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Nano World: Say "Hello" to Classical Rules March 2008
Recent discoveries by researchers at MITRE have given fresh meaning to the old adage, "everything old is new again." Discoveries in the new field of nanotechnology—the science of the very small—reveal that rules much like those from traditional, classical physics govern key goings-on in the "nano world" of atoms and molecules. This is the surprising conclusion of research published by three MITRE investigators. Their findings seem to contradict much of the conventional wisdom about how the sizes and shapes of tiny bits of matter are connected to their behavior. Knowing the sizes and the shapes of atoms and molecules, their structures, plus how much electrical charge they can hold, is a key to understanding most of chemistry and molecular biology. "It's also important to advances in nanotechnology, the engineering and development of systems integrated on the scale of atoms and molecules," explains James Ellenbogen, leader of MITRE's Nanosystems Group. Since 1992, MITRE's Nanosystems Group has been performing broadly based research and development in nanotechnology. The field of nanotechnology is multidisciplinary, drawing from other fields such as applied physics, materials science, and even mechanical and electrical engineering. For several years, Ellenbogen and his Nanosystems Group collaborators, lead scientist Carl Picconatto, and student technical aide Jacob Burnim, examined in detail how the charge-holding ability of nanometer-scale building blocks, like atoms and molecules, is connected to their sizes and shapes. Following common practice, the team used computer programs that solve the esoteric equations of quantum mechanics, the branch of modern physics that is known to prevail in this tiny world. What did they find? Trends that look a lot like old-fashioned classical physics. Their surprising finding was presented in a paper published in the April 2007 issue of Physical Review A, the foremost journal in the field of atomic and molecular physics. Small World, Big Breakthrough "The tiny, tiny nano world of atoms and molecules is supposed to be a quantum world, which is weird and very different than that predicted by the staid rules of 19th-century classical physics," Picconatto points out. "That's why we had trouble making sense of and believing our own results for a long time. After awhile, though, the data became overwhelming." Picconatto, who is director of MITRE's Nanotechnology Laboratory, bore the brunt of the job of performing the many thousands of hours of computer calculations and experiments that led to the revelation. From 2003 through 2007, he and Ellenbogen collaborated in trying to interpret the trends they discovered in the computational results. Ultimately, these new trends reveal that the connection of the dimensions of molecules to their charging behavior and their energies happens in a very simple way. And contrary to all expectations, the trends look like the ones predicted by classical physics. "What we discovered seems to fly in the face of much of the common thinking in modern physics and chemistry," Ellenbogen says. "But we arrived at our conclusions only after six years of detailed quantum mechanical calculations—and much head scratching. We discovered that the 21st-century quantum world obeys some rules with which a 19th-century electrical engineer or physicist would be right at home." Ellenbogen is quick to add, though, "This work doesn't contradict quantum mechanics. It merely finds a deeper, unsuspected, and simple regularity amidst the quantum complexities." According to the investigators, this linear regularity smoothly joins, along the same straight line, the unusual behaviors observed in the tiny quantum world of atoms and molecules with the more familiar charge storage behavior of large objects in our everyday world. Key Role for a Student Investigator The research from which these new insights arose was initiated in 2000 and 2001 by the third member of the trio, Burnim. At the time, he was a high school student working with Ellenbogen on the design and systems engineering of a nanoelectronic memory system. In fact, that nanomemory design research enabled Burnim to become a finalist in the national 2001-02 Intel Corporation Science Talent Search contest. As they conducted their research, however, Burnim and Ellenbogen noticed unexpected—and hard to understand—regularities predicted in the electrical charging behavior of the molecular wires that were part of the memory design. When Burnim became a full-time university undergraduate student, it fell to Ellenbogen and Picconatto to spend the next several years sorting out what they were observing. The team's efforts were sponsored by MITRE's active research and development program, which seeks both to create new technologies and to apply existing tools and technologies in innovative ways to deliver value for customers. The Nanosystems Group's efforts in nanotechnology focus on systems engineering that starts at the tiny molecular scale and builds up from there. Its work includes the development of systems such as nanoelectronic computers, nano-enabled power systems, nanosensors, and millimeter-scale robots. The resulting insights are typically used to offer wide-ranging assistance to the U.S. government's nanotechnology efforts. This assistance includes collaboration with officials in planning major nanotechnology R&D programs, as well as in tackling key technical tasks on the path to program success—e.g., the simulation, design, and physical testing of nanotechnology-enabled system prototypes. The MITRE team envisions practical applications for their new discoveries. "We believe the simple new 'classical' rules for atoms and molecules will be useful for designing new materials with novel properties," says Ellenbogen. "The new results also are likely to be applied for simulating and analyzing the behavior of molecular-scale electrical devices for next-generation nanocomputers." So it seems that in the nano world, MITRE researchers have made the "old" rules of classical physics new again. And in this new domain, the old rules may very well pave the way to new innovations and opportunities. —by Cheryl B. Scaparrotta Related Information Articles and News
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