Publications by authors named "Arezoo Emadi"

4 Publications

  • Page 1 of 1

Capacitive Based Micromachined Resonators for Low Level Mass Detection.

Micromachines (Basel) 2020 Dec 25;12(1). Epub 2020 Dec 25.

Department of Electrical and Computer Engineering, University of Windsor, Windsor, ON N9B 3P4, Canada.

Advancements in microfabrication technologies and novel materials have led to new innovations in miniaturized gas sensors that can identify miniscule changes in a complex environment. Micromachined resonators with the capability to offer high sensitivity and selectivity in array integration make mass loading a potential mechanism for electronic nose applications. This paper investigates the mass sensing characteristics of progressive capacitive based micromachined resonators as potential candidates for volatile organic compound detection where also there is a need for miniaturized array configuration. In this paper, a detailed investigative review of the major three geometric designs of capacitive based micromachined resonators, namely, the microcantilever, the microbridge and the clamped membrane sensors is performed. Although many reviews are present in literature regarding mass sensors, however there is a gap in the literature regarding the common capacitive based micromachined mass sensors. This research gives a review on the foundation for capacitive based micromachined mass sensors while highlighting the potential capabilities of each geometric design to be developed further. Moreover, this paper also introduces the advancements based on the geometric designs of the capacitive based micromachined mass sensors. An in-depth analysis is done for each geometric design, to identify the critical design parameters, which affect the sensors' performances. Furthermore, the theoretically achievable mass sensitivity for each capacitive based micromachined mass sensor is modeled and analyzed using finite element analysis with mass variation in the picogram range. Finally, a critical analysis is done on the sensor sensitivities and further discussed in detail wherein each design is compared to each other and its current advances. Additionally, an insight to the advantages and disadvantages associated with each simulated geometry and its different advances are given. The results of the investigative review and analysis indicate that the sensitivities of the capacitive based micromachined sensors are dependent not only on the material composition of the devices but also on the varying degrees of clamping between the sensor geometries. In essence, the paper provides future research the groundwork to choose proper candidate geometry for a capacitive based micromachined mass sensor, with its several advantages over other mass sensors, based on the needed application.
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http://dx.doi.org/10.3390/mi12010013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823894PMC
December 2020

A Method to Enhance Stroke Level of a MEMS Micromirror with Repulsive Electrostatic Force.

Micromachines (Basel) 2020 Apr 11;11(4). Epub 2020 Apr 11.

Department of Electrical and Computer Engineering, University of Windsor, Windsor, ON N9B 3P4, Canada.

This paper presents a method to enhance the stroke level of a MEMS micromirror that, unlike conventional micromirrors, is actuated using a repulsive electrostatic force. The designed and proposed micromirror is held by L-shaped arms suspended over a set of bottom electrodes. In this configuration, three bottom electrodes are centered below each arm and are separated with a designed gap from each other to optimize the generated repulsive force. Using this approach, the micromirror surface is forced to deflect upward compared with the conventional downward deflection. The designed micromirror is proposed to utilize the PolyMUMPs fabrication technique from MEMSCAP Inc. In this work and in an unconventional approach, an air cavity of 2.75 µm can be achieved by combining the two available oxide layers through an additional removal of a polysilicon structural layer. It is shown that this design can significantly enhance the stroke level of the proposed micromirror to 5 µm at 150 V DC.
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http://dx.doi.org/10.3390/mi11040401DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7231325PMC
April 2020

Advanced Micro- and Nano-Gas Sensor Technology: A Review.

Sensors (Basel) 2019 Mar 14;19(6). Epub 2019 Mar 14.

Department of Electrical and Computer Engineering, University of Windsor, Windsor, ON N9B 3P4, Canada.

Micro- and nano-sensors lie at the heart of critical innovation in fields ranging from medical to environmental sciences. In recent years, there has been a significant improvement in sensor design along with the advances in micro- and nano-fabrication technology and the use of newly designed materials, leading to the development of high-performance gas sensors. Advanced micro- and nano-fabrication technology enables miniaturization of these sensors into micro-sized gas sensor arrays while maintaining the sensing performance. These capabilities facilitate the development of miniaturized integrated gas sensor arrays that enhance both sensor sensitivity and selectivity towards various analytes. In the past, several micro- and nano-gas sensors have been proposed and investigated where each type of sensor exhibits various advantages and limitations in sensing resolution, operating power, response, and recovery time. This paper presents an overview of the recent progress made in a wide range of gas-sensing technology. The sensing functionalizing materials, the advanced micro-machining fabrication methods, as well as their constraints on the sensor design, are discussed. The sensors' working mechanisms and their structures and configurations are reviewed. Finally, the future development outlook and the potential applications made feasible by each category of the sensors are discussed.
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http://dx.doi.org/10.3390/s19061285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6470538PMC
March 2019

An Air-Coupled Multiple Moving Membrane Micromachined Ultrasonic Transducer With Inverse Biasing Functionality.

IEEE Trans Ultrason Ferroelectr Freq Control 2016 08 30;63(8):1140-7. Epub 2016 May 30.

A novel air-coupled multiple moving membrane-capacitive micromachined ultrasonic transducer ( [Formula: see text]-CMUT) with individually biased deflectable plates has been developed. Unlike the conventional capacitive micromachined ultrasonic transducer, this device cell structure includes an additional deflectable plate that is suspended underneath the transducer top plate. This added flexible plate contributes to the device signal transmission and reception. It is demonstrated that due to the presence of this added moving plate, the transducer is capable of operating under inverse bias condition, where the driving voltage is sandwiched between two grounded electrodes. COMSOL electromechanical simulations were conducted to investigate the influence of the transducer additional moving plate. A set of three individuals and an array of [Formula: see text]-CMUT transducers were fabricated using a sacrificial technique and with resonant frequencies ranging from 0.8 to 2.1 MHz. Electrical, optical, and pitch-catch acoustic measurements were performed to characterize the transducers properties under inverse bias condition. The experimental results are shown to be in good agreement with the simulation results for all of the fabricated transducers. It is shown that these transducers are fully functional under both normal and inverse bias conditions without any degradation in the transducer performance.
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http://dx.doi.org/10.1109/TUFFC.2016.2574336DOI Listing
August 2016