Dissertations / Theses on the topic 'Microelectromechanical system sensors'
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Xu, Wenjun. "Carbon material based microelectromechanical system (MEMS): fabrication and devices." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39554.
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This PhD dissertation presents the exploration and development of two carbon materials, carbon nanotubes (CNTs) and carbon fiber (CF), as either key functional components or unconventional substrates for a variety of MEMS applications. Their performances in three different types of MEMS devices, namely, strain/stress sensors, vibration-powered generators and fiber solar cells, were evaluated and the working mechanisms of these two non-traditional materials in these systems were discussed. The work may potentially enable the development of new types of carbon-MEMS devices.
Firstly, a MEMS-assisted electrophoretic deposition (EPD) technique was developed, aiming to achieve controlled integration of CNT into both conventional and flexible MEMS systems. Selective deposition of electrically charged CNTs onto desired locations was realized in the EPD process through patterning of electric field lines created by the microelectrodes fabricated using MEMS techniques. A variety of 2-D and 3-D micropatterns of CNTs with controllable thickness and morphology have been successfully achieved in both rigid and elastic systems at room temperature with relatively high throughput. Studies also showed that high surface hydrophobicity of the non-conductive regions in microstructures was critical to accomplish well-defined selective micropatterning of CNTs through this strategy.
A patterned PDMS/CNT nanocomposite was then fabricated through the aforementioned approach, and was incorporated, investigated and validated in elastic force/strain microsensors. The gauge factor of the sensor exhibited a strong dependence on both the initial resistance of the device and the applied strain. Detailed analysis of the data suggests that the piezoresistive effect of this specially constructed bi-layer composite could be three folds, and the sensing mechanism may vary when physical properties of the CNT network embedded in the polymer matrix alter.
The feasibility of the PDSM/CNT nanocomposite serving as an elastic electret was further explored. The nanocomposite composed of these two non-traditional electret materials exhibited electret characteristics with reasonable charge storage stability. The power generation capacity of the corona-charged nanocomposite has been characterized and successfully demonstrated in both a ball drop experiment and the cyclic mechanical load experiments.
Lastly, in an effort to develop carbon-material-based substrates for MEMS applications, a carbon fiber-based poly-Si solar cell was designed, fabricated and investigated. This fiber-type photovoltaics (PV) takes advantage of the excellent thermal stability, electrical conductivity and spatial format of the CF, which allows CF to serve as both the building block and the electrode in the PV configuration. The photovoltaic effects of the fiber PV were demonstrated with an open-circuit voltage of 0.14 V, a short-circuit current density of 1.7 mA/cm2, and output power density of 0.059mW/cm2. The issues of this system were discussed as well.
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Li, Weizhuo. "Wavelength Multiplexing of MEMS Pressure and Temperature Sensors Using Fiber Bragg Gratings and Arrayed Waveguide Gratings." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123972586.
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Kok, Wing Hang (Ronald). "Development of a wireless MEMS inertial system for health monitoring of structures." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-11244-122741/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: angular rate; cantilever; wireless; RF; microcontroller; tilt and rotation; health monitoring; inertial sensors; MEMS. Includes bibliographical references (p. 139-145).
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Lee, Jin-Hwan. "MEMS Needle-Type Multi-Analyte Microelectrode Array Sensors for In Situ Biological Applications." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212146149.
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Mangels, John Donald III, Syed Ammar Raza, Kevin Mueller, Namrah Habib, Josh Raymond, Daniel Brauer, Mohammed Azri Adb Rahim, et al. "Micro-Air Vehicle Control Using Microelectromechanical Systems Sensors." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625078.
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Micro Air Vehicles (MAV) are small unmanned aircraft that are highly sensitive to environmental
disturbances causing dynamic changes in attitude and flight stability compared to more traditional
unmanned air vehicles. Controlling the stability of an MAV is difficult and a significant research issue.
The goal of this project is to perform a proof of concept study based on literature to demonstrate that
Microelectromechanical Systems (MEMS) sensors can control the longitudinal stability of an MAV.
MEMS sensors, specifically flow sensors used in this project, predict perturbations and aerodynamic
effects which is critical for MAV performance because flight predictions can be used to prevent stall and
failure in an MAV. The project focused on developing a control system that implemented MEMS sensors
on a wing section and was tested in The University of Arizona's Educational Wind Tunnel.
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Raza, Syed Ammar, Kevin Mueller, Daniel Brauer, Namrah Habib, John Mangels, Azri Rahim, Joshua Raymond, et al. "Micro-Air Vehicle Control Using Microelectromechanical Systems Sensors." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625128.
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Micro Air Vehicles (MAV) are small unmanned aircraft that are highly sensitive to environmental disturbances causing dynamic changes in attitude and flight stability compared to more traditional unmanned air vehicles. Controlling the stability of an MAV is difficult and a significant research issue. The goal of this project is to perform a proof of concept study based on literature to demonstrate that Microelectromechanical Systems (MEMS) sensors can control the longitudinal stability of an MAV. MEMS sensors, specifically flow sensors used in this project, predict perturbations and aerodynamic effects which is critical for MAV performance because flight predictions can be used to prevent stall and failure in an MAV. The project focused on developing a control system that implemented MEMS sensors on a wing section and was tested in The University of Arizona’s Educational Wind Tunnel.
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Neelisetti, Raghu Kisore Lim Alvin S. "Improving reliability of wireless sensor networks for target tracking using wireless acoustic sensors." Auburn, Ala., 2009. http://hdl.handle.net/10415/1931.
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Lee, Wook. "Diffraction-based integrated optical readout for micromachined optomechanical sensors." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-09292006-115918/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.F. Levent Degertekin, Committee Chair ; David S. Citrin, Committee Member ; Paul E. Hasler, Committee Member ; Peter J. Hesketh, Committee Member ; Zhiping Zhou, Committee Member.
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Jacobson, Carl P. "Code Division Multiplexing of Fiber Optic and Microelectromechanical Systems (MEMS) Sensors." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27486.
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Multiplexing has evolved over the years from Emile Baudot's method of transmitting six simultaneous telegraph signals over one wire to the high-speed mixed-signal communications systems that are now commonplace. The evolution started with multiplexing identical information sources, such as plain old telephone service (POTS) devices. Recently, however, methods to combine signals from different information sources, such as telephone and video signals for example, have required new approaches to the development of software and hardware, and fundamental changes in the way we envision the basic block diagrams of communication systems. The importance of multiplexing cannot be overstated. To say that much of the current economic and technological progress worldwide is due in part to mixed-signal communications systems would not be incorrect.
