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In this paper present, an electrostatic actuation mechanism based on the interdigitated electrode for the Biomedical Micro Electro Mechanical Systems (Bio-MEMS) sensors was mainly used for sensing or actuation in analytical and different detection applications. One of the main things interdigitated electrode (IDE) for capacitance derived from multiple electrode pairs has been connected in parallel with wide proof mass, folded spring beam attached as anchor in the sensor construction. The total capacitance was a sum of capacitance contributed by neighbouring electrodes. Hence the opposite walls of comb electrodes in the overlapping region form a parallel plate capacitor and contribute a capacitance C easily analyzed with fringe capacitance can be estimated to analytically difficult one. However, the nearly accurate way to estimate for the fringe capacitance is by using the finite element method (FEM). The major importance of the geometric dimensions on interdigitated electrode sensors are studied with an analytical model. The design of capacitive based IDE sensors are simulated and demonstrated on visualizing of the electrical properties by COMSOL Multiphysics software. [ABSTRACT FROM AUTHOR]

We present HapTable; a multi–modal interactive tabletop that allows users to interact with digital images and objects through natural touch gestures, and receive visual and haptic feedback accordingly. In our system, hand pose is registered by an infrared camera and hand gestures are classified using a Support Vector Machine (SVM) classifier. To display a rich set of haptic effects for both static and dynamic gestures, we integrated electromechanical and electrostatic actuation techniques effectively on tabletop surface of HapTable, which is a surface capacitive touch screen. We attached four piezo patches to the edges of tabletop to display vibrotactile feedback for static gestures. For this purpose, the vibration response of the tabletop, in the form of frequency response functions (FRFs), was obtained by a laser Doppler vibrometer for 84 grid points on its surface. Using these FRFs, it is possible to display localized vibrotactile feedback on the surface for static gestures. For dynamic gestures, we utilize the electrostatic actuation technique to modulate the frictional forces between finger skin and tabletop surface by applying voltage to its conductive layer. To our knowledge, this hybrid haptic technology is one of a kind and has not been implemented or tested on a tabletop. It opens up new avenues for gesture–based haptic interaction not only on tabletop surfaces but also on touch surfaces used in mobile devices with potential applications in data visualization, user interfaces, games, entertainment, and education. Here, we present two examples of such applications, one for static and one for dynamic gestures, along with detailed user studies. In the first one, user detects the direction of a virtual flow, such as that of wind or water, by putting their hand on the tabletop surface and feeling a vibrotactile stimulus traveling underneath it. In the second example, user rotates a virtual knob on the tabletop surface to select an item from a menu while feeling the knob's detents and resistance to rotation in the form of frictional haptic feedback. [ABSTRACT FROM AUTHOR]

• A mode-localized mass sensor composed of two different cantilevers is presented. • The initial asymmetric system is balanced with the electrostatic force. • The design allows to overcome manufacturing imperfections. • The mechanical coupling is taken into account in the proposed model. • The designed device is fabricated and the proposed model is experimentally validated. This paper presents a sensor using the mode localization phenomenon to detect a mass perturbation. It is composed of two cantilevers with different lengths and connected by a coupling beam. The short cantilever is electrostatically actuated and by changing the applied DC voltage, we can reduce its stiffness and reach the veering point, which corresponds to a balanced system. This principle allows us to overcome the manufacturing defect which perturbs the initial system. An analytical model using the Euler-Bernoulli beam theory is developed for the design. The equation of the continuous system is discretized with the Galerkin method and simulations are performed. The designed device composed of polysilicon coupled microbeams is then fabricated with the Multi-User MEMS Processes and an experimental investigation is carried out. Three devices with different coupling are considered with a length ratio of 0.98. This ratio is suitable to reach the veering point by using a DC balancing voltage around the half of the pull-in voltage. The comparison between theoretical and experimental results shows a good agreement for each device. [ABSTRACT FROM AUTHOR]

This article gives a condensed review of the MEMS actuators that have seen light in the past three decades. Since the electrostatic drive comes almost natural when creating mechanical devices with the available MEMS technology, greater importance is highlighted. Nevertheless, by introducing more non-IC related materials, other devices are presented, and range from magnetic and piezo-electric drive, to applications based on hydraulics and pneumatic actuation. [ABSTRACT FROM AUTHOR]

