Sree Sailaja Suravarapu (Y5ec089)

ELECTRONIC NOSE

Sree sailaja Suravarapu (y5ec089)

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Vijaya Kolli (y5ec116)

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ABSTRACT

The term "electronic nose" was first used in a jocular sense during our early work with sensor arrays in the 1980's.An electronic nose (e-nose) is a device that identifies the specific components of an odor and analyzes its chemical makeup to identify it.Of all the five senses, olfaction uses the largest part of the brain and is an essential part of our daily lives.

Our human nose is elegant, sensitive, and self-repairing, but the E-nose sensors do not fatigue or get the "flu". Further, the E-nose can be sent to detect toxic and otherwise hazardous situations that humans may wish to avoid.An electronic nose can be regarded as a modular system comprising a set of active materials which detect the odour, associated sensors which transduce the chemical quantity into electrical signals, followed by appropriate signal conditioning and processing to classify known odours or identify unknown odours.The signals generated by an array of odour sensors need to be processed in a sophisticated manner.An odor is composed of molecules, each of which has a specific size and shape. Each of these molecules has a correspondingly sized and shaped receptor in the human nose. When a specific receptor receives a molecule, it sends a signal to the brain and the brain identifies the smell associated with that particular molecule. Electronic noses based on the biological model work in a similar manner, albeit substituting sensors for the receptors, and transmitting the signal to a program for processing, rather than to the brain.

Electronic noses are useful in various fields.Currently, the biggest market for electronic noses is the food industry.Environmental applications of electronic noses include analysis of fuel mixtures, detection of oil leaks, testing ground water for odors, and identification of household odors. Potential applications include identification of toxic wastes, air quality monitoring, and monitoring factory emissions. Sensors can detect toxic CO, which is odorless to humans.An electronic nose has applicability as a diagnostic tool. The tragic bombings in London on the 7 July 2005 have caused many to call for bag searching at the ticket barriers on the Underground.This would cause huge delays, apart from finding the manpower to do it. A possible alternative is using an “electronic nose” to sniff out possible explosives so that only selected bags need to be searched by staff.

1.0 INTRODUCTION:

Scientists have endowed computers with eyes to see, thanks to digital cameras, and ears to hear, via microphones and sophisticated recognition software. Now they're taking computers further into the realm of the senses with the development of an artificial nose. The term "electronic nose" was first used in a jocular sense during our early work with sensor arrays in the 1980's. As the technology developed, it became apparent that the animal and human olfactory systems operate on the same principle: A relatively small number of nonselective receptors allow the discrimination of thousands of different odors.Electronic/artificial noses are being developed as systems for the automated detection and classification of odors, vapors, and gases. An electronic nose (e-nose) is a device that identifies the specific components of an odor and analyzes its chemical makeup to identify it.

2.0 WHAT IS AN ELECTRONIC NOSE?

An electronic nose can be regarded as a modular system comprising a set of active materials which detect the odour, associated sensors which transduce the chemical quantity into electrical signals, followed by appropriate signal conditioning and processing to classify known odours or identify unknown odours. The "electronic nose" is a relatively new tool that may be used for safety, quality, or process monitoring, accomplishing in a few minutes procedures that may presently require days to complete.The two main components of an electronic nose are the sensing system which consists of chemical sensors and the automated pattern recognition system. The sensing system can be an array of several different sensing elements (e.g., chemical sensors), where each element measures a different property of the sensed chemical, or it can be a single sensing device (e.g., spectrometer) that produces an array of measurements for each chemical, or it can be a combination. The quantity and complexity of the data collected by sensors array can make conventional chemical analysis of data in an automated fashion difficult. Gas sensors tend to have very broad selectivity, responding to many different substances. This is a disadvantage in most applications, but in the electronic nose, it is a definite advantage. ENose can detect an electronic change of 1 part per million. Although every sensor in an array may respond to a given chemical, these responses will usually be different. Figure 1 shows sets of responses of a typical sensor array to different pure chemicals:

3.0 ELECTRONIC NOSE SCHEME:

FIGURE-2 ELECTRONIC NOSE SCHEME

Using variants of molecules found in biology it is possible to create 'senses' from electrical charges caused by the binding of the molecules to mimic the human nose. With this approach, the sensitivity of the device can be a thousand times better than the currently available electronic nose.