Along the vein of advancing the state-of-the-art, this dissertation research addresses a new area of multiplexing by taking a novel approach to network different-type sensors using software and signal processing. Two different sensor types were selected, fiber optics and MEMS, and were networked using code division multiplexing. The experimentation showed that the interconnection of these sensors using code division multiplexing was feasible and that the mixed signal demultiplexing software unique to this research allowed the disparate signals to be discerned. An analysis of an expanded system was performed with the results showing that the ultimate number of sensors that could be multiplexed with this technique ranges from the hundreds into the millions, depending on the specific design parameters used. Predictions about next-next generation systems using the techniques developed in the research are presented.Ph. D.
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Mendonça, Lucas Gonçalves Dias. "Desenvolvimento de um micro-transdutor acústico capacitivo." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-17102014-113303/.
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Neste trabalho é proposto um dispositivo MEMS do tipo micro-transdutor acústico capacitivo, CMUT (sigla em inglês - Capacitive Micromachined Ultrasonic Transducer). Em vez de usar piezoeletricidade, o CMUT tem um array de capacitores, onde cada capacitor possui um eletrodo inferior fixo, uma cavidade e o eletrodo superior composto de uma placa flexível. Quando submetida a uma tensão CC adequada, a placa se deflete se aproximando do eletrodo inferior devido à força eletrostática. Assim a placa fica tensionada podendo vibrar quando excitada por uma tensão CA. Neste caso o CMUT opera como emissor de ondas acústicas. A placa também pode ser excitada por uma onda acústica agindo em sua superfície. Neste caso o dispositivo opera como sensor. Uma das contribuições desse trabalho é o processo de fabricação simplificado com o uso do fotorresiste SU-8 como parte da estrutura do dispositivo. Sua facilidade de processamento e suas propriedades físicas lhe conferem estabilidade e rigidez adequadas para tal fim. Foram realizadas modelagens e simulações analíticas e computacionais do comportamento da placa. Os resultados auxiliaram no melhor entendimento do comportamento do dispositivo sob tensão mecânica devido a uma carga ou uma tensão de polarização. Esses resultados também auxiliaram na definição de parâmetros iniciais do processo de fabricação. Durante o processo de fabricação, foram realizados diversos testes a fim de se encontrar o processo mais adequado à infraestrutura disponível. No processo escolhido, a base do dispositivo é fabricada num substrato de vidro com eletrodos inferiores de alumínio depositados por evaporação. Os pilares são fabricados em SU-8, depositado por spin coatting. A placa é colada posteriormente utilizando-se fotorresiste AZ. O AZ é depositado sobre um pedaço de folha de cobre ou alumínio. As duas partes são colocadas em contato e para promover a colagem é aplicada pressão durante a cura. As amostras foram caracterizadas eletricamente utilizando-se um medidor de impedância RCL. Foram levantadas curvas de impedância, capacitância e ângulo de fase em função da frequência (1 kHz a 1 MHz). Além do sinal CA utilizado pelo instrumento durante a medição foi aplicado um nível CC que variou conforme as dimensões dos protótipos. Também foram levantadas curvas de impedância, capacitância e angulo de fase em função de uma carga mecânica aplicada. Para valores de polarização mais elevados, foram montados circuitos específicos. Estes circuitos são capazes de polarizar o CMUT, aplicar um sinal CA para medição e proteger demais componentes e instrumentos dos aparatos de medição. O dispositivo respondeu bem a aplicação de carga mecânica, excitação por sinal CA e excitação com onda mecânica. Os resultados mostraram que o dispositivo apresenta bom potencial para ser aplicado na análise de fluidos.This work presents a new process to fabricate an acoustic micro transducer to be used as a microsensor or a microactuator. The acoustic transducers are based on the electrostatic effect and consist on arrays of microfabricated capacitors. Such devices are commonly referred as CMUT, Capacitive Micromachined Ultrasonic Transducer. The bottom electrode (evaporated aluminum) of each capacitor is fixed on the surface of glass substrate, while the top electrode is a thin plate structure of copper or aluminum suspended on a cavity surrounded by posts. Since the top electrode is flexible, it bends toward the bottom electrode when a DC bias is applied. In this way, the top electrode can be forced to vibrate using an AC signal to be used as an acoustic wave emitter. Conversely, an ultrasound receiver is achieved as the measured capacitance changes when the DC biased top electrode moves following an external acoustic wave pressure. An innovation of this work is the use of the photoresist SU-8 to fabricate the post structures surrounding the cavities of the capacitive micro transducers. Its relatively simple processing steps and adequate mechanical properties make the SU-8 a convenient choice as an inexpensive structural material. The bottom part of the device is prepared on a glass substrate using an aluminum layer evaporated and etched to form the bottom electrodes. Then, SU-8 is spin coated, baked and etched adequately to form the posts surrounding the cavities. The top part is prepared by simply spinning an AZ-type photoresist on aluminum or copper plate. Finally, both halves are bonded under pressure on a hot plate. Several modeling and simulation analyses were performed in order to estimate the working performance of the micro transducers. The results of simulations helped to define the initial parameters and materials for the fabrication process. Samples submitted to a DC bias were initially characterized using an RCL meter in order to infer impedance, capacitance and phase angle behavior as a function of frequency (from 1 kHz to 1 MHz). Protection circuits were used in order to test CMUTs with high DC bias. These circuits allow to apply high DC bias, and an AC signal while other measuring equipments are protected. The device responded to application of mechanical loading, excitation by an AC signal and excitation by mechanical wave as well. The results showed that the device has good potential to be applied to the analysis of fluids.
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Mustafa, Haithem Ali Babiker. "Development of a noncontact current sensor based on MEMS technology." Thesis, Cape Peninsula University of Technology, 2007. http://hdl.handle.net/20.500.11838/1082.
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Thesis (MTech (Technology))--Cape Peninsula University of Technology, 2007Most ofMEMS sensors are based on the micro-cantilever technology, which use wide range of different design materials and structures. The benefit ofMEMS technology is in developing devices having lower cost, lower power consumption, higher performance, and integration. A free-end cantileverbeam made of magnetic material (PerrnaIloy) and a movable mass attached to the free-end has been designed using MEMS software tools. The magnetic material was used to improve the sensitivity of the cantilever-beam to an external applied magnetic field. The deflection of the cantilever was detected using capacitive sensing method. The aim of this research was to develop a non-contact current sensor based on MEMS technology by analysing the simulation of the system design of the micro cantilever when subjected to a magnetic field produced by a current-carrying conductor. When the signal, a sinusoidal current with a constant frequency is applied, the cantilever-beam exhibits a vibration motion along the vertical axis when it is placed closer to the line current. This creates corresponding capacitance changes and generates a voltage output proportional to the capacitive change in the signal processing circuitry attached to the micro cantilever. Modelling of the magnetic moment of a magnetic cantilever-beam placed in a field, the deflection of { the beam, the natural frequency of the cantilever-beam, the maximum deflection, the change in differential capacitive sensing technique, linearity of the differential capacitive, and capacitive sensitivity the circuit designed for readout was derived.
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Black, Richard Allyn. "A flush mounted microelectromechanical system (MEMS) pressure and flow sensor based air data system /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10012.
