E-nose Devices Research Articles

Electronic Nose with Digital Gas Sensors Connected via Bluetooth to a Smartphone for Air Quality Measurements.

This paper introduces a miniaturized personal electronic nose (39 mm × 33 mm), which is managed through an app developed on a smartphone. The electronic nose (e-nose) incorporates four new generation digital gas sensors. These MOx-type sensors incorporate a microcontroller in the same package, being also smaller than the previous generation. This makes it easier to integrate them into the electronics and improves their performance. In this research, the application of the device is focused on the detection of atmospheric pollutants in order to complement the information provided by the reference stations. To validate the system, it has been tested with different concentrations of NOx including some tests specifically developed to study the behavior of the device in different humidity conditions. Finally, a mobile application has been developed to provide classification services. In this regard, a neural network has been developed, trained, and integrated into a smartphone to process the information retrieved from e-nose devices.

A Barcoded Polymer-Based Cross-Reactive Spectroscopic Sensor Array for Organic Volatiles.

The development of cross-reactive sensor arrays for volatile organics (electronic noses, e-noses) is an active area of research. In this manuscript, we present a new format for barcoded polymer sensor arrays based on porous polymer beads. An array of nine self-encoded polymers was analyzed by Raman spectroscopy before and after exposure to a series of volatile organic compounds, and the changes in the vibrational fingerprints of their polymers was recorded before and after exposure. Our results show that the spectroscopic changes experienced by the porous spectroscopically encoded beads after exposure to an analyte can be used to identify and classify the target analytes. To expedite this analysis, analyte-specific changes induced in the sensor arrays were transformed into a response pattern using multivariate data analysis. These studies established the barcoded bead array format as a potentially effective sensing element in e-nose devices. Devices such as these have the potential to advance personalized medicine, providing a platform for non-invasive, real-time volatile metabolite detection.

Multi-layer graphene as a selective detector for future lung cancer biosensing platforms.

Highly selective, fast detection of specific lung-cancer biomarkers (CMs) in exhaled human breath is vital to the development of enhanced sensing devices. Today, e-nose is a promising approach for the diagnosis of lung cancer. Nevertheless, considerable challenges to early-stage disease diagnostics still remain: e.g. decrease in sensor sensitivities in the presence of water vapor, sensor drift leading to the inability to calibrate exactly, relatively short sensor lifetimes, and difficulty discriminating between multiple diseases. However, there is a wide scope for breath diagnostics techniques, and all advanced electrodes applicable to e-nose devices will benefit them. Here, we present the promising sensing capabilities of bare multi-layer graphene (MLG) as a proof of concept for advanced e-nose devices and demonstrate its utility for biomolecule discrimination of the most common lung CMs (ethanol, isopropanol, and acetone). We report on a comparative study involving exposure of the three CM solutions on flat MLG (f-MLG) and patterned MLG (p-MLG) electrodes, where the electrical conductivity of p-MLG is significantly increased while applying acetone. Based on sensitivity tests, we demonstrate the ability to monitor the electrical response of graphene electrodes employing graphene of various wettabilities. Specifically, the f-MLG electrode displays almost 2 times higher sheet resistance (30 Ω sq-1) compared to the hydrophilic p-MLG (12 Ω sq-1). We show significant sensitivity to selected specific molecules of pristine f-MLG and p-MLG while applying CM solutions with a 1.4 × 105 ppm concentration. Finally, we show the selectivity of f-MLG and p-MLG-based sensors when exposed to 2.0 × 105 ppm solutions containing different CM combinations. Both sensors were selective in particular to acetone, since the presence of acetone leads to a sheet resistance increase. We demonstrate that an advanced e-nose approach integrated with MLG electrodes has significant potential as a design concept for utilization of molecular detection at variable concentrations such as in early-stage disease diagnosis. This early-stage approach will provide convenient and reusable complex monitoring of CMs compared to typical contact sensors which require target analysis and are limited by disposable measuring. Moreover, further integration of the Internet of Things will introduce advanced e-nose devices as a biotechnological innovation for disease resilience with the potential for commercialization.

