Similar tactics can be used to track down materials used to create illegal drugs. Sailor says dealers and illegal manufacturers buy what are known as “precursors” from legitimate chemical warehouses. If those agents were treated with differently coded smart dust, he says tracing the drug back to the original warehouse and then to the buyer would be much easier.While smart dust may serve as a unique chemical fingerprint, it could be even more useful as a sensor, Sailor says. That’s because the particles can be made to reflect light differently in the presence of certain chemicals-a change that can identify chemical and biological contaminants, including pollution and biological weapons.
As a demonstration, Sailor encoded the dust to detect MTBE, an additive in gasoline. “MTBE is not destroyed biologically,” says Sailor, “so once it gets in the ground, it stays there and can easily end up in drinking water.” A company called Trex Industries has licensed the process and is developing the technology to monitor pollutants and pesticides.
Toxic nerve agents like Sarin, the chemical used in the Tokyo subway attack carried out by the Aum Shinrikyo cult, are particularly sensitive to smart dust. Because pesticides like DDT are chemically similar to nerve gases, Sailor says the particles can be prepared to detect them as well.
Smart dust can be deployed several ways. For environmental applications, Sailor says the dust “can be sprinkled on walls or put in paint that coats surfaces.” The treated surface would then light up when, for example, gas vapors reach undesirable levels in the air around an oil processing facility. In combat scenarios, he says it would be easy to paint the wings of [a drone] with the dust, fly it through air that may be laden with nerve agents, and hit it with a laser from a safe distance away. In terrorist situations like the World Trade Center, Sailor says robots could be painted with the dust, equipped with a self-monitoring camera, and sent into a wrecked building to detect natural gas leaks. A similar tactic could be used in detecting deadly agents like anthrax that could have contaminated a building.
At present the dust cannot be detected by lasers from more than 25 meters away. That’s not a problem for environmental applications, but it is a major hurdle for battlefield use. So Sailor and his team are working to make the dust detectable from a kilometer or more-and say they may succeed within a year. They are also working to ensure that the smart dust preserves its properties in harsh outdoor conditions or even through an explosion. If he succeeds, Sailor will have created the total package: dust that’s smart and tough.