For centuries, archivists have noted a curious relationship between “quantity” and “quality” of items in their collections. That is, typically a storage medium’s durability is inversely proportional to the amount of information it can hold. For instance, Sumerian scribes could perhaps only fit a dozen lines of cuneiform onto a typical clay slab, but some of their inscriptions can still be read on surviving tablets six millennia later. Even something as fragile as printed words on paper can endure for hundreds, sometimes thousands of years if properly preserved.
Modern electronic storage media like CDs, DVDs, and computer hard drives can store vastly greater amounts of information, but typically don’t last more than decades at best. Environmental disturbances like fluctuating electromagnetic fields or changing temperature and humidity can corrupt and destroy digitally stored data very quickly. Furthermore, the fast pace of technological progress quickly renders electronic media formats obsolete, leaving users with few options to retrieve data stored on defunct media types.
Perversely, our culture’s explosive production of information may in time wipe out almost all records of our accumulated knowledge and achievements.
To solve that problem, a team led by Alex Zettl, a physics professor at the University of California, Berkeley, has devised a robust nanoscale system that could store massive amounts of digital information for very long periods of time. Any products that eventually emerge from this work could conceivably be the last archival storage devices we would ever need.
The system consists of a minuscule particle of iron encased in a carbon nanotube and represents information in binary notation—the zeroes and ones of “bits.” Using an electric current, information can be written into the system by shuttling the iron particle back and forth inside the nanotube like a bead on an abacus—the left half of the nanotube corresponds to zero, the right half corresponds to one. The encoded information can then be read by measuring the nanotube’s electrical resistance, which changes according to the iron particle’s position.
Because of their very small size, a square-inch array of these nanotube memory systems could store at least one terabit—a trillion bits—of information, approximately five times more than can be packed into a square inch of a state-of-the-art magnetic hard drive. But Zettl believes the technology could be pushed to much higher information densities.
“We can manipulate this particle and read out its position so accurately, we could divide the nanotube’s length into 10 or even 100 units instead of just two,” Zettl says. “Whether this is worthwhile to implement right away, I’m not sure, because it adds complexity, but it could immediately give us 10 or 100 times the information density with the same device.”
As promising as the technology is, much work remains to be done before it could result in a product competitive with other established storage options.
“What you’d want to do is make arrays of these things to get very high capacity, high density storage. Right now we only have high density since we’ve only made a few of these systems,” Zettl says. “You need something that can be scaled up, that’s easy to manufacture, with a low price and high reliability.”
The system certainly seems reliable—Zettl and his team have estimated that information stored within it would be essentially impervious to degradation.
“The key is to make sure that the particle doesn’t slide too easily by itself at room temperature because if it did, you’d eventually lose the memory.” Zettl says. Other memory-degrading processes include the random kinetic jiggling of atoms and the rusting, or oxidization, of a device’s components. But since the chemical bonds between a nanotube’s carbon atoms are so strong, Zettl says, it forms a hermetically sealed system that protects the iron particle from a wide range of environmental contamination.
The team determined the lifetime of a bit stored in their system by finding the threshold energy required to jostle the iron particle so that its information was lost, then modeling the particle’s motion and stability at room temperature. Their result showed that the iron particle—and thus the bit—should be stable within the nanotube for more than a billion years.
Zettl hastens to point out that this system is only the core element of a potential commercial storage device, and that additional necessary components could have shorter lifetimes, lowering the total longevity. But, he says, “Whether it’s stable for 1 million years or 1 billion years, this very small, very high-density component still has an excellent archival timescale associated with it.” Indeed, if the system does store information for a billion years, it seems unlikely we will be present to confirm it: Scientists estimate complex plant and animal life on Earth may only persist for another 500 million years or so. After that, an aging Sun and plummeting levels of atmospheric CO2 should transform our blue-green planet into a dismal brown orb—though that’s probably cold comfort for anyone whose every Facebook and Flickr foible could be immortalized within some descendant of Zettl’s system.
Originally published June 15, 2009