Hydrogen gas sensor using double SAW resonator system

This paper presents a hydrogen gas sensor based on Double Surface Acoustic Wave Resonator (DSAWR) system configuration. Two commercial SAW resonators were employed to develop the DSAWR system. The sensing layer was prepared using functionalized Carbon Nanotubes (CNT) with polyaniline nanofibers. The sensing layer was integrated into the DSAWR system and measurements were carried out for hydrogen gas between 1% to 2% concentrations. Results obtained showed response of the sensor to hydrogen gas with a minimum detection limit of 1% and good response and recovery time

Sensing Materials for Surface Acoustic Wave Chemical Sensors

Online real‐time monitoring of gases requires a miniaturized, passive, and accurate gas sensor. Surface acoustic wave (SAW) devices possess these properties which make them suitable for gas‐sensing applications. They have shown remarkable results in sensing of different gases in terms of sensitivity, selectivity, response, and recovery times. One of the important prerequisites a designer should know is to have knowledge on the different types of sensing material suitable for gas‐sensing applications, prior to design and fabrication of the sensor. Different sensing materials, including metal oxides, polymers, carbon nanotubes, graphene, nanocomposites, etc. have been used for SAW gas sensors. In this article, different sensing materials for SAW gas sensors will be discussed

Relation of parallel resistance to the passive double SAW resonator

This paper presents the relationship of parallel resistor to the frequency response of the passive remote acoustic wave resonators (SAWRs) sensor system in 433.42MHz and 433.92MHz. Impedance matching is achieved with the connection of L-network to the parallel SAW resonator. The main objective of this finding is to improve the sensor of narrow bandwidth application. Circuit with high quality factor (Q factor) has better suppression for narrow band application. Parallel resistor improves the system by increasing the Q factor. Increasing the parallel resistance will decreased the bandwidth of the resonant frequency. Simulation results of the system are presented and discussed

Synthesis and characterization of carbon nano structures on Gallium Phosphate

Carbon nano structures were grown on Gallium Phosphate substrate by using Alcohol Catalytic Chemical Vapor Deposition (ACCVD) method. The aim of this paper is to study the structure and the morphology of the carbon nano structures growth on Gallium Phosphate. Gallium Phosphate is known as piezoelectric materials which are more stable and similar to quartz in its crystal structure. The ACCVD is chosen because of its simplicity and economical method for the growth of carbon nano structure. Mixture of ethanol and Iron Nitrate in a ratio of 1:25 was used as the catalyst to impregnate the carbon nano structures. The carbon nano structures were grown at 800oC. The ethanol liquid which was used as a carbon source was injected into the furnace tube with flow rate of 2.0 ml/min. The furnace was flowed by Argon gasses throughout the experiment. FE-SEM and EDX are used to investigate the morphology of the carbon structure. Finally Raman measurements have been performed and equipped with laser diode emitting at 632nm

E-band slotted microstip patch antenna array for 5G broadband applications

An antenna is one of solution for wireless devices which can be proposed for future 5G systems for high data rate broadband, communications. The antenna system can be design for multiple-input-multiple-output (MIMO) system at a waveband of millimeter (mm) range. The MIMO system consists of the mm-wave array of 2 by 1 slot antennas. The combination of the antenna array system covers the range of frequency from 83.581GHz to 86.483GHz of mm-wave band at 85 GHz. The antenna array dimension is 0.94 mm by 2.28 mm by 0.16 mm. Results obtained from simulation across the 5G band showed peak gain values of 5.82dBi, VSWR of 1.09 with -10dB return loss of -27.5dB

Easy determination of radiation absorption in brain tissue from mobile phones using finite element method

ZULKIFLY BIN ABBAS////// Abu Bakar Yakubu,Zainab Yunus

Growth of multi-walled carbon nanotubes on platinum

In this paper, Multi-Walled Carbon Nanotubes were grown on a surface of a substrate that consists of a quartz piezoelectric substrate with titanium under layer and platinum electrodes. The Carbon Nanotubes (CNT) was grown using thermal CVD with Iron Nitrate as the catalyst. The growth of the carbon nanotubes was carried out at a temperature of 800°C with hydrogen as the process gas and benzene as the hydrocarbon. Characterization of the as grown CNT was done using Scanning Electron Microscope (SEM) and Raman Spectroscopy. The Raman spectroscopy was carried out on a selected area of 100micron by 100 micron and the peaks of the D-band, G-band and the second order modes were observed from the Raman spectra. Image j image processing software was also used for the extraction of the diameter of the nanotube in which the average diameter was computed to be 46nm