The receptors, which will be housed within an artificial membrane, remain in a closed steady state until approached by smell molecules, when they will open and transmit an electrical signal which will indicate the nature of the odour

FIGURE-3 CHEMICAL SENSOR

ENose uses a collection of 16 different polymer films. These films are specially designed to conduct electricity. When a substance -- such as the stray molecules from a glass of soda -- is absorbed into these films, the films expand slightly, and that changes how much electricity they conduct.Because each film is made of a different polymer, each one reacts to each substance, or analyte, in a slightly different way. And, while the changes in conductivity in a single polymer film wouldn't be enough to identify an analyte, the varied changes in 16 films produce a distinctive, identifiable pattern.

4.0 DATA PROCESSING METHODS:

The signals generated by an array of odour sensors need to be processed in a sophisticated manner. The electronic nose research group has obtained considerable experience in the use of various parametric and non-parametric pattern analysis techniques. These include the use of linear and non-linear techniques, such as discriminant function analysis, cluster analysis, genetic algorithms, fuzzy logic, and adaptive models. An odor is composed of molecules, each of which has a specific size and shape. Each of these molecules has a correspondingly sized and shaped receptor in the human nose. When a specific receptor receives a molecule, it sends a signal to the brain and the brain identifies the smell associated with that particular molecule. Electronic noses based on the biological model work in a similar manner, albeit substituting sensors for the receptors, and transmitting the signal to a program for processing, rather than to the brain. Electronic noses are one example of a growing research area called biomimetics, or biomimicry, which involves human-made applications patterned on natural phenomena.

Figure-4 electronic nose

5.0 ANALOGY BETWEEN THE BIOLOGICAL NOSE AND E-NOSE:

Of all the five senses, olfaction uses the largest part of the brain and is an essential part of our daily lives. Indeed, the appeal of most flavors is more related to the odor arising from volatiles than to the reaction of the taste buds to dissolved substances. Our olfactory system has evolved not only to enhance taste but also to warn us of dangerous situations. We can easily detect just a few parts per billion of the toxic gas hydrogen sulfide in sewer gas, an ability that can save our life. Olfaction is closely related to the limbic or primitive brain, and odors can elicit basic emotions like love, sadness, or fear

The term, "electronic nose" or "E-nose" has come into common usage as a generic term for an array of chemical gas sensors incorporated into an artificial olfaction device, after its introduction in the title of a landmark conference on this subject in Iceland in 1991. The term E-nose is not pejorative.There are striking analogies between the artificial noses of man and the "Bio-nose" constructed by Nature. Figure 2 illustrates a biological nose and points out the important features of this "instrument". Fig-5the "Biological Nose" (by Mother Nature)

Figure 3 illustrates the artificial electronic nose. Comparing the two is instructive.

Fig-6 Artificial Electronic Nose

The human nose uses the lungs to bring the odor to the epithelium layer; the electronic nose has a pump. The human nose has mucous, hairs, and membranes to act as filters and concentrators, while the E-nose has an inlet sampling system that provides sample filtration and conditioning to protect the sensors and enhance selectivity. The human epithelium contains the olfactory epithelium, which contains millions of sensing cells, selected from 100-200 different genotypes that interact with the odorous molecules in unique ways. The E-nose has a variety of sensors that interact differently with the sample. The human receptors convert the chemical responses to electronic nerve impulses. The unique patterns of nerve impulses are propagated by neurons through a complex network before reaching the higher brain for interpretation. Similarly, the chemical sensors in the E-nose react with the sample and produce electrical signals. A computer reads the unique pattern of signals, and interprets them with some form of intelligent pattern classification algorithm. From these similarities we can easily understand the nomenclature. However, there are still fundamental differences in both the instrumentation and software! The Bio-nose can perform tasks still out of reach for the E-nose, but the reverse is also true

October 6, 2004: Onboard the space station, astronauts are surrounded by ammonia. It flows through pipes, carrying heat generated inside the station (by people and electronics) outside to space. Ammonia helps keep the station habitable.

