'Digital Dog Nose' can identify explosives, drugs and more

A new sensor developed at The University of Rhode Island (URI) is said to be so powerful that it can detect threats at the molecular level — whether it’s explosive materials, particles from a potentially deadly virus or illegal drugs entering the country.

The sensor has been developed by Professor Otto Gregory and chemical engineering doctoral student Peter Ricci, after a long period of testing and refinement. The work was originally funded 20 years ago by the Defense Advanced Research Projects Agency (DARPA), a research and development agency of the US Department of Defense. After two years of DARPA funding, the Army funded the project for a year. The Department of Homeland Security has provided funding ever since.

“Anything that can typically be sniffed out by a dog, we can do,” Prof Gregory said. “That’s why we’ve called it the Digital Dog Nose.”

Originally the size of a toolbox, the Digital Dog Nose has now been reduced to a quarter of the size of a pack of cigarettes. As explained by Prof Gregory, “By decreasing the thermal mass of the sensor, we’ve decreased the amount of power required to run the sensor. We started with a thermal mass on the order of grams; now the thermal mass of our sensor is on the order of micrograms.”

One of the keys to making a device this small and powerful is to find the right battery. Prof Gregory said, “We have partnered with a company that makes very thin, low-mass batteries in Colorado called ITN Energy Systems. They make lithium batteries that are no thicker than a piece of paper. The process has been about finding the right partners, which helps us improve our catalysts and improve our sensor platform.”

In March 2021, the Naval Research Laboratory brought its mobile testing unit to URI to put the explosives sensors and others to the test. Ricci recalled, “They set up a field test outside using their vapour test bed. They were able to select an explosive molecule and deliver it to the sensor system. Knowing what the level was, they wanted to see how our sensor would respond. One of the tests was at the part-per-quadrillion level.”

This sensitivity bodes well for the detection of further explosives in future. As noted by Prof Gregory, “The Department of Homeland Security has asked us to be flexible enough to anticipate and adapt to emerging threats that may come several years down the road. We can tweak our catalysts for a specific molecule that is the current threat. That’s what we do with biomarkers. That’s what we do with drugs. What’s nice about this platform is that it’s flexible.

“The platform is broad based, so you can apply it to lots of different venues, with lots of different end users.”

In addition to the Department of Homeland Security, other government agencies have also taken notice of the sensor and its potential applications. For example, the Department of Defense may be interested in using it to monitor wounds in soldiers and to detect roadside improvised explosive devices (IEDs). If a soldier or first responder suffered an open wound from shrapnel, the sensors could help determine if the wound became infected.

“Hydrogen peroxide generated by the human body for wounds is an indication of how good or how bad antibiotics are working to fight the wound,” Ricci noted. “Our sensor could be used as a wearable device to sniff out peroxide coming from the wound at the part-per-billion level.”

The US Coast Guard has meanwhile shown an interest in using the technology to ‘sniff out’ illegal drugs being smuggled into the United States aboard ships. The sensor could also be used to detect COVID-19 in humans, replacing sniffer dogs that are finding traces of COVID-19 coming from the pores in people’s skin.

“Where dogs are detecting it from the skin, our sensors would detect it from biomarkers in people’s breath,” Ricci said.

The sensors’ reduced size and weight means they could also be attached to drones, leading to even more applications. Prof Gregory noted, “Drones need very lightweight, portable power supplies and you have to tap into their wireless communication. It’s a much different set of engineering conditions than using a robot arm that the Army is looking to use for roadside IEDs.”

The researchers are also working on sensor arrays to differentiate one explosive, or threat, from another. Ricci noted, “We’ll need an array of sensors to detect a specific explosive in the presence of other explosives or precursors. If there’s a plume of three different explosives, we may need to identify one from the others.”

Now that the sensors have proven to be effective, implementing them in real-world situations is just a matter of funding.

“Our sensor is not an off-the-shelf commercial product yet, but we have a potential partner,” Prof Gregory said. “We just need a customer to step up to the plate and say ‘here’s an order for 1000 of these, can you deliver them?’

“This is potentially life-saving technology,” Prof Gregory concluded. “We have detected things at the part-per-quadrillion level. That’s really single-molecule detection.”

Image caption: URI doctoral student Peter Ricci and Professor Otto Gregory test the Digital Dog Nose sensor platform in Prof Gregory’s Thin Film Sensors Laboratory at URI. The blue devices on the table represent the two latest versions of the Digital Dog Nose. Image credit: Mike Platek.

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