Adaptive optical (AO) components play an important role in numerous optical applications, from astronomical telescopes to microscope imaging systems. For most of these AO components, the induced wavefront correction, respectively added optical power, is based on a rotationally symmetric or segmented design of the AO component. In this work, we report on the design, fabrication, and characterization of a micro-electronic-mechanical system (MEMS) adaptive membrane mirror in the shape of a parabolic cylinder. In order to interpret the experimental characterization results correctly and provide a tool for future application development, this is accompanied by the setup of an optical simulation model. The characterization results showed a parabolically deformable membrane mirror with an aperture of 8 × 2 mm2 and an adaptive range for the optical power from 0.3 to 6.1 m−1 (dpt). The optical simulation model, using the Gaussian beamlet propagation method, was successfully validated by laser beam profile measurements taken in the optical characterization setup. This MEMS-based adaptive astigmatic membrane mirror, together with the accompanying simulation model, could be a key component for the rapid development of new optical systems, e.g., adaptive laser line generators.

In this paper we present a detailed evaluation of a micro-opto-electromechanical system (MOEMS) for active focusing which is realized using an electrostatically deformed thin silicon membrane. The evaluation is done using finite element methods and experimental characterization of the device behavior. The devices are realized in silicon on insulator technology. The influence of internal stress especially resulting from the high compressive buried oxide (BOX) layer is evaluated. Additionally, the effect of stress gradients in the crystalline device layer and of high reflective coatings such as aluminum is discussed. The influence of variations of some important process steps on the device performance is quantified. Finally, practical properties such as focal length control, long-term stability, hysteresis and dynamical response are presented and evaluated. The evaluation proves that the proposed membrane focusing device is suitable for high performance imaging (wavefront errors between λ/5–λ/10) with a large aperture (5 mm).

In this work, we present an experimental technique to detect the onset of bifurcation and measure the extent of hysteresis in electrostatic MEMS. The device-under-test comprises a microcantilever beam actuated via a side electrode. The beam vibrations result in varying the resonator's capacitance, therefore inducing a current that can be measured and used for characterization and performance analysis. The motion-induced current is measured, and its harmonics are extracted using a lock-in amplifier. Locking on the third harmonic of the induced current enables us to bypass parasitic capacitance and extract a signal directly related to the resonator motions. We show that this signal can be used to investigate the nonlinear dynamic behavior of MEMS resonators undergoing large motions. Specifically, our experiments demonstrate our technique's ability to detect various bifurcations, to track the onset of hysteresis, and to measure the hysteresis bandwidth. We also use our technique to analyze the quantitative relationships between the actuation voltage, the location of the bifurcation point, and the hysteretic bandwidth. Finally, we show that our technique can be used to generate the calibration curves for inertial MEMS sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rapid actuation of anisotropic polymer films driven by electrostatic Coulombic force was achieved. • Spatial control of electrostatic actuation was demonstrated by engineering electric fields. • The electric resistance, elastic modulus, and anisotropy of polymers were critical for determining actuation performance. Liquid crystal elastomers (LCEs) are a fascinating class of anisotropic soft actuating materials that can respond to various stimuli. However, achieving both fast actuation and a high degree of freedom (DOF) in the LCE is one of the main challenges to overcome. In this study, we demonstrate rapid actuation (∼25 Hz) of LCEs driven by electrostatic force via direct charging. Notably, the end of the LCE film in our system is physically separated from the electrode, unlike conventional dielectric elastomer actuators, which allow a high DOF actuation when applying the DC or AC voltage in a spatially controlled manner. As a proof-of-concept, various functional actuators, including popup letters, a Kirigami-inspired spring, a dynamic segments device, a freeform oscillator, and a flapping motion of beetle, are successfully demonstrated. We envision our electrostatically actuating LCEs with sophisticatedly engineered electric fields in 1D, 2D, and 3D environments as a valuable platform for investigating the fundamental mechanics of electric field-driven soft actuators. [ABSTRACT FROM AUTHOR]

An important aspect that must be considered when designing micro-electro-mechanical systems (MEMS) for all domains, including robotics, is the thermoelastic damping which occurs when the MEMS material is subjected to cyclic stress. This paper is focused on a model for the thermoelastic damping developed based on the generalized thermoelastic theory with the non-Fourier thermal conduction equation. The model was implemented in MATLAB and several simulations were performed. The theoretical results show a decrease in the deflection amplitude with the increase in time. The deflection amplitude decrease was validated by the experimental investigations, consisting of measuring the loss in amplitude and velocity of oscillations as a function of time. Moreover, this paper also presents the influence of the geometric dimensions on the mentioned decrease, as well as on the initial and final values of the amplitude for several polysilicon resonators investigated in this paper.

