The most powerful explosive detection device to date has been developed by a group of European researchers, but the idea behind the system isn’t entirely new, in fact a little moth species has been using it for quite some time.
Nature has developed highly efficient and structured systems, which can now be investigated in detail with advanced high-resolution technologies. The more scientists learn about natures’ mechanisms, the more awe-struck they become by such genius innovation and powerful engineering. For a research team at the French-German Institute of Saint-Louis, the inspiration behind an extremely sensitive explosive detection system came from the beautifully structured antennae of the humble little silkmoth (Bombyx mori). These biological “˜levers’ are capable of sensing just a few tiny pheromone molecules drifting among billions of molecules of air.
The detector is a little antenna-like structure (200 µm long and 30 µm wide), called a microcantilever. The structure contains around 500 000 vertically aligned titanium dioxide nanotubes, which have a high affinity to the explosive molecules of trinitrotoluene (TNT). Like the silkmoth antennae, the microcantilever vibrates at a given frequency. Because explosive molecules are attracted to the nanotubes, they stick onto the lever, making it heavier and decreasing the frequency at which it vibrates. This decrease in vibration is the key sign that an explosive compound is present — or in the case of the silkmoth, that a pheromone releasing mate is around.
It’s an exciting new device because it is so much more sensitive than the ones currently available, and therefore it will improve security in bomb-threat prone places such as airports.
“With this work we decreased the detection level [of explosives], and we have also contributed to making systems that can detect explosives in real time for practical screening operations,” explained Denis Spitzer, lead author of the study published in Angewandte Chemie. “The system is also cheap so they can be widely disseminated in airports, railway stations and other public locations.”
The researchers tested the effectiveness of their device by releasing very low concentrations of TNT in a controlled environment. They found that the level of sensitivity was 800 ppq, which means it could detect 800 TNT molecules per million billion (1015) molecules of air. No current device even comes close to detecting concentrations in this low range, with most having sensitivities of around 1 part per billion molecules of air (ppb).
In future research the scientists hope to adapt their device for targeting other types of explosives, as well as for the detection of various illicit drugs. The system could also have environmental applications in the detection of organic volatile pollutants. But for the time being, some more research and developmental work is still required before the device can go on the market.
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