Search for: electrostatics
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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  

    Suppression of dynamic pull-in instability in electrostatically actuated strain gradient beams

    , Article 2014 2nd RSI/ISM International Conference on Robotics and Mechatronics, ICRoM 2014 ; 2014 , pp. 155-160 ; ISBN: 9781479967438 Edalatzadeh, M. S ; Vatankhah, R ; Alasty, A ; Sharif University of Technology
    In this paper, vibration suppression of micro-or nano-scale beams subjected to nonlinear distributed electrostatic force is studied. For the sake of precision, we use the beam model derived from strain gradient elasticity theory aimed at prediction of size effect. In addition, the electrostatic force is considered with first order fringing field correction. The continuous model of the strain gradient beam is truncated by using Kantorovich method as a semi-analytical finite element method. A boundary control feedback law is proposed to suppress forced vibrations of the beam. Both measurements and actuations are taken place in the boundary to avoid spillover instabilities. Simulation results... 

    Size-dependent instability of carbon nanotubes under electrostatic actuation using nonlocal elasticity

    , Article International Journal of Mechanical Sciences ; Vol. 80 , 2014 , pp. 144-152 ; ISSN: 00207403 Seyyed Fakhrabadi, M. M ; Rastgoo, A ; Taghi Ahmadian, M ; Sharif University of Technology
    In this paper, the classical and nonlocal elasticity are applied to investigate the deflection and instability of electrostatically actuated carbon nanotubes. The results are presented for different geometries and boundary conditions. They reveal that increasing radius and gap and decreasing length confine to increasing pull-in voltages of the carbon nanotubes. The results prove that application of the nonlocal elasticity theorem leads to stiffer structures with higher pull-in voltages. Thus, in order to obtain more accurate results about the mechanical and electromechanical behaviors of the carbon nanotubes, one should apply the nonclassical elasticity theories such as that applied in this... 

    Non-linear behaviors of carbon nanotubes under electrostatic actuation based on strain gradient theory

    , Article International Journal of Non-Linear Mechanics ; Vol. 67, issue , 2014 , p. 236-244 Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    The paper deals with studying the deflection and pull-in voltages of the carbon nanotubes under electrostatic actuation with various dimensions and boundary conditions. The size-dependent behaviors of the carbon nanotubes (CNTs) are considered via application of the strain gradient theory. The results obtained from the strain gradient theory are compared to those estimated using the classical elasticity. The outcomes reveal that the classical elasticity theory underestimates the pull-in voltages of the carbon nanotubes and strain gradient theorem results in stiffer nano-structures with higher pull-in voltages. Increasing of the deflection due to the higher voltages increases the differences... 

    Wideband tunable photonic crystal cavity with electrostatic actuation

    , Article 2012 IEEE Photonics Conference, IPC 2012, 23 September 2012 through 27 September 2012 ; September , 2012 , Pages 266-267 ; 9781457707315 (ISBN) Miri, M ; Sodagar, M ; Eftekhar, A. A ; Mehrany, K ; Rashidian, B ; Adibi, A ; Sharif University of Technology
    We present a wideband tunable optical cavity based on electrostatic actuation. Over 60nm shift in wavelength is achieved by applying less than 1 Volt corresponds to a mechanical displacement of 30nm  

    The oscillatory behavior of doubly clamped microgyroscopes under electrostatic actuation and detection

    , Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 1 , 2013 ; 9780791855843 (ISBN) Mojahedi, M ; Firoozbakhsh, K ; Ahmadian, M. T ; Computers and Information in Engineering Division; Design Engineering Division ; Sharif University of Technology
    American Society of Mechanical Engineers  2013
    In MEMS gyroscopes, it is essential to use matched resonance frequencies of the drive and sense vibrational modes for improving the sensitivity. For this end, the natural frequencies can be tuned by voltages. In this study, a new model is utilized to determine the natural frequencies of the doubly clamped beam microgyroscope. In the model, nonlinear electrostatic forces, fringing fields and mid-plane stretching of thebeam are considered. The system is actuated and sensed by electrostatic force and its natural frequencies and stiffness are detuned by DC voltages. The oscillatory problem of the gyroscope is analytically solved versus DC voltages for different design parameters. Copyright  

