An electronic nose is a technology that mimics the human sense of smell, analyzing and storing odors as electrical signals, which allows it to distinguish between different smells. This technology plays an important role in industries that utilize smell, such as perfume and coffee, as well as in the detection of harmful substances, medical diagnostics, and more.
Someone walks through the door of a café and is greeted by the aroma of an unidentifiable, bitter coffee. But he quickly realizes that it’s Blue Mountain beans from Jamaica. Who is this person who can identify the type of coffee in such a short time? A common answer would be a barista, but here his identity is an electronic nose, or e-nose. An electronic nose is an electronic device that mimics the human sense of smell and is used to distinguish between different odors and analyze their composition. Until now, cameras and recorders have recorded our sight and hearing as electrical signals. The advent of the electronic nose means that the human sense of smell can also be recorded as an electrical signal.
With the advent of the electronic nose, advances in science and technology have opened up new possibilities for more precise measurement and utilization of our senses. The sense of smell is often overlooked in our daily lives, but it plays a very important role. It’s an essential sense for tasting food, and it’s also an important component of memory and emotion. The development of electronic noses is notable because it provides a way to technologically expand the role of the sense of smell.
Electronic noses are designed to mimic the way humans perceive odors. The human olfactory perception process involves three main steps. First, an odor molecule binds to an olfactory receptor, then this binding is transmitted to the brain as an electrical signal, and finally, the brain analyzes the signal to recognize the odor. There are about 390 olfactory receptors in the nose, which are the first step in recognizing an odor. What would happen if a single olfactory receptor could only bind one odorant molecule? We’d be limited to only 390 different odors! So, in order to smell a variety of odors, a single olfactory receptor must be able to bind multiple similar odor molecules. To distinguish between the different molecules, the olfactory receptor sends an electrical signal to the brain with different strengths depending on the type of molecule that is bound. The brain, which receives the electrical signals, patterns the different electrical signals from the different olfactory receptors into a mosaic and recognizes the pattern as a single odor. Through this process, humans are able to distinguish between more than 10,000 different odors.
Our ability to recognize so many different odors is a product of evolution and has played an important role in our survival. In nature, we could smell harmful substances or spoiled food and avoid them, and we could identify edible resources through the scent of flowers and fruits. Attempting to replicate this ability to smell with technology is more than just a convenience; it has implications for industrial and medical applications.
Electronic noses incorporate a variety of technologies to mimic the human sense of smell. First of all, e-noses developed to date use the same process as the human nose, which involves the binding of odor molecules to olfactory receptors. Previously, electronic olfactory receptors were used for reasons such as the conservation of the receptors. However, in recent years, researchers have been actively working on electronic noses that use actual human olfactory receptor cells to reproduce the human sense of smell. However, human olfactory receptor cells have a significant drawback: their lifespan is only about 60 days. Therefore, it is necessary to be able to culture large amounts of olfactory receptor cells in a short period of time, which is where genetic recombination technology comes in. Genetic recombination is a technique in which the gene of the cell you want to obtain is cut out of the DNA of the cell and inserted into the DNA of a cell that replicates quickly, allowing you to quickly grow large quantities of the desired cells. E. coli is often used in this technique to take advantage of its incredible DNA replication rate. Every 20 minutes, E. coli divides, doubling its DNA genes, which is very fast, and after just 2 hours and 20 minutes, the DNA is more than 1000 times the original. Genetic recombination in E. coli allowed us to obtain olfactory receptors quickly and in large quantities. This allowed the e-nose to overcome the short-lived nature of olfactory receptors.
Just as olfactory receptors in the human body bind to odor molecules and send electrical signals to the brain through wires called nerve cells, electronic noses need materials that can act as wires. There are several materials that can do this, including carbon nanotubes, conductive polymer nanotubes, and microelectrode arrays (MEAs), of which carbon nanotubes are the most actively studied. Carbon nanotubes are extremely microscopic tubes with a diameter of about 1 nm, made up of a single layer of carbon that makes them conductive. In e-noses, olfactory receptors are bonded to carbon nanotubes so that electrical signals sent by the receptors can travel along the nanotubes to sensors that analyze the electrical signals.
Research on e-noses is advancing every day, and their applications are expanding. To date, only two olfactory receptors have been successfully mass-produced: one that detects banana scent and one that detects sour scent. Analyzing the complex patterns of electrical signals from different olfactory receptors has not been well studied. But it’s a start. Once the technology is in place to mass-produce a wider variety of olfactory receptors, research will be able to flourish. Such research would improve the accuracy of electronic noses and provide the basis for precise distinctions between different odors. This is where the introduction of artificial intelligence (AI) technology is essential, as it is necessary to synthesize various types of electrical signals and recognize them as patterns. Once we have accumulated data on which combinations of electrical signals produce specific odors, electronic noses will be able to distinguish most odors.
Currently, electronic noses can smell more than 10 times better than the human nose. This shows that the sensitivity of odors that e-noses can detect has surpassed the limits of humans. Therefore, e-noses can contribute significantly to businesses that basically utilize the smell of coffee, perfume, wine, etc. Moreover, the ability of e-noses can also be applied in the field of agriculture. For example, it can be utilized to check the freshness of fruits or evaluate the aging stage of wine. These technologies will play an important role in improving the quality of products and providing consumers with better choices.
They can also be used to detect harmful substances or poisons that humans cannot smell directly. These applications will also play a vital role in the safety sector. In the event of a chemical leak, e-noses can quickly detect hazardous substances and help reduce the size of the accident. They can also store odors as electrical signals, which will play a key role in the development of context-sensitive TVs. It is also expected to be used in the medical industry to diagnose lung cancer by measuring the odor of a person’s exhaled breath. As e-noses begin to smell, a new paradigm of olfaction is on the horizon.
These advances in e-nose technology will pave the way for a better life in the future by extending our senses with technology. The time is coming when we will be able to gain information through smell and use that information to create new possibilities in various industries. The e-nose is not just a replacement for the sense of smell, but a tool for more precise and broader applications beyond the human senses.