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Leichle, Thierry C. "A micromachined resonant magnetic field sensor." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13833.
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Yi, Yudan. "On improving the accuracy and reliability of GPS/INS-based direct sensor georeferencing." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1186671990.
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Yoo, Seung-jin. "Micromachined wavelength selective microbolometer sensors operating at room temperature /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004406.
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Toh, Edwin. "Implementation of an optical readout system for high-sensitivity terahertz microelectromechanical sensor array." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44019.
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Approved for public release; distribution is unlimitedIn this thesis, an optical readout scheme was successfully developed based on the Fourier 4F optical configuration and integrated with a custom-fabricated microelectromechanical system (MEMS)-based, terahertz (THz), detector array. The MEMS THz detector array and 4F Fourier optics were able to transduce the THz scene into an optical signal that was captured by a commercial charged coupled device (CCD) camera for generating images. A quantum cascade laser (QCL) provided the THz illumination for generating images while post-image processing performed background subtraction in order to obtain the THz scene. The Fourier 4F optical readout system that was implemented was able to profile the general shape of the QCL beam pattern and displayed good linearity of response of about 23 gray level values per Kelvin. The concept of optical readout from a micromechanical sensor array was also validated.
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Zhang, Qiliang Lec Ryszard. "Characterization of the interfacial interactions between microparticles and surfaces using piezoelectric sensors /." Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1778.
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Cookson, Jeremy L. "A method for testing the dynamic accuracy of Microelectro-Mechanical Systems (MEMS) Magnetic, Angular Rate, and Gravity (MARG) sensors for Inertial Navigation Systems (INS) and human motion tracking applications." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Jun/10Jun%5FCookson.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2010.Thesis Advisor(s): Yun, Xiaoping ; Second Reader: Romano, Marcello. "June 2010." Description based on title screen as viewed on July 14, 2010. Author(s) subject terms: micro-electro-mechanical systems, MEMS, magnetic, angular rate, gravity sensor, MARG sensors, inertial navigation system, INS, inertial test, MicroStrain, 3DM-GX1, 3DMGX3, CompactRIO, MATLAB GUI, dynamic accuracy test. Includes bibliographical references (p. 187-189). Also available in print.
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Arecco, Daniel. "Analysis and preliminary characterization of a MEMS cantilever-type chemical sensor." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0511104-150948.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: frequency; vibration; vibrometry; detection; resonance; micromechanical; polymer; absorption; AFM; SEM; holography; optoelectronic; silicon; hydrogen; palladium. Includes bibliographical references (p. 151-161).
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Sohn, Young-Soo. "MEMS based microfluidic structure for biological and chemical sensor array /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008446.
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Haneef, Ibraheem. "SOI CMOS MEMS flow sensors." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611843.
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Zhang, Peng. "Design and fabrication of chemiresistor type micro/nano hydrogen gas sensors using interdigitated electrodes." Orlando, Fla. : University of Central Florida, 2008. http://purl.fcla.edu/fcla/etd/CFE0002478.
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Tulabandula, Sridhar. "Localization of wireless sensor networks using multidimensional scaling." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4986.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2008) Includes bibliographical references.
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Kulkarni, Vinod Dilip. "Integration of micromachined thermal shear stress sensors with microchannels : design, fabrication and testing /." Online version of thesis, 2005. http://hdl.handle.net/1850/5201.
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Jeedigunta, Sathyaharish. "Growth and characterization of nanocrystalline diamond films for microelectronics and microelectromechanical systems." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002532.
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Liu, Ting-Hung. "Testing and Packaging for MEMS Acoustic Emission Sensors." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7692.
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The goal of this research is to improve the structure and dimension of the MEMS acoustic emission sensor. Acoustic emission sensor (AE sensor) based on the piezoelectric transducer is a well-developed technology in non-destructive testing that is widely used to determine permanent damage such as cracks and corrosions in buildings and structures. The AE sensor can be used to monitor cracks in structures and to check leakage in pressurized systems. The location of cracks in a structure or system leakage causes a high-frequency surface vibration while releasing ultrasonic energy. The frequency of this energy is typically between 30 kHz to 1MHz. The AE sensor can detect this high frequency transient acoustic wave. By using this AE sensor, the structure and pressurized system can be monitored to generate an evaluation report in order to facilitate maintenance and structure repair.
Currently, the commercial AE sensor is bulky because it is made of a piezoelectric transducer. It also needs a lot of wires to connect with the pre-amplifier and signal conditioning systems. Because of the cost, brittleness and the volume of the commercial AE sensor, new affordable AE sensor technology is desired to replace the commercial AE sensor. The new AE sensor should be economical, small, and lightweight. The performance of the output signal should be comparable with the commercial AE sensor in terms of signal strength and signal to noise ratio. The MEMS AE sensors provide the potential solution to this problem. The MEMS AE sensors can overcome the problems of the commercial AE sensor. The MEMS AE sensor combines the pre- amplifier on the chip in a single package. Through the MEMS technology, the AE sensor can be manufactured in mass quantity and high quality.
This study focuses on simulating and measuring the performance of the MEMS acoustic emission sensors. Through simulation, the capacitance value is influenced by the gap between the suspended membrane (top perforated metal plate), metal ground, and also influenced by the effective area of the perforated top layer. The perforation is introduced to reduce the squeeze film damping effect. Through measurement verification, the MEMS AE sensors have exhibited comparable performance before and after inclusion of the 3D printed package that serves as the housing for the completed sensor assembly. The C-V measurement is the key method to extract the capacitance value, which is the key parameter to determine the signal strength and signal to noise ratio for capacitive MEMS acoustic emission sensors. The damping coefficient is also the key factor to receive the time domain measurement data in a fashion that resemble the bulky commercial piezoelectric AE transducers.
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Alsaleem, Fadi M. "Dynamics of hybrid MEMS sensors and switches for mass and acceleration detection." Diss., Online access via UMI:, 2009.
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Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009.Includes bibliographical references.
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Ghassemi, Parham. "Multi-Constriction Microfluidic Sensors for Single-Cell Biophysical Characterization." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/89947.
