WASHINGTON - Researchers said on Thursday they have created a sophisticated sensor small and portable enough to be worn like a badge that could monitor the environment for harmful chemicals, allowing people to protect against exposure to toxic substances and spoiled foods.
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 military, 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 woven 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.
New research involving liquid crystal technology similar to that used in digital watches and laptop computers may soon help you determine if the meat you buy is fresh or whether your kids are exposed to pesticides while playing in the garden.
The technology, developed by researchers at the University of Wisconsin, should allow the development of inexpensive personal sensors, which can be worn like badges to detect real-time exposure to certain chemical agents.
The findings were reported in the Aug. 17 issue of the journal Science. In a separate report, Harvard University researchers detailed the development of personal sensors designed to radically simplify the detection of certain cancer markers. Pending FDA approval, the medical advance could be commercially available within the decade.
Although techniques to detect chemical exposures already exist, they are too bulky and complex for personal use. In addition to measuring immediate exposure to certain synthetic organic chemicals, the sensors developed by University of Wisconsin researchers Nicholas L. Abbott, PhD, and Rahul R. Shah, can be designed to measure cumulative exposure over time.
"The badge could be worn by children or even agricultural workers to measure personal exposure to pesticides," Abbott tells WebMD.
"There are also potential applications for the Department of Defense in terms of chemical exposure," he says. "One of the problems the army has is keeping track of the useful life of protective clothing. With this they can easily tell, for example, if a protective mask is halfway through its useful life."
The sensors could also be used in food packaging, Abbott says, to monitor chemical markers of food spoilage. And the technology may one day allow simple detection of toxic nerve gases like sarin, the deadly, odorless gas that has been used by terrorists and in warfare. Badges incorporating the sensor technology should cost less than a dollar to produce.
The sensors consist of an ultrathin gold film with nanoscale corrugation. The surface of the gold film is dotted with chemical receptors that weakly anchor liquid crystal along the film's surface. Researcher Charles M. Lieber, PhD, and colleagues at Harvard used nanowire technology to develop chemical and biological sensors with the potential to detect a single protein molecule or piece of DNA.
"If you imagine a hair from your head next to a redwood tree, that is what a nanowire looks like next to your hair," Lieber tells WebMD. "They are incredibly tiny."
Lieber says the tiny sensors could lead to the first simple, immediate diagnostic test for protein markers of certain cancers, and may also simplify the screening of experimental drugs.
"One of the biggest problems with cancer recurrence is that right now people are tested every six months or every year, and if a tumor is found it might be too late," Lieber says. "There are proteins associated with certain cancers, like breast cancer and prostate cancer, but the tests for these proteins currently involve a lot of biology. This would be a real-time detector of these cancer markers."
Cheap sensors that change colour when exposed to minute amounts of dangerous chemical compounds, such as chemical weapons or pesticides, have been developed by a US team. Small patches containing the sensors could be attached to military uniforms or children's clothing.
The patches should prove to be a huge advance over the bulky, expensive chemical sensing equipment currently available, says the team at the University of Wisconsin, US. Unlike these detectors, the chemical patch is also resistant to water.
Nicholas Abbott and his colleagues created the sensors by bonding liquid crystals to a thin, nano-engineered corrugated gold surface. When the crystals bind to a 'matched' chemical, they change orientation. This changes the way the crystals refract light and hence alters the colour or brightness of the patch.
Depending on the chemical to be detected, different crystals would be used. The system is sensitive enough to detect target chemicals in concentrations as low as a few parts per billion.
Dupont Durst, a research chemist at the US Army's Aberdeen Proving Ground in Maryland, says it is currently impossible to give an early warning against chemical weapons without complicated equipment. "We are very interested," he told New Scientist. "The technical thrust is, can you give a soldier something when they get on the plane? It could be very useful."
Early warning
The sensors could be used to detect many different compounds, says Abbott. So far, they have been shown to work with the chemicals produced by decaying food and organophosphate pesticides.
This suggests they could be used in food factories or supermarkets, to detect meat in the very early stages of decay, for example. People living in agricultural areas could also use the sensor badge to alert them to high levels of pesticides in the air.
Abbott says that the manufacturing process would allow different segments of a sensor patch to be designed to react to different chemical compounds, providing a multipurpose detector.
Expired breath
Other researchers are excited by the breakthrough. "This raises the prospect of producing a wide range of devices from artificial noses and safety devices to biochemical sensors that can check the state of your health from your expired breath," says Vince Craig, of the Australian National Laboratory in Canberra.
"These researchers have been accumulating the knowledge and skills to produce this sort of a result over a number of years."
Abbott's team created the sensors by evaporating gold to produce an ultra-thin corrugated film. The process allows liquid crystal molecules to be anchored to the surface so that the crystals have a particular orientation.
Most chemical weapons sensors currently used by the military detect chemicals by monitoring their impact on a vibrating surface. These devices may be portable, but require electrical power.
Journal reference: Science (vol 293, p 1296)
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