August 20, 2002
Good things come in small packages, people say. Yunfeng Lu, assistant professor in Tulane's chemical engineering department, agrees, and he's engaged in research to create some of the most interesting and useful small things around. Lu's specialty is the emerging field of nanotechnology, the study of extremely small structures.
"Nanometer means 10-9 meters--one billionth of a meter," says Lu. "A nanostructure material is a material having the critical dimension of usually less than 100 nanometers."
Nanoscientists are therefore concerned with objects the size of molecules and aggregates of molecules. One high-profile success story fueling the desire to create and control extremely small objects is the miniaturization of electronic and especially of computer components that has been achieved over the last several decades.
Nanotechnology, with its vision of new methods of fabrication geared to an entirely new scale, holds out the promise of even smaller and faster computer components. Interest in nanotechnology and its many possible benefits is worldwide. In January 2000, President Bill Clinton issued an executive order establishing the National Nanotechnology Initiative, together with a budget request for $225 million to fund a full spectrum of nanotechnology research projects.
Since then, the United States has increased its research budget to some $500 million. Other countries around the globe are generously funding nanoresearch as well, each one competing to be the first nation to sponsor breakthrough developments. Behind this investment is the conviction that nanotechnology presents humanity with an opportunity amounting to a new industrial revolution. Developing the ability to manipulate matter precisely at the molecular level, it will revolutionize the way medicines, electronic components, and other products are manufactured and used, says Lu.
A few of the anticipated benefits include detecting cancers before they spread, creating materials with super strength and vastly increasing data storage and processing capabilities. Some of these goals may not be achieved for years, but many aspects of nanotechnology are already moving from the realm of fundamental research to commercial applications.
Lu's research at Tulane is on this track. A 1998 doctoral graduate of the University of New Mexico, Lu worked for a year at Sandia National Laboratory in Albuquerque, N.M., then briefly for a private company before coming to Tulane. One focus of his work is on developing new materials for use in fabricating computer microchips.
"Right now I have a research grant to develop a thin film material for use in separating the different layers making up a computer microchip," says Lu. One of the distinguishing features of nanotechnology is the exotic set of forces at work in the nano-realm. "When you get down to the nanostructure scale," says Lu, "there are all kinds of unique properties that may be totally different from those possessed by conventional bulk."
Using a fabrication process unique to the scale of nanostructures, Lu's computer chip film is "self-assembled" by the predictable, spon-taneous actions of individual molecules. Nanostructure manufacturing techniques rely on an understanding of the structural and interactive properties of materials at the molecular level. "These are what we call bottom-up fabrication methods, contrasted with top-down methods," says Lu.
Another commercial application Lu is developing is the use of nanostructure materials as chemical sensors for water pollution. "We use a highly porous material that entraps molecules of all the pollutants," says Lu. "Then we can determine what kinds and how much pollution there is." He has designed fabrication techniques for nano-composite thin films for use as super-tough coatings.
"These films are modeled on the structure of seashells," says Lu. "If you look at a section of an abalone shell under an electron microscope, you see layers of calcium carbonate. Between them are layers of organic bio-polymer, a protein. Cracking cannot propagate through the whole structure--you can only break individual layers. So the structure is very tough."
Lu also is working on materials with medical and biological applications. He has developed a nanomaterial that self-assembles in the form of an onion-like structure of concentric spheres. The structure can be used for the timed-release of drugs or other chemicals by placing them inside the spheres at the manufacturing stage. Nanotechnology for a greener environment also is being advanced at Tulane.
Lu and C.J. Li, professor of chemistry, are together developing nanostructured catalysts that can improve the emission control of vehicles or can reduce the use of atmosphere-harming solvents by enabling water to function as a solvent in industrial cleaning applications. "That's the magic of nanostructure materials," says Lu.
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