Who likes to have bad breath? I doubt there is anyone who loves to have bad breath, especially when visiting friends and family, at a job interview and especially not on a first date. Bad breath can make things embarrassing, but it is also a sign of serious dental problems. Now, a research team has built a thumb-sized portable device that diagnoses bad breath by quickly “sniffing” the fumes for the gas that makes it stinky: hydrogen sulfide. To use a term dear to Elio: electronic “La conchetta”, Gentlemen.
A little friend who does awkward work
Most people cannot smell their breath. It's a problem, and asking someone to "test" it is embarrassing. There are some halitosis devices that measure small amounts of hydrogen sulfide, but require analysis with (expensive) instruments in the laboratory, which is not feasible for consumers. Previous studies have shown that when some metal oxides react with sulfur-containing gases, their electrical conductivity changes.
For this, to develop a small real-time bad breath analyzer, Kak Namkoong, Il-Doo Kim and colleagues looked for the right combination of substances that would elicit the fastest and strongest response to hydrogen sulfide in the air blown directly onto it. I study was published on ACS Nano.
How the device that analyzes halitosis was born
First, the researchers mixed sodium chloride nanoparticles (an alkali metal salt) and platinum (a noble metal catalyst) with tungsten. They then electrospun the solution into nanofibers which they heated, converting the tungsten to its metal oxide form.
In preliminary tests of the halitosis sniff device, the mix of equal parts of each metal showed the greatest reactivity to hydrogen sulfide, measuring changes in less than 30 seconds. Although this nanofiber reacted with some sulfur-containing gases, it was more sensitive to hydrogen sulfide, creating a response 9,5 and 2,7 times greater, respectively, than dimethyl sulfide or methyl mercaptan.
Finally, the team coated interdigitated gold electrodes with the nanofibers and combined the gas sensor with humidity, temperature and pressure sensors. Result? A small prototype device about the size of a human thumb.
The device correctly identified bad breath 86% of the time in which people's actual breaths were exhaled directly on it. Researchers say this sensor it could be incorporated into very small devices for quick and easy self-diagnosis of halitosis.