Applications of Electronic-Nose Technologies for Noninvasive Early Detection of Plant, Animal and Human Diseases

The development of electronic-nose (e-nose) technologies for disease diagnostics was initiated in the biomedical field for detection of biotic (microbial) causes of human diseases during the mid-1980s. The use of e-nose devices for disease-diagnostic applications subsequently was extended to plant and animal hosts through the invention of new gas-sensing instrument types and disease-detection methods with sensor arrays developed and adapted for additional host types and chemical classes of volatile organic compounds (VOCs) closely associated with individual diseases. Considerable progress in animal disease detection using e-noses in combination with metabolomics has been accomplished in the field of veterinary medicine with new important discoveries of biomarker metabolites and aroma profiles for major infectious diseases of livestock, wildlife, and fish from both terrestrial and aquaculture pathology research. Progress in the discovery of new e-nose technologies developed for biomedical applications has exploded with new information and methods for diagnostic sampling and disease detection, identification of key chemical disease biomarkers, improvements in sensor designs, algorithms for discriminant analysis, and greater, more widespread testing of efficacy in clinical trials. This review summarizes progressive advancements in utilizing these specialized gas-sensing devices for numerous diagnostic applications involving noninvasive early detections of plant, animal, and human diseases.

Development of an Electronic Nose for Olfactory System Modelling using Artificial Neural Network

Electronic nose (e-nose) devices have received considerable attention in the field of sensor technology because of their many potential uses such as in identification of toxic wastes, monitoring air quality, examining odors in infected wounds and in inspection of food. Notwithstanding the vast amount of literature on the usage of e-noses for specific purposes, the technology originally and ultimately aims to mimic the capability of mammals to discriminate odors from all sorts of objects. This study demonstrates the theoretical and practical feasibility of designing an e-nose towards general odor classification. A multi-sensor array hardware unit was carefully constructed for data collection and odor detection. Important hardware design considerations such as sensor calibration, aeration, circuit protection, and voltage/current requirements were satisfied. A highly fine-tuned artificial neural network (ANN) was integrated to the hardware to interpret and relate the data to a target odor class from a set of 10 primary odors identified in a previous study. Various network architecture considerations, such as neuron count, number of layers and activation function, as well as various data treatment methods, such as normalization, and data partitioning, were investigated. The results showed that careful hardware integration with an ANN having sufficiently deep internal structure can yield accurate classification to at least half of the ten primary odor classes, namely fragrant (96%), fruity (98%), chemical (99%), peppermint (98%), and popcorn (90%). The results demonstrate the feasibility of making e-noses for general odor classification, which could lead to further broadening of e-nose applications.

Application of Electronic-Nose Technologies and VOC-Biomarkers for the Noninvasive Early Diagnosis of Gastrointestinal Diseases †.

Conventional methods utilized for clinical diagnosis of gastrointestinal (GI) diseases have employed invasive medical procedures that cause stress, anxiety and pain to patients. These methods are often expensive, time-consuming, and require sophisticated chemical-analysis instruments and advanced modeling procedures to achieve diagnostic interpretations. This paper reviews recent applications of simpler, electronic-nose (e-nose) devices for the noninvasive early diagnosis of a wide range of GI diseases by collective analysis of headspace volatile organic compound (VOC)-metabolites from clinical samples to produce disease-specific aroma signatures (VOC profiles). A different “metabolomics” approach to GI disease diagnostics, involving identifications and quantifications of disease VOC-metabolites, are compared to the electronic-nose approach based on diagnostic costs, accuracy, advantages and disadvantages. The importance of changes in gut microbiome composition that result from disease are discussed relative to effects on disease detection. A new diagnostic approach, which combines the use of e-nose instruments for early rapid prophylactic disease-screenings with targeted identification of known disease biomarkers, is proposed to yield cheaper, quicker and more dependable diagnostic results. Some priority future research needs and coordination for bringing e-nose instruments into routine clinical practice are summarized.

