Using dogs to sniff out land mines or catch drug smugglers may seem a primitive approach in these high-tech times, but canines still thrive in these "professions." However, these dogs' days may be numbered as new types of noses -- electronic ones -- sniff their way into the market.
Scientists at the Oak Ridge National Laboratory, the California Institute of Technology (Caltech), and a commercial offshoot of Caltech called Cyrano Sciences Inc., are developing sensing technologies that use circuits to "smell" the TNT used in land mines, as well as a variety of chemicals in other military, commercial, and environmental applications.
"We're developing land-mine detectors that don't get bored or need treats to keep going," said Richard Payne, chief technology officer of Cyrano Sciences. "There's only so long that a dog can run around a field before it starts chasing a rabbit."
The electronic-nose technologies, under development separately by those organizations, each employ an array of small sensors on one integrated circuit (IC), and electronics on another IC. Sensors are being developed to monitor such things as mercury, natural gas, carbon monoxide, petrochemicals, and even whiskey and wine. "The land mine problem is at the high end of the spectrum of problems we are trying to solve," said Payne.
Low-cost e-nose technologies have been dreamed about for close to a decade, but have never really come close to commercialization. Scientists have used so-called gas chromatograph tools to analyze smells in the lab by breaking down a chemical into its constituent parts. But the lab tools cost upwards of US$30,000 each, and scientists are striving to get the price down to a tenth of that. The Oak Ridge and Caltech projects reached their ends through different technological means, and are still at least a year or two away from field deployment.
"What we're reporting on is not vaporware. It's real," said Chuck Britton, an integrated circuit designer for the Oak Ridge project. "We're trying to develop a basic, physical platform to which we can attach sensors for different kinds of applications. We're in the early stages. But we have shown that the thing works."
The Oak Ridge and Caltech sensors make contact with an odor, and molecules in the odor then match up with the surface of the sensors and provide resistance to an electrical current flowing through the sensor. The data about the resistance of the sensor is then read by software in the integrated circuit, which compares the information with a databank of stored smells for a match.
The Caltech sensors use polymers, or chemical blends, which absorb the chemicals in an odor like a sponge, said Payne. The Oak Ridge technology uses tiny slivers of metal which "bend" in the presence of certain chemicals. Each of the slivers of metal, or cantilevers, can be coated in a sensor with a different substance to make them sensitive to different chemicals, said Britton. There are limits to detection that even the e-noses can reach, if the chemical is diluted to 10 parts per billion, said Nathan Lewis, professor of chemistry at Caltech.
Funding for the research project at Caltech is coming from the Defense Advanced Research Projects Agency, a Pentagon agency. Financing for the Oak Ridge project is coming from the Department of Energy's Laboratory-Directed R&D program.
Standard semiconductor manufacturing processes can probably be used to make the technologies, and Oak Ridge has already worked with a microelectronic machine manufacturer in North Carolina to develop early stage versions, said Britton.
In addition to the sensors' military uses, Britton and Payne reckon that the sensors can be deployed for environmental monitoring. For example, a factory is supposed to cut emissions of a certain chemical, and claims to have installed the scrubbers in the smokestacks to reduce pollution. A sensing device could be implanted by the Environmental Protection Agency to verify the pollution level, and it could be linked via a wireless technology to the agency offices for continued monitoring, said Britton.
Several European firms are developing similar sensor technologies as well, including Sweden's Nordic Sensor Technologies, Alpha MOS of France, and Britain's Neotronics. "The applications are mind-boggling," said Britton.
According to a forecast by Germany's Intotech Consulting Group, the market for these products will be $1.1 billion by 2004. The United States, Europe, and Japan are expected to be the biggest consumers of the sensing technologies. "Sensing is a hot topic," said Britton. "There are a lot of sensors that work in the lab. But, ultimately, we can replace the dog in the field."
