Clarifying how and why materials undergo sometimes dramatic changes when confined to nanoscale dimensions is the focus of a $400,000 National Science Foundation Early Career Development (CAREER) award received by Thomas Truskett, a chemical engineer at The University of Texas at Austin.

CAREER awards, given to future academic leaders, are the foundation's most prestigious grants for young teacher-scholars.

Understanding the classical physics behind the hyper-miniaturization of different types of materials has practical implications.

“We’d like to know how materials with very small dimensions differ from regular materials in their properties,” said Truskett, an assistant professor in chemical engineering. “That knowledge could help guide the development of smaller, faster computer chips, new medical devices and composite materials for more reliable military armor or sporting equipment.”

When a material extends millimeters or longer in length, most of its atoms are buried below the surface and interact only with each other, so they behave uniformly. Surface exposure for molecules becomes much more pervasive when a material’s dimensions are limited to tens of nanometers, and this change in environment causes the molecules to behave in very different and unexpected ways. For example, liquid water at room temperature will spontaneously vaporize when squeezed between oily nanoborders, while solids can abruptly become runny like a liquid, changes that have broad implications for the performance of nanodevices.

To study nanomaterial stability, Truskett’s laboratory initially will focus on “nanocomposite” metals, which have been created to have atomic structure on nanometer lengthscales. These “metallic glasses” are so-named because their atoms are arranged randomly, as occurs in common window glass. This randomness makes the material more flexible than steel, but also makes it more challenging to predict how the material will behave under different circumstances.

Truskett’s solution begins with an equation scientists use to represent how the potential, or usable, energy of a standard-sized material varies in comparison to its density and other properties. He will determine how this “potential energy landscape” changes when the same material is miniaturized. By comparing the energy landscapes of the material at the different length scales, he will gain insight into what factors cause a material to lose solidity and mechanical stability, or undergo other changes, when nano-sized.

Computer simulations suggest the approach successfully predicts these changes.

“No matter what we’re looking at – mechanical properties, thermal properties, or a dynamic property such as how fast the material responds to stimuli – all of these can potentially be predicted from this one comprehensive approach,” Truskett said.
       
Last fall Truskett also received a five-year, $625,000 David and Lucile Packard Fellowship in Science and Engineering to further his group’s work in understanding nanomaterials and the behavior of protein molecules in pharmaceutical and biological environments. In addition to furthering this work, he will use the current CAREER grant to develop new courses that increase engineering majors’ nano-knowledge based on his expertise.

Note: For photos of Dr. Truskett, go to: www.engr.utexas.edu/news/action_shots/pages/Truskett_2005NSFCareer.cfm