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Unraveling the nature of sensing in electrostatic MEMS gas sensors

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Microsystems & Nanoengineering 2024年第3期10卷 109-117页

作者： Yasser S.Shama Sasan rahmanian Hamza Mouharrar Rana abdelrahman Alaaeldin Elhady eihab M.abdel-rahman Systems Design Engineering University of Waterloo200 University Ave WWaterloo N2L 3G1 ONCanada Mechanical Engineering Benha Faculty of EngineeringBenha UniversityBenha 13511Egypt

This paper investigates the fundamental sensing mechanism of electrostatic MEMS gas *** compares among the responsivities of a set of MEMS isopropanol sensors before and after functionalization,and in the presence and absence of electrostatic fields when operated in static and dynamic detection *** the static mode,we found that the sensors do not exhibit a measurable change in displacement due to added *** the other hand,bare sensors showed a clear change in displacement in response to isopropanol *** the dynamic mode,functionalized sensors showed a measurable frequency shift due to the added mass of isopropanol *** the presence of strong electrostatic fields,the measured frequency shift was found to be threefold larger than that in their absence in response to the same concentration of isopropanol *** enhanced responsivity of dynamic detection allows the sensors to measure the vapor mass captured by the functional material,which is not the case for static *** detection of isopropanol by bare sensors in static mode shows that change in the medium permittivity is the primary sensing *** enhanced responsivity of dynamic mode sensors when operated in strong electrostatic fields shows that their sensing mechanism is a combination of a weaker added mass effect and a stronger permittivity *** findings show that electrostatic MEMS gas sensors are independent of the direction of the gravitational field and are,thus,robust to changes in *** is erroneous to refer to them as‘gravimetric’sensors.

关键词： mechanism electrostatic measurable

Frequency unlocking-based MEMS bifurcation sensors

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微系统与纳米工程(英文) 2023年第3期9卷 171-181页

作者： Yan Qiao Zhan Shi Yutao Xu Xueyong Wei Alaaeldin Elhady eihab abdel-rahman Ronghua Huan Wenming Zhang State Key Laboratory of Mechanical System and Vibration School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghaiChina Department of Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang UniversityHangzhouChina State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’anChina Department of Systems Design Engineering University of WaterlooWaterlooONCanada

MEMS resonators exhibit rich dynamic behaviors under the internal resonance regime. In this work, we present a novel MEMS bifurcation sensor that exploits frequency unlocking due to a 1:3 internal resonance between two electrostatically coupled micro-resonators. The proposed detection mechanism allows the sensor to operate in binary (digital) and analog modes, depending on whether the sensor merely detects a significant jump event in the peak frequency upon unlocking or measures the shift in the peak frequency after unlocking and uses it in conjunction with a calibration curve to estimate the corresponding change in stimulus. We validate the success of this sensor paradigm by experimentally demonstrating charge detection. High charge resolutions are achieved in binary mode, up to 0.137 fC, and in analog mode, up to 0.01 fC. The proposed binary sensor enables extraordinarily high detection resolutions due to the excellent frequency stability under internal resonance and the high signal-to-noise ratio of the shift in peak frequency. Our findings offer new opportunities for high-performance ultrasensitive sensors.

关键词： locking bifurcation binary

Male-killer dynamics in the tropical butterfly, Acraea encedana （Lepidoptera： Nymphalidae）

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Insect Science 2013年第6期20卷 717-722页

作者： Sami Saeed M. Hassan eihab Idris Michael E. N. Majerus Department of Biology Faculty of Science University of Hail Hail Kingdom of Saudi Arabia Department of Zoology Faculty of Science University of Khartoum P.O. Box 321 Khartoum 11115 Sudan Department of Genetics University of Cambridge Deceased Department of Genetics University of Cambridge Cambridge CB2 3EH United Kingdom

Sex ratio distortion in the tropical butterfly Acraea encedana is caused by infection with a male-killing bacterium of the genus Wolbachia. Previous research on this species has reported extreme female bias, high bacterial prevalences, and full sex role reversal. In this paper, we provide an assessment for the dynamics of the male-killer, based on a survey for sex ratios and Wolbachia prevalences among wild populations of A. encedana in Uganda. The study reveals that Wolbachia infection showed considerable variation over both spatial and temporal scales.

关键词： female bias PCR population dynamics prevalence Wolbachia Uganda

Optimization of Injection Timing and Injection Duration of a Diesel Engine Running on Pure Biodiesel SME (Soya Methyl Ester)

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Open Journal of Applied Sciences 2020年第7期10卷 486-502页

作者： Abdullah Alghafis eihab A. Raouf Mechanical Engineering Department Unaizah Engineering College Qassim University Unaizah KSA

This study was carried out to predict the impact of injection timing and injection duration on engine brake power and Nitrogen Oxides emissions in a diesel engine using biofuel Soya Methyl Ester (SME). Predictions were accomplished at three different injection timings 10°, 5° Crank Angle (CA) before Top Dead Center (bTDC) and 0° CA at Top Dead Center (TDC) and four injection durations 20°, 25°, 30°, 35° CA. The study was conducted using a simulation software (Diesel-RK). The predicted results showed that the powers produced by all the setups of the different injection timings are almost equal, but they differ in injection durations, e.g. the power at setup (10° CA-bTDC) duration 20° CA and 2500 rpm equal to 52 kW, at setup (5° CA

Accuracy of Fine Needle Aspiration Cytology of Solitary Thyroid Nodules in Tertiary versus Community Hospital

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Surgical Science 2013年第11期4卷 494-499页

作者： H. M. El Hennawy H. O. Abu Zaid Imaad Bin Mujeeb eihab A. El Kahlout El S. M. Bedair Medicine Department Al Khor Hospital Hamad Medical Corporation Doha Qatar Pathology Department Hamad General Hospital Hamad Medical Corporation Doha Qatar Radiology Department Al Khor Hospital Hamad Medical Corporation Doha Qatar Surgery Department Al Khor Hospital Hamad Medical Corporation Doha Qatar Trauma Surgery Department Hamad General Hospital Hamad Medical Corporation Doha Qatar

Background: Fine needle aspiration cytology (FNAC) is considered as the gold standard diagnostic test for the diagnosis of solitary thyroidnodules (STN). Aim: To compare the accuracy of FNAC in diagnosis of thyroid nodules in Al Khor community hospital versus that of tertiary hospital (Hamad General Hospital) in Qatar. Methods: Retrospective, descriptive and comparative study of 320 patients of any age group and both sexes who have thyroid nodules and are subjected to surgical treatment [160 patients from Al Khor community hospital (group A) and 160 patients from Hamad General Hospital (group B)] during the period from May 2005 to Dec 2012. Each group was subdivided into free hand FNAC (done by physicians) and ultrasonography guided FNAC. All samples were prepared in the same histopathology laboratory and interpreted by the same histopathology team. Results: Free hand FNAC in group A and group B achieved a sensitivity of (10% vs. 50%), specificity of 93% in both groups, positive predictive value of (25% vs. 17%), negative predictive value of (82% vs. 98%), and a total accuracy of (82% vs. 94%) respectively, while US guided FNAC in group A and group B achieved a sensitivity of (10% vs. 86%), specificity of (98% vs. 94%), positive predictive value of (50% vs. 60%), negative predictive value of (86% vs. 98%), and a total accuracy of (85% vs. 97%) respectively. Conclusion: The overall accuracy of FNAC of STN in tertiary hospital was better than community hospital. More training is required for community hospital staff.

关键词： Needle Aspiration Solitary Thyroid Nodules Accuracy