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Cancer is a major health issue that has been associated with over 80 million deaths worldwide in the last decade. Recently, significant improvements have been made in terms of treatment and diagnosis. However, despite these advancements there is still a demand for low-cost, high-accuracy, and easy-to-use technologies capable of classifying cells. Analysis of cell behavior in microfluidic deformability assays provides a label-free method of observing cell response to physical and chemical stimuli. This body of work shows advancements made toward reaching our goal of a robust and cost-effective biosensing device that allows for the identification of normal and cancer cells. These devices can also monitor cell responses to physical and chemical stimuli in the form of mechanical deformation and chemotherapeutic drugs, respectively. Our initial design was a microfluidic device that consisted of three channels with varying deformation and relaxation regions. Cell velocities from the deformations regions allowed us to distinguish between normal and cancer cells at the single-cell level. The next design used a singular deformation channel that was embedded with an array of electrodes in order to measure entry time, transit time and velocities as a single cell passes through the channel. These factors were found to reveal information about the biomechanical properties of single cells. Embedded electrodes were implemented in order to reduce post processing times of the data analysis and provide more insight into the bioelectrical information of cells. Finally, we report a microfluidic device with parallel deformation channels and a single electrode pair to improve throughput and automate data collection of deformability assays. This thesis demonstrates how microfluidic deformability assays, with and without embedded electrodes, show promising capabilities to classify different cells based on their biophysical traits which can be utilized as a valuable tool for testing responses to physical and chemical stimuli.MS
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Beardslee, Luke Armitage. "Liquid-phase operation of mems resonators for biochemical sensing in point of care and embedded applications." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44924.
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The purpose of this work is the development of MEMS-based resonant sensors for liquid-phase biochemical sensing applications. Specifically, the sensors developed here are aimed at embedded or point-of-sampling applications: (1) when there is not enough time to send a sample to a lab for analysis, (2) in resource-poor settings, (3) when collecting analyte and shipping it to a lab would damage the sample, or (4) for in-situ monitoring. To this end, a bulk micromachined resonant cantilever sensor and a surface micromachined sensor based on the spring-softening effect are investigated as transducer elements.
The developed cantilever resonators are operated in an in-plane vibration mode to reduce fluid damping and mass loading by the surrounding fluid. The surface of the resonator is either coated with a chemically sensitive polymer film for chemical sensing or with a layer of protein or antibody for biosensor testing. Chemical tests for sensing volatile organic compounds using polymer-coated in-plane resonators in the liquid-phase give estimated limits of detection below 100 ppb. In addition, biosensor tests for the detection of anti-IgG yield estimated limits of detection around 100 ng/ml.
In an attempt to further improve sensor reliability and to further lower the limits of detection, a second sensing concept has been investigated. The presented sensing scheme is capacitive with a resonator acting as an analog-to-digital converter. The resonator and the sensing capacitors are coupled via the spring softening effect. Through this mechanism a change in capacitance causes a shift in resonant frequency. Extensive device modeling has been performed and a process has been developed allowing for fabrication and on-chip packaging of these sensor structures. Initial mechanical characterization data show that the resonators do in fact vibrate.
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Avila, Gomez Adrian Enrique. "Development MEMS Acoustic Emission Sensors." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7392.
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The purpose of this research is to develop MEMS based acoustic emission sensors for structural health monitoring. Acoustic emission (AE) is a well-established nondestructive testing technique that is typically used to monitor for fatigue cracks in structures, leaks in pressurized systems, damages in composite materials or impacts. This technology can offer a precise evaluation of structural conditions and allow identification of imminent failures or minor failures that can be addressed by planned maintenances routines. AE causes a burst of ultrasonic energy that is measured as high frequency surface vibrations (30 kHz to 1 MHz) generated by transient elastic waves that are typically emitted from growing cracks at the interior of the structure.
The AE sensor marketplace is currently dominated by bulky and expensive piezoelectric transducers that are wired to massive multichannel data acquisition systems. These systems are complex to operate with the need of signal conditioning units and near proximity pre-amplifiers for each sensor that demands a fairly complicated wiring requirements. Furthermore, due to the high prices of conventional AE sensors and associated instrumentation, and the current requirements in sensor volumes for smart transportation infrastructure, it is undeniable that new AE technology is required for affordable structural health monitoring. The new AE technology must deliver comparable performance at one or two orders of magnitude lower cost, size and weight. MEMS acoustic emission (AE) sensors technology has the potential to resolve several of these traditional sensor’s shortcomings with the advantage of possible integration of on-chip preamplifier while allowing substantially cost reduction due to the batch processing nature of MEMS technology.
This study will focus on filling some of the major existing gaps between current developments in MEMS acoustic emission sensors and commercial piezoelectric sensors, such as sensor size, signal-to-noise ratio (SNR), cost and the possibility to conform to sharply curved surfaces. Basically, it is proposed to develop a new class of micro-machined AE sensors or sensor arrays through strategic design of capacitive and piezoelectric MEMS sensors, which will focus on optimizing the following performance aspects: Creating geometric designs to manipulate the sensor resonant frequency and to optimize Q factor under atmospheric pressure and ambient environment. Developing a strategic selection of materials according to its acoustic impedance as insulator, structure and backing material. Developing strategies to improve the signal to noise ratio SNR with and without integrated amplification/signal processing. Performing a comparison between MEMS and commercial piezoelectric sensors.
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Park, Jong-Jin. "Design of a new arrayed temperature sensor system and thermal interface materials /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/7062.
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Shakir, Ali M. "A prototype multifunction differential pressure-flow sensor for medical and industrial applications." Diss., Online access via UMI:, 2009.
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Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2009..Includes bibliographical references.
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Fonseca, Michael Agapito. "Polymer/Ceramic Wireless MEMS Pressure Sensors for Harsh Environments: High Temperature and Biomedical Applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19789.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Mark G. Allen; Committee Co-Chair: Dr. Oliver Brand; Committee Member: Dr. Andrew Peterson; Committee Member: Dr. Elliot Chaikof; Committee Member: Dr. Gregory Durgin; Committee Member: Dr. Robert Butera.
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Reiman, Stephen E. "Exploitation of Nonlinear Behavior to Improve the Performance of a Magnetic Sensor." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5244.
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While nonlinear behavior in mechanical systems typically degrades the behavior and performance the devices, the presence of system nonlinearities can sometimes improve the quality of the system. A reason for avoiding nonlinearities within a device is the difficulty in controlling the device due to the effects of the nonlinearities on system behavior. However, careful analysis of nonlinear systems can allow for one to take advantage of the nonlinear behavior to improve system performance.
The objective of this thesis is to exploit the use of nonlinearities to enhance system performance, specifically the sensitivity of a micromachined magnetic sensor. A device design will be presented that is similar to a prototype that has been fabricated by a student within the Electrical and Computer Engineering Department at Georgia Tech. The operating principle of the device is that changes in the orientation and the strength of an external magnetic field will result in changes in the dynamic behavior of the sensor. While previous device provided a proof of the design concept, it was unable to achieve a sensitivity that would allow for its use as a compass. Improvements in the sensitivity of the sensor are achieved through the modeling and optimization of the magnetic sensor. The optimization and redesign of the magnetic sensor will improve the quality of the device and provide another step towards sensor commercialization. A new design that incorporates the use of variable force comb drives will be proposed that will further improve the sensitivity of the device by modifying the dynamic behavior of the sensor.