Nowadays, the concept of programmable matter paves the way for promising applications such as reshaping an object to test different configurations, modeling or rapid prototyping. Based on elementary modules, such matter can be arranged and disassembled easily according to the needs of the designers. Several solutions have been proposed to implement this concept. Most of them are based on modular self-reconfigurable robotics (SMR) that can work together and move relatively to one another in order to change their configuration. Achieving such behavior requires to solve some technological challenges in particular module’s geometry and actuation. In this paper, we build and develop a proof of concept for a catom based on electrostatic actuation. The modeling and analysis of the actuator functioning as catom is given after a comparison of various possible actuation. Simulations as well as experiments validations are afterwards carried out to confirm and demonstrate the efficiency of electrostatic actuation to achieve latching capabilities of the proposed catom.

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

Soft actuators based on liquid crystalline elastomers (LCEs) are captivating significant interest because of their unique properties combining the programmable liquid crystalline molecular order and elasticity of polymeric materials. For practical applications, the ability to perform multimodal shape changes in a single LCE actuator at a subsecond level is a bottleneck. Here, we fabricate a monodomain LCE powered by electrostatic force, which enables fast multidirectional bending, oscillation, rotation, and complex actuation with a high degree of freedom. By tuning the dielectric constant and resistivity in LCE gels, a complete cycle of oscillation and rotation only takes 0.1 s. In addition, monodomain actuators exhibit anisotropic actuation behaviors that promise a more complex deployment in a potential electromechanical system. The presented study will pave the way for electrostatically controllable isothermal manipulation for a fast and multimode soft actuator.

This paper investigates the mass sensing capability of an array of a few identical electrostatically actuated microbeams, as a first step toward the implementation of arrays of thousands of such resonant sensors. A reduced-order model is considered, and Taylor series are used to simplify the nonlinear electrostatic force. Then, the harmonic balance method associated with the asymptotic numerical method, as well as time integration or averaging methods, is applied to this model, and its results are compared. In this paper, two- and three-beam arrays are studied. The predicted responses exhibit complex branches of solutions with additional loops due to the influence of adjacent beams. Moreover, depending on the applied voltages, the solutions with and without added mass exhibit large differences in amplitude which can be used for detection. For symmetric configurations, the symmetry breaking induced by an added mass is exploited to improve mass sensing. [ABSTRACT FROM AUTHOR]

Most gas sensors suffer from the cross sensitivity to environmental temperature, which significantly reduces the accuracy and reliability of measurements. Current solutions require the fabrication of a thermometer in close proximity to the gas sensor or an identical reference sensor to compensate for the sensor drift due to temperature. This increases the device size, fabrication cost, and the power required to operate the sensor; and also adds to the complexity of the device circuit for signal processing. Here, we demonstrate a single resonant gas sensor, based on a microbeam uniformly coated with metal-organic frameworks (MOFs), capable of simultaneously measuring environmental temperature and gas concentration (water vapor). Using the electrostatic harmonic voltage, we actuate the microbeam simultaneously near the first and second vibration modes. The frequency shifts of these two modes due to physical stimuli changes are monitored in real time. The lower electrode of the clamped-clamped microbeam resonator is perforated to reduce the effect of squeeze film damping, thereby allowing operation under atmospheric pressure. We demonstrate experimentally the effectiveness of this technique to measure the environmental temperature and gas concentration. Based on the theoretical analysis and the Allan deviation results, a minimum detectable temperature of 0.03 °C and water vapor concentration of 4.6 ppm is demonstrated. [ABSTRACT FROM AUTHOR]

