2.2. New Approaches 707 2.2.1. Optical Sensor Systems 707 2.2.2. Mass Spectrometry 708 2.2.3. Ion Mobility Spectrometry 708 2.2.4. Gas Chromatography 709 2.2.5. Infrared Spectroscopy 709 2.2.6. Use of Substance-Class-Specific Sensors 709 2.3. Combined Technologies 710 3. Companies 710 4. Application Areas 710 4.1. Food and Beverage 712 4.2. Environmental Monitoring 715 4.3. Disease Diagnosis 716 5. Research and Development Trends 718 5.1. Sample Handling 719 5.2. Filters and Analyte Gas Separation 719 5.3. Data Evaluation 720 6. Conclusion 721 7. References 722

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Electronic nose: current status and future trends.

Introduction to multi-layer feed-forward neural networks

This review presents an overview of 20 years of worldwide development in the field of biosensors based on special types of surface acoustic wave (SAW) devices that permit the highly sensitive detection of biorelevant molecules in liquid media (such as water or aqueous buffer solutions). 1987 saw the first approaches, which used either horizontally polarized shear waves (HPSW) in a delay line configuration on lithium tantalate (LiTaO3) substrates or SAW resonator structures on quartz or LiTaO3 with periodic mass gratings. The latter are termed “surface transverse waves” (STW), and they have comparatively low attenuation values when operated in liquids. Later Love wave devices were developed, which used a film resonance effect to significantly reduce attenuation. All of these sensor approaches were accompanied by the development of appropriate sensing films. First attempts used simple layers of adsorbed antibodies. Later approaches used various types of covalently bound layers, for example those utilizing intermediate hydrogel layers. Recent approaches involve SAW biosensor devices inserted into compact systems with integrated fluidics for sample handling. To achieve this, the SAW biosensors can be embedded into micromachined polymer housings. Combining these two features will extend the system to create versatile biosensor arrays for generic lab use or for diagnostic purposes.

