Review on Smart Gas Sensing Technology

Abstract

With the development of the Internet-of-Things (IoT) technology, the applications of gas sensors in the fields of smart homes, wearable devices, and smart mobile terminals have developed by leaps and bounds. In such complex sensing scenarios, the gas sensor shows the defects of cross sensitivity and low selectivity. Therefore, smart gas sensing methods have been proposed to address these issues by adding sensor arrays, signal processing, and machine learning techniques to traditional gas sensing technologies. This review introduces the reader to the overall framework of smart gas sensing technology, including three key points; gas sensor arrays made of different materials, signal processing for drift compensation and feature extraction, and gas pattern recognition including Support Vector Machine (SVM), Artificial Neural Network (ANN), and other techniques. The implementation, evaluation, and comparison of the proposed solutions in each step have been summarized covering most of the relevant recently published studies. This review also highlights the challenges facing smart gas sensing technology represented by repeatability and reusability, circuit integration and miniaturization, and real-time sensing. Besides, the proposed solutions, which show the future directions of smart gas sensing, are explored. Finally, the recommendations for smart gas sensing based on brain-like sensing are provided in this paper.

Review on Smart Electronic Nose Coupled with Artificial Intelligence for Air Quality Monitoring

“…It imitates the human brain, and solves several practical problems in different fields [36]. ANN performs its tasks as follows: As shown in Figure 2, each neuron receives and adds the signal from the previous layer that has a weight relation, compares weighted sum to threshold values and generates outputs by activation function such as sigmoid function, radial basis [37]. There are two simple separate single layer and multilayer versions.…”

Love Wave Sensors with Silver Modified Polypyrrole Nanoparticles for VOCs Monitoring

“…Apart from the competing advantages of those sensing materials, polymers-based SAW structures demonstrated improved performance in gas sensing, owing to their low density and shear velocity. Additionally, polymers also have high sensitivity at room temperature (as opposed to semiconducting metal oxides) and report good cost-effectiveness (compared to carbon based materials) [6,11]. Among various types of SAW structures (e.g., Rayleigh, shear horizontal SAW, Love, leaky), those based on Love waves (L-SAW) have been identified to have high mass sensitivity, generally, due to the surface confinement of energy in the thin guiding layer, which makes the surface extremely sensitive to any perturbations [12].…”

Humidity-Resistive Optical NO Gas Sensor Devices Based on Cobalt Tetraphenylporphyrin Dispersed in Hydrophobic Polymer Matrix

“…Although breath contains many kinds of gas species, including water (H 2 O), carbon monoxide (CO), carbon dioxide (CO 2 ), nitrogen (N 2 ), ammonia (NH 3 ), nitrogen monoxide (NO), hydrogen sulfide (H 2 S), and more than 1,000 kinds of volatile organic compounds (VOC) [13], the simple molecular structures of these low molecular compounds make it difficult to achieve specific molecular recognition compared with biomarkers having complex molecular structures, such as proteins. Therefore, a recent strategy is based on chemometrics, which are comprised of pattern-recognition protocols of multiple signals obtained from sensor arrays with different selectivities [14].…”

“…To fabricate a sensor array with different selectivities, an effective strategy is to change the materials of the sensing interface. Various materials have been utilized as components of sensor arrays, including ionic liquids [15], single-stranded DNAs [16], reduced graphene oxide [17], and metalloporphyrin [14]. In particular, metalloporphyrin with different metal ligands has been preferably utilized as a sensing interface because of the ligands' different reactivities toward gas molecules in spite of their similar structures.…”