Another approach that is presented to exploit the nonlinear behavior of the magnetic sensor involves a frequency detection scheme that uses nonlinear vibrations to characterize sensor behavior. Some benefits of this detection technique are that it is insensitive to noise in the vibration of the sensor and is also independent of the damping present within the system. In addition, the implementation of this sensing technique can be readily applied to variety of sensors types without the redesign of a system or the addition of complex components such as vacuum packaging or signal processing electronics.
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Teves, André da Costa. "Otimização de acelerômetros MEMS eletroestáticos de alto desempenho." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-01082013-144527/.
Full textAbstract:
Microssistemas eletromecânicos ou Micro-Electro-Mechanical Systems (MEMS), representam uma classe de dispositivos que combinam funções mecânicas e eletrônicas em escala micrométrica. Através do uso de técnicas de microfabricação, adaptadas da indústria de semicondutores, é realizada a integração entre estruturas móveis, sensores, atuadores e eletrônica, tornando possível a implementação de sistemas completos miniaturizados. Acelerômetros eletrostáticos estão entre os dispositivos MEMS mais comercializados hoje em dia, com venda anual em todo o mundo superior a 100 milhões de unidades e crescente a cada ano. Eles são geralmente fabricados utilizando-se três lâminas de silício espessas, coladas uma sobre a outra. A camada intermediária é obtida por processos de corrosão e consiste de uma grande massa de prova suspensa por uma ou mais vigas. Ela é separada das lâminas superior e inferior por um pequeno espaço vazio (gap), dando origem a dois conjuntos de capacitores de placas paralelas. A flexibilidade das vigas permite que a massa se mova proporcionalmente à aceleração externa e o seu deslocamento é estimado pela variação da capacitância do conjunto. O projeto destes sensores é uma tarefa complexa, já que os seus diversos requisitos de desempenho são, na maioria das vezes, conflitantes, isto é, se o projeto é modificado para melhorar uma característica, as demais são inevitavelmente afetadas e por isso técnicas de otimização devem ser utilizadas na etapa de projeto. Com o intuito de melhorar o desempenho de micro-acelerômetros capacitivos, são então propostas e avaliadas no atual trabalho duas técnicas de otimização distintas, sendo uma delas baseada em Otimização Paramétrica (OP) e a outra no Método da Otimização Topológica (MOT). A OP parte de uma topologia previamente definida e adota algumas de suas características geométricas como variáveis de projeto. Para levar em consideração incertezas nas dimensões e propriedades dos materiais, que é um elemento-chave na concepção e fabricação de dispositivos MEMS, neste trabalho a OP é combinada com o método da Otimização de Projeto Baseado em Confiabilidade ou Reliability-based Design Optimization (RBDO). Análises de confiabilidade de primeira ordem através do Método de Confiabilidade de Primeira Ordem, ou First-Order Reliability Method (FORM), são utilizadas para o cálculo das probabilidades envolvidas nesta formulação. Já o MOT combina o Método dos Elementos Finitos (MEF) e um modelo de material com algoritmos de otimização para encontrar a distribuição ótima de material em um domínio de projeto pré-estabelecido. As variáveis de projeto são as pseudo-densidades que descrevem a quantidade de material em cada ponto do domínio. Na modelagem pelo MEF utiliza-se elementos de placa estrutural do tipo Mixed Interpolation of Tensorial Components (MITC). Exemplos práticos utilizando ambas as abordagens são apresentados e os seus resultados discutidos com o intuito de se avaliar o potencial de cada técnica para o projeto de micro-acelerômetros capacitivos.Micro-Electro-Mechanical Systems (MEMS) are a class of devices that combine mechanical and electronic functions on a micrometric scale. Through the use of microfabrication techniques, adapted from the semiconductor industry, the integration of mobile structures, sensors, actuators and electronics is performed, allowing the implementation of fully miniaturized systems. Electrostatic accelerometers are among the highest volume MEMS products nowadays, with worldwide annual sales topping 100 million units and growing steadily. Bulk-type accelerometers are generally manufactured using three thick silicon wafers, bonded together one on top of the other. The intermediate layer is obtained by etching processes and consists of a big proof mass suspended by one or more beams. It is separated from the upper and lower wafers by a small gap, resulting in two sets of parallel plate capacitors. The flexibility of the beams allows the mass to move proportionally to the external acceleration and its displacement is estimated by the change in capacitance of the set. The design of such sensors is a complex task, since they depend on many performance requirements, which are most often conflicting. If a design is modified to improve one characteristic, others are inevitably affected. Therefore, optimization techniques are regularly used in the design stage of MEMS sensors. Aiming to improve the performance of capacitive micro-accelerometers, in the present work two optimization techniques are presented, the first is based on Parametric Optimization (PO) and the other is the Topology Optimization Method (TOM). The PO starts from a predefined topology and uses some of its geometric characteristics as design variables. In order to account for uncertainties in the dimensions and material properties, which is a key element in the design and fabrication of MEMS devices, in this work the PO is combined with the Reliability-based Design Optimization (RBDO) method. The First-Order Reliability Method (FORM) is applied to calculate the probabilities involved in the RBDO formulation. The TOM combines the Finite Element Method (FEM) and a material model with optimization techniques to find the best constrained material distribution in a fixed design domain. The design variables are the pseudo-densities that describe the amount of material at each point of the domain. The FE model is discretized using the Reissner-Mindlin plate element with the Mixed Interpolation of Tensorial Components (MITC) formulation. Practical examples using both approaches are presented and discussed in order to evaluate the potential of each technique to the design of capacitive micro-accelerometers.
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Palasagaram, Jithendra N. Riggs Lloyd Stephen. "Efforts towards the design and development of an electromagnetic induction sensor optimized for detection and discrimination of unexploded ordnance." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/master's/PALASAGARAM_NAGASANJEEVA_44.pdf.
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Lee, Jung Chul. "Fabrication, characterization, and application of multifunctional." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22697.
Full textAbstract:
Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2007.Committee Chair: King, William; Committee Member: Allen, Mark; Committee Member: Brand, Oliver; Committee Member: Glezer, Ari; Committee Member: Joshi, Yogendra.
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Ellern, Ilya. "Metal organic frameworks based microcantilever gas sensors for detection of volatile organic compounds." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49127.
Full textAbstract:
Metal Organic Frameworks (MOFs) are a new class of nanoporous materials with
high surface area, thermal/chemical stability and a taylorable pore size. These properties
make MOFs ideal for storage and gas separation applications. Piezoresistive
microcantilever sensors are microfabricated devices that are highly sensitive to surface
strain due to doped single crystal silicon regions. Changes in resistance generated by
surface strain can be measured with a high degree of accuracy using a Wheatstone bridge
and basic instrumentation. This thesis will discuss the use of piezoresistive
microcantilever sensors as a transduction mechanism for detection of volatile organic
compounds (VOC's) using MOF coatings. It will be shown that by coating a
microcantilever with MOFs it is possible to detect low levels of different VOC's
(hundreds of parts per million). Excellent sensitivity and a simple transduction
mechanism make these devices low power and highly compact. Such devices would be
capable of detecting a plethora of different analytes at low concentrations. Devices were
engineered for maximum response and microfabricated in the cleanroom with high yield.