Surface acoustic wave biosensors: a review

PART 1: INTRODUCTION TO OLFACTION: PERCEPTION, ANATOMY, PHYSIOLOGY AND MOLECULAR BIOLOGY.Introduction to Olfaction.Odor Classification Schemes Based on Adjective Descriptors.Odor Classification Based on Chemical Properties.Physiology and Anatomy of Olfaction.Molecular Biology of Olfaction.Taste.Final Comment.PART 2: CHEMICAL SENSING IN HUMANS AND MACHINES.Human Chemosensory Perception of Airborne Chemicals.Nasal Chemosensory Detection.Olfactory and Nasal Chemesthetic Detection of Mixtures of Chemicals.Physicochemical Determinants of Odor and Nasal Pungency.Human Chemical Sensing: Olfactometry.Instruments for Chemical Sensing: Gas Chromatography-Olfactometry.PART 3: ODOR HANDLING AND DELIVERY SYSTEMS.Introduction.Physics of Evaporation.Sample Flow System.Static System.Preconcentrator.Measurement of Sensor Directly Exposed to Ambient Vapor.Summary.PART 4: INTRODUCTION TO CHEMOSENSORS.Introduction.Survey and Classification of Chemosensors.Chemoresistors.Chemocapcitors.Potentiometric Odor Sensors.Gravimetric Odor Sensors.Optical Odor Sensors.Thermal (Calorimetric) Sensors.Amperometric Sensors.Summary of Chemical Sensors.PART 5: SIGNAL CONDITIONING AND PREPROCESSING.Introduction.Interface Circuits.Signal Conditioning.Signal Preprocessing.Noise in Sensors and Circuits.Outlook.Conclusions.Acknowledgements.PART 6: PATTERN ANALYSIS FOR ELECTRONIC NOSES.Introduction.Statistical Pattern Analysis Techniques.'Intelligent' Pattern Analysis Techniques.Outlook and Conclusions.PART 7: COMMERCIAL ELECTRONIC NOSE INSTRUMENTS.Introduction.Commercial Availability.Some Market Considerations.PART 8: OPTICAL ELECTRONIC NOSES.Introduction.Optical Vapor Sensing.The Tufts Artificial Nose.Conclusion.PART 9: HAND-HELD AND PALM-TOP MICROSENSOR SYSTEMS FOR GAS ANALYSIS.Introduction.Conventional Hand-Held Systems.Silicon-Based Microsensors.Summary and Outlook.PART 10: INTEGRATED ELECTRONIC NOSES AND MICROSYSTEMS FOR CHEMCIAL ANALYSIS.Introduction.Microcomponents for Fluid Handling.Integrated E-Nose Systems.Microsystems for Chemical Analysis.Future Outlook.PART 11: ELECTRONIC TONGUES AND COMBINATIONS OF ARTIFICIAL SENSES.Introduction.Electronic Tongues.The Combination or Fusion of Artificial Senses.Conclusions.PART 12: DYNAMIC PATTERN RECOGNITION METHODS AND SYSTEM IDENTIFICATION.Introduction.Dynamic Models and System Identification.Identifying a Model.Dynamic Models and Intelligent Sensor Systems.Outlook.PART 13: DRIFT COMPENSATION, STANDARDS, AND CALIBRATION METHODS.Physical Reasons for Drift and Sensor Poisoning.Examples of Sensor Drift.Comparison of Drift and Noise.Model Building Strategies.Calibration Transfer.Drift Compensation.Conclusions.PART 14: CHEMICAL SENSOR ARRAY OPTIMIZATION: GEOMETRIC AND INFORMATION THEORETIC APPROACHES.The Need for Array Performance Definition and Optimization.Historical Perspective.Geometric Interpretation.Noise Considerations.Non-linear Transformations.Array Performance as a Statistical Estimation Problem.Fisher Information Matrix and the Best Unbiased Estimator.Performance Optimization.Conclusions.PART 15: CORRELATING ELECTRONIC NOSE AND SENSORY PANEL DATA.Sensory Panel Methods.Applications of Electronic Noses for Correlating Sensory Data.Algorithms for Correlating Sensor Array Data with Sensory Panels.Correlations of Electronic Nose Data with Sensory Panel Data.Conclusions.PART 16: MACHINE OLFACTION FOR MOBILE ROBOTS.Introduction.Olfactory-Guided Behavior of Animals.Sensors and Signal Processing in Mobile Robots.Trail Following Robots.Plume Tracking Robots.Other Technologies in Developing Plume Tracking Systems.Concluding Remarks.PART 17: ENVIRONMENTAL MONITORING.Introduction.Special Considerations for Environmental Monitoring.Case Study 1: Livestock Odor Classification.Case Study 2: Swine Odor Detection Thresholds.Case Study 3: Biofilter Evaluation.Case Study 4: Mold Detection.Future Directions.PART 18: MEDICAL DIAGNOSTICS AND HEALTH MONITORING.Introduction.Special Considerations in Medical/Healthcare Applications.Monitoring Metabolic Defects in Humans Using a Conducting Polymer Sensor Array to Measure Odor.The Use of Electronic Nose for the Detection of Bacterial Vaginosis.Conclusion.PART 19: RECOGNITION OF NATURAL PRODUCTS.Introduction.Recent Literature Review.Sampling Techniques.Case-Study: The Rapid Detection of Natural Products as a Means of Identifying Plant Species.Case Study: Differentiation of Essential Oil-Bearing Plants.Conclusion and Future Outlook.PART 20: PROCESS MONITORING.Introduction.Previous Work.Special Considerations.Selected Process Monitoring Examples.Future ProspectsPART 21: FOOD AND BEVERAGE QUALITY ASSURANCE.Introduction.Literature Survey.Methodological Issues in Food Measurement with Electronic Nose.Selected Case.Conclusions.Future Outlook.PART 22: AUTOMOTIVE AND AEROSPACE APPLICATIONS.Introduction.Automotive Applications.Aerospace Applications.Polymer Composite Films.Electronic Nose Operation in Spacecraft.Method Development.Future Directions.Conclusion.PART 23: DETECTION OF EXPLOSIVES.Introduction.Previous Work.State-of-the-Art of Various Explosive Vapor Sensors.Case Study.Conclusions.Future Directions.PART 24: COSMETICS AND FRAGRANCES.Introduction.The Case for an Electronic Nose in Perfumery.Current Challenges and Limitations of Electronic Noses.Literature Review of Electronic Noses in Perfumery and Cosmetics.Special Considerations for using Electronic Noses to Classify and Judge Quality of Perfumes, PRMs, and Products.Case Study 1: Use in Classification of PRMs with Different Odor Character but of Similar Composition.Case Study 2: Use in Judging the Odor Quality of a Sunscreen Product.Conclusions.Future Directions.Index.