    Charged nanorods at heterogeneously charged surfaces

    , Article Journal of Chemical Physics ; Volume 149, Issue 13 , 2018 ; 00219606 (ISSN) Naji, A ; Hejazi, K ; Mahgerefteh, E ; Podgornik, R ; Sharif University of Technology
    We study the spatial and orientational distribution of charged nanorods (rodlike counterions) as well as the effective interaction mediated by them between two plane-parallel surfaces that carry fixed (quenched) heterogeneous charge distributions. The nanorods are assumed to have an internal charge distribution, specified by a multivalent monopolar moment and a finite quadrupolar moment, and the quenched surface charge is assumed to be randomly distributed with equal mean and variance on the two surfaces. While equally charged surfaces are known to repel within the traditional mean-field theories, the presence of multivalent counterions has been shown to cause attractive interactions between... 

    Nonlinear analysis of carbon nanotube-based nanoelectronics devices

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Vol. 228, issue. 13 , 2014 , p. 2426-2439 Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    The paper deals with the investigation of nonlinear static and dynamic behaviors of electrostatically actuated carbon nanotubes with different geometries and boundary conditions. The deflection and pull-in properties are studied in detail in the presence of DC and combined DC+AC electrostatic voltages accompanying the interatomic interactions. The considered nano system can be applied in a wide range of nanoelectronics devices such as nano switches, nano resonators, nano transistors, nano capacitors and random access memories. Moreover, a useful mathematical model of the nano sensor application of the studied nano system to sense the stiffness of the nano particles is presented  

    A density functional theory study of the reactivity descriptors and antioxidant behavior of Crocin

    , Article Computational and Theoretical Chemistry ; Volume 1013 , June , 2013 , Pages 123-129 ; 2210271X (ISSN) Akhtari, K ; Hassanzadeh, K ; Fakhraei, B ; Fakhraei, N ; Hassanzadeh, H ; Zarei, S. A ; Sharif University of Technology
    The molecular characteristics of Crocin (digentiobiosyl-8,8'-diapocarotene-8,8'-oate; C44H64O24), naturally occurring carotenoid pigment compound, such as: the ionization potential (I), electron affinity (A), electronegativity (χ), electrophicility (ω), and hardness have been calculated using Density Functional Theory (DFT) approach with B3LYP/6-31G(d,p) level of theory. The plots of Frontier Molecular Orbital and molecular electrostatic potential (MEP) for Crocin molecule along with the spin density distribution for its cation radical have been demonstrated. For the first time, we indicated the chemically active sites of the Crocin molecule by Fukui functions. Calculated components of... 

    Oscillatory behavior of the nonlinear clamped-free beam microgyroscopes under electrostatic actuation and detection

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 10 , 2013 ; 9780791856390 (ISBN) Mojahedi, M ; Firoozbakhsh, K ; Ahmadian, M. T ; Barari, A ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Vibratory micromachined gyroscopes use suspending mechanical parts to measure rotation. They have no gyratory component that require bearings, and for this reason they can be easily miniaturized and batch production using micromachining methods. They operate based on the energy interchange between two modes of structural vibration. The objective of this paper is to study the oscillatory behavior of an electrostatically actuated vibrating microcantilever gyroscope with proof mass at its end. In the modelling, the effects of different nonlinearities, fringing field and base rotation are considered. The microgyroscope is subjected to coupled bending oscillations around the static deflection... 