A custom setup for testing the devices was designed and machined. A number of MOFs
were selected and tested, their response was recorded and analyzed. Twelve different
analytes including eleven VOC's and water were used to characterize the MOFs.
Microcantilever sensors were shown to be durable, reliable and stable in long term testing
despite being subjected to many different analytes. MOF coatings proved flexible,
durable, stable and reversible. This work will show a promising new technology for a
next generation gas sensor.
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Davis, Bradford S., and T. Gordon Brown. "COMBINING SENSORS WITH AIRBORNE TELEMETRY INSTRUMENTATION TO MAKE RANGE MEASUREMENTS AND OBTAIN AERODYNAMICS." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/608710.
Full textAbstract:
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaObtaining a projectile’s free-flight motion profile and its aerodynamic coefficients is typically accomplished at indoor test ranges using photographic techniques synchronized to timing stations. Since these ranges are relatively short, many discrete tests are necessary to compile a complete understanding of the projectile’s behavior. When Time Space Position Information (TSPI) is requested over long-range flights, it has been gathered with expensive video, laser, and radar trackers. These can be inaccurate at times and are limited to locations where the range equipment is able to track the projectile’s entire flight. With the ever-increasing sophistication of ordnance, such as smart and competent munitions that have multi-stage thrusting and maneuvering capability, it is becoming increasingly difficult to make the necessary measurements using current measurement techniques. Microelectromechanical Systems (MEMS) sensors and other electro-optical and magnetic sensors referenced to the sun and earth allow the projectile’s angular rates (spin, pitch, and yaw) and accelerations (axial and radial) to be measured throughout the flight. These sensors have been packaged into miniaturized telemetry instrumentation systems and placed within empty voids of the munition or in place of the fuze or warhead section. By combining this sensor data with a 6-DOF trajectory code, many of the projectiles aerodynamic coefficients including drag, static moment, and damping moment over a large Mach Number range and over multiple flight paths have been obtained. These techniques decrease the number of test shots required, reduce the complexity of the test setup, and reduce the test costs. Test data from instrumented tank, artillery, and rocket flight tests are presented in this report to show the current capability of making inflight measurements using telemetry-based techniques.
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Enriquez, Karla Cecilia. "Development of an ultra-low power sensor for highway health monitoring." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Mendonça, Lucas Gonçalves Dias. "Micro-sensor capacitivo para avaliação da qualidade de combustíveis automotivos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-30092008-173401/.
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Neste trabalho é proposto um sensor capacitivo do tipo eletrodos interdigitados para avaliação da qualidade de combustíveis automotivos. Os eletrodos interdigitados apresentam algumas características adequadas ao sensor em questão. Entre elas o fato de elevar significativamente a capacitância por apresentar grande quantidade de capacitores em paralelo e de ser uma estrutura possível de se fabricar por processos convencionais de microfabricação. Além disso, esses eletrodos permitem que o combustível preencha seus espaçamentos funcionando como seu dielétrico. Foram feitas modelagens e simulações do sensor para verificação da influência de diversos parâmetros de projeto. Protótipos foram fabricados em substratos de alumina com eletrodos de níquel eletrodepositado. Os eletrodos têm larguras entre 50m e 100m, com espaçamento entre eletrodos tendo valores dessa mesma ordem. O comprimento dos eletrodos é de 800m. A altura dos eletrodos varia entre 20m e 40m. O sensor como um todo tem área em torno de 4cm². Foram realizadas medições com misturas álcool e água, gasolina e álcool, gasolina e querosene entre outras. As caracterizações mostraram bons resultados comprovando a validade do princípio proposto. O sensor se mostrou capaz de detectar os tipos de adulteração mais comuns no Brasil, adição de água ao álcool combustível e adição solventes orgânicos ou de álcool além do permitido à gasolina.This work proposes a capacitive sensor with interdigitated electrodes in order to evaluate the quality of automotive fuel. Interdigitated electrodes have some interesting features for this type of sensor. Among them, they increase the capacitance by having several capacitors in parallel, and by having a structure feasible to be manufactured by conventional microfabrication processes. In addition, automotive fuel, serving as the dielectric material, fills the gaps of the electrodes. Modeling and computational simulations of the sensor were carried out in order to realize the influence of several design parameters. Samples were manufactured using alumina substrates with electroplated nickel electrodes. The width of the electrodes was chosen to be between 50m and 100m, with gaps of similar size. The paired length of the electrodes was 800m. The height of the electrodes varied between 20m and 40m. The whole sensor was around 4cm² in area. Several measurements were carried out using mixtures of alcohol and water, gasoline and alcohol, gasoline and kerosene, and others. Characterizations showed good results, validating the method. The sensor was capable of detecting the main types of fuel adulteration used in Brazil: addition of water to alcohol, and addition of organic solvents or alcohol to gasoline beyond the acceptable limit.
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FENG, Zhifu. "Electron Beam Lithography and Focused Ion Beam Techniques for the Development of Low Power Consumption Microelectromechanical Systems-based Chemiresistive Gas Sensors." Doctoral thesis, Università degli studi di Ferrara, 2023. https://hdl.handle.net/11392/2502108.
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I sensori di gas sono ampiamente utilizzati per rilevare gas tossici per la protezione ambientale, il monitoraggio industriale, la sicurezza domestica, l'analisi del respiro e il deterioramento degli alimenti. A parte i sensori di gas elettrochimici, che hanno una breve durata, e i sensori di gas ottici di grandi dimensioni con un costo elevato, i sensori di gas chemiresistivi basati su ossidi metallici semiconduttori (OMS) risultano essere una soluzione tecnologica estremamente interessante, grazie alla sua bassa produzione costo, proprietà fisiche stabili e versatilità chimica. Tuttavia, per via dell'elevata temperatura operativa dei sensori di gas OMS, la riduzione del consumo energetico è di fondamentale importanza per una loro futura integrazione su dispositivi portatili, quali gli smartphones. A tale scopo, la miniaturizzazione dei sensori di gas OMS, principalmente per quanto riguarda il microriscaldatore, che funge da supporto meccanico del materiale di rilevamento e della parte riscaldatore/elettrodo, è un modo efficace per migliorare l'efficienza energetica. I sistemi microelettromeccanici (MEMS) offrono l'opportunità di raggiungere tale obiettivo. Questa dissertazione, focalizzata principalmente alla miniaturizzazione del microriscaldatore, si è concentrata sulla simulazione della dissipazione del calore del microriscaldatore mediante analisi agli elementi finiti, e sulla fabbricazione degli stessi utilizzando la litografia a fascio di elettroni (EBL) e il fascio di ioni focalizzati (FIB) per lo sviluppo di sensori di gas a bassissimo consumo energetico.
