Although an electronic nose won’t replace the human nose, for the time being, it can help detect sources of offensive odours and monitor their levels in our environment. Justyna Jońca, PhD of Wrocław Tech’s Faculty of Environmental Engineering is developing the device.

The W7 researcher is a graduate of the University of Warsaw who developed her PhD thesis in collaboration with the Laboratory of Geophysical Research and Satellite Oceanography (LEGOS) of the National Centre for Scientific Research (Toulouse, France) and the Interdisciplinary Centre for Nanotechnology at Aarhus University (in collaboration with UNISENSE A/S) in Denmark.

Justyna Jońca, PhD worked on electrochemical sensors for measuring phosphates and silicates in seawater and tested her devices in conditions including two ocean expeditions.

– Phosphates and silicates are macronutrients essential for phytoplankton to thrive. It absorbs CO2 from the air and converts it into organic matter. By analysing the concentration of these macronutrients on the surface and at different depths in ocean waters, we can follow different types of microbiological processes as well as the movement of water masses, as well as drawing conclusions about the past and future of our climate – says the researcher.

She did her postdoctoral placement at the Laboratory of Coordination Chemistry of the National Centre for Scientific Research in Toulouse. During this time, she worked on the synthesis and application of metal nanoparticles and metal oxides for the design of electronic noses for air quality testing and applications in the catalytic removal of carbon monoxide from exhaust gases.

After returning to Poland, she became involved in popularising science and, after a break due to maternity leave, she applied for a grant under the Marie Skłodowska-Curie Programme and joined the team headed by University professor Izabela Sowka, PhD, Dsc, Eng. of the Faculty of Environmental Engineering. It is at Wrocław Tech that she will spend the next three years carrying out her project to create an innovative electronic nose called SENSODOR.

How to evaluate a fragrance?

– It’s very difficult to measure smell. Typical analytical techniques allow us to determine the chemical composition of the mixture responsible for the occurrence of an odour, but they don’t answer the questions of whether it’s pleasant or what is its concentration or intensity – explains Justyna Jońca, PhD. – By far the best instrument for assessing odour nuisance is our nose. Techniques to estimate odour nuisance are called olfactometry – she adds.

In a nutshell, it can be said that the technique of so-called dynamic olfactometry makes use of human noses. A team of at least four people, a so-called panel of human noses, with appropriate training and procedures, can accurately determine the olfactory concentration and intensity, as well as the hedonic quality of different types of olfactory mixtures. The electronic noses that our researcher wants to create are intended to be a complement to this type of research.

– Assembling a team and carrying out an assessment is costly and time-consuming, and in the meantime, the source of the odour nuisance may be abated by a change to the nature of the emissions and the conditions surrounding them. The solution may be electronic noses making up a monitoring network around the subject of interest, e.g. a municipal waste management plant. This will enable continuous monitoring of the site – explains Justyna Jońca, PhD.

This is important because while fragrances are not usually dangerous to human life, prolonged exposure to them can cause problems with concentration or eye and throat irritation, among other things, which translates into a reduced quality of life and work.

A sensor network

And how will the electronic nose be constructed? These types of devices consist primarily of a sensor array, and at the heart of each sensor is a so-called sensing layer, which can be made of polymers or semiconductor metal oxides, i.e. zinc oxide, tin oxide, or copper oxide, for example.

– In each device, there will be several or more such sensors, but they won’t be selective. This means that they won’t detect a specific compound, but each of the selected sensors will react differently with the analysed mixture, explains Dr Justyna Jońca. The whole device will be enclosed in a protective box with an integrated airflow system.

Based on the signals collected from the array, a so-called odour imprint will be created. Notably, like a person’s fingerprint, each fragrance mixture has its own unique pattern. Samples will also be analysed by a panel of human noses.

The results from both measurements will be entered into a computer, which will learn progressively thanks to machine learning algorithms. So much so that it will ultimately be able to determine, on its own, the concentration and intensity of the odour from a sample unknown to it. 

– I hope that by using nanotechnology, I’ll be able to achieve better performance than that of the sensors used so far. By designing the sensing layer in the nanoscale, properties including higher device sensitivity can be achieved. The final stage of the project, once the electronic nose has been developed and a monitoring network created, will be to install it on a drone. This type of autonomous device could be used for purposes including the search for sources of odour nuisance – announces Justyna Jońca, PhD.

International cooperation

The three-year-long project will be possible thanks to a grant amounting to 224,000 EUR. At Wrocław University of Science and Technology, in addition to the team led by Prof. Izabela Sowka also Jarosław Szrek, PhD, Eng. of the Faculty of Mechanical Engineering has become involved in the project. 

Part of the research will be carried out at the Laboratory of Coordination Chemistry of the National Centre for Scientific Research in Toulouse. Adalbert Arsen, PhD – a graduate and former employee of Wrocław Tech – will be responsible for issues related to machine learning. Tests of the electronic nose, on the other hand, will most likely be carried out in cooperation with a Waste Management Plant in the Lower Silesian Voivodship.

– When the device is ready, I’d also like to start cooperation with relevant voivodship services and maybe we could implement permanent monitoring in selected places in Lower Silesia – concludes Justyna Jońca, PhD.