    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  

    Ultrathin carbon nanoparticle composite film electrodes: distinguishing dopamine and ascorbate

    , Article Electroanalysis ; Volume 19, Issue 10 , 2007 , Pages 1032-1038 ; 10400397 (ISSN) Amiri, M ; Shahrokhian, S ; Marken, F ; Sharif University of Technology
    Ultrathin carbon nanoparticle-poly(diallyldimethylammonium chloride) films (CNP-PDDAC films) are formed on tin-doped indium oxide (ITO) electrodes in a layer-by-layer electrostatic deposition process employing 9-18 nm diameter carbon particles. Transparent and strongly adhering films of high electrical conductivity are formed and characterized in terms of their electrochemical reactivity. When immersed in aqueous 0.1 M phosphate buffer pH 7, each layer of CNP-PDDAC (of ca. 5-6 nm average thickness) is adding an interfacial capacitance of ca. 10 μF cm-2. Absorption into the CNP-PDDAC nanocomposite film is dominated by the sites in the PDDAC cationomer and therefore anionic molecules such as... 

    A study of solvent effects on the stereoselectivity of Diels-Alder reactions through molecular surface electrostatic potentials

    , Article Tetrahedron Letters ; Volume 44, Issue 41 , 2003 , Pages 7681-7685 ; 00404039 (ISSN) Gholami, M. R ; Talebi, B. A ; Khalili, M ; Sharif University of Technology
    Elsevier Ltd  2003
    Statistical models for the study of solvent effects on the endo/exo selectivity of Diels-Alder reactions using molecular surface electrostatic potentials was obtained. The models show that hydrogen bond interactions of solvent molecules favor the predominance of the endo isomer for the reaction of methyl acrylate, methyl methacrylate and methyl trans-crotonate with cyclopentadiene whereas the effect of solvophobicity seems to be negligible. © 2003 Published by Elsevier Ltd  

    Characterization of static behavior of a nonlinear doubly clamped microbeam under electrostatic actuation and detection

    , Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 1 , August , 2013 ; 9780791855843 (ISBN) Ahmadian, M. T ; Barari, A ; Mojahedi, M ; Firoozbakhsh, K ; Sharif University of Technology
    American Society of Mechanical Engineers  2013
    In this study, the static deflection and pull-in instability of the doubly clamped microbeam with a mass attached to its midpoint are investigated. Nonlinear electrostatic forces, fringing fields, base rotation and mid-plane stretching of the beam in this model are considered. First, a system of two nonlinear integro-differential equations are expressed in partial derivatives which describe coupled flexural-flexural motion of electrostatically actuated microbeam gyroscopes under rotation. Then static deflection and pull-in instability of the microgyroscopes acted upon by DC voltages in both (direction and sensing) directions are studied. The equations of static motion are reduced by... 

    Analytical closed form model for static pull-in analysis in electrostatically actuated torsional micromirrors

    , Article Journal of Mechanical Science and Technology ; Volume 27, Issue 5 , 2013 , Pages 1443-1449 ; 1738494X (ISSN) Moeenfard, H ; Ahmadian, M. T ; Sharif University of Technology
    The objective of this work is to create an analytical framework to study the static pull-in and also equilibrium behavior in electrostatically actuated torsional micromirrors. First the equation governing the static behavior of electrostatic torsion micromirrors is derived and normalized. Perturbation method, the method of straight forward expansion is utilized to find the pull-in angle of the mirror. Comparison of the presented results with numerical ones available in the literature shows that the proposed second order perturbation expansion gives very precise approximations for the pull-in angle of the mirror. Then straightforward perturbation expansion method is used again to analytically... 

