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    Conceptual design of a micro gripper with electrostatic micro stepper-motor actuation

    , Article Life Science Journal ; Volume 10, Issue SUPPL 8 , 2013 , Pages 290-293 ; 10978135 (ISSN) Shadbakhsh, F ; Shahriari, M ; Zabihollah, A ; Sharif University of Technology
    Micro grippers are essential tools for manipulation of objects in micron size. An electrostatic micro stepper-motor is used for actuating a proposed gripper mechanism and performance of this gripper is compared with the previous ones. The characteristic of the proposed mechanism is analyzed by simulation and it is shown that the designed gripper has the capability of doing manipulation in micron dimension with an acceptable performance  

    Design, simulation and fabrication of a MEMS accelerometer by using sequential and pulsed-mode DRIE processes

    , Article Journal of Micromechanics and Microengineering ; Volume 27, Issue 1 , 2017 ; 09601317 (ISSN) Gholamzadeh, R ; Jafari, K ; Gharooni, M ; Sharif University of Technology
    Institute of Physics Publishing  2017
    A sensitive half-bridge MEMS accelerometer fabricated by sequential and pulsed-mode processes is presented in this paper. The proposed accelerometer is analyzed by using conventional equations and the finite element method. The micromachining technology used in this work relies on two processes: sequential and pulsed-mode. In the sequential deep reactive ion etching process, a mixture of hydrogen and oxygen with a trace value of SF6 is used instead of polymeric material in the passivation step. The pulsed-mode process employs periodic hydrogen pulses in continuous fluorine plasma. Because of the continuous nature of this process, plus the in situ passivation caused by the hydrogen pulses,... 

    Application of direct simulation Monte Carlo for development of micro gas sensor

    , Article Bulgarian Chemical Communications ; Volume 50, Issue 2 , 2018 , Pages 298-305 ; 08619808 (ISSN) Gerdroodbary, M. B ; Ganji, D. D ; Taeibi Rahni, M ; Vakilipour, Sh ; Moradi, R ; Sharif University of Technology
    Bulgarian Academy of Sciences  2018
    Development of a new micro gas sensor is essential for the analysis of the outcome of gas separation devices. In this paper, direct simulation Monte Carlo (DSMC) modeling of low-pressure gas sensor was performed to investigate the effect of physical parameters on the performance and main characteristics of this type of actuator in various operating conditions. Extensive parametric studies were done and the effect of ambient pressure, temperature and gap of arms were comprehensively investigated. Our findings showed that gap size significantly influences the flow features and force generation inside the sensor. © 2018 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria  

    Study of nonlinear dynamics and chaos in MEMS/NEMS resonators

    , Article Communications in Nonlinear Science and Numerical Simulation ; Volume 22, Issue 1-3 , May , 2015 , Pages 611-622 ; 10075704 (ISSN) Miandoab, E. M ; Yousefi Koma, A ; Pishkenari, H. N ; Tajaddodianfar, F ; Sharif University of Technology
    Elsevier  2015
    With the successes in numerous applications from signal filtering to chemical and mass sensing, micro- and nano-electro-mechanical resonators continue to be one of the most widely studied topics of the micro-electro-mechanical systems community. Nonlinearities arising out of different sources such as mid-plane stretching and electrostatic force lead to a rich nonlinear dynamics in the time response of these systems which should be investigated for appropriate design and fabrication of them. Motivated by this need, present study is devoted to analyzing the nonlinear dynamics and chaotic behavior of nano resonators with electrostatic forces on both sides. Based on the potential function and... 

    Developing a new pressure measurement mechanism based on squeeze film damping effect

    , Article Proceedings - 2011 2nd International Conference on Control, Instrumentation and Automation, ICCIA 2011, 27 December 2011 through 29 December 2011 ; Dec , 2012 , Pages 800-803 ; ISBN: 9781467316897 Ghafari, A ; Ghanbari, A ; Kamanzadeh, S ; Abbasian, K ; Saghir, H ; Sharif University of Technology
    IEEE Computer Society  2012
    This paper introduces a novel approach for measuring low pressures based on MEMS technology. In this technique the mechanism of squeeze film damping is used. A voltage is applied to a fixed-fixed MEMS beam and its step response is obtained; for each pressure there is a different response. Then the settling time is measured and we can relate each settling time with a defined pressure. Here, first we use some equations to relate pressure with the squeeze film damping effect; after that we use a micro beam model and relate its parameters with pressure. Then we use numerical analysis and simulation to show the procedure of pressure measuring. All simulation results are shown and discussed  