Extensive modeling and simulation of the damping phenomenon, electrostatic actuation, and structural vibration analysis are performed. The governing partial differential equations of cantilever plate are obtained, and the resonant frequencies are calculated from the equilibrium equations. The damping forces of squeeze film are analyzed by obtaining the damping ratio and spring constant. Electrostatic actuation is applied to oscillate the cantilever to ensure that the displacement of the plate is above the thermal noise floor. Electrostatic actuating forces, displacement, and capacitance are calculated both numerically and analytically from the Poisson's equations. Squeeze film damping effects naturally occur if structures are subjected to loading situations such that a very thin film of fluid is trapped within structural joints, interfaces, etc. An accurate estimate of squeeze film effects is important to predict the performance of dynamic structures. Squeeze film effects are simulated by the finite element method. The accuracy of the compact model is studied by comparing its response to the numerical results calculated with the finite element method. The agreement is very good in a wide frequency band. The numerical study and the compact model are directly applicable in predicting the damping force and damping factors of squeeze film. [ABSTRACT FROM AUTHOR]

Similar to elasticity and viscoelasticity, anelasticity is one of the rheological models of materials. Like the viscoelastic materials, anelastic deformation is time dependent, while unlike viscoelasticity, it is full recoverable. Anelastic behavior is very sensitive to microstructure and is significant when things become small. In this paper, the nonlinear vibrations of an electrostatically actuated micro-beam made of anelastic material are studied based on the modified couple stress theory and considering compressible fluid media. The constitutive equation of micro-beams has been developed regarding the stress-strain behavior of classic anelastic materials. Considering the dependency of the effective viscosity on variable gap distance, an analytical model of an electrostatically actuated anelastic micro-beam has been developed through the variable Knudsen number. Then, multiple scales method has been applied to obtain an approximate analytical solution for nonlinear resonant curves. Additionally, the effects of different mechanical behaviors of materials including elasticity, viscoelasticity and anelasticity on the nonlinear dynamic response have been studied. Furthermore, influences of some effective parameters such as length scale, anelastic relaxation time, relaxation intensity, mid-plane stretching force, residual axial force, air-gap pressure and compressible fluid media on the nonlinear vibration analysis have been investigated and discussed in detail. The results demonstrate that resonance curves are strongly dependent on the mechanical behavior of materials. It is found that the relaxation intensity, relaxation time and air-gap pressure change the resonant amplitude significantly. Moreover, the results reveal that considering compressible fluid media, both the frequency response and the softening behavior of the system decrease. [ABSTRACT FROM AUTHOR]

This paper proves that critical geometric dimensions of a capacitive resonator can be estimated from nondestructive electrical measurements. In particular, the gap between the electrodes at rest is precisely determined. The imperfect verticality of flanks introduced by defects of the manufacturing process is also quantified. The presented approach is especially interesting compared to time-consuming observations with conventional microscopy techniques (optical, SEM,…) which are complex to automate. Furthermore, it is the first available nondestructive way to determine the fabrication defects coming from imperfect etching processes such as DRIE. After presenting the theoretical developments, experimental characterization is performed on a fabricated capacitive comb drive resonator. The estimated parameters are compared to optical microscope observations. Our method paves the way to novel reverse-engineering techniques, simultaneously combining process control and system characterization. [ABSTRACT FROM AUTHOR]

In this paper, in the domain of 1D-membrane micro-electro-mechanical systems in which the electrostatic field is expressed in terms of geometric curvature of the membrane, we present a numerical approach based on shooting techniques to reconstruct the membrane profile in the device in steady-state case. In particular, starting from known results in literature about existence achieved by Schauder-Tychonoff’s fixed point approach and uniqueness, and focusing on two physical-mathematical parameters appropriately indicative of the applied voltage and electromechanical properties of the membrane, respectively, we will discuss what operation parameters (applied voltage, amplitude of electrostatic field) and for which electromechanical membrane characteristic of the device is permitted or not a convergence of the method with respect to analytical results. Finally, we will discuss in detail the detected ghost solutions. [ABSTRACT FROM AUTHOR]

Most parallel-plate electrostatic MEMS feature an electrode moving vertically against a fixed electrode. Operating these systems in air triggers squeeze film damping and results in a low quality factor. In this paper, we present a new class of low-damping laterally actuated MEMS. Side actuation electrodes drive in-plane motions in order to take advantage of low damping couette flow resulting in a quality factor of 128. The design compensates for the small actuation electrodes area by amplifying the fringing electrostatic fields and reducing in-plane compliance which limits the actuation voltage to 40 V. A simple two mask process is proposed to fabricate the MEMS in the device layer of an SOI wafer. A lumped-mass model is developed as a design tool for this class of MEMS. It is validated by comparison to two finite element models. [ABSTRACT FROM AUTHOR]

