18-02-2017, 11:28 AM
Abstract
In an ever-developing world, where electronic devices are duplicating every other sense of perception, the sense of smell is lagging behind. Yet, recently, there has been an urgent increase in the need for detecting odors, to replace the human job of sensing and quantification.
Some of the most important applications fail in the category where human beings can not afford to risk smelling the substance. Other important applications are continuous monitoring, medical applications, etc. These applications allow man to perform tasks that were once considered impossible.The fast paced technology has helped to develop sophisticated devices that have brought the electronic nose to miniature sizes and advanced capabilities. The trend is such that there will be accurate, qualitative and quantitative measurements of odour in the near future.
Living beings interact with the surrounding environment through particular interfaces called senses, which can be divided into two groups: those detecting physical quantities and those detecting chemical quantities.
Physical interfaces (that deals with acoustic, optic, temperature and mechanic interaction mechanisms) are quite well known and a wealth of successful studies to construct their artificial counterparts have been done in the past years. On the other side the chemical interfaces (bio transducers of chemical species in air: olfaction, and in solution: taste) even if well described in literature, present some aspects of their physiological working main that are still unclear. It has also remarked to psychological difference, in human beings, between the two groups.
Indeed the information from the physical senses can be adequately elaborated, verbally expressed, firmly memorized and fully communicated. On the contrary chemical information, coming from nose and tongue, are surrounded by vagueness and this is reflected in the poor description and memorization capacity in reporting olfactory and tasting experiences. Chemical information is of primary importance for the major part of the animals; For many of them, indeed, chemistry is the unique realm of which they are concerned, while for human beings evolution has enhanced about the physical interfaces, leaving little care of the chemical interface, if we exclude unconscious acquisition and side behaviors.
For these intrinsic difficulties towards the understanding of the nature of these senses for many years only sporadic research on the possibility of fabricating artificial olfactory systems were performed. Only at the end of the eighties a new and promising approach was introduced. It was based on the assumption that an array of non-selective chemical sensors, matched with a suitable data processing method, could mimic the functions of olfaction.
In the past decade, electronic nose instrumentation has generated much interest internationally for its potential to solve a wide variety of problems in fragrance and cosmetics production, food and beverages manufacturing, chemical engineering, environmental monitoring, and more recently, medical diagnostics and bioprocesses. Several dozen companies are now designing and selling electronic nose units globally for a wide variety of expanding markets. An electronic nose is a machine that is designed to detect and discriminate among complex odors using a sensor array. The sensor array consists of broadly tuned (non-specific) sensors that are treated with a variety of odour-sensitive biological or chemical materials.
An odor stimulus generates a characteristic fingerprint (or smell-print) from the sensor array. Patterns or fingerprints from known odors are used to construct the database and train the pattern recognition system so that unknown odors can subsequently be classified and identified. Thus, electronic nose instruments are comprised of hardware components to collect and transport to the sensor array - as well as electronic circuitry to digitize and stored the sensor responses for signal processing.
Top E-nose
Mimicking the nose is a difficult task. The human nose can smell 10,000 different odor molecules mixed in the air. The odor in a substance is due to certain volatile organic compounds (VOCs), which evaporate easily and are transported by a stream of air. An e-nose can smell and estimate odors quickly, although it has little or no resemblance to the human nose.
The human nose has receptors, which serve the binding sites for VOCs. The receptor is only a molecular structure on the surface of the nerve cell to which an odorous molecule attaches to the correct form. The receptor and the binding molecule are adjusted exactly as in a key and lock arrangement. These nerve cells that detect odors align the top of the cavity in the human nose.
Once an odor molecule is attached to a receptor, a chain reaction is followed which ultimately transmits an electrical signal to the brain. A specific smell of coffee or wine is usually caused by one, but a mixture of hundreds of organic compounds. Therefore, the brain has a gigantic task of processing signals received from nerve cells from the nose, to identify the nature of the smell. The exact functioning of the brain in the processing of these signals is not yet fully understood.