Rice Odours’ Readings Investigation Using Principal Component Analysis

The use of electronic nose (e-nose) devices plus principal component analysis can help the process of categorizing the 16 different rice into its type. Generally, the physical feature of an e-nose own more than one hole to capture the odour of rice. For example, the portable e-nose so-called Insniff does have 10 holes (or variables). In this situations, we will have a dataset that consist high-dimension dataset where lead to the presence of interdependencies between all variables under study. Therefore, this study is presented to investigate the odour of rice for identifying the most important variables contributing to the rice odour readings. The principal component analysis (PCA) is implemented to determine the component that best represent the all 10 variables in order to eliminate the interdependency problem, and (2) to identify which variable is considered as important and influential to the newly-formed principle component (PC). The results from PCA suggested that the first two principle components is chosen. It is based on three assessments which are Kaiser’s criterion larger than 1, cumulative proportion of total variance, and scree plot. These two principle components explained 89% of total variance. Results showed that sensor 1 (0.931) and sensor 2 (0.966) are the two important variables that highly contribute to PC1. On the other hand, for PC2, the highest contribution is from sensor 8 (0.828). This study demonstrate that PCA is effective for investigating rice odour readings.

Training and Validating a Portable Electronic Nosefor Lung Cancer Screening.

Profiling volatile organic compounds in exhaled breath enables the diagnosis of several types of cancer. In this study we investigated whether a portable point-of-care version of an electronic nose (e-nose) (Aeonose, [eNose Company, Zutphen, the Netherlands]) is able to discriminate between patients with lung cancer andhealthy controls on the basis of their volatile organic compound pattern. In this study, we used five e-nose devices to collect breath samples from patients with lung cancer and healthy controls. A total of 60 patients with lung cancer and 107 controls exhaled through an e-nose for 5 minutes. Patientswere assigned either to a training group for building an artificial neural network model or to a blinded control group for validating this model. For differentiating patients with lung cancer from healthy controls, the results showed a diagnostic accuracy of 83% with a sensitivity of 83%, specificity of 84%, and area under the curve of 0.84. Results for the blinded group showed comparable results, with a sensitivity of 88%, specificity of 86%, and diagnostic accuracy of 86%. This feasibility study showed that this portable e-nose can properly differentiate between patients with lung cancer and healthy controls. This result could have important implications for future lung cancer screening. Further studies with larger cohorts, including also more participants with early-stage tumors, should be performed to increase the robustness of this noninvasive diagnostic tool and to determine its added value in the diagnostic chain for lung cancer.

Cutting Edge Methods for Non-Invasive Disease Diagnosis Using E-Tongue and E-Nose Devices.

Biomimetic cross-reactive sensor arrays (B-CRSAs) have been used to detect and diagnose a wide variety of diseases including metabolic disorders, mental health diseases, and cancer by analyzing both vapor and liquid patient samples. Technological advancements over the past decade have made these systems selective, sensitive, and affordable. To date, devices for non-invasive and accurate disease diagnosis have seen rapid improvement, suggesting a feasible alternative to current standards for medical diagnostics. This review provides an overview of the most recent B-CRSAs for diagnostics (also referred to electronic noses and tongues in the literature) and an outlook for future technological development.

A Web-Based Approach for Classifying Environmental Pollutants Using Portable E-nose Devices

Poor air quality is a major public health concern in both developed and developing countries. Continued exposure to environments with high pollutant content is estimated to cause nearly 2.5 million premature deaths per year all over the world, including 370,000 in Europe. The worldwide concern about pollution is reflected in the development and implementation of increasingly stringent policies to limit the wide range of contaminants that contribute to poor air quality. However, the sensing of these contaminants in a comprehensive, reliable, and low-cost manner still remains a major challenge. Electronic noses are intelligent systems that can classify and quantify different gases and odors. In this article, the authors evaluate which classification approaches are most effective for identifying and distinguishing between environmental pollutants, and they describe a novel Web-based software framework that incorporates these classifiers to detect pollutants.

Recent progress in the design and clinical development of electronic-nose technologies