    On the dynamics of bistable micro/nano resonators: Analytical solution and nonlinear behavior

    , Article Communications in Nonlinear Science and Numerical Simulation ; Volume 20, Issue 3 , March , 2015 , Pages 1078-1089 ; 10075704 (ISSN) Tajaddodianfar, F ; Nejat Pishkenari, H ; Hairi Yazdi, M. R ; Maani Miandoab, E ; Sharif University of Technology
    Elsevier  2015
    With the rapid development of micro/nano-electro-mechanical systems (MEMS/NEMS), arch shaped resonators are becoming increasingly attractive for different applications. Nevertheless, the dynamics of bistable resonators is poorly understood, and the conditions for their appropriate performance are not well known. In this paper, an initially curved arch shaped MEMS resonator under combined DC and AC distributed electrostatic actuation is investigated. A reduced order model obtained from first mode Galerkin's decomposition method is used for numerical and analytical investigations. We have used the Homotopy Analysis Method (HAM) in order to derive analytical solutions both for the amplitude and... 

    Dynamic Analysis of Microelectromechanical Accelerometers and Designing a Elastic Stopper to Protect Them Against Mechanical Shock

    , M.Sc. Thesis Sharif University of Technology Daeichi, Meysam (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Meghdari, Ali (Supervisor)
    Nowadays, Microelectromechanical accelerometers are of the main parts of inertial navigation systems, and so it is essential to characterize and understand the parameters affecting their performance in order to design them in a way that enables them to survive different practical applications. Mechanical shock is one of the factors existing in almost every industrial environment and cause damages or even permanent failures in MEMS devices. Identifying these damages and protecting the microstructure against them seems inevitable for the designer and engineer of this field.
    In general, approaches of protecting microstructures against mechanical shock are categorized into two major... 

    Promising technology for electronic cooling: Nanofluidic micro pulsating heat pipes

    , Article Journal of Electronic Packaging, Transactions of the ASME ; Volume 135, Issue 2 , 2013 ; 10437398 (ISSN) Jahani, K ; Mohammadi, M ; Shafii, M. B ; Shiee, Z ; Sharif University of Technology
    Currently, the thermal management of microelectromechanical systems (MEMS) has become a challenge. In the present research, a micro pulsating heat pipe (MPHP) with a hydraulic diameter of 508 lm, is experimented. The thermal performance of the MPHP in both the transient and steady conditions, the effects of the working fluid (water, silver nanofluid, and ferrofluid), heating power (4, 8, 12, 16, 20, 24, and 28 W), charging ratio (20, 40, 60, and 80%), inclination angle (0 deg, 25 deg, 45 deg, 75 deg, and 90 deg relative to horizontal axis), and the application of magnetic field, are investigated and thoroughly discussed. The experimental results show that the optimum charging ratio for water... 

    Nonlinear analysis of pull-in voltage for a fully clamped microplate with movable base

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 10 , 2012 , Pages 71-75 ; 9780791845264 (ISBN) Karimzade, A ; Moeenfard, H ; Ahmadian, M. T ; Sharif University of Technology
    Micro-electro-mechanical systems (MEMS) such as sensors and actuators are rapidly gaining popularity in a variety of industrial applications. Usually these systems are constructed by a cantilever beam or plate along with a fixed substrate. The movable beam or plate deflects due to applied voltage between the plates. Pull-in voltage and contact time are the most important characteristic of these systems. Allowing the substrate to be movable in vertical direction pull-in voltage in comparison with the fixed substrate is expected to be much smaller. In this paper the pull-in voltage and the point at which pull-in takes place for a fully clamped microplate is evaluated. The nonlinear... 