    Static and dynamic analysis of a clamp-clamp nano-beam under electrostatic actuation and detection considering intermolecular forces

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 10 , 2013 ; 9780791856390 (ISBN) Mojahedi, M ; Barari, A ; Firoozbakhsh, K ; Ahmadian, M. T ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Micro/nano gyroscopes which can measure angular rate or angle are types of merging gyroscope technology with MEMS/NEMS technology. They have extensively used in many fields of engineering, such as automotive, aerospace, robotics and consumer electronics. There are many studies of a variety of gyroscopes with various drive and detect methods and different resonator structures in last years. In case of electrostatically actuated and detected beam micro/nano-gyroscopes, DC voltages are applied in driving and sensing directions and AC voltage is utilized in driving direction in order to excite drive oscillation. The intermolecular surface forces are especially significant when the gyroscopes are... 

    Characterization of static behavior of electrostatically actuated micro tweezers using modified couple stress theory

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 9 November 2012 through 15 November 2012 ; Volume 9, Issue PARTS A AND B , Novembe , 2012 , Pages 581-585 ; 9780791845257 (ISBN) Darvishian, A ; Moeenfard, H ; Ghaderi, N ; Ahmadian, M. T ; Sharif University of Technology
    In this paper, static behavior and pull-in of micro tweezers is studied. The micro tweezer is modelled as two cantilever beams. Static behavior of the micro tweezer under the effect of electrostatic actuation is modelled using the Euler-Bernoulli beam theory. In order to capture size effects on the behavior of micro tweezers, modified couple stress theory is utilized. It is shown when the voltage between two electrodes increased from some specific value, micro beams adhere to each other and it is observed that the pull-in voltage predicted by the modified couple stress theory considerably differs with that of the classical theory of elasticity. Results of this paper can be used for accurate... 

    A novel 3-dimentional ultra high precision positioning platform for micro machining cutting tools

    , Article 3rd International Conference on Control, Automation and Robotics, ICCAR 2017, 22 April 2017 through 24 April 2017 ; 2017 , Pages 284-288 ; 9781509060870 (ISBN) Zabihollah, A ; Yadegari, A ; Rashidi, D ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Ultra-high precision machining is proposed by externally actuating the work piece in linear motions in the X-Y plane and linear motion in the Z-axis. To solve the problems in the machining process such as nonlinearity and low repeatability positioning accuracy of machining tools in a larger scale, a novel platform for cutting tools in micro machining based on electrostatic linear micromotors and piezoelectric stack actuator system is presented. © 2017 IEEE  

    Corotational nonlinear finite element formulation and modeling of electrostatically actuated microbeams

    , Article JVC/Journal of Vibration and Control ; Volume 15, Issue 4 , 2009 , Pages 617-640 ; 10775463 (ISSN) Ahmadian, M. T ; Borhan, H ; Esmailzadeh, E ; Sharif University of Technology
    A complete nonlinear finite element model for coupled-domain microelectromechanical system devices with electrostatic actuation and squeeze film effect was developed. for this purpose, a corotational finite element formulation for the dynamic analysis of planer Euler-Bernoulli microbeams considering geometrical nonlinearities due to both large structural deformation and electrostatic actuation is developed. In this method, the internal forces due to deformation and residual stresses, the elemental inertias, and the damping effect of the squeeze-film are systematically derived by consistent linearization of the fully geometrically nonlinear beam theory using d'Alembert and the virtual work... 

    Micro-plasma actuator mechanisms in interaction with fluid flow for wind energy applications: Physical parameters

    , Article Physics of Fluids ; Volume 32, Issue 7 , 2020 Omidi, J ; Mazaheri, K ; Sharif University of Technology
    American Institute of Physics Inc  2020
    Plasma actuator is a flow control device to improve the aerodynamic performance of wind turbine blades at low airspeeds. One of the most robust numerical models for simulation of plasma actuator interaction with the fluid flow is the electrostatic model. This model is improved recently and is extensively verified by the authors. Due to the high cost of performing experimental optimizations, the optimized geometrical dimensions and materials of a plasma actuator may be sought by this numerical model. The aim of the present study is the aerodynamic enhancement of a DU21 wind turbine blade airfoil in which the effect of geometric parameters and the dielectric material is examined separately....