Handbook of Machine Olfaction: Electronic Nose Technology

https://www.repository.cam.ac.uk/bitstream/1810/264501/1/Fu_et_al-2017-Progress_in_Material_Science-VoR.pdf

Advances in piezoelectric thin films for acoustic biosensors, acoustofluidics and lab-on-chip applications

Acoustic waves are currently being used in a wide range of sensor fields including physical sensing, chemical sensing and biosensing. Their implementation requires specific knowledge of materials, acoustic wave properties, device design and the sensing mechanisms involved for a wide range of applications. In this paper, the authors report on commonly used acoustic wave devices in sensor applications as well as the design techniques and fabrication processes. Sensing mechanisms and a portable sensor array system are described. The development of IC-based processes, thin-film deposition and sensitive layer fixation will allow for the integration of a total physical and chemical analysis system in the one IC package, leading to the evolution of smart sensors.

https://www.uta.edu/rfmems/BMC/0720/0902_backup/Background/sm7601.pdf

Acoustic wave sensors: design, sensing mechanisms and applications

The acoustoelectric interaction between a shear horizontally polarised surface acoustic wave (SH-SAW) sensor and different commercial brands of natural still spring water is investigated. Transient frequency responses for the samples are presented where the sensing mechanism is based upon perturbation of the electrical properties of the adjacent liquid. SH-SAW devices were fabricated on 36° rotated Y-cut, X propagating LiTaO 3 and implemented in an oscillator configuration. Modelling and simulation of the SH-SAW sensor/liquid interface is achieved using a high frequency electronic simulation software package. Theoretical and experimental results are compared and show good agreement and support the validity of the SH-SAW sensor model. Pattern recognition using a neural network algorithm is applied for the discrimination between the four types of sample liquids, with an initial recognition probability of 90%.

Identification of natural spring water using shear horizontal SAW based sensors

In the field of temperature measurements, microsensors are based on different physical transduction principles, such as semiconductor parameters (conductivity, p–n junction voltage), metallic junction voltage (thermocouple) or elastic wave velocity variations (bulk or surface acoustic waves). This paper discusses acoustic-based temperature microsensors. Thermal effects are modelled and applications to bulk and surface acoustic wave microsensors are presented. Moreover, the use of temperature sensing for other measurements (thermal flow and humidity sensors) is described. Improvements of sensitivities and response time by varying the operating temperature are also pointed out for gas detectors. Possibilities of temperature compensation in silicon acoustic wave microsensors are discussed.

Acoustic wave thermal sensitivity: Temperature sensors and temperature compensation in microsensors

Among the various hygrometric techniques, the dew point method is considered as the most accurate. Its principles are based on cooling a surface until water vapour condensation. Then, the measurement of the dew point temperature allows the relative humidity to be determined. This classical method consists of using an optical dew detection (light diffusion) and an additional temperature sensor to measure the dew point temperature. In order to increase the accuracy of this type of hygrometer, surface acoustic wave (SAW) devices are very useful because of their dual ability to detect the dew deposition and to measure the temperature with great accuracy. In this paper, Rayleigh wave properties were investigated in order to study the influence of dew deposition. The experimental device was cooled by means of a Peltier element until dew deposition. Because of polarization of the Rayleigh wave, the dew position induces a substantial attenuation of the wave amplitude and a shift in the wave velocity (mass-loading effect). In order to combine the influence of the temperature and of the dew deposition, a thermocouple has been deposited on an LST-cut quartz plate. The frequency versus temperature response was used for the dew point detection. Preliminary results confirm the great SAW sensitivity to dew deposition. Moreover, because of the thermal sensitivity, the accuracy of the relative humidity measurement may be considerably improved.

Surface acoustic wave (SAW) dew point sensor: application to dew point hygrometry

The use of gas sensor arrays has taken a growing place in the field of gas sensor research. One of the main drawbacks of this method is the large amount of time necessary to collect the amount of calibration data, for a convenient task [1]. The purpose of this paper is to present a brand new method for fast and reproducible characterization and calibration of gas sensors. Surface acoustic wave (SAW) gas sensors are very sensitive [2,3], nevertheless their chemical adsorbant layer must still be optimized with respect to the gas species to be detected. For food control purposes, it has been shown that SnO2 sensors may be useful [4–6]. This paper therefore deals with integrated semiconducting sensors and their ability to detect flavours. Experimental results will be presented and discussed and finally some aspects of sensor array processing, using artificial neural networks, will be explored.

Moussa Hoummady

Papers

Acoustic wave sensors: design, sensing mechanisms and applications

Identification of natural spring water using shear horizontal SAW based sensors

Acoustic wave thermal sensitivity: Temperature sensors and temperature compensation in microsensors

Surface acoustic wave (SAW) dew point sensor: application to dew point hygrometry

A fast and reproducible method for gas sensor screening to flavour compounds