Sniffer dog’s got company

RDX when wrapped in multiple layers makes its detection difficult even in high security zones like airports. Mere screening devices are not sufficient to sniff traces of RDX.

The government of India entrusted the department of electrical engineering of the Indian Institute of Technology (IIT), Mumbai, with the task of developing an electronic device which would detect traces of RDX that existing machines cannot. The IIT faculty took on the challenge, and the result of five years of concerted effort was the Electronic Nose, endearingly called E-dog.

Professor V Ramgopal Rao from the department explains the working of the wireless explosive detector, “The Electronic Nose is made from cantilevers, each of which is the main nano sensor element that is 200 times thinner than a strand of human hair.”

The cantilever is coated with a chemical that reacts with the explosive. The chemical binds with the RDX molecule generating stress, which is converted into an electrical signal. This signal is wirelessly transmitted to a control station. “It is this chemical that ‘sniffs’ the RDX out.”

Currently available screening devices installed at sensitive areas need traces of molecules of explosives for detection and cannot sense explosives in their vapour state.

Consider the standard procedure followed at the airport. Your handbag is only scanned towards the end once you reach security check. This means that from the time you enter the airport till security check, no machine is used to scan your handbag. This is where the vapour detection capability will come into play.

No existing technology can match the capabilities of a sniffer dog. “But maintenance and training of sniffer dogs prove expensive.
The E-dog, on the other hand, is not expensive and would cost about Rs1,000 each. Given the minimal cost, a network of such sensors can be deployed at public places” says Rao.

The Electronic Nose can be placed in strategic areas where it can discreetly do its job without restricting movement. This nano-scale cantilever technology took five years to develop. Seena V, a research scholar, worked on the cantilever technology while another scholar, Sudip Nag, worked on the electronics to go with the sensors.

The project is truly interdisciplinary in that it involved faculty and students from multiple departments not only from the IIT but other institutions as well.

Seena says, “The performance of the cantilever sensors depends on sensitivity and selectivity. The sensitivity part is solved; that these sensors are as sensitive as the sniffer dogs has been demonstrated by United States. We are presently tackling the selectivity issue, that is how selective is the sensor to the molecule in question. It should not raise a false positive alarm.”

Pattern recognition needs to be incorporated in the E-dog to address the selectivity aspects. There are many things that have the same chemical composition. RDX, shoe polish and certain perfumes have many similar elements, namely carbon, hydrogen, nitrogen and oxygen.

“The device needs to be modelled in a way that it sniffs out only the explosive. Explosives create a pattern of response with these sensors. Hence pattern recognition and identification are important. It is equivalent to training a dog,” says Rao.

There are multiple challenges, some of which still need resolving. Dr Soumyo Mukherji, an IIT professor who is part of the team working on the Electronic Nose, says, “This is a highly complex project that involves many stages of intricate work. And at each stage, one may face difficulties. The Electronic Nose has not been field-tested till now. But we can predict some field conditions and be prepared for them. But there are others that have not been taken into account yet. And after field testing, there might be some technical hitches that can arise.”

Another difficulty encountered by the scientists is that RDX is a very stable explosive and does not smell if properly wrapped, making its detection difficult. The professors are up for the challenge.

IIT will make a few prototypes which they will hand over to the security agencies. From there, the government will select a manufacturer who will mass produce them.

Rao hopes the E-dog will be fully operational by next year, given that no unexpected issues arise. Until then, it’s up to the good old sniffer dog to save the day.