United Press International February 28, 2001, Wednesday
Snake proteins may make good sensors
By KELLY HEARN, UPI Technology Writer
WASHINGTON, Feb. 28
The U.S. Air Force is seeking a new, ultra-sensitive class of heat-seeking systems among the most efficient sensors of them all: those of nature's own pit vipers.
Heat sensors based on biological systems could make night-vision equipment, heat-seeking missiles and other civilian and military devices smaller and cheaper yet more sensitive, the program's manager told United Press International.
A class of snakes that includes copperheads, rattlesnakes and water moccasins, the pit viper has small depressions, or pits, on either side of its head. Those pits hold membranes capable of sensing temperature changes as small as two thousandths of a degree, a capability far exceeding state-of-the-art manmade sensors.
The sensors are particularly responsive to infrared light, which is given off by hot objects, allowing the snakes to find prey even in the dark. Scientists believe a light-sensitive protein may be the key, and they hope to mimic its action.
"We're taking a comprehensive look at the physiological, genetic and molecular dynamics of these animals' infrared systems to develop new and novel detection schemes," said Robert Cohn, U.S. Air Force program manager.
Since the mid 1990s the Air Force has funded the investigations to the tune of $1 million annually, he told UPI.
Infrared detectors are ubiquitous but expensive components in civilian and military devices such as night vision equipment, burglar alarms, airplanes and heat-seeking missiles.
But man-made sensors, unlike their biological counterparts, are large, expensive and must be cryogenically cooled with liquid nitrogen in order to function, making them impractical for many uses.
Researchers originally thought the snake's system worked when infrared energy caused its body solutions to generate heat. But Cohn and some project scientists said they now believe a light-sensitive protein capable of responding to low temperatures is the key component.
"If the infrared-detection capability that we find in these snakes is caused by a protein or is enhanced by protein in the pit cells, then we should be able to extract that protein and incorporate it into some kind of a smart nano device," he said.
Evolution has spent billions of years refining the processing capabilities in living organisms. Biomemetics is the field of science that tries to decipher, mimic and improve those processes for technological use.
The scientists are also studying a similar heat-finding capacity in two kinds of beetles that find forest fires in order to lay eggs in the protective confines of burned logs and underbrush. But the search for the beetle's heat-seeking secrets is not likely to prove as successful as research on the pit vipers, said Prof. A.J. Welch, a professor of electrical and computer engineering at The University of Texas at Austin.
"The snake's device works because water and other proteins in its tissue absorb the light and generate heat that then cause a response in the receptors," said Dr. Massoud Motamedi, director for center of bioengineering at the University of Texas Medical Branch at Galveston. "We have determined that the pit vipers can detect changes in temperature as small as .002 to .003 of a degree."
Researchers said pit vipers do not rely solely on infrared detection but use it in conjunction with vision and taste. With that in mind the scientists are also studying the structure of anatomical features such as the skin around a viper's pit or the organelles in a beetle that help it select frequencies of light. They are also interested in how sensor cells generate neural impulses -- in other words, how the cell machines send messages to the brain once they sense infrared light.
Motamedi said because the project is "uncharted territory" it is difficult to say when scientists will be able to build a device that operates using a snake protein.
Thermal sensing technologies are becoming more and more common, however. Cadillac, for example, is now offering night vision technologies, based on thermal sensing, in some of its cars.
But besides improving existing devices, nanosensors could also produce novel ones. Cohn said he could imagine sensors so tiny they could be injected into the blood to locate cancer cells by honing in on their particular heat signature.
Cohn would not discuss potential military applications. But experts said the military has numerous uses for improved sensors.
"The military has many functions for infrared detectors but generally they are used in heat-seeking, air-to-air missiles and air-to-ground heat seekers," said John Pike, director of GlobalSecurity.org, a non-profit policy research firm in Alexandria, Va. "Generally, the systems are expensive, costing anywhere from as many as tens of thousands of dollars to about $200,000, so a discovery like this could be quite helpful."
Copyright 2001 U.P.I.
