Smell success
We often take our sense of smell for granted but it is an incredibly sophisticated bit of human programming using 100 million sensors to identify and distinguish each smell. A team at the University of Warwick and Leicester University has taken on the challenge of mimicking our sense of smell with an electronic nose, replicating the mucus of the natural nose to enhance the electronic sense of smell.

Electronic noses use the same method for detecting smells but often have less than 50 sensors.  This means that electronic noses discern a smaller range of smells than the natural nose. They are used for quality control and detection in the food industry or in hospitals.

Mimicking nature
The natural nose has a thin layer of mucus that dissolves scents and separates out different odour molecules as they arrive at the nose’s receptors at different speeds. Humans are then able to use the differences in time taken to reach different nose receptors to pick apart a diverse range of smells.

The Warwick and Leicester team used artificial mucus, made from a thin layer of polymer, on the sensors in their electronic nose to separate the odour molecules. They tested it on a range of compounds and discovered that their artificial mucus substantially improved the performance of the electronic nose, allowing it to tell apart smells such as milk and banana. These had previously been challenging smells for the device.  

Distinguishing smells
University of Warwick researcher Professor Julian Gardner says, ‘There are two issues: sensitivity and, more importantly, selectivity. Whereas previous electronic or e-noses had the sensitivity to detect the odours, they couldn’t tell them apart and that's where the cleverness comes in. We are addressing the issue of selectivity rather than sensitivity.’

Professor Gardner explains that in a busy environment such as a hospital, where there are many different smells, ‘you've got a chemical soup from which you’re trying to extract key odorants related to the pathogen. This process is called “odour segmentation” and that's the real problem, which we want to solve. Most e-noses can't do it at the moment.’

Being able to distinguish different smells is crucial for commercial development. The electronic nose may provide a crucial early warning system in future security and medical applications.