Finite element simulation of miniaturized ZnO/Si SAW sensor for rapid detection of dichloromethane gas

Air quality control is very crucial as poor air quality can lead to chronic respiratory organ diseases. Hence, detection of numerous toxic and hazardous gas is utmost significance. A low cost and high sensitivity gas sensor is crucial to monitor the excessive presence of the dangerous gas that can harm human’s health. In recent years, various type of gas sensors have been developed for various applications such as medicine, industry, automotive and environmental monitoring. One of the harmful gas is the dichloromethane gas. Dichloromethane (DCM) gas, CH2Cl2 is widely used in industry due to its organic characteristics. However, the excessive of the amount of the gas could bring harm to human’s health. Hence, a lot of sensing devices have been developed including surface acoustic wave (SAW) gas sensor. This paper presents the 2D finite element simulation of miniaturized ZnO/Si SAW gas sensor for rapid detection of DCM gas. Using a powerful finite element analysis software known as COMSOL Multiphysics, the gas sensor is modelled according to the specific criteria using 2D approach. The effect of different thickness of ZnO thin film as piezoelectric layer is investigated on the SAW propagation characteristics. The resonance frequency of simulated ZnO/Si SAW gas sensor is 300 MHz with wavelength of 11.67μm. The shift in frequency is the measurement used to measure the changes occured to sense the presence or absence of DCM gas. The shift of resonance frequency is observed in the absence and presence of dichloromethane gas. This work has high potential to realize single chip gas sensor due to its silicon compatibility for rapid detection of harmful gas for environmental monitoring

Flexible PVDF thin film as piezoelectric energy harvester

This aim of this paper is to study the potential of Polyvinylidene Fluoride (PVDF) polymeric piezoelectric film as an energy harvester for daily application use. PVDF offers several advantages over other piezoelectric materials such as high chemical strength and stability, high piezoelectric properties and biocompatible. Several investigations were carried out in this project which comprises of simulation, functionality test and application test. For functionality test, the highest voltage produced for a single film PVDF is 0.368 V which charges up a capacitor to 0.219 V in one minute. The highest voltage produced by multiple PVDF films is 1.238 V by stacking 10 films of PVDF in parallel which charges up to 0.688 V in one minute. For application test, 5 pieces of PVDF films were attached to a glove to generate some voltage during fingers bending activity. The highest output voltage recorded is 0.184 V which stores 0.101 V in a capacitor after 200 times of hand bending and releasing. As a conclusion, PVDF has a good potential as an alternative energy for daily application use. Combination of PVDF energy harvester system with proper power optimization circuit will open up rooms of research opportunities in energy harvester system with promising prospect in self-powered wireless electronics devices for Internet of Things application

Application of Taguchi signal to noise ratio design method to ZnO thin film CMOS SAW resonators

A systematic approach using Taguchi method is proposed for optimization of complementary metal oxide semiconductor microelectromechanical system surface acoustic wave (SAW) resonators. The aim of the present method is to enhance the performance of SAW devices in terms of electromechanical coupling coefficient while reducing the design and development cost. Controllable factors such as a number of transducers, N t , the distance between input and output transducers, L c , and the thickness of the piezoelectric materials, T c have been optimized. L 27 (3 13 ) orthogonal array was chosen to conduct 27 simulations with three level parameters. Time and cost efficient 2D finite element simulations were done using COMSOL Multiphysics TM for two-step analysis Eigen frequency and frequency domain analysis. The orthogonal array, signal to noise ratio, and analysis of variance (ANOVA) were calculated to determine the best settings of the design parameters. The maximum electromechanical coupling coefficient is achieved at the optimal condition of N t = 6; L c =1.6 μm; T c =2.5 μ m with increased performance by 4.68% for κ 2 and 9.62% for G 12 (f) compared to the initial conditions. The interaction between pairs of factors has also been investigated. The Taguchi method reveals that both N t and L c , and the interaction of N t × L c plays crucial roles in optimizing the electroacoustic conversion of the SAW devices. Hence, the experiment shows that the performance of the SAW device has been successfully optimized

Gm/ID approach for low power sustaining amplifier circuit for GHz range MEMS SAW oscillator

This paper presents the design and simulation of microelectromechanical system (MEMS) based oscillator based on CMOS MEMS surface acoustic wave (SAW) resonator and regulated cascode configuration (RGC) transimpedance amplifier (TIA). The proposed TIA is designed in a standard 0.18 μm Silterra CMOS prosess via Cadence Virtuoso software. Gm/ID technique is used to achieve higher gain and low power TIA. The simulation result shows that the voltage gain of the design circuit is 35.5dB and 2.08 GHz -3dB bandwidth. The circuit consume 1.6mW power at 1.8 V supply voltage. When integrate with 1.4GHz resonator, the phase noise of this oscillator is -105.27 dBc/Hz at 1kHz and -116.03 dBc/Hz 10kHz

An investigation of the sensitivity of polymer-coated surface acoustic wave-based gas sensors in the detection of volatile organic compounds

