The e-nose consists of gas sensors made of semiconductor materials. When a molecule of interest interacts with this semiconductor, it changes its degree of electrical resistance. This resistance can be measured to determine how much of that molecule is present in the environment. This is not a novel technology, but the size of these sensors is shrinking, which is making them much more suitable for use in a wearable device, like the eyeglasses demonstrated by the researchers.
— Read more in A New Scent-sation: This artificial sniffer may one day restore the sense of smell to those that lost it to COVID-19 or other medical conditions at Hackster.io.