What Is an Electronic Nose?

Electronic nose, also known as odor scanner, is a novel instrument for rapid food detection developed in the 1990s. It uses specific sensors and pattern recognition systems to quickly provide overall information about the sample under test, indicating the underlying characteristics of the sample. ^[1]

Electronic nose

Electronic nose, also known as odor scanner, is a novel instrument for rapid food detection developed in the 1990s. It uses specific sensors and pattern recognition systems to quickly provide overall information about the sample under test, indicating the underlying characteristics of the sample. ^[1]

The electronic nose is mainly composed of a gas sensor array, signal preprocessing, and pattern recognition. An odor is presented in front of a sensor of an active material. The sensor converts chemical input into an electrical signal. The response of multiple sensors to an odor constitutes the response spectrum of the sensor array to the odor. Obviously, various chemical components in the odor will interact with sensitive materials, so this response spectrum is the broad-spectrum response spectrum of the odor. In order to realize the qualitative or quantitative analysis of the odor, the signal of the sensor must be properly pre-processed (noise removal, feature extraction, signal amplification, etc.) and then processed by a suitable pattern recognition analysis method. Theoretically, each odor will have its characteristic response spectrum. According to its characteristic response spectrum, it is possible to distinguish the odor of the same. At the same time, the cross-sensitivity of multiple gases can be measured using an array of gas-sensitive sensors, and mixed gas analysis can be achieved through appropriate analysis methods.

The electronic nose uses the characteristics that each gas-sensitive device responds to complex component gases but is different from each other. With the help of data processing methods, multiple odors are identified to analyze and evaluate the odor quality.

The main mechanism of electronic nose recognition is that each sensor in the array has different sensitivity to the measured gas. For example, gas number one can generate a high response on one sensor and a low response to other sensors; similarly, The sensor with high response of No. 2 gas is not sensitive to No. 1 gas. After all, the response pattern of the entire sensor array to different gases is different. It is this difference that enables the system to identify the gas based on the response pattern of the sensor.

The work of the electronic nose can be simply summarized as follows: sensor array-signal preprocessing-neural network and various algorithms-computer identification (qualitative and quantitative analysis of gas). Functionally, the gas sensor array is equivalent to a large number of olfactory receptor cells in a biological olfactory system, neural networks and computer recognition are equivalent to biological brains, and the rest is equivalent to the olfactory nerve signal transmission system.

In 1964, Wilkens and Hatman used the oxidation-reduction reaction of gas on the electrode to simulate the olfactory process electronically. This is the earliest report on the electronic nose.

In 1965, Buck et al. Measured the gas using changes in the conductance of metals and semiconductors, and Dravieks et al. Used the change in contact potential to measure gas.

However, the concept of a smart chemical sensor array for gas classification was proposed by Persuad et al. Of the University of Warwick until 1982. Their electronic nose system includes a gas sensor array and a pattern recognition system. The sensor array is composed of three semiconductor gas sensors. This simple system can distinguish the odors of volatile chemicals such as tree brain, rose oil, and lilac tooth oil. In the following five years, electronic nose research did not attract widespread attention from the international academic community.

In 1987, the eighth annual meeting of the European Chemical Sensing Research Organization held at the University of Warwick in the United Kingdom was a turning point in electronic nose research. At this conference, the Gaswick Sensing Research Group of Warwick University, headed by Gardner, published a paper on the application of sensors in gas measurement, focusing on the concept of pattern recognition, which aroused widespread interest in the academic community.

In 1989, the North Atlantic Treaty Research Organization specifically organized a high-level symposium on chemical sensor information processing, dedicated to the two topics of artificial olfactory and its system design. In August 1991, the North Atlantic Treaty Research Organization called in Iceland.

The first electronic nose conference was held. Electronic nose research has developed rapidly since then.

In 1994, Gardne: published a review article on electronic nose, formally proposed the concept of "electronic nose", marking that the electronic nose technology has entered a mature and development stage.

Since 1994, after more than ten years of development, the research of electronic nose has made rapid progress. At present, the research on electronic nose mainly focuses on the design of sensors and electronic nose hardware, pattern recognition and its theory, the application of electronic nose in the fields of food, agriculture, medicine, biology, and the relationship between electronic nose and biological systems. Among them, the design of sensor and electronic nose hardware and the application of electronic nose in the field of food and agriculture are hot spots in the research of electronic nose.