Recent progress in the design and clinical development of electronic-nose technologies Alphus D Wilson Forest Insect and Disease Research (FIDR), Southern Hardwoods Laboratory, Center for Bottomland Hardwoods Research, Southern Research Station, USDA Forest Service, Stoneville, MS, USA Abstract: Electronic-nose (e-nose) devices are instruments designed to detect and discriminate between precise complex gaseous mixtures of volatile organic compounds derived from specific organic sources, such as clinical test samples from patients, based on electronic aroma signature patterns (distinct digital sensor responses) resulting from the combined outputs of a multisensor array. E-nose tools allow the identification of complex gaseous samples at relatively low costs, making them useful in a diverse range of clinical situations, particularly for assessments of a patients' metabolic (physiological) health and for diagnostic applications. The acquisition and analysis of e-nose clinical "breathprints" or "smellprints", taken from patients' exhaled air, allow for the potential detection of a wide range of human ailments due to abnormal metabolic activities, disorders, and diseases that may be present in the lungs, other organs, and various compartments of the human body. E-nose instruments have shown strong capabilities for detecting inflammatory lung diseases, various types of cancers, patients' exposure to toxins and harmful drugs, organ failures, and many other abnormal human conditions. The increasing trend of medical procedures to move toward the use of noninvasive diagnostic methods, such as breath analysis of complex gases and metabolic biomarkers using e-nose devices, is likely to continue because these methods are quicker, more efficient, and cause less stress, anxiety, and pain to patients. The need for standardization of e-nose analysis methods for use in clinical applications will be resolved with new research, eventually allowing the use of portable e-nose devices in clinical practice to become routine and accepted as the preferred tools of choice by physicians for many clinical tasks. This review provides a brief summary of recent progress in the development of e-nose applications for clinical examinations, general medical practice, and for other branches of medical science and research. Keywords: breath analysis, electronic aroma detection, e-nose, point-of-care diagnostic testing, volatile organic compounds

Machine Olfaction Device (MOD) Chambers with Two Sensors

The Electronic Nose (or eNose) presently possesses a number of challenges, such as short life-time of the sensors; sensitivity towards moisture; narrow selectivity; relatively expensive; mostly used as a laboratory tool and in some cases results can be difficult to reproduce due to the presence of multiple sensors. The present available devices either lack mobility or are not designed for a long term use. Most of these devices use arrays of sensors, i.e. eNoses, rather than two sensors. Also, the design of the chamber in most present devices can add problems, such as replacement of the sensor, long term functionality and other related issues. This paper is aimed at developing a novel and improved machine olfaction device (MOD) with on-board data processing capability for monitoring applications. Such a system will be able to use two sensors rather than an array of sensors, as is the case with the present eNose devices. The aim is for a real time MOD which can be used inside and outside the laboratory and for domestic and commercial purposes as well. This new approach can be achieved within the design provided in this paper.

Advances in electronic-nose technologies for the detection of volatile biomarker metabolites in the human breath.

Recent advancements in the use of electronic-nose (e-nose) devices to analyze human breath profiles for the presence of specific volatile metabolites, known as biomarkers or chemical bio-indicators of specific human diseases, metabolic disorders and the overall health status of individuals, are providing the potential for new noninvasive tools and techniques useful to point-of-care clinical disease diagnoses. This exciting new area of electronic disease detection and diagnosis promises to yield much faster and earlier detection of human diseases and disorders, allowing earlier, more effective treatments, resulting in more rapid patient recovery from various afflictions. E-nose devices are particularly suited for the field of disease diagnostics, because they are sensitive to a wide range of volatile organic compounds (VOCs) and can effectively distinguish between different complex gaseous mixtures via analysis of electronic aroma sensor-array output profiles of volatile metabolites present in the human breath. This review provides a summary of some recent developments of electronic-nose technologies, particularly involving breath analysis, with the potential for providing many new diagnostic applications for the detection of specific human diseases associated with different organs in the body, detectable from e-nose analyses of aberrant disease-associated VOCs present in air expired from the lungs.

Coupling gas chromatography and electronic nose detection for detailed cigarette smoke aroma characterization

Aroma characterization of whole cigarette smoke samples using sensory panels or electronic nose (E-nose) devices is difficult due to the masking effect of major constituents and solvent used for the extraction step. On the other hand, GC in combination with olfactometry detection does not allow to study the delicate balance and synergetic effect of aroma solutes.To overcome these limitations a new instrumental set-up consisting of heart-cutting gas chromatography using a capillary flow technology based Deans switch and low thermal mass GC in combination with an electronic nose device is presented as an alternative to GC–olfactometry. This new hyphenated GC–E-nose configuration is used for the characterization of cigarette smoke aroma. The system allows the transfer, combination or omission of selected GC fractions before injection in the E-nose. Principal component analysis (PCA) and discriminant factor analysis (DFA) allowed clear visualizing of the differences among cigarette brands and classifying them independently of their nicotine content. Omission and perceptual interaction tests could also be carried out using this configuration. The results are promising and suggest that the GC–E-nose hyphenation is a good approach to measure the contribution level of individual compounds to the whole cigarette smoke.

