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The Frontier of Microelectronics
Building Nano-machines, Part by Part
Nanocomputers, higher resolution screens, and millibots? What kinds of gadgets will the next generation of innovation bring? The answer to questions like these depend on nanotechnology, a rapidly developing field that crosses a spectrum of sciences with studies at the nano-scale, smaller than a human cell.
Leading scientists in the field of nanotechnology are discussing recent developments in microelectronics, at the 2003 American Association for the Advancement of Science (AAAS) Annual Meeting.
What would you do with a nanocomputer? James Ellenbogen of MITRE is networking tiny computers to control tiny machines. Building a millirobot involves many levels of research, said James Ellenbogen of MITRE, who is testing a prototype for a silicon chip with motorized legs. If all goes right with the first generation of development, a 10x10 millimeter chip would have legs "wave like a cheering section at a football game." Ellenbogen is fine-tuning the leg and motor designs of the test chip, and the plan is to further refine these before moving on to make six-legged insect-like "walkers" that would only be a fraction of the size of the test chip: 3x5 millimeters, no larger than a small housefly.
The robots do not reproduce, and the idea behind Ellenbogen's research is not to make machines that assemble themselves, but to test the application of a nanocomputer. The millirobot's purpose is to be an "exercise of control," to understand the mechanics of how to wire up the chip, little motors, and little legs that wiggle and walk. Instead of figuring out how to make a Cadillac cruise, it's about how to make many little machines on a tiny systemlegsmove in a well-coordinated way. "Once we decide on the right fit, I'd be pleased as punch if we have one next year that would scuttle across the table and avoid objects." Ellenbogen will also discuss ongoing developments of nanocomputers.
"We overestimate what we can achieve in a year and underestimate what we can do in ten years. Nowhere is that truer in the world of nanotechnology, which is a weaving of basic science, realization of fundamental limits, and inspiration based on science fiction and the IT revolution of the last century," said another AAAS speaker James Gimzewski of University of California-Los Angeles.
Basic experiments and exploration of new ways to do things in nanotechnology are important to lay out the groundwork for the future of molecular electronics, in order for the realization of new opportunities for simpler, cheaper, disposable electronic devices, Gimzewski said. "If you take a longer term look, there are many more opportunities than if you look at the short term, inside the box," he said. Gimzewski will also talk about fundamental issues of single molecular devices and the California NanoSystems Institute (CNSI).
Changing the function of optical devices, like CD and DVD players, is the focus of Evelyn Hu of University of California-Santa Barbara and co-director of the CNSI, who is creating nanoorgan pipes, or nano-scale resonators, to study how quantum dots may one day be used as light-guiding components. What do music and nanophotonics have in common? "An organ pipe is a resonator that gives different pure tones, or frequencies. One tone or its harmonics will be emitted. We're doing an analog for that for light, not sound," said Hu. "We make these resonators and they hum when they encounter the exactly right optical frequencies," Hu explained.
What results is a "unique exchange of energy between the optical emission of the quantum dot and the response of the nanostructured resonator." Quantum dots are clusters of 100s or 1000s of atoms.
In other words, devices can be developed where the optical energy is channeled much more efficiently than we can obtain now. By improving on functional changes in key components of optical devices, such as a laser in a CD player, the product's efficiency also becomes more optimized. "By engineering a structure at the nanoscale, you might be able to pump in energy, and immediately excite a dramatic optical response." If a chip can be made with components that guide light energy waves in a way similar to current electronic circuits, this could bring some advancement for optics as communications conduits, Hu said.
The organ pipe concept might be comparable to the similar technological advantage that allows us to have personal computers or cell phones that are growing smaller and smaller. In those kinds of electronics, "The ability to have all that computational and information-crunching power that's really compact, means you can do a lot with components that are very portable," Hu said. "If we can make optical components at the nanoscalesmall enough to integrate different optical components onto a single chipthen we can achieve the same powerful economy of scale that electronics, or integrated circuits, now achieve," she explained.
By sending information through wavelengths of light, by overlaying different long and short wavelengths, more frequencies, and therefore more information, can come in at any given time, and "At those frequencies, we can do more accurate renditions of video and moving images," Hu said. "In some cases, when you make a component small, you may also see exciting new physical principles showing up, resulting in new kinds of devices and new capabilities; that's the case with the quantum dots and their resonator 'organ pipes.'"
13 February 2003