Nanomechanical switch recharges computer chip technology
By David J. Craig
Most scientists and engineers look at a computer chip and see a marvel of modern technology. Pritiraj Mohanty sees profound limitations.
Thanks to the vision of Mohanty, a CAS assistant professor of physics and a faculty member at the Photonics Center, and graduate students Alexei Gaidarzhy (ENG’06), Robert Badzey (GRS’05), and Guiti Zolfagharkhani (GRS’06), computers soon could store much more data than today’s machines. The researchers recently designed a nanomechanical memory cell that is smaller and can operate at far greater physical densities than the memory cells in today’s magneto-electronic computer chips, dramatically improving a computer’s ability to store, retrieve, and process data.
“By looking at the old technology, we have produced memory cells that are faster and better than those currently used,” Mohanty says. “This mechanical device is a completely new approach to improving data storage. It can read and write 1,000 to 100,000 times faster than the current speed. With these nanomechanical chips, a video editor could load a two-minute high-resolution film instantaneously.”
The research, which was supported by grants from the Nanoscale Exploratory Research Program of the National Science Foundation and the Department of Defense Army Research Laboratory, was published in the October 18 issue of the American Institute of Physics journal Applied Physics Letters.
Mohanty’s innovation is a silicon switch 1,000 times smaller than a human hair. It functions similarly to the millions of switches in current computer chips: by responding to an electric current in ways that correspond to the “0” and “1” conditions commonly used to describe the process for accessing stored data. It was created using electron-beam lithography, which is the staple fabrication technique for microelectromechanical (MEMS) devices, the ultra-small sensors, switches, and gears integral to the microtechnology and nanotechnology industries.
The new switch is special because of its tiny dimensions, which allow it to vibrate quickly, achieving a millions-of-cycles-per-second frequency of 23.57 megahertz. That speed reflects the rate at which the device can read data. The switches in current laptops, in comparison, move between the 0 and 1 conditions at only thousands of cycles per second, or a few hundred kilohertz. “Because the structures are so small,” says Mohanty, “they can be packed into the computer chip much more densely than those switches in your hard drive now.”
Other advantages of Mohanty’s switch include its minuscule range of motion, which allows it to vibrate between states using only femtowatts of power, compared with the milliwatts or microwatts of power needed for read-write functions in current machines. Although technology exists to make electronic chips with more memory capacity, Mohanty says, computer manufacturers have leveled off the number of electronic switches per chip because of the amount of power needed to operate the machine. “The fact that it requires a million times less power for each bit is a huge gain,” he says.
Part of the research team’s goal also was to create a very durable computer chip. They succeeded: the new switch is “extremely robust,” according to research team member Robert Badzey. “Not only can these mechanical switches withstand radiation disturbances, like solar flares, they also are tough enough to work even after being dropped.”
Mohanty, whose research also involves developing nanomechanical sensors for use in disease detection, says the new technology could be commercialized relatively quickly. The University filed a provisional patent for it earlier this year. “This could happen as early as within the next two, three, or five years,” he says, “depending on the demand.”
Danielle Masterson and Ann Marie Menting contributed to this story.