Electronic Nose Based on Nanomaterials: Issues, Challenges, and Prospects

The ability to precisely control the morphology and dimension coupled with the tunable surface reactivity has led to the widespread investigation of nanomaterials for various device applications. The associated high surface area to volume ratio implies that large numbers of atom are residing on the surface and are available for interaction. Accordingly, nanomaterials have demonstrated the potential to realize sensors with ultrahigh sensitivities and fast response kinetics. The smaller size further provides the possibility of miniaturization and integration of large number of devices. All these properties makes them an attractive candidate for the fabrication of electronic nose or e-nose. E-nose is an intelligent chemical-array sensor system that mimics the mammalian olfactory system. The present paper critically reviews the recent development in the field of nanomaterials based e-nose devices. In particular, this paper is focused on the description of nanomaterials for e-nose application, specifically on the promising approaches that are going to contribute towards the further development of this field. Various issues related to successful utilization of different nanomaterials for commercial application are discussed, taking help from the literature. The review concludes by briefing the important steps taken towards the commercialization and highlighting the loopholes that are still to be addressed.

Effect of transportation and storage using sorbent tubes of exhaled breath samples on diagnostic accuracy of electronic nose analysis

Many (multi-centre) breath-analysis studies require transport and storage of samples. We aimed to test the effect of transportation and storage using sorbent tubes of exhaled breath samples for diagnostic accuracy of eNose and GC-MS analysis. As a reference standard for diagnostic accuracy, breath samples of asthmatic patients and healthy controls were analysed by three eNose devices. Samples were analysed by GC-MS and eNose after 1, 7 and 14 days of transportation and storage using sorbent tubes. The diagnostic accuracy for eNose and GC-MS after storage was compared to the reference standard. As a validation, the stability was assessed of 15 compounds known to be related to asthma, abundant in breath or related to sampling and analysis. The reference test discriminated asthma and healthy controls with a median AUC (range) of 0.77 (0.72–0.76). Similar accuracies were achieved at t1 (AUC eNose 0.78; GC-MS 0.84), t7 (AUC eNose 0.76; GC-MS 0.79) and t14 (AUC eNose 0.83; GC-MS 0.84). The GC-MS analysis of compounds showed an adequate stability for all 15 compounds during the 14 day period. Short-term transportation and storage using sorbent tubes of breath samples does not influence the diagnostic accuracy for discrimination between asthma and health by eNose and GC-MS.

In Tube Integrated Electronic Nose System on a Flexible Polymer Substrate

The fabrication of electronic devices, such as gas sensors on flexible polymer substrates, enables the use of electronics in applications where conventional devices on stiff substrates could not be used. We demonstrate the development of a new intra-tube electronic-nose (e-nose) gas sensor device with multiple sensors fabricated and integrated on a flexible substrate. For this purpose, we developed a new method of fabricating a sensor array of four gas sensors on a flexible polymer substrate. The method allowed the use of lithography techniques to pattern different polymers with a broad range of solubility parameters. Conductive polymer composites were used as a gas sensitive layer due to the high stretchability of the material. Each of the 30 e-nose devices on one substrate was designed to fit on a polymer strip with a width of 2 mm. A single e-nose strip was successfully integrated into the inlet tube of a gas-measurement apparatus with an inner-tube diameter of 3 mm. Using the e-nose, we were able to differentiate between four different volatile solvent vapors. The tube-integrated e-nose outperformed a chamber-integrated e-nose of the same type in terms of response time and flow-rate influences. The sensor array inside the tube showed a faster response time and detected short pulses of analyte exposure compared to the same sensor array outside of the tube. We measured gas flow rates from 1,000 to 30 sccm without significant changes in sensor performance using this intra-tube e-nose prototype. The tube could be bent to radii <15 mm with a sensor performance similar to an unbent sensor.

