Advances in SAW Gas Sensors Based on the Condensate-Adsorption Effect

Cheng

Hong

et al. 2012

Sensors

1,269

688

Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity for performance indicators to compare different sensing technologies, analyzes the factors that influence these two indicators, and lists several corresponding improved approaches.

Section: Metal Oxide Semiconductormentioning

confidence: 99%

A Survey on Gas Sensing Technology

Cheng

Hong

et al. 2012

Sensors

1,269

688

“…The schematic of the resonator structure is shown in Figure 9, which consists of three interdigital transducers (IDTs) and two identical shorted grating reflectors [24].…”

Section: Pm 25 Mass Detectionmentioning

confidence: 99%

“…The schematic of the resonator structure is shown in Figure 9, which consists of three interdigital transducers (IDTs) and two identical shorted grating reflectors [24]. Prior to the fabrication of the SAW sensor chip, the design parameters of the SAW resonator are determined by using the COM model [25].…”

Section: Pm25 Mass Detectionmentioning

confidence: 99%

A Novel Particulate Matter 2.5 Sensor Based on Surface Acoustic Wave Technology

Hao²,

et al. 2018

Applied Sciences

Self Cite

Design, fabrication and experiments of a miniature particulate matter (PM) 2.5 sensor based on the surface acoustic wave (SAW) technology were proposed. The sensor contains a virtual impactor (VI) for particle separation, a thermophoretic precipitator (TP) for PM 2.5 capture and a SAW sensor chip for PM 2.5 mass detection. The separation performance of the VI was evaluated by using the finite element method (FEM) model and the PM 2.5 deposition characteristic in the TP was obtained by analyzing the thermophoretic theory. Employing the coupling-of-modes (COM) model, a low loss and high-quality SAW resonator was designed. By virtue of the micro electro mechanical system (MEMS) technology and semiconductor technology, the SAW based PM 2.5 sensor detecting probe was fabricated. Then, combining a dual-port SAW oscillator and an air sampler, the experimental platform was set up. Exposing the PM 2.5 sensor to the polystyrene latex (PSL) particles in a chamber, the sensor performance was evaluated. The results show that by detecting the PSL particles with a certain diameter of 2 µm, the response of the SAW based PM 2.5 sensor is linear, and in accordance with the response of the light scattering based PM 2.5 monitor. The developed SAW based PM 2.5 sensor has great potential for the application of airborne particle detection.

“…Different methods such as chromatography [ 13 ], spectrophotometry [ 14 ], differential optical absorption spectroscopy (DOAS), Fourier transform infrared absorption, and laser induced fluorescence spectroscopy (LIFS), have been developed for monitoring formaldehyde. For small-size and real-time monitoring devices, in addition, many microscale gaseous formaldehyde detection systems [ 15 ] and various metal oxide semiconductor materials, such as SnO 2 [ 16 , 17 , 18 ], doped ZnO [ 19 , 20 , 21 ], CdO/In 2 O 3 [ 22 ], and nanostructured materials [ 23 ] were also investigated.…”

Section: Introductionmentioning

confidence: 99%

A Room-Temperature Operation Formaldehyde Sensing Material Printed Using Blends of Reduced Graphene Oxide and Poly(methyl methacrylate)

Chuang

Yang

et al. 2015

Sensors

This work demonstrates a printable blending material, i.e., reduced graphene oxide (RGO) mixed with poly(methyl methacrylate) (PMMA), for formaldehyde sensing. Based on experimental results, 2% RGO/10% PMMA is an optimal ratio for formaldehyde detection, which produced a 30.5% resistance variation in response to 1000 ppm formaldehyde and high selectivity compared to different volatile organic compounds (VOCs), humidity, CO, and NO. The demonstrated detection limit is 100 ppm with 1.51% resistance variation. Characterization of the developed formaldehyde sensing material was performed by Fourier-transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), and Raman spectroscopy. Based on Raman spectroscopy, the basic sensing mechanism is the band distortion of RGO due to blending with PMMA and the adsorption of formaldehyde. This work establishes insights into the formaldehyde sensing mechanism and explores a potential printable sensing material for diverse applications.