Butterflies inspire GE's sensor research

Butterflies inspire GE's sensor research

BUSINESSWEEK 11, Dec, 2007

Admirers of beautiful South American butterflies known as Morphos have long included scientists intrigued by their brilliant iridescence.

Add General Electric Co. researchers to the butterfly fan club.

The conglomerate is attempting to replicate unique properties of the insects' wings that make them appear to shimmer colorfully. Far from mere aesthetic curiosity, however, GE's goal is to devise next-generation "colorimetric" sensors that someday might be deployed to detect everything from airborne hazardous chemicals to spoiled meat inside of a deli package.

Microscopic structures on the butterfly wings "selectively respond to different vapors" in the air, said Radislav A. Potyrailo, principal scientist in GE's chemical and biological sensing laboratory.

"You get very slight, small changes in color based on what vapor (the wing) is exposed to," he said.

If GE can effectively replicate and manipulate the structures -- which are about 100 times smaller than the width of a human hair -- Potyrailo thinks it can use them to design extremely sensitive, long-lasting sensors that change color upon exposure to various airborne molecules and then revert to normal when the molecules are no longer present.

Such gas sensors have the potential to be highly selective -- able to detect multiple substances without false alarms -- and they also wouldn't require a power source, he said.

GE doesn't expect the research to bear fruit for five years or so, in terms of commercial products, because the work is still in the early stages. But the company is optimistic nonetheless, saying such butterfly-inspired sensors could spark broad demand in sectors ranging from security to healthcare.

Market trends appear to support the contention. Sales of all manner of sensors have been on the upswing, fueled by technological advances and health and security concerns, as well as a desire to free up humans from mundane monitoring tasks.

Industry research firm Freedonia Group Inc. estimates that overall sales of chemical-property sensors will grow to about $2 billion in 2015, from about $1.1 billion in 2005.

To be sure, so-called colorimetric sensors -- meaning sensors that undergo color-changing reactions upon exposure to designated chemicals -- are already commonplace and relatively cheap. The most basic models that generally detect a single chemical, such as those incorporated into wearable employee badges for industrial settings, range from about $2.50 to $3 each.

But industry players acknowledge ample room exists to improve the sensitivity and versatility of the existing technology, and to make such devices stay effective longer.

Richard Lally, president of privately held Oceana Sensor, thinks GE's effort holds promise. Lally, whose company is developing systems to help corporations operate wireless sensor networks, heads the National Association of Sensor Science & Technology, a trade group.

Lally described himself as a big fan of looking to nature and biological systems for "clues" to solving technical problems.

"Living things have the advantage of thousands and thousands of years of evolution," he said. "A phenomenon that has the big advantage of evolution...is going to be, at least potentially, far more resilient than something we're going to be able to invent over the span of an engineer's life."

The colorful iridescence exhibited by Morpho butterflies is believed to have evolved as a means for them to locate each other over long distances amid thick tropical forests.

Potyrailo and his team of GE researchers are hardly the first profit-motivated scientists to be captivated by the insects. The Morphos' iridescent properties have been studied for possible insights into the development of everything from cutting-edge flat-panel displays to new forms of women's makeup.

For its part, GE is focusing on a relatively rare Morpho species called Morpho sulkowskyi.

Scales on the insect's wings are arrayed with microscopic structures shaped like tiny Christmas trees. Airborne molecules, depending upon size and configuration, interact with different "branches" of the tree-shaped structures, triggering color changes by altering how light is absorbed and reflected.

Potyrailo said GE has successfully tested the butterfly structures in the laboratory using a variety of common gases, observing "more highly selective and acute" performance than obtainable by many existing chemical sensors. The challenge now is to duplicate and refine the performance using man-made structures, he said.

The work "could enable us to achieve a big step change (forward) in the performance" of chemical sensors, Potyrailo said.

It's too early for GE to have any specific products in mind, Potyrailo said. But he contends the technology could be broadly useful, leading to development of everything from new chemical sensors for homeland security to small "button" sensors on meat packages that alert consumers to freshness.

Doron Pely, a vice president at Homeland Security Research Corp., a market research firm, called GE's effort intriguing, saying the security industry has been looking for autonomous, "intelligent" chemical sensors that can distinguish between various substances.

"The ability (for a sensor) to say something like, 'I smell oxygen and not nitrogen,' is unique," he said. "If you can move away from giving very general indications of a threat to a specific threat, then you're in a very good place."

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