Theoretical and practical considerations for teaching diagnostic electronic-nose technologies to clinical laboratory technicians

The rapid development of new electronic technologies and instruments, utilized to perform many current clinical operations in the biomedical field, is changing the way medical health care is delivered to patients. The majority of test results from laboratory analyses, performed with these analytical instruments often prior to clinical examinations, are frequently used for management decisions pertaining to patient care rather than as aids to diagnosis. The introduction of novel, improved electronic methods and portable tools for diagnosing diseases and for administering treatments has required continuous retraining of laboratory technicians for routine clinical operations and point-of-care testing. Continuous education and competency of clinical laboratory technicians in the proper use of these new healthcare tools, such as electronic-nose (e-nose) devices, is required to obtain the highest quality information possible for management decisions and to develop efficient treatments for patients. E-nose devices often provide more accurate and timely information than conventional chemical methods. Electronic-nose devices of various types and operational technologies are beginning to be used at increasing frequency in hospitals and clinical settings because of the capability of these instruments to provide rapid, accurate information of a patient's physiological state and health in real-time, eliminating the need for time-consuming chemical tests. E-nose devices are ideal instruments for the detection and diagnosis of disease and for the rapid recognition (sensing) of chemical-bioindicator compounds as indicators of disease within human fluid and tissue samples sent to diagnostic clinical laboratories for analysis. The proper training of technicians in the effective use of e-nose instruments for healthcare applications requires thorough understanding of the theoretical workings of e-nose devices and practical knowledge of operational methodologies that must be followed in order to effectively use e-nose devices to obtain the essential patient information required by medical doctors to make accurate diagnoses and administer rapid effective treatments. This paper provides a review of the most important theoretical and practical considerations to include in the development of training courses to teach clinical laboratory technicians how to properly operate e-nose devices for effective clinical analyses.

Review of Electronic-nose Technologies and Algorithms to Detect Hazardous Chemicals in the Environment

Novel mobile electronic-nose (e-nose) devices and algorithms capable of real-time detection of industrial and municipal pollutants, released from point-sources, recently have been developed by scientists worldwide that are useful for monitoring specific environmental-pollutant levels for enforcement and implementation of effective pollution-abatement programs. E-nose devices are ideal instruments for measuring and monitoring carbon and greenhouse-gas emissions due to their sensitivity to a wide diversity of volatile organic compounds (VOCs). A large number of e-nose instrument types, based on a wide diversity of technologies and operational mechanisms, are available to monitor gaseous and particulate pollutants released into the atmosphere, or liquid and dissolved organic pollutants released into municipal and industrial waste-water systems. Some commonly used e-nose technologies include conducting polymers (CP), metal-oxide semiconductor (MOS), quartz crystal microbalance (QCM), and surface acoustic wave (SAW) sensors. Potential pollution-detection applications of e-noses range from atmospheric pollutant (gas-leak) detection of carbon emissions from biofuel production plants and fossil-fuel production sources in the oil and gas industry to VOC-releases from numerous other industries. E-nose technologies are potentially capable of monitoring all phases of industrial manufacturing processes to minimize production of pollutants and maintain efficient, clean production lines. E-nose devices are also useful in designing more environmentally-friendly, clean technologies for energy production, various industrial processes and product-manufacturing systems. This paper is a review of recent novel electronic-nose systems and algorithms, developed over the past decade, that have potential applications for detecting specific types of harmful VOC pollutants in the environment to meet carbon-capture and emission-reduction targets of worldwide environmental protection agencies.

Advanced Methods for Teaching Electronic-Nose Technologies to Diagnosticians and Clinical Laboratory Technicians

Electronic-detection technologies and instruments increasingly are being utilized in the biomedical field to perform a wide variety of clinical operations and laboratory analyses to facilitate the delivery of health care to patients. The introduction of improved electronic instruments for diagnosing diseases and for administering treatments has required new training of laboratory technicians in order that they may perform routine clinical operations, point-of-care testing, and laboratory analyses using these new diagnostic tools. Continuous education and competency of clinical laboratory technicians in the proper use of these new healthcare tools, such as electronic-nose (e-nose) devices, is required to obtain accurate and timely information needed for making patient management decisions and for developing better and more efficient treatments for patients than are possible with conventional methods. E-nose devices are ideal instruments for the rapid detection and diagnosis of disease via detection of specific volatile organic compounds (VOCs) that are effective bioindicators of disease found within human breath, fluid and tissue samples sent to clinical laboratories for analysis. The proper training of technicians in the effective use of e-nose instruments for healthcare applications requires thorough understanding of the theoretical workings of e-nose devices and practical knowledge of specialized methodologies. This paper provides a summary of some advanced e-nose methodologies and techniques necessary for training clinical laboratory technicians in the proper use and operation of e-nose devices.