IBM Tuesday revealed another experiment from one of its many laboratories this year. Using aspects of an increasingly popular trend in the high-tech sector called nanotechnology , the Armonk, N.Y. concern has demonstrated a data storage density of a trillion bits per square inch, which is some 20 times higher than the densest magnetic storage currently offered.
The achievement was made under the aegis of a research project called "Millipede." To get an idea of just how encompassing the storage achievement is, Big Blue estimated that Millipede is dense enough to house 25 million printed textbook pages on a surface the size of a postage stamp. This is significant because the technology may boost the storage capacity of handheld devices -- personal digital assistants (PDAs) and cell phones -- often criticized for their low storage capabilities.
How is it possible for Millipede to be so dense? Millipede uses thousands of nano-sharp tips to punch indentations representing individual bits into a thin plastic film. The result is akin to a nanotech version of the data processing 'punch card', but with key differences. First, Millipede is re-writeable, meaning it may be used over and over. Second, it may be able to store more than 3 billion bits of data in the space occupied by just one hole in a standard punch card.
And IBM is concentrating on making Millipede even more dense. The terabit demonstration employed a single "nano-tip "making indentations only 10 nanometers (millionth of a millimeter) in diameter. IBM's research team is now building a prototype that deploys more than 4,000 tips working simultaneously over a 7 mm-square field. This would enable a high-capacity data storage system to be packed into the smallest format used now for flash memory.
"The Millipede project could bring tremendous data capacity to mobile devices such as personal digital assistants, cellular phones, and multifunctional watches," says Peter Vettiger, Millipede project leader. "In addition, we are also exploring the use of this concept in a variety of other applications, such as large-area microscopic imaging, nanoscale lithography or atomic and molecular manipulation."
For those interested in the technical specifications, read on.
Millipede consists of a two-dimensional array of v-shaped silicon cantilevers that are 0.5 micrometers thick and 70 micrometers long. At the end of each cantilever is a tip less than 2 micrometers long. The current experimental setup contains a 3 mm by 3 mm array of 1,024 cantilevers, which are created by silicon surface micromachining. Time-multiplexed electronics, similar to that used in DRAM chips, address each tip individually for parallel operation. Electromagnetic actuation moves the storage medium beneath the array in both the x- and y-directions, enabling each tip to read and write within its own storage field of 100 micrometers on a side.
How does the device function? To ensure the tips writes or erases, etc., they are brought into contact with a thin polymer film coating a silicon substrate only a few nanometers thick. Bits are written by heating a resistor built into the cantilever to a temperature of typically 400 degrees Celsius. The hot tip softens the polymer and sinks into it, generating an indentation. For reading, the resistor is operated at lower temperature, such as 300 degrees Celsius, which does not soften the polymer. When the tip drops into an indentation, the resistor is cooled by the resulting better heat transport, and a measurable change in resistance occurs.
In IBM's ongoing interest in cutting power consumption in the industry, how much power is used depends on the data rate at which the device is operated. When operated at data rates of a few megabits per second, Millipede is expected to consume about 100 milliwatts, which is in the range of flash memory technology and considerably below magnetic or electronic recording, which are the more traditional means of storage.