Almost all animals have some ability to detect smells their environment and there are countless odorant molecules and combinations of molecules in the environment that our systems are challenged with identifying. The sense of smell is important in many biological processes such as finding food, mates, and detecting threats. Scents may also conjure up memories and affect our emotions.
About 5% of the population either has no (anosmia) or very little (hyposmia) ability to detect smells and there are currently no medical devices available to restore the sense of smell. Across species, the ability to smell relies on receptors in the nose that detect chemicals, the activation of neurons that send this information to the brain, which processes the signal and perceives the smell. The olfactory system and its varying levels of complexity has been studied in vertebrates as well as invertebrates. While the system is less complex in invertebrates, it maintains much the same design and function.
In a pioneering study published in 1982, scientists created electronic sensors in an attempt to create an “electronic nose”. Since then, many researchers have been building on this work to create artificial systems that can detect airborne chemicals. Although these systems have been useful in security applications (drug and explosives detection), they have not led to the creation of devices small enough to be useful in helping individuals with anosmia smell their environment.
A comprehensive article published recently in Physiological Reviews sought to bridge the gap between understanding of biological and artificial odorant sensing in an effort to foster collaborations that not only advance each field, but also in the hope of inspiring the creation of artificial sensors for humans. The biological nose is very complex and has many receptors with varying sensitivities for detecting a number of different molecules. This sensitivity and overlap mean that molecules with similar structures can actually be perceived as different smells. This complexity is one of the many factors that make biological olfactory systems very difficult to replicate in artificial systems.
I Manzini, D Schild, C Di Natale. Principles of odor coding in vertebrates and artificial chemosensory systems. Physiological Reviews. 102(1): 61-154,2021.