    Nonlinear tracking control of a microbeam displacement by electrostatic actuation

    , Article World Academy of Science, Engineering and Technology ; Volume 79 , 2011 , Pages 232-236 ; 2010376X (ISSN) Karami, F ; Layeghi, H ; Salarieh, H ; Alasti, A ; Sharif University of Technology
    In this study tracking problem of tip of a micro cantilever, actuated by electrostatic, is investigated. Dynamic model of the system is a PDE. Using electrostatic actuation introduced significant nonlinearity in dynamic model of the system. Control goals are achieved by means of backstepping for SI and feedback linearization for MI system. Performance of control system is inspected for some assumptions and simplifications. The results are in according to numerical simulations  

    Effects of linear acceleration in a harmonically excited proof mass MEMS rate gyroscope

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 232, Issue 19 , 2018 , Pages 3551-3563 ; 09544062 (ISSN) Mohammadi, Z ; Salarieh, H ; Sharif University of Technology
    SAGE Publications Ltd  2018
    MEMS rate gyroscopes are prone to different errors because of environmental conditions and manufacturing errors. These errors can result to mismatch between the fabricated gyros and the designed ones. Different environmental conditions and disturbances can change the parameters and specifications of a gyro, and its sensitivity may deteriorate, since the parameters are different from the optimal ones. External linear acceleration is one of the main environmental disturbances that may change the behavior of an MEMS rate gyro that its effect on the accuracy of an MEMS proof mass gyroscope is found here. This is done by finding the equations of motion of gyroscope in presence of acceleration and... 

    Application of homotopy analysis method in studying dynamic pull-in instability of microsystems

    , Article Mechanics Research Communications ; Volume 36, Issue 7 , 2009 , Pages 851-858 ; 00936413 (ISSN) Moghimi Zand, M ; Ahmadian, M. T ; Sharif University of Technology
    In this study, homotopy analysis method is used to derive analytic solutions to predict dynamic pull-in instability of electrostatically-actuated microsystems. The model considers midplane stretching, initial stress, distributed electrostatic force and fringing fields effect. Influences of different parameters on dynamic pull-in instability are investigated. Results are in good agreement with numerical and experimental findings. © 2009 Elsevier Ltd. All rights reserved  

    Fabrication and Theoretical Investigation of a Single Bubble Nozzle-Diffuser Micropump

    , M.Sc. Thesis Sharif University of Technology Pirouzpanah, Sahand (Author) ; Saeedi, Mohammad Hassan (Supervisor) ; Saeedi, Mohammad Saeed (Supervisor)
    The potential of phase change process in liquids at microscale has been a favorite for the scientists to fabricate this type of micropumps. To hold unidirectional flow in microchannels usually nozzle-diffuser arrangement is used. Due to the existence of difference in pressure drop in the nozzle and diffuser sections, one can see unidirectional flow through diffuser direction. The objective of this article is to analyze analytically the thermo-hydrodynamic behavior of the Isopropyl Alcohol (IPA) bubble of a phase change micropump. Considering the simultaneous effects of hydrodynamic and thermal characteristics of the bubble in the bubble generation chamber, and temperature-saturation... 

    Simulating Flow over Nanoparticles through Microchannels Using Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Setayeshgar, Alireza (Author) ; Darbandi, Masoud (Supervisor)
    Novel manufacturing technologies in micro scales, such as micro machining, guide us through constructing micro scale systems known as MEMS. These systems have a wide range of applications, from fabrication of electrostatic, magnetic, pneumatic sensors and actuators to micro mechanical gears and motors. Also, MEMS applications involve the manipulation of one or more fluids, known as microfluids. Simulation of flow through microchannels over nano particles has important applications in solid particles transport. In this flow, the rarefaction phenomenon will affect the flow behavior and its subsequent impacts such as aerodynamic drag forces. In this work, we use the Lattice Boltzmann method... 

    Hybrid Switching of Harvesting Energy Systems Based on Peizoelectric Material

    , M.Sc. Thesis Sharif University of Technology Tahmasbi, Mohammad (Author) ; Alasty, Aria (Supervisor) ; Salarieh, Hasan (Supervisor)
    For many low-powered portable and wireless electronic applications the finite energy density of chemical batteries places limits on their functional lifetime. Through the use of energy harvesting techniques, ambient vibration energy can be captured and converted into usable electricity in order to create self-powering systems which are not limited by finite battery energy. Typical energy harvesting systems are composed of two components, a transducer that converts the mechanical vibrations into electrical energy and a power converter that efficiently delivers the harvested energy to the electronic load. The practical design of energy harvesting systems must include both components and... 