In this study, control design of a T shaped mass connected to the clamped-clamped microbeam excited by electrostatic actuation is investigated. The actuation force is generated by applying an electric voltage between the horizontal part of T shaped mass and an opposite electrode plate. In this model, the micro-beam is modeled by Euler-Bernoulli theory as a continuous beam. The T-shaped assembly connected to the the microbeam is assumed as a rigid body and nonlinear effect of electrostatic force is considered. Equations of motion and associated boundary condition are derived using the Lagrange’s principle. The differential equation of nonlinear vibration around the static position is discretized using Galerkin method.. The discretized equations are solved by the perturbation theory. To improve the dynamics behavior of systems, nonlinear control feedback has been presented. The controller regulates the pass band of microcantilever and analytically approximate the nonlinear resonance frequency and amplitudes of the periodic solutions when the microcantilever is subjected to one point and fully distributed feedback forces. The results of paper may be used for improving the design of mass sensors based on nonlinear jump phenomena. [ABSTRACT FROM AUTHOR]

We demonstrate a resonant gas sensor uniformly coated with a metal-organic framework (MOF) and excited near the second vibration mode for enhanced sensitivity. The possibility of realizing a smart switch triggered upon exceeding a threshold mass is demonstrated when operating the resonator near the dynamic pull-in instability. The resonator is based on an electrostatically excited clamped–clamped microbeam. The microbeam is fabricated from a polyimide layer coated from top with Cr/Au and from bottom with Cr/Au/Cr layer. The geometry of the resonator is optimized to reduce the effect of squeeze film damping, thereby allowing operation under atmospheric pressure. The electrostatic electrode is designed to enhance the excitation of the second mode of vibration with the minimum power required. Significant frequency shift in kilohertz is demonstrated for the first time upon water, acetone, and ethanol vapor exposure due to the MOF functionalization and the higher order mode excitation. The adsorption dynamics and MOF selectivity are investigated by studying the decaying time constants of the response upon gas exposure. [2017–0218] [ABSTRACT FROM PUBLISHER]

In this work, a real-time capacitive sensing scheme based on electromechanical amplitude modulation is developed to detect the scanning angle and phase of a uniaxial electrostatic comb-drive micromirror for close loop control. In this scheme, a sine-wave voltage signal superimposed with a high frequency carrier signal is applied to the shared comb drives of the micromirror for both sensing and driving. The driving/sensing circuit is fully analyzed in both frequency and time domain for feedthrough elimination and signal distortion minimization. Experimental results have shown that using a carrier signal with 2.5 V pp and 1 MHz, the measurement accuracy of the scanning angle of the micromirror reaches 0.15° and the time delay can be controlled within 0.47 μs. The effect of the temperature change on the phase response of the micromirror is also investigated for a better understanding of the micromirror's scanning stability. When the temperature changes from 25 °C to 35 °C, the measured time delay of the micromirror actuated at 3840 Hz changes from 0 to 2.4 μs. The proposed capacitive sensing scheme can be used to effectively measure the angular position and phase of electrostatic comb-drive MEMS mirrors simultaneously without the need of adding any external components. [Display omitted] • A capacitive angular sensing circuit developed for electrostatic micromirrors. • Simultaneous real-time detection of the angle and phase of the micromirror has been achieved. • The phase change of the scanning micromirror on the temperature variation has been investigated experimentally. • The relation between the scan angle and the circuit output voltage can be accurately modelled through piecewise fitting. [ABSTRACT FROM AUTHOR]

This paper presents a microelectromechanical system (MEMS)-based oscillator based on a Lamé-mode capacitive micromachined resonator and a fully differential high-gain transimpedance amplifier (TIA). The proposed TIA is designed using TSMC 65 nm CMOS technology and consumes only 0.9 mA from a 1-V supply. The measured mid-band transimpedance gain is 98 dB Ω and the TIA features an adjustable bandwidth with a maximum bandwidth of 142 MHz for a parasitic capacitance C P of 4 pF. The measured input-referred current noise of the TIA at mid-band is below 15 pA/ Hz . The TIA is connected to a Lamé-mode resonator, and the oscillator performance in terms of phase noise and frequency stability is presented. The measured phase noise under vacuum is −120 dBc/Hz at a 1-kHz offset, while the phase noise floor reaches −127 dBc/Hz. The measured short-term stability of the MEMS-based oscillator is ±0.25 ppm.