An electronic nose may be defined as an instrument comprising a series of electronically sensors with partial specificity and an appropriate pattern recognition system capable of recognizing simple or complex odors (and other gaseous mixtures). The ability of an electronic nose to discriminate rapidly between slight variations in complex mixtures makes the techniques ideal for on-line process diagnosis and screening in a wide range of application areas. An electronic nose is a machine that is designed to detect and discriminate between complex odors using a series of sensors.
The sensor set consists of highly tuned (non-specific) sensors that are treated with a variety of biological or chemical materials sensitive to odors. An odor stimulus generates a characteristic fingerprint (or fingerprint) of the sensor set. Patterns or fingerprints of known odors are used to construct the database and train the pattern recognition system so that unknown odors can be classified and identified. Therefore, electronic nose instruments are made up of hardware components to collect and transport to the sensor array - as well as electronic circuitry to digitize and store the sensor responses for signal processing.
The two main components of an electronic nose are the detection system and the automated pattern recognition system. The detection system may be an array of several different detection elements (eg, chemical sensors), wherein each element measures a different property of the detected chemical, or may be a single detection device (eg, spectrometer) that produces An array of measurements for each Chemist, or may be a combination. Each chemical vapor presented to the sensor set produces a signature or pattern characteristic of the vapor. By presenting many different chemicals to the sensor array, the signature database is created. This database of tagged signatures is used to train the pattern recognition system.
The purpose of this training process is to configure the recognition system to produce unique classifications of each chemical so that an automated identification can be implemented. The amount and complexity of the data collected by the sensor set may hinder conventional chemical analysis of data in an automated manner. One approach to chemical vapor identification is to construct an array of sensors, where each sensor in the array is designed to respond to a specific chemical. With this approach, the number of unique sensors must be at least as large as the number of chemicals being monitored. It is expensive and difficult to construct highly selective chemical sensors. Artificial neural networks (RNA), which have been used to analyze complex data and recognize patterns, are showing promising results in chemical vapor recognition.
In an ever-developing world, where electronic devices are duplicating every other sense of perception, the sense of smell is lagging behind. Yet, recently, there has been an urgent increase in the need for detecting odors, to replace the human job of sensing and quantification.
Some of the most important applications fail in the category where human beings can not afford to risk smelling the substance. Other important applications are continuous monitoring, medical applications, etc. These applications allow man to perform tasks that were once considered impossible.The fast paced technology has helped to develop sophisticated devices that have brought the electronic nose to miniature sizes and advanced capabilities. The trend is such that there will be accurate, qualitative and quantitative measurements of odour in the near future.
Living beings interact with the surrounding environment through particular interfaces called senses, which can be divided into two groups: those detecting physical quantities and those detecting chemical quantities.
Physical interfaces (that deals with acoustic, optic, temperature and mechanic interaction mechanisms) are quite well known and a wealth of successful studies to construct their artificial counterparts have been done in the past years. On the other side the chemical interfaces (bio transducers of chemical species in air: olfaction, and in solution: taste) even if well described in literature, present some aspects of their physiological working main that are still unclear. It has also remarked to psychological difference, in human beings, between the two groups.
Indeed the information from the physical senses can be adequately elaborated, verbally expressed, firmly memorized and fully communicated. On the contrary chemical information, coming from nose and tongue, are surrounded by vagueness and this is reflected in the poor description and memorization capacity in reporting olfactory and tasting experiences. Chemical information is of primary importance for the major part of the animals; For many of them, indeed, chemistry is the unique realm of which they are concerned, while for human beings evolution has enhanced about the physical interfaces, leaving little care of the chemical interface, if we exclude unconscious acquisition and side behaviors.
For these intrinsic difficulties towards the understanding of the nature of these senses for many years only sporadic research on the possibility of fabricating artificial olfactory systems were performed. Only at the end of the eighties a new and promising approach was introduced. It was based on the assumption that an array of non-selective chemical sensors, matched with a suitable data processing method, could mimic the functions of olfaction.