    An Active Control of a Piezoelectric Energy Harvester for Energy Storage Optimization

    , M.Sc. Thesis Sharif University of Technology Tavakkoli Anbarani, Mostafa (Author) ; Alasti, Aria (Supervisor) ; Salarieh, Hassan (Supervisor)
    Piezoelectric Energy Harvesters (PEH)’s are devices that by means of Piezoelectric effect, convert ambient vibrations directly into electricity.
    PEHs are often modeled as a cantilever beam with two piezoelectric layer attached to its sides. Due to their high energy density, small dimensions and adaptability to harsh environment, PEHs are referred to be a suitable substitute for batteries in the near future.
    In this study, a new design of PEH is introduced in which a piezoelectric actuator is placed within web of a PEH so that by applying appropriate voltage to it, the distance between the two flanges of the beam, and accordingly the moment of inertia of the beam, is adjusted such... 

    Analysis of a 3-Linksmicro Robot under Piezoelectric Actuation

    , M.Sc. Thesis Sharif University of Technology Jafari Shad, Hamed (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
    In this research a microrobot constructed from three series connected microcantilever has been introduced and its behavior has been evaluated. Length of each microcantilever is about several hundred microns. Due to actuation of microrobot, piezoelectric has been employed. Considering one DOF of each microcantilever, this microrobot has three DOF. Manipulation and microscopy in nano and micron scale can be mentioned as main duties for this microrobot. In devices which are used for these purposes commonly parallel mechanisms are employed. Also in some devices such as AFM, samples are needed to be placed on platform. However in this study a serial mechanism has been employed which make this... 

    Finite volume simulation of gaseous microflows using modified boundary conditions

    , Article 45th AIAA Aerospace Sciences Meeting 2007, Reno, NV, 8 January 2007 through 11 January 2007 ; Volume 16 , 2007 , Pages 11313-11321 ; 1563478900 (ISBN); 9781563478901 (ISBN) Darbandi, M ; Vakilipour, S ; Rikhtegar, F ; Schneider, G. E ; Sharif University of Technology
    The rapid progress in fabricating and utilizing micro-electromechanical systems during the last decade has not been matched by the corresponding advances in our understanding from the unconventional physics involved in manufacturing and operation of micro devices. To avoid the complexity encountered in modeling of nonlinear Boltzmann equations, the Navier-Stokes equations can be solved considering the slip flow regime concepts. The modeling can be achieved via employing suitable slip velocity boundary conditions at the solid walls. The modified first-order slip models can, in some cases, extend the range of applicability of the Navier-Stokes solvers to around and beyond Kn=0.1, where the... 

    Design and Simulation (& Manufacturing) of A Micro-Gyroscope

    , M.Sc. Thesis Sharif University of Technology Soltani, Arman (Author) ; Akbari, Javad (Supervisor)
    Nowadays, microgyroscopes are among the most important products of MEMS. The production of small, precise and inexpensive gyroscopes has become possible as the result of recent developments in fabrication technology. In this thesis it is intended to introduce a new method for manufacturing more precise microgyroscopes regarding manufacture facilities. Using this new method, sensitivity and resistance of microgyroscopes are increased against noises which are primarily caused by vibration and rotation about undesirable axes. The rotational movement imposed on the gyro is detected through fluid flow within its torus channel. This transformation facilitates the measurement of the initial motion.... 

    Satellite Attitude Estimation Using MEMS

    , M.Sc. Thesis Sharif University of Technology Mirzaei Teshnizi, Masoud (Author) ; Pourtakdoost, Hossein (Supervisor)
    This thesis deals with the attitude estimation based on low cost sensor for a micro satellite in a circular, low earth orbit (LEO) and sensor calibration. With two body problem theory and Quaternion formulation, rotational motion is modeled. In addition gravity gradient effect is considered on satellite orbital elements. Using a 3-axis MEMS-based magnetometer and a sun sensor as two measurement systems, low cost attitude estimation is proposed. Bias and Scale factor are presented to model deterministic sensor error and white Gaussian noise to model stochastic sensor error. It is shown that by sensor calibration the estimation accuracy will improve. Non-linear estimation methods EKF, SRUKF...