Surface acoustic wave sensors (SAWs) are excellent at detecting volatile organic compounds (VOCs) since a sensing layer can be created by spreading a thin film of material across the delay line. This critically enhances performance as it is sensitive to the physical phenomena of interest. This study aims to provide a thorough investigation of the sensitivity of polymer-coated SAW-based gas sensors to VOCs using simulations via the finite element method (FEM). As such, quartz was chosen as the piezoelectric substrate while polymeric materials were chosen as the sensing layers due to their high sensitivity, low energy consumption, short response time, performance at room temperature, and reversibility after exposure to an analyte. The polymeric materials chosen were: (1) polyisobutylene (PIB), (2) polydimethylsiloxane (PDMS), (3) polyisoprene (PIP), (4) polyimide (PI), and (5) phenylmethyldiphenylsilicone (OV25). The VOCs chosen for investigation were: (1) dichloromethane (DCM), (2) trichloroethylene (TCE), (3) 1,2-dichloroethylene (DCE), and (4) carbon tetrachloride (CCl4). The performance of each polymer-coated SAW sensor was evaluated in terms of frequency shift and sensitivity to each VOC in FEM simulations. Our study found that the PIB-coated sensor had the highest sensitivity (4.0571 kHz/ppm) to DCM vapor and good sensitivity (45.257 kHz/ppm) to TCE vapor. However, the performance of each polymer-coated sensor varied depending on the type of VOC being tested. As an example, while the OV25-coated sensor was more sensitive (52.57 kHz/ppm) than the PIB-coated sensor (53.54 kHz/ppm) to TCE vapor regardless of the concentration, the PIB-coated sensor was more sensitive to DCM vapor at both low (4.06 kHz/ppm) and high (3.54 kHz/ppm) concentrations than the OV25-coated sensor. Therefore, the results of our FEM simulations indicate that polymer-coated SAW-based gas sensors are highly capable of self-powered VOC detection

Magnetically plucked piezoelectric energy harvester via hybrid kinetic motion

Piezoelectric energy harvesting is a possible breakthrough to reduce the global issue of electronic waste as they can efficiently convert the ambient vibration to the electrical energy without any additional power. This work presents the design and development of a piezoelectric energy harvester that is capable of transforming vibration from ambient sources into electricity. It focuses on a magnetically plucked piezoelectric beam as an alternative to the mechanically induced harvesters, as the latter are subjected to wear and tear. A prototype comprising of a 40 mm PZT-5H piezoelectric beam with a permanent magnet mounted at one end of the beam, as well as a series of permanent magnets of same types attached on an eccentric rotor was developed along with a National Instruments® data acquisition device. Mean output voltages of 2.98 V, 1.76 V and 0.34 V were recorded when the eccentric rotors were slowly rotated at 8.4 rad/s with increasing distances of 5 mm, 7.5 mm and 10 mm respectively, between the magnets on the rotor and the beam. These results have proven that voltage could also be generated by magnetically plucking the piezoelectric beam, and by reducing the distance between magnets, the amount of voltage generated will be higher. The outcome of this work signifies the possibility for implementation of energy harvesters that are capable of powering electronic devices from hybrid kinetic motion, with a reduced risk of equipment fatigue. © 2019, International Islamic University Malaysia-IIUM

Design and hardware implementation of conditioning circuit for accurate reading from transducers with nonlinear responses

This chapter is about design and hardware implementation of a signal conditioning circuit that has the ability to read the output response of a non-linear sensor and produce corresponding linear results. This design is based on piecewise linearization technique. First the non-linear output of the sensor's curve divided into the linear segment each segment is identified by its corresponding slope. A couple of comparators has used for selecting the individual line segment (voltage range) and then by the help of instrumentation amplifier circuit the input voltage interpret into desired output voltage. The simulation of the whole circuit is done in order to make everything easy to understand and visible

Design and analysis of a boosted pierce oscillator using MEMS SAW resonators

This paper highlights the design and analysis of a pierce oscillator circuit for CMOS MEMS surface acoustic wave resonators. The boosted pierce topology using two, three-stage cascode amplifiers provides sufficient gain to counteract the high insertion losses of - 65 dB at 1.3 GHz of the SAW resonator. For accurate prediction of the oscillator’s performance before fabrication, circuit design utilized touchstone S2P measurement results of the MEMS SAW resonator, which provides better results compared to the conventional method of using equivalent circuit simulations. This circuit was designed using Silterra’s 0.13 lm CMOS process. It has low power consumption of 1.52 mW with high voltage swing 0.10–0.99 V. All simulations were conducted using Cadence Design Systems and results indicate that phase noise of 92.63 dBc at 1 MHz

Material characterization of a doped triangular silicon nanowire using raman spectroscopy

A top-down silicon nanowire fabrication using a combination of optical lithography and orientation dependent etching (ODE) has been developed using a doped Silicon-on Insulator (SOI) as the starting substrate. The use of ODE etchant such as potassium hydroxide (KOH) and Tetra-Methyl Ammonium Hydroxide (TMAH) is known to create geometrical structures due to its anisotropic mechanism of etching. The SOI is doped with an n-type dopant (phosphorus) and the doped silicon nanowire is then characterized using Raman Spectroscopy. Due to the changes in the silicon structure, the result shows that the highly doped silicon nanowire has a wider Full Width Half Maximum (FWHM) as compared to the undoped silicon substrate