run "thought experiments" in which they tweak a material atom by atom.

The discoveries Li has made while using these programs have earned him the Materials Research Society's Outstanding Young Investigator award. The award recognizes superb, interdisciplinary scientific work in materials research by a young scientist or engineer who shows exceptional promise as a developing leader in the materials area. The society chose Li for his "innovative work on the atomistic and first-principles modeling of nanoindentation and ideal strength in revealing the genesis of materials deformation and fracture."

Li said he learned early on how theory, computation and experiments complemented each other.

"As a teenager I was theory-oriented, not as good at experiments," he said. "But I had a buddy who was really good at building stuff like a telescope and model plane, and we got along really well discussing science."

Li graduated from the University of Science and Technology of China and began his doctoral studies at MIT at age 19. Along the way, he worked out his own preference for "doing theory."

"The traditional way was to sit with pen and a scrapbook and think," he said. "But now people are finding that computation and theory are a great help to each other. There are many things in nature that are so complex that you can't easily think about them without a computer, which is sort of like an extended scrapbook.

"But the paper scrapbook part is still key, and will never go out of fashion," he added.

Since coming to Ohio State as an assistant professor of materials science and engineering in 2002, Li has simulated alloys in jet engines and catalysts for fuel cells - materials that are too expensive for scientists to perform many experiments on them. If simulation can reveal what happens inside these materials at a fundamental level, scientists can save time and money. That, Li pointed out, is the theme of the university's Center for the Accelerated Maturation of Materials, where he is an active member.

Li's biggest discovery so far concerns the conditions that cause defects to form in materials. Scientists long wondered how defects, such as a crack, initiate under stress. Li determined that under certain circumstances, vibrational waves can collapse to form a singularity within a material. He and his colleagues developed a model that predicts where a defect will start and what type of defect it will be.

He also is modeling electrically conductive polymers and biological materials. He's just published a paper in Physical Review Letters on how charge carriers called solitons cause polymer chains to bend and twist. He has another paper in the Biophysical Journal that explains how a red blood cell can undergo Houdini-like shape changes to squeeze through a capillary only half its size.

Li will receive his award and a $5,000 prize in a ceremony April 19 at the Materials Research Society meeting in San Francisco. He is the first Ohio State professor to receive this award.

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