This paper introduces both optical and mechanical design and simulation of large static deflection MOEMS actuator. The designed device is in the form of an adjustable optical wedge (AOW) laser scanner. The AOW is formed of 1.5-mm-diameter plano-convex lens separated by air gap from plano-concave fixed lens. The convex lens is actuated by staggered vertical comb drive and suspended by rectangular cross-section torsion beam. An optical analysis and simulation of air separated AOW as well as detailed design, analysis, and static simulation of comb-drive are introduced. The dynamic step response of the full system is also introduced. The analytical solution showed a good agreement with the simulation results. A general global minimum optimization algorithm is applied to the comb-drive design to minimize driving voltage. A maximum comb-drive mechanical deflection angle of 12 deg in each direction was obtained under DC actuation voltage of 32 V with a settling time of 90 ms, leading to 1-mm one-dimensional (1-D) steering of laser beam with continuous optical scan angle of 5 deg in each direction. This optimization process provided a design of larger deflection actuator with smaller driving voltage compared with other conventional devices. This enhancement could lead to better performance of MOEMS-based laser beam scanners for imaging and low-speed applications. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of dynamic excitation and its utility for enhancement of stable displacement range for a double cantilever-based electrostatic microactuator. A coupled electromechanical problem has been formulated using Galerkin method and solved considering dynamic actuation. The effect of excitation frequency is analyzed thoroughly to estimate the maximum stable displacement range of the actuator. Extensive studies illustrate that for suitable ac voltage-frequency combination, the maximum stable tip deflection for the cantilevers can be obtained even in the range of 50% to 90% of initial gap under specific damping. Such inherent dynamic characteristic of the actuator has been exploited here to achieve larger travel range. Furthermore, the theoretical observation has been experimentally demonstrated with a double microcantilever-based structure fabricated using silicon-on-insulator based process. The experimentation has been carried out using a developed in-house set-up. The major advantage in the present study is that unlike reported literature, the extended range has been achieved here without any additional complex circuits or design modifications. The proposed concept can be extended further to improve the displacement range of other microstructures toward different applications. [ABSTRACT FROM AUTHOR]

Various phenomena are emerging in existing micro-electro-mechanical systems (MEMS). In order to fully exploit the potential of such systems, a synergy of multiple engineering fields should be reached through a careful analysis of the designed system and its optimization. It is common practice that complex multi-physics finite element method (FEM)-based models are created to analyze the system. Nevertheless, without a clear understanding of the occurred phenomena, an optimal design will be hard to attain. In this paper, we demonstrate that only minimal design changes in existing MEMS actuators can potentially lead to noticeable improvements of the system. We present a case study considering an electrostatic rotational parallel-plate actuator under sliding mode control. This type of actuator is one of the most successful commercial examples of this actuator widely applied in MEMS-based optical switches. The results of this paper confirm that the control strategy of the actuator is a substantial part of the system and should be taken into account; specifically, it can affect the parameters of the designed actuator in order to modify the dynamics of the system in a desired way. In our case, this can reduce the amplitude of output chattering or reduce the switching time of the actuator. Moreover, this paper points out various design flaws, namely when synergy between various system requirements was not reached successfully and only a suboptimal solution was discovered. [ABSTRACT FROM AUTHOR]

This paper introduces a novel method for designing of low actuation voltage, high tuning ratio electrostatic parallel plate RF MEMS variable capacitors. It is feasible to achieve ultra-high tuning ratios way beyond 1.5:1 barrier, imposed by pull-in effect, by the proposed method. The proposed method is based on spring strengthening of the structure just before the unstable region. Spring strengthening could be realized by embedding some dimples on the spring arms with the precise height. These dimples shorten the spring length when achieved to the substrate. By the proposed method, as high tuning ratios as 7.5:1 is attainable by only considering four dimple sets. The required actuation voltage for this high tuning ratio is 14.33 V which is simply achievable on-chip by charge pump circuits. Brownian noise effect is also discussed and mechanical natural frequency of the structure is calculated. [ABSTRACT FROM AUTHOR]