A Recent Approach towards Fluidic Microstrip Devices and Gas Sensors: A Review

This paper aims to review some of the available tunable devices with emphasis on the techniques employed, fabrications, merits, and demerits of each technique. In the era of fluidic microstrip communication devices, versatility and stability have become key features of microfluidic devices. These fluidic devices allow advanced fabrication techniques such as 3D printing, spraying, or injecting the conductive fluid on the flexible/rigid substrate. Fluidic techniques are used either in the form of loading components, switching, or as the radiating/conducting path of a microwave component such as liquid metals. The major benefits and drawbacks of each technology are also emphasized. In this review, there is a brief discussion of the most widely used microfluidic materials, their novel fabrication/patterning methods

Development of a Hydrogen Gas Sensor Using a Double Saw Resonator System at Room Temperature

A double SAW resonator system was developed as a novel method for gas sensing applications. The proposed system was investigated for hydrogen sensing. Commercial Surface Acoustic Wave (SAW) resonators with resonance frequencies of 433.92 MHz and 433.42 MHz were employed in the double SAW resonator system configuration. The advantages of using this configuration include its ability for remote measurements, and insensitivity to vibrations and other external disturbances. The sensitive layer is composed of functionalized multiwalled carbon nanotubes and polyaniline nanofibers which were deposited on pre-patterned platinum metal electrodes fabricated on a piezoelectric substrate. This was mounted into the DSAWR circuit and connected in parallel. The sensor response was measured as the difference between the resonance frequencies of the SAW resonators, which is a measure of the gas concentration. The sensor showed good response towards hydrogen with a minimum detection limit of 1%

Development of double surface acoustic wave resonator system for hydrogen nd ammonia gas sensing

Acoustic wave technology has been used for gas sensing applications for several decades. A SAW device consists of a piezoelectric substrate; inter digital transducers (IDTs) and reflectors. Rayleigh waves have two types of configuration namely SAW resonator and SAW delay line. Each configuration has different structure but has similar output characteristic when employed as a sensor. The Surface Acoustic Wave (SAW) sensor has offered the development of small, lightweight, battery-free, maintenance free and multiple sensor wireless interrogation operation. Double SAW resonator (DSAWR) is a configuration that involves two SAW resonators and it has proven to be reliable in sensing applications such as temperature and strain sensor. Carbon nanotubes (CNTs) have been proven to be good sensing material with high metallic behavior. However, when they are employed as sensing materials for SAW gas sensor they cause short circuit to the IDTs. Previous works based on single SAW resonator gas sensor requires the fabrication of a guiding or protective layer which is made up of oxides so as to avoid the short circuiting of the IDTs. Based on literature reviewed, previous works have employed the DSAWR for strain and temperature sensors but it has never been deployed for gas sensing. Therefore, in this thesis, DSAWR resonator based gas sensor was developed and been deployed for gas sensing applications for the first time. The advantage of this technique is that the CNT sensor was fabricated and integrated independently which eliminates fabrication of any guiding or protective layer for the SAW resonator. Another advantage of this technique is that the same system could be used with different types of sensing layer which makes it more economical and less time consuming. In this thesis the Double Surface Acoustic Wave Resonator System (DSAWR) for gas sensing application was proposed and developed. DSAWR system consists of two commercial SAW resonators with resonant frequencies of 433.92 and 433.42 MHz. The DSAWR system was fabricated on a PCB and deployed for gas sensing application. There are 2 types of system that were used for DSAWR gas sensing application but the systems differ in the sensing material been employed and is been configured as system 1 and system 2 sensors. System 1 sensing layer composed of functionalized multi walled carbon nanotubes with polyaniline layer which was deployed for hydrogen sensing while system 2 sensing layer composed of polyaniline as a sensing material and was deployed for ammonia sensing. Results obtained showed that system 2 sensor was better than system 1 sensor in terms of sensitivity. The sensitivity of system 1 sensor was found to be 3Hz/ppm at room temperature while it doubles to 6 Hz/ppm at 40 0C. System 2 sensing results obtained showed that the system has detection limit of 0.125 % with a sensitivity of 8 Hz/ppm at room temperature. In order to investigate the sensing behavior of a new material, system 3 sensor was developed which is based on Graphene Nanoribbon (GNR) and was deployed for ammonia sensing. Results obtained showed that the novel structure could be a potential material for ammonia sensing with good sensitivity and a detection limit of 1250 ppm