Less than perfect is better for nanotech

VANDERBILT (US) — Suppressing natural variability to increase reliability works well in some cases, but not so much on the nanoscale.

That’s because objects at the nanoscale behave in a fundamentally different way than large-scale objects, says Peter Cummings, professor of chemical engineering at Vanderbilt University.

The defining difference between the behaviors of large-scale and nanoscale objects is the role that noise—random disturbance—plays. At the level of atoms and molecules, that random motion can dominate to such an extent that making reliable devices becomes extremely difficult.

By exploiting that random behavior, nature has managed to figure out how to put these fluctuations to work, allowing living organisms to operate reliably and far more efficiently than comparable man-made devices.

“Contrarian investing is one strategy for winning in the stock market,” Cummings says, “but it may also be a fundamental feature of all natural processes and holds the key to many diverse phenomena, including the ability of the human immunodeficiency virus to withstand modern medicines.”

In a paper published in the journal ACS Nano, Cummings and Michael Simpson, professor of materials science and engineering at University of Tennessee, Knoxville, maintain that in any given population, these random fluctuations, or the noise, cause a small minority to act in a fashion contrary to the majority and can help the group respond to changing conditions.

In this fashion, less perfection can actually be good for the whole.

Mimicking cells
At Oak Ridge National Laboratory, the researchers are exploring this basic principle through a combination of virtual simulations and physical cell mimics, which are synthetic systems constructed on the biological scale that exhibit some cell-like characteristics.

“Instead of trying to make perfect decisions based on imperfect information, the cell plays the odds with an important twist: it hedges its bets. Sure, most of the cells will place bets on the likely winner, but an important few will put their money on the long shot,” Simpson says.

“That is the lesson of nature, where a humble bacterial cell outperforms our best computer chips by a factor of 100 million, and it does this in part by being less than perfect.”

Following the lead of nature means understanding the role of chance. For example, in the AIDS virus, most infected cells are forced to produce new viruses that infect other cells. But a few of the infected cells flip the virus into a dormant state that escapes detection.

“Like ticking bombs, these dormant infections can become active sometime later, and it is these contrarian events that are the main factor preventing the eradication of AIDS,” Simpson says.

“Our technology has fought against this chance using a brute force approach that consumes a lot of power,” Cummings says. As a result, one of the factors limiting the building of more powerful computers is the grid-busting amount of energy they require.

Oak Ridge National Laboratory science writer Ron Walli contributed to this story.

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