Successful Visualization of the Odor Discrimination Process in an AI-Assisted Olfactory Sensor

The sense of smell plays an essential role in our daily lives, including food safety, environmental monitoring, medical diagnosis and the creation of comfortable living spaces. Artificial olfaction technologies (olfactory sensors), which mimic the human sense of smell, use multiple chemical sensors to detect odorant molecules and employ artificial intelligence (AI) to classify and identify them.
However, current AI-assisted artificial olfaction has yet to reach practical application due to the limited sensitivity and discrimination accuracy of existing chemical sensors. Addressing this challenge will require higher-performance chemical sensors, particularly through the development of receptor materials capable of more effectively detecting odorant molecules.
In conventional artificial olfaction systems, AI has classified and identified odorant molecules without a full understanding of which receptor materials respond to which molecules. Revealing the response characteristics of specific receptor materials will enable the development of optimal materials for discriminating target odorants and the selection of receptor materials that achieve more accurate odor discrimination.

NIMS measured the responses of 94 odorant molecules using an MSS (membrane-type surface stress sensor) equipped with 14 receptor materials and analyzed the data with explainable AI (XAI), a technique that visualizes which parts of the data the AI relies on when discriminating among odorant molecules.
The analysis revealed that the key portions of sensor responses used for identification vary depending on the specific combinations of odorant molecules and receptor materials. For example, receptor materials containing aromatic rings were found to be important for identifying aromatic molecules.
This approach is expected to enable efficient selection of receptor materials tailored to target odorant molecules and guide the development of materials capable of identifying molecules that are otherwise difficult to detect. In addition, by revealing not only how the AI discriminates but also on what basis it makes predictions, XAI may offer important clues to understanding the mechanisms of odors and human olfaction.

This technology can be used not only to facilitate the development of receptor materials but also to select the optimal sensor from multiple options based on the intended application. In addition to supporting material development, it can contribute to the advancement of olfactory sensor devices, thereby accelerating the practical application of artificial olfaction and deepening our understanding of human olfaction.

• This project was carried out by Yota Fukui (Trainee, Center for Basic Research on Materials (CBRM), NIMS at the time of this project), Koji Tsuda (Invited Researcher, CBRM, NIMS), Ryo Tamura (Team Leader, CBRM, NIMS), Kosuke Minami (Principal Researcher, Research Center for Macromolecules and Biomaterials (RCMB), NIMS) and Genki Yoshikawa (Group Leader, RCMB, NIMS).
• This research was published online in ACS Applied Materials & Interfaces on September 9, 2025.