Robots are getting better at sniffing out smells thanks to improvements in electronic noses (e-noses). A comprehensive review of the state of robot olfaction, published in the journal npj Robotics, has surveyed recent advances in the technology. It highlights how these digital noses are becoming more sensitive and more adept at identifying the source of an odor. This is leading to improvements in a range of areas, from search and rescue missions to detecting hazardous gas leaks.
Four ways to smell
The researchers reviewed the four main types of electronic noses that act as a robot’s nostrils. These are metal oxide sensors which use a tiny, heated plate to detect gases, electrochemical sensors that rely on chemical reactions to detect specific molecules and optical sensors that use light to detect gases. They also looked at field-effect transistors, which are built on a chip and change their electrical conductivity when different gas molecules land on them.
The team compared how these different e-noses perform outside the lab by analyzing hundreds of research papers and real-world case studies. They found that while each type has its strengths, there is no perfect e-nose just yet. For example, metal oxide sensors are great at detecting faint signals but humid environments can lead to false readings. Electrochemical sensors can identify a specific gas very well, but have a shorter lifespan because the chemicals inside them dry out.
The most advanced e-noses overcome these limitations by integrating multiple sensors into a single array and using gas source localization (GSL) algorithms. These mathematical models process wind speed and odor concentration in real time to pinpoint exactly where a smell is coming from. This means a robot can ignore background odors and move toward the source of a gas leak even when the air is moving.
Challenges to overcome
But even with these impressive technological advances, robot e-noses are still falling short, according to the review. Often, they lose their accuracy over time because they become nose-blind. That is, they stop reacting to a smell because they have been exposed to it for too long. This is similar to how our noses stop noticing the smell of a room after being in it for a while. Another issue is losing a scent trail in windy conditions or when the wind shifts.
Despite these current hurdles, the researchers are optimistic about the technology’s future, especially when combining better sensor materials with AI. As they note in their paper, “By addressing these challenges and embracing cross-disciplinary innovations, e-noses will become an essential component of intelligent robotics, unlocking transformative applications across industries and significantly improving the quality of life.”
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More information:
Weiqi Zhang et al, Advanced electronic noses for future robotic olfaction, npj Robotics (2026). DOI: 10.1038/s44182-025-00071-y
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