Osmitec has successfully developed an electronic nose in Crewe, Cheshire, UK. Tests have shown that it can "smell" bacteria that erode patients' skin wounds, reminding doctors to take appropriate measures in a timely manner.

The electronic nose he studied is a matrix composed of 32 different organic polymer sensors, which is very sensitive to the odor emitted by various volatile compounds. Different compounds have different reactions. Generally, bacteria emit a chemical odor when they grow. When the electronic nose contacts the odor, the resistance of each sensor changes individually. Since each sensor corresponds to a different chemical substance, the "formats" of 32 different resistance changes represent the "fingerprints" of different odors, respectively.

Tests have shown that the electronic nose only needs hours to detect the presence of bacteria. In the past, laboratory testing methods were used, and the results were usually obtained within 1 to 3 days.

Researchers believe that electronic noses could revolutionize the way wounds look for MRSA and other bacteria. MRSA refers to a group of bacteria that are resistant to increasingly popular antibiotic therapies. In addition, electronic nose technology can also be used to check infections in other parts, helping patients to detect and treat early.

In 1993, Pearce et al. Applied sensors to beer detection for the first time. A laboratory-made system consisting of 12 organic conductive polymer sensors detected three similar commercial wines, two of which were stored after brewing. There is also a light-colored beer, and the results show that these three types of beer are easily identified, and a human-infected beer and an uninfected alcohol are quickly identified.

Electronic nose technology has a short response time and fast detection speed. Unlike other instruments, such as gas chromatography sensors and high performance liquid chromatography sensors, it requires a complex pretreatment process. Its measurement and evaluation range is wide, and it can detect a variety of foods; It can avoid human error and good repeatability; it can also detect some gases that human nose cannot detect, such as poisonous gas or some irritating gas. It plays an increasingly important role in many fields, especially the food industry. And with the help of graphic cognitive equipment, its specificity has been greatly improved, and the development of sensor materials has also promoted its reproducibility. With the development of biochips, biotechnology and integrated technology, and some nanomaterials, Application, the electronic nose will have broader application prospects.

Studies have found that the electronic nose that NASA uses to monitor certain gas components inside the International Space Station and the Space Shuttle can also be used to detect cancer cells in the brain. The electronic nose, called "Enose", was developed by NASA's Jet Propulsion Laboratory and is designed to detect trace ammonia leaks from the shuttle and the International Space Station. A research team composed of experts in neurosurgery, cancer and aerospace, when using this electronic nose to study brain cancer cell metastasis, found that the electronic nose can distinguish different "tastes" of healthy cells and cancer cells, so that medical personnel can accurately Determine the specific location of the cancer cell population and avoid confusion with surrounding healthy cells.

Israeli scientists have developed an "electronic nose" that can detect patients with lung, breast, bowel, and prostate cancer through a simple breath test. The research team found that the sensor, which detects changes in chemicals, can not only distinguish the breathing of healthy people and patients with malignant tumors, but also detect these four common tumors. Although more work is needed to improve this detection technology, initial success has given hope to the development of a cheap, easy-to-use, and portable early-stage cancer diagnostic technology. "If the results of early research can be confirmed through large-scale experiments, respiration testing will become a convenient means of early cancer diagnosis like imaging technology," said Kuten of the Israel Institute of Technology. Kuten and his colleagues told 177 people, including healthy people Breath tests were performed with patients with different cancers to find out the different chemicals emitted from the surface of cancer cells as they grow. Their research is published in the British Journal of Cancer. The institute discovered last year that sensors made of gold nanoparticles could detect lung cancer through breathing tests. ^[2]

1. The host computer has a built-in microcomputer system, which can analyze, store and output data without the need to configure an external computer.

2. The world's top imported sensors, containing 16 interactive sensitive sensors, each of which can work independently and can be removed and replaced independently;

3. Sensor working temperature: 200 ~ 500 ;

4. Gas receiving chamber: The overall stainless steel structure can be used for a long time without deformation, and each sensor has an independent and evenly distributed gas chamber;

5. Scope of application: flavors and fragrances, food and beverages, liquor, seasonings, oils and fats, Chinese medicine, tobacco, medicine, packaging materials, etc

6. Sample flow: 0 ~ 1.5L / min, adjustable;

7. Sensor cleaning flow: 6.5L / min, adjustable;

8. Equipped with air and oxygen dual channel cleaning;

9. A large number of data processing methods are available for users to choose, and the analysis results are intuitive and reliable.