But it's also a poison. And if it leaks, the astronauts will need to know quickly. Ammonia becomes dangerous at a concentration of a few parts per million (ppm). Humans, though, can't sense it until it reaches about 50 ppmAnd then there's fire. Before an electrical fire breaks out, increasing heat releases a variety of signature molecules. Humans can't sense them either until concentrations become high.Astronauts need better noses!That's why NASA is developing the Electronic Nose, or ENose for short. It's a device that can learn to recognize almost any compound or combination of compounds. It can even be trained to distinguish between Pepsi and Coke. Like a human nose, the ENose is amazingly versatile, yet it's much more sensitive

figure-7 working process

6.0 ADVANTAGES OF E-NOSE: Our human nose is elegant, sensitive, and self-repairing, but the E-nose sensors do not fatigue or get the "flu". Further, the E-nose can be sent to detect toxic and otherwise hazardous situations that humans may wish to avoid. 6.1 ELECTRONIC NOSE FOR ENVIRONMENTAL MONITORING:

Enormous amounts of hazardous waste (nuclear, chemical, and mixed wastes) were generated by more than 40 years of weaponsÕ production in the U.S. Department of EnergyÕs weaponsÕ complex. The Pacific Northwest National Laboratory is exploring the technologies required to perform environmental restoration and waste management in a cost effective manner. This effort includes the development of portable, inexpensive systems capable of real-time identification of contaminants in the field. Electronic noses fit this category. Environmental applications of electronic noses include analysis of fuel mixtures, detection of oil leaks, testing ground water for odors, and identification of household odors. Potential applications include identification of toxic wastes, air quality monitoring, and monitoring factory emissions. Sensors can detect toxic CO, which is odorless to humans.

6.2 ELECTRONIC NOSES FOR MEDICINE:

Because the sense of smell is an important sense to the physician, an electronic nose has applicability as a diagnostic tool. An electronic nose can examine odors from the body (e.g., breath, wounds, body fluids, etc.) and identify possible problems. Odors in the breath can be indicative of gastrointestinal problems, sinus problems, infections, diabetes, and liver problems. Infected wounds and tissues emit distinctive odors that can be detected by an electronic nose. Odors coming from body fluids can indicate liver and bladder problems. A more futuristic application of electronic noses has been recently proposed for telesurgery

6.3 ELECTRONICS NOSE FOR THE FOOD INDUSTRY:

Currently, the biggest market for electronic noses is the food industry. Applications of electronic noses in the food industry include quality assessment in food production, inspection of food quality by odor, control of food cookingprocesses, inspection of fish, monitoring the fermentation process, verifying if orange juice is natural, monitoring food and beverage odors, grading whiskey, inspection of beverage containers, checking plastic wrap for containment of onion odor, and automated flavor control to name a few. In some instances electronic noses can be used to augment or replace panels of human experts. In other cases, electronic noses can be used to reduce the amount of analytical chemistry that is performed in food production especially when qualitative results will do.

6.4 ELECTRONIC NOSE FOR MULTIMEDIA APPLICATIONS:

Multimedia systems are widely used in consumer electronics environments today, where humans can work and communicate through multi-sensory interfaces. Unfortunately smell detection and generation systems are not part of today's multimedia systems. Hence we can use electronic nose in multimedia environment.

6.5 ELECTRONIC NOSE USED IN DETECTION OF BOMBS:

The tragic bombings in London on the 7 July 2005 have caused many to call for bag searching at the ticket barriers on the Underground. This would cause huge delays, apart from finding the manpower to do it. A possible alternative is using an “electronic nose” to sniff out possible explosives so that only selected bags need to be searched by staff. The concept has been around for a long time, and was initially ridiculed. The basic idea is a device that identifies the specific components of an odour and analyzes its chemical makeup to identify it. One mechanism would be an array of electronic sensors would sniff out the odours while a second mechanism would see if it could recognize the pattern.

6.6 OTHER APPLICATIONS:

Electronic nose can be used for early fire detection. E-nose offers an opportunity to develop an instrumental approach for the human analytical endpoints like odor, flavor, hazardous, contaminated, spoiled, and the like.

7.0 CONCLUSION:

Humans are not well suited for repetitive or boring tasks that are better left to machines. No wonder the E-nose is sometimes referred to as a "sniffer".The E-nose has the interesting ability to address analytical problems that have been refractory to traditional analytical approaches.GOSPEL is a European network of excellence in Artificial Olfaction.

8.0 REFERENCE:

1.Electronics for u August 2006 edition.

2. E:\enose\Electrochemistry encyclopedia --- Electrochemical nose.mht

4.E:\enose\The Electronic Nose.mht

5.E:\enose\12.mht

6.E:\enose\Artificial Noses ___ and Taste.mht