Quindi sono stati studiati e utilizzati due diversi approcci presso le strutture della Fondazione Bruno Kessler per fabbricare i microriscaldatori. Il primo metodo ha combinato le tecniche EBL e FIB per definire il layout del riscaldatore stesso. EBL è stato utilizzato per esporre la parte dell'elettrodo di dimensioni micrometriche, mentre il FIB è stato utilizzato per fresare la parte del circuito del riscaldatore con caratteristiche nanometriche. Nel secondo metodo, è stata utilizzata un'esposizione EBL in due fasi, senza utilizzo del FIB: i) bassa energia del fascio di elettroni con bassa dose e ampia area di scrittura per la definizione della struttura degli elettrodi; ii) alta energia del fascio di elettroni con dose elevata e piccolo campo di scrittura per la definizione del circuito del riscaldatore.
Dopo che questi microriscaldatori sono stati fabbricati, le loro proprietà elettriche e termiche sono state valutate sperimentalmente. Successivamente sono stati sviluppati sensori chemiresistivi sfruttando i microriscaldatori sviluppati. In particolare, il nanofilm ZnO di materiale sensibile di tipo n è stato depositato su MHP2 e NHP1 mediante magnetron sputtering. Il SEM ha rivelato le dimensioni nanometriche delle particelle di ZnO. La struttura cristallina di ZnO è stata caratterizzata dalla diffrazione della polvere di raggi X (XRD) e la spettroscopia fotoelettronica a raggi X (XPS) ha dimostrato il rapporto atomico di Zn e O. Il nanofilm di ZnO non ha mostrato una forte risposta all'umidità, mentre ha mostrato una buona sensibilità nei confronti del NO2.
Successivamente, i microriscaldatori MHP1 sono stati testati anche come substrati per sensori chemiresistivi a film spesso, utilizzando come materiale sensibile SnO2 altamente drogate con antimonio (ATO), concentrazione atomica del 10% e 15% in peso. Questi materiali sono stati caratterizzati da SEM, XRD e XPS, il che ha suggerito che il drogaggio di antimonio ha modificato la morfologia rispetto alla polvere di SnO2 non drogata, prevenendo la crescita delle particelle di polvere e diminuendo quindi la dimensione media delle nanoparticelle. La caratterizzazione XPS ha dimostrato che la concentrazione di antimonio era maggiore sulla superficie delle nanoparticelle di SnO2 rispetto al bulk. È stato riscontrato che i sensori ATO hanno portato a un’alta selettività e sensibilità all'NO2.Gas sensors are widely used for detecting toxic gases for environmental protection, industrial monitoring, household safety, breath analysis and food deterioration. Apart from the electrochemical gas sensors, which have a short lifetime, and optical gas sensors with large volume size with high cost, semiconductor metal oxide (SMO) gas sensors as one of the chemiresistive type gas sensors are now developing fast owing to its low production cost, stable physical properties and chemical versatility. However, regarding the high operational temperature of SMO gas sensors, reduction of power consumption is extremely important for its application in smartphones and other portable devices. For this purpose, miniaturization of SMO gas sensor devices, primarily for the hotplate part acting as mechanical support of the sensing material and heater/electrode part, is an effective way to improve the power efficiency. Microelectromechanical systems (MEMS) offer an opportunity to achieve such goal. This dissertation addressed to miniaturization of the hotplate, was focused on hotplate fabrication by using Electron Beam Lithography (EBL) and Focused Ion Beam (FIB). Then two different approaches were studied and used at Bruno Kessler Foundation facilities to microfabricate the hotplates. First method combined EBL and FIB techniques to define the layout. EBL was used to exposure the micro-level size electrode part (or pad part), and FIB was used to mill the heater circuit part with fine and dense structure. The patterned hotplate structure was characterized by Scanning Electron Microscope (SEM), and the milling result was analyzed by Secondary-ion Mass Spectrometry (SIMS). By studying these results, the optimized parameters for EBL and FIB were selected. The second method used two-step EBL exposure. Low energy of electron beam with low dose and large writing field for the electrode part exposure and high energy of electron beam with high dose and small writing field for the dense heater circuit patterning. After these hotplates were fabricated, their electrical and thermal properties were experimentally evaluated. Subsequently, chemiresistive sensors based on the developed hotplates were developed. In particular, n-type sensing material ZnO nano film was deposited on MHP2 and NHP1 by magnetron sputtering technique. SEM revealed the nano size of ZnO particle, and the calcination condition effect on the size of ZnO. ZnO crystal structure was characterized by X-ray Powder Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS) proved the atom ratio of Zn and O. ZnO nanofilm did not show strong response to humidity, but humidity could decrease the response toward NO2, and increase the response toward ethanol. Thick films of SnO2 highly doped by antimony with concentration of 10 wt% (ATO1) and 15wt% (ATO2) were drop coated on MHP1. These materials were characterized by SEM, XRD and XPS. It suggested that antimony doping modified the morphology of SnO2 powder by preventing the growth of powder particles. The results of the XPS experiment demonstrated that the concentration of antimony was higher on the surface of SnO2 than its inside. It was found that ATO sensors led to a particularly high selectivity and sensitivity to NO2 when compared to the other gases at 400 °C in dry air. Additionally, the sensing response of ATO1 and ATO2 was only moderately affected by humidity, which made them ideal candidates to detect NO2 in the actual atmosphere.
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Swafford, Robert D. "Development of a new generation of electric current sensors through advances in manufacturing techniques and material design." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50306.
Full textAbstract:
Electrical systems have become ubiquitous, and with them come the need to
accurately monitor electric current. The aerospace industry is no exception. Modern
aircraft may contain more than one hundred current sensors, each one critical to a
properly functioning vehicle. While these sensors function acceptably, several areas
have been identified for improvement: size, weight, and cost. Each sensor is bulky,
taking up valuable space. They are also costly to manufacture. The existing design
is based on the Hall effect, and has remained fundamentally unchanged for decades.
With the recent progress in manufacturing techniques and materials, it would be beneficial
to reexamine these sensors and determine if improvements can be made using
the accomplishments of recent years. Of particular interest are microelectromechanical
systems, also known as MEMS. Using a sensor based on MEMS technologies in
which design, function, and fabrication are closely intertwined would automatically
meet two of the three goals: reducing size and weight. MEMS additionally have the
potential to allow existing systems to be miniaturized. Also of interest are advanced
materials, some of which can behave as transducers, linking different physical phenomenon.
The goal of this dissertation is to use advances in manufacturing techniques
and materials, specifically those discussed above, to design a better current sensor.
As part of this goal, several potential solutions were studied and optimized. Finally,
proof-of-concept prototypes were fabricated and tested to validate the feasibility of
the designs and offer insight into continued sensor development.
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Patil, Nishad. "Design And Analysis Of MEMS Angular Rate Sensors." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/291.
