Sophisticated new type of chemical sensor created
Date: 20-Aug-01
Country: USA
Author: Christopher Doering
The liquid crystal sensor, about the size of a small Band-Aid, could provide real-time detection of airborne chemicals that until now have been difficult to detect using technology that still is mostly confined to the laboratory, according to research in the journal Science.
In the future, these sensors could be used in food safety applications, such as monitoring levels of the compounds produced by rotting fish and meat, the researchers said. The sensors also could be used to detect environmental exposure to pesticides, and could possibly certain deadly nerve gases such as sarin.
Technology to detect such compounds already exists, but primarily is confined to the laboratory and is too bulky and complex to provide real-time, portable detection.
University of Wisconsin researcher Nicholas Abbott, who co-authored the study, said the sensor, if used in a broad range of applications, could turn the technology into a multibillion-dollar product.
The sensor "has the potential to be formatted as a broad technology with quite a diverse number of applications ... from the miliary, to health care, to food safety and occupational safety," Abbott said in an interview.
"The strength of the technology is that it is something that can be realized as a patch or a badge, some low-profile object that could be confined to a person," he said.
Abbott added that early uses of the sensor could be available within between two to three years. Researchers say they will continue to study the technology and develop other applications including a flexible version that could be weaved into clothing.
GOLD FILM AND LIQUID CRYSTALS
The sensor, which can detect tiny levels down to parts-per-billion of vapor concentrations in the air, consists of an ultra-thin layer of gold film. The surface is then coated with chemical receptors that weakly bond to a liquid crystal.
Liquid crystal is a substance that possesses the mobility of a liquid and the molecular structure of a solid. It is what's seen in displays found on calculators and laptop computers.
When the receptors interact with a specific chemical in the air, they change colors by displacing the liquid crystal and bonding with the toxin. The sensor can return to its original color after being removed from the targeted chemical.
Another version of the technology could be used to measure cumulative exposure to chemicals such as pesticides. The U.S. Army has expressed interest in using it as an indicator for holes in clothing that chemicals could penetrate, researchers said.
The sensor would be manufactured using a process similar to photographic film in which multiple layers of chemicals are applied, and each liquid crystal would likely cost less then $1, Abbott said.
Broad use of the liquid crystal is still a few years away, but government officials applauded the move, saying it could help make the country's food supply safer.
"Any new technology that we can develop to make food safer is something we would encourage," said Beth Gaston, a spokesperson with the Food Safety and Inspection Service, a division of the U.S. Department of Agriculture.
"We have the safest food supply in the world, but certainly it can always been made safer," she said.
The technology already has attracted the attention of several large American chemical companies, Abbott said. Rahul Shah, who co-authored the study while at the University of Wisconsin, is now employed by diversified industrial group Minnesota Mining and Manufacturing Co.
"I am aware that a number of companies are interested in the technology," said Abbott who would not name the other companies.