In the past decade, electronic nose instrumentation has generated much interest internationally for its potential to solve a wide variety of problems in fragrance and cosmetics production, food and beverages manufacturing, chemical engineering, environmental monitoring, and more recently, medical diagnostics and bioprocesses. Several dozen companies are now designing and selling electronic nose units globally for a wide variety of expanding markets. An electronic nose is a machine that is designed to detect and discriminate among complex odors using a sensor array. The sensor array consists of broadly tuned (non-specific) sensors that are treated with a variety of odour-sensitive biological or chemical materials.
An odor stimulus generates a characteristic fingerprint (or smell-print) from the sensor array. Patterns or fingerprints from known odors are used to construct the database and train the pattern recognition system so that unknown odors can subsequently be classified and identified. Thus, electronic nose instruments are comprised of hardware components to collect and transport to the sensor array - as well as electronic circuitry to digitize and stored the sensor responses for signal processing.
Top E-nose
Mimicking the nose is a difficult task. The human nose can smell 10,000 different odor molecules mixed in the air. The odor in a substance is due to certain volatile organic compounds (VOCs), which evaporate easily and are transported by a stream of air. An e-nose can smell and estimate odors quickly, although it has little or no resemblance to the human nose.
The human nose has receptors, which serve the binding sites for VOCs. The receptor is only a molecular structure on the surface of the nerve cell to which an odorous molecule attaches to the correct form. The receptor and the binding molecule are adjusted exactly as in a key and lock arrangement. These nerve cells that detect odors align the top of the cavity in the human nose.
Once an odor molecule is attached to a receptor, a chain reaction is followed which ultimately transmits an electrical signal to the brain. A specific smell of coffee or wine is usually caused by one, but a mixture of hundreds of organic compounds. Therefore, the brain has a gigantic task of processing signals received from nerve cells from the nose, to identify the nature of the smell. The exact functioning of the brain in the processing of these signals is not yet fully understood.
An electronic nose may be defined as an instrument comprising a series of electronically sensors with partial specificity and an appropriate pattern recognition system capable of recognizing simple or complex odors (and other gaseous mixtures). The ability of an electronic nose to discriminate rapidly between slight variations in complex mixtures makes the techniques ideal for on-line process diagnosis and screening in a wide range of application areas. An electronic nose is a machine that is designed to detect and discriminate between complex odors using a series of sensors.
The sensor set consists of highly tuned (non-specific) sensors that are treated with a variety of biological or chemical materials sensitive to odors. An odor stimulus generates a characteristic fingerprint (or fingerprint) of the sensor set. Patterns or fingerprints of known odors are used to construct the database and train the pattern recognition system so that unknown odors can be classified and identified. Therefore, electronic nose instruments are made up of hardware components to collect and transport to the sensor array - as well as electronic circuitry to digitize and store the sensor responses for signal processing.
The two main components of an electronic nose are the detection system and the automated pattern recognition system. The detection system may be an array of several different detection elements (eg, chemical sensors), wherein each element measures a different property of the detected chemical, or may be a single detection device (eg, spectrometer) that produces An array of measurements for each Chemist, or may be a combination. Each chemical vapor presented to the sensor set produces a signature or pattern characteristic of the vapor. By presenting many different chemicals to the sensor array, the signature database is created. This database of tagged signatures is used to train the pattern recognition system.
The purpose of this training process is to configure the recognition system to produce unique classifications of each chemical so that an automated identification can be implemented. The amount and complexity of the data collected by the sensor set may hinder conventional chemical analysis of data in an automated manner. One approach to chemical vapor identification is to construct an array of sensors, where each sensor in the array is designed to respond to a specific chemical. With this approach, the number of unique sensors must be at least as large as the number of chemicals being monitored. It is expensive and difficult to construct highly selective chemical sensors. Artificial neural networks (RNA), which have been used to analyze complex data and recognize patterns, are showing promising results in chemical vapor recognition.