Full textAbstract:
Design and analysis of polysilicon and single crystal silicon gyroscopes have been carried out. Variations in suspension design have been explored. Designs that utilize in-plane and out-of-plane sensing are studied.
Damping plays an important role in determining the sense response. Reduction in damping directly affects sensor performance. The various damping mechanisms that are prevalent in gyroscopes are studied.
Perforations on the proof mass are observed to significantly reduce the damping in the device when operated in air. The effects of perforation geometry and density have been analyzed. The analysis results show that there is a two orders of magnitude reduction in damping of thick gyroscope structures with optimized perforation design.
Equivalent circuit lumped parameter models have been developed to analyze gyroscope performance. The simulation results of these models have been compared with results obtained from SABER, a MEMS specific system level design tool from Coventor-ware. The lumped parameter models are observed to produce faster simulation results with an accuracy comparable to that of Coventorware
Three gyroscopes specific to the PolyMUMPS fabrication process have been designed and their performance analyzed. Two of the designs sense motion out-of-plane and the other senses motion in-plane. Results of the simulation show that for a given damping, the gyro design with in-plane modes gives a resolution of 4◦/s. The out-of-plane gyroscopes have two variations in suspension. The hammock suspension resolves a rate of 25◦/s in a 200 Hz bandwidth while the design with folded beam suspension resolves a rate of 2◦/s in a 12 Hz bandwidth. A single crystal silicon in-plane gyroscope has been designed with vertical electrodes to sense Coriolis motion. This design gives an order of magnitude higher
capacitance change for a given rotation in comparison to conventional comb-finger design.
The effects of process induced residual stress on the characteristic frequencies of the polysilicon gyroscopes are also studied. The in-plane gyroscope is found to be robust to stress variations. Analysis results indicate that the tuning fork gyroscope with the hammock suspension is the most susceptible to compressive residual stress, with a significant drop in sensitivity at high stress values.
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Kranz, Michael S. "Micro-mechanical sensor for the spectral decomposition of acoustic signals." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39496.
Full textAbstract:
An array of electret-biased frequency-selective resonant microelectromechanical system (MEMS) acoustic sensors was proposed to perform analysis of stress pulses created during an impact between two materials. This analysis allowed classification of the stiffness of the materials involved in the impact without applying post-impact signal processing. Arrays of resonant MEMS sensors provided filtering of the incident stress pulse and subsequent binning of time-domain waveforms into frequency-based spectra. Results indicated that different impact conditions and materials yielded different spectral characteristics. These characteristics, as well as the resulting sensor array responses, are discussed and applied to impact classification. Each individual sensor element in the array was biased by an in situ charged electret film. A microplasma discharge apparatus embedded within the microsensor allowed charging of the electret film after all device fabrication was complete. This enabled electret film integration using high-temperature surface micromachining processes that would typically lead to discharge of traditionally formed electret materials. This also eliminated the traditional wafer-bonding and post-fabrication assembly processes required in conventional electret integration approaches. The microplasma discharge process and resulting electret performance are discussed within the context of the MEMS acoustic sensor array.
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Choi, Seungkeun. "A micromachined magnetic field sensor for low power electronic compass applications." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-04092007-105302/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.Allen, Mark, Committee Chair ; Brand, Oliver, Committee Member ; Kenney, James, Committee Member ; Hesketh, Peter, Committee Member ; Michaels, Jennifer, Committee Member.
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Jalil, Jubayer. "Micromachined Vibrating-reed Electrometer in Silicon-on-Glass Technology." Thesis, Griffith University, 2019. http://hdl.handle.net/10072/389082.
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Charge sensors (also known as charge electrometers) have a broad range of applications, such as those involving the measurement of ionization radiation, detection of bio-analyte and aerosol particles, mass spectrometry, scanning tunneling microscopy, and quantum computation. Designing charge sensors for electrometry is deemed significant because of the sensitivity and resolution issues in the range of micro-scales. A microelectromechanical systems (MEMS) vibrating-reed electrometer has been developed based on micromechanical variable capacitors. An electrostatically actuated MEMS resonator is utilized as one of the terminals or electrodes of a variable or vibrating capacitor, whereas another electrode is used as a sense electrode. By using vibrating-reed technique, the resonator is driven above the flicker noise and charge measurement is performed in the second harmonic of the resonator's frequency in the white noise floor. This research aims to design and develop a high resolution micromachined charge sensor for room temperature applications. By doing so, designing a highly sensitive MEMS sensing devices and a low noise front-end circuit has been explored to improve the overall charge resolution performance of electrometry systems. A sensing device has been fabricated in silicon-on-glass (SOG)-MEMS process compared to silicon-on-insulator (SOI)-MEMS counterparts. Advantage of adopting this fabrication technology is to reduce the parasitic capacitance for high sensitivity. For readout circuits, a non-inverting operational amplifier-based preamplifier (preamp) has been constructed. To block DC leakage current and to reset the DC charge, an R-C network has been introduced in the preamplifier design. A charge sensor's sensitivity of 1.43x1011 V/C has been achieved at room temperature and atmospheric pressure. Finally, the best charge resolution of 1.03 e/√Hz@5.7 kHz has been attained by optimizing and calibrating both the MEMS sensing device and preamp circuit.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Deng, Kangfa, Gerald Gerlach, and Margarita Guenther. "Force-compensated hydrogel-based pH sensor." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35185.
Full textAbstract:
This paper presents the design, simulation, assembly and testing of a force-compensated hydrogel-based pH sensor. In the conventional deflection method, a piezoresistive pressure sensor is used as a chemical-mechanical-electronic transducer to measure the volume change of a pH-sensitive hydrogel. In this compensation method, the pH-sensitive hydrogel keeps its volume constant during the whole measuring process, independent of applied pH value. In order to maintain a balanced state, an additional thermal actuator is integrated into the close-loop sensor system with higher precision and faster dynamic response. Poly (N-isopropylacrylamide) (PNIPAAm) with 5 mol% monomer 3-acrylamido propionic acid (AAmPA) is used as the temperature-sensitive hydrogel, while poly (vinyl alcohol) with poly (acrylic acid) (PAA) serves as the pH-sensitive hydrogel. A thermal simulation is introduced to assess the temperature distribution of the whole microsystem, especially the temperature influence on both hydrogels. Following tests are detailed to verify the working functions of a sensor based on pH-sensitive hydrogel and an actuator based on temperature-sensitive hydrogel. A miniaturized prototype is assembled and investigated in deionized water: the response time amounts to about 25 min, just half of that one of a sensor based on the conventional deflection method. The results confirm the applicability of the compensation method to the hydrogel-based sensors.
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Waterfall, Tyler Lane. "Design of Piezoresistive MEMS Force and Displacement Sensors." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1549.pdf.
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Aiyar, Avishek R. "Microfabrication of a MEMS piezoresistive flow sensor - materials and processes." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24696.
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