Scientists from ETH Zurich have developed what they claim is the "smallest and cheapest" electronic nose for sniffing out people, designed with earthquake and avalanche rescue in mind. The nose is an array of sensors to detect various substances which, when found together, would provide the crucial "chemical fingerprint" showing the presence of human life.

The array builds on the team's previous work on building sensors to detect acetone, ammonia and isoprene which are all by-products of human metabolism and which leave our bodies either as we breath, or through our skin. Separate research has shown that these chemicals can accumulate quickly where a human is trapped.

The new "nose" combines these sensors with commercially-available ones which detect carbon dioxide and moisture, which could also indicate the presence of a person. It could be fitted to a handheld device, or to a robot or drone for reaching inaccessible locations. The team's own sensors are made from metal-oxide films with a high surface area, which makes them sensitive to trace concentrations of the target chemicals.

"The combination of sensors for various chemical compounds is important, because the individual substances could come from sources other than humans," lead author Andreas Güntner explains in a press release. "CO2, for example, could come from either a buried person or a fire source."

Though the team's sensors are the fraction of the size of your fingernail, they're shown to be as sensitive as suitcase-sized spectrometers which are much more expensive.

"Our easy-to-handle sensor combination is by far the smallest and cheapest device that is sufficiently sensitive to detect entrapped people," lead researcher Sotiris Pratsinis says in the same release. "In a next step, we would like to test it during real conditions, to see whether it is suited for use in searches after earthquakes or avalanches."

The team tested its array on people enclosed in a plethysmographic chamber, which is usually used to detect changes in volume in the body, or an organ. The scientists would next like to test it in a real-world simulation of earthquake conditions.

Though trained dogs are great at finding people trapped in snow or rubble, they come with certain disadvantages. They're not always located near to disaster areas, so travelling to where they're needed uses precious time, then once on the scene they need to take breaks from time to time. These disadvantages could be overcome with their device, the scientists say. The chances of survival drop enormously in the first hours after an earthquake strikes.

Though electronics are used in earthquake searches, they tend to be microphones and cameras rather than sensors. The researchers' device could prove more adaptable – locating those who are unconscious as well as those able to make noise. The research points out that 780,000 people have died due to earthquakes over the last 10 years. The team suggests the device could also be used to expose human trafficking.

The nose joins similar technology developed to detect nerve gas, Chron's disease, explosives and narcotics, and prostate cancer.

The team's research was published in the journal Analytical Chemistry, and can be read online.

Source: ETH Zurich

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