Chemical Gas Sensors: Recent Developments, Challenges, and the Potential of Machine Learning—A Review

Abstract

Nowadays, there is increasing interest in fast, accurate, and highly sensitive smart gas sensors with excellent selectivity boosted by the high demand for environmental safety and healthcare applications. Significant research has been conducted to develop sensors based on novel highly sensitive and selective materials. Computational and experimental studies have been explored in order to identify the key factors in providing the maximum active location for gas molecule adsorption including bandgap tuning through nanostructures, metal/metal oxide catalytic reactions, and nano junction formations. However, there are still great challenges, specifically in terms of selectivity, which raises the need for combining interdisciplinary fields to build smarter and high-performance gas/chemical sensing devices. This review discusses current major gas sensing performance-enhancing methods, their advantages, and limitations, especially in terms of selectivity and long-term stability. The discussion then establishes a case for the use of smart machine learning techniques, which offer effective data processing approaches, for the development of highly selective smart gas sensors. We highlight the effectiveness of static, dynamic, and frequency domain feature extraction techniques. Additionally, cross-validation methods are also covered; in particular, the manipulation of the k-fold cross-validation is discussed to accurately train a model according to the available datasets. We summarize different chemresistive and FET gas sensors and highlight their shortcomings, and then propose the potential of machine learning as a possible and feasible option. The review concludes that machine learning can be very promising in terms of building the future generation of smart, sensitive, and selective sensors.

Flexible IoT Gas Sensor Node for Automated Life Science Environments Using Stationary and Mobile Robots

“…Many research groups deal with the field of gas detection and monitoring. This high interest is on the one hand attributable to novel innovations and possibilities in sensor design [9,10] and on the other hand to the increasing demand of technical solutions, for example, the air pollution monitoring in urban environments [11][12][13], the supporting measures against the COVID-19 pandemic [14,15] and the protection of working environments against hazardous situations by the exposure of pollutants [16][17][18].…”

Selective multiple analyte detection using multi-mode excitation of a MEMS resonator

“…We should mention that in case of a mixed gas with three gases or more, the proposed technique does not lead to fully selective detection technique, and thus, it is not possible to discriminate the nature of the tested gases. Hence, to address the cross-sensitivity in mixed gas sensing, one of the solution is based on using data processing or machine learning technique 18 , 19 .…”

“…Nevertheless, these filter membranes might be restricted to a very small size target analyte as the bigger pores may allow diffusion of several other gases/chemicals with similar diameters resulting in cross-sensitivity 16 . Alternatively, electronic nose systems (E-nose) based on arrays of sensors have been used to significantly improve the selectivity through signal processing (features extraction) and subsequent implementation of pattern recognition algorithms for the model training 18 , 19 . However, they are complex, expensive, consume high power, and require a large hardware setup for their implementation in a realistic application.…”

Development of a Portable and Modular Gas Generator: Application to Formaldehyde Analysis

“…To overcome this drawback for gaseous formaldehyde quantification, the current trend in this analytical field is to develop real-time measurement tools such as sensors [30][31][32][33][34][35], analysers [36][37][38] or even microanalyzers [14,[39][40][41][42]. Chemical sensors are based on various gas detection mechanisms [43], namely resistive/chemoresistive, electrochemical, metaloxide-semiconductor field effect transistors (MOSFET), optical (surface plastic resonance (SPR)) and surface acoustic. Although the development of increasingly efficient sensors is currently in vogue for many gaseous organic pollutants [43][44][45], it should be noted that they do not (yet) provide the necessary selectivity and sensitivities for continuous measurement of these pollutants in outdoor or indoor air, which limits the use of such chemical sensors for air monitoring.…”