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MEMS‐based Fabry–Perot filter components (MEMS‐FPC) have garnered significant attention in the field of micro‐spectrometers due to their ability to perform high‐efficiency spectral analysis at the microscale. However, achieving optimal peak transmission performance across a broad spectral range remains a core challenge in the development of MEMS‐FPC modules. In this work, a novel dual‐channel is presented, electrostatically actuated NIR MEMS‐FPC filter module that overcomes the limitations of electrostatic tuning in spectral detection through the integration of an innovative tuning structure and dual‐channel filtering. Fabricated using wafer‐level bulk micromachining techniques, the module enables continuous tuning and precise detection under a driving voltage of 0–40 V. The two channels cover spectral ranges of 814–946 nm and 968–1211 nm, respectively, achieving peak transmittance over 79% with full‐width at half maximum (FWHM) values ranging from 7.59 to 43.29 nm, setting a new standard for performance in this spectral range. The results demonstrate the potential of MEMS‐FPC as a high‐performance spectral sensor, demonstrating its future application as a NIR microspectrometer when integrated with commercial CCDs. With its low power consumption and compact size, this module is well‐suited for integration into portable devices such as smartphones and drones, offering real‐time NIR spectral sensing capabilities. [ABSTRACT FROM AUTHOR]

A Galerkin-based nonlinear normal mode approach based on the concept of invariant manifolds is adopted to analyze the effect of thermoelastic damping on the nonlinear vibrations of a microbeam with mid-plane stretching and electrostatic actuation. The derivation of the mathematical model starts with two coupled equations: a general Euler–Bernoulli equation for microbeam vibrations, which includes thermal moment and thermal force terms due to the thermoelastic damping effect; and a thermal equation describing the generation of the thermal moment due to bending vibrations. Given the available information about the material properties and geometry of conventional microbeams, and a physical reasoning based on it about the time constant of the thermal equation, the two governing equations are integrated into a single nonlinear partial differential equation. Galerkin discretization is used to transform the governing equation into a system of coupled nonlinear ordinary differential equations that are uncoupled at linear order. The modal analysis is then followed by finding an invariant manifold leading to a nonlinear ordinary differential equation that governs the vibration behavior of the system. The results of the case study showed that the amount of thermoelastic damping is dependent on the excitation voltage, and the damping increases with increasing voltage. Furthermore, in the presence of thermoelastic damping, by applying the step voltage and starting the vibrations, the frequency increases over time until it reaches a certain limit. With a higher excitation voltage, the frequency increases at a higher rate, but to a lower final limit. In an undamped system, the frequency of oscillations is constant over time, but a higher excitation voltage causes lower frequency vibrations. The results of pull-in analysis showed that thermoelastic damping has no significant effect on static or dynamic pull-in voltage. [ABSTRACT FROM AUTHOR]

Despite major advances in the field of actuator technology for microsystems, miniaturized microfluidic actuation systems for mobile devices are still not common in the market. We present a micropump concept and an associated mass flow sensor design, which, in combination, have the potential to form the basis for an integrated microfluidic development platform for microfluidic systems in general and microdosing systems in particular. The micropump combines the use of active valves with an electrostatic drive principle for the pump membrane and the valves, respectively. With a size of only 1.86 mm × 1.86 mm × 0.3 mm, the first prototypes are capable of pumping gaseous media at flow rates of up to 110 μL/min. A specific feature of the presented micropump is that the pumping direction is perpendicular to the chip surface. The corresponding flow sensor combines the principle of hot-wire anemometry with a very small footprint of only 1.4 mm × 1.4 mm × 0.4 mm. The main innovation is that the hot wires are fixed inside a through-hole in the substrate of the microchip, so that the flow direction of the fluid to be measured is perpendicular to the chip surface, which enables direct integration with the presented micropump. Detection thresholds of around 10 μL/min and measuring ranges of up to 20 mL/min can be achieved with the first prototypes, without dedicated evaluation electronics. [ABSTRACT FROM AUTHOR]

Within the framework of the nonlocal strain gradient and the Euler–Bernoulli beam theories, a model of electrostatically actuated functionally graded (FG) microbeams is developed taking into account the intermolecular interaction forces in it. In addition to the electrostatic forces resulting from the applied DC voltage between a fixed substrate and the FG microbeam, the Casimir and van der Waals forces were also considered. The governing equation of motion of FG microbeams was derived by employing the Hamilton principle. Utilizing the Galerkin and the equivalent linearization methods, an analytical solution was obtained for the nonlinear vibration problem with zero initial conditions. To validate the accuracy of the results obtained, our solution was compared with the numerical and analytic solutions published in the literature. [ABSTRACT FROM AUTHOR]

This paper shows the multiphysics simulation process of a rotary MEMS stepper motor with electrostatic actuation, where the solid mechanics, electrostatics, and moving mesh simulations through COMSOL are considered in a time-dependent study. The rotary MEMS motor comprises the aluminum structural layer from a 0.5μm CMOS technology used for integrated circuit fabrication. Both the rotor and the stator are immersed in a dielectric; for this reason, the simulation requires a moving mesh to model the electrical characteristics of the medium. A mesh convergence study is conducted to ensure the accuracy and mesh independence of the results. The simulation also considers the frequency of the stator electrodes alternating signal and the frequency response of the rotor to define the solver time stepping. Through this simulation, it was possible to verify that the micrometric electrostatic actuator has an angular displacement with a linear trend, which allows the proposed design to be verified. [ABSTRACT FROM AUTHOR]

Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically increased by using a sophisticated switch design with extended lateral dimensions, although a simple and compact cantilever is more preferable. The paper describes for the first time a comprehensive approach to enhance the force of an electrostatically actuated switch. The strategy is applied to a miniature device based on a 50 µm long cantilever. The contact force is increased from 10 to 112 µN, making the switch strong enough to achieve low and stable contact resistance. The restoring force is also enhanced in order to ensure reliable de-actuation. The growth of forces is accompanied by a reduction in the pull-in voltage. Connecting several cantilevers in parallel and manipulating the number and position of contact bumps additionally improves the force and mechanical stability of the switch. An optimal design contains a triple cantilever with two bumps. It provides 50% higher force per contact compared to the single-cantilever switch at the same pull-in voltage and keeps the advantages of a miniature device. The proposed design strategy may be used for building reliable MEMS switches. [ABSTRACT FROM AUTHOR]

We report on theoretical and experimental investigation of parametric amplification of acoustically excited vibrations in micromachined single-crystal silicon cantilevers electrostatically actuated by fringing fields. The device dynamics are analyzed using the Mathieu–Duffing equation, obtained using the Galerkin order reduction technique. Our experimental results show that omnidirectional acoustic pressure used as a noncontact source for linear harmonic driving is a convenient and versatile tool for the mechanical dynamic characterization of unpackaged, nonintegrated microstructures. The fringing field's electrostatic actuation allows for efficient parametric amplification of an acoustic signal. The suggested amplification approach may have applications in a wide variety of micromechanical devices, including resonant sensors, microphones and microphone arrays, and hearing aids. It can be used also for upward frequency tuning. [ABSTRACT FROM AUTHOR]

Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically increased by using a sophisticated switch design with extended lateral dimensions, although a simple and compact cantilever is more preferable. The paper describes for the first time a comprehensive approach to enhance the force of an electrostatically actuated switch. The strategy is applied to a miniature device based on a 50 µm long cantilever. The contact force is increased from 10 to 112 µN, making the switch strong enough to achieve low and stable contact resistance. The restoring force is also enhanced in order to ensure reliable de-actuation. The growth of forces is accompanied by a reduction in the pull-in voltage. Connecting several cantilevers in parallel and manipulating the number and position of contact bumps additionally improves the force and mechanical stability of the switch. An optimal design contains a triple cantilever with two bumps. It provides 50% higher force per contact compared to the single-cantilever switch at the same pull-in voltage and keeps the advantages of a miniature device. The proposed design strategy may be used for building reliable MEMS switches.

In the past few decades, advances in micro-electromechanical systems (MEMS) have produced robust, accurate, and high-performance devices. Extensive research has been conducted to improve the selectivity and sensitivity of MEMS sensors by adjusting the device dimensions and adopting nonlinear features. However, sensing multiple parameters is still a challenging topic. Except for the limited research focus on multi-gas and multimode sensing, detecting multiple parameters typically relies on combining several separate MEMS sensors. In this work, a new triple sensing scheme via nonlinear weakly coupled resonators is introduced, which could simultaneously detect three different physical stimuli (including longitudinal acceleration) by monitoring the dynamic response around the first three lowest vibration modes. The Euler–Bernoulli beam model with three-mode Galerkin discretization is used to derive a reduced-order model considering the geometric and electrostatic nonlinearities to characterize the resonator's nonlinear dynamics under the influence of different stimuli. The simulation results show the potential of the nonlinear coupled resonator to simultaneously perform triple detection. [ABSTRACT FROM AUTHOR]

Artificial muscle actuators that can exert both high work capacity and high power density is highly desired for robotic applications. In this work, we fabricate fiber-based actuators via wet spinning of the liquid crystalline graphene oxide together with conducting polymers with well-controlled alignment and close packing. After reduction of graphene oxide, the resulting fibers and their plied yarns exhibit fast and strong actuation via the electrostatic-repulsion mechanism. [Display omitted] Soft materials are known for their compliance, adaptivity and dexterity. They have been well-pursued to create artificial muscles for robotic applications, however, at the cost of load bearing, bit rates and energy efficiency compared with their rigid body counterparts. Despite significant efforts to improve their performance, very few can match the biological muscles, achieving fast speed, high elasticity, and high power density simultaneously. Here, we self-assemble composite fibers by wet-spinning graphene oxide (GO) nanosheets in their lyotropic liquid crystal (LLC) phase mixed with conducting polymers and depleting agent, poly(ethylene glycol), followed by chemical reduction of GO. The resulting reduced GO (rGO) nanosheets are highly aligned and closely packed, which is essential to their high mechanical strength and toughness and actuation behaviors. The composite fiber exhibits fast (80 ms) and reversible bending via electrostatic repulsion between the rGO sheets. When the fibers are plied with nylon yarns, our actuators can achieve 75 J/kg work capacity and 924 W/kg power density without diminishing the bending strain and efficiency up to 10,000 cycles. [ABSTRACT FROM AUTHOR]

A new multi-sensing scheme via nonlinear weakly coupled resonators is introduced in this paper, which can simultaneously detect two different physical stimuli by monitoring the dynamic response around the first two lowest modes. The system consists of a mechanically coupled bridge resonator and cantilever resonator. The eigenvalue problem is solved to identify the right geometry for the resonators to optimize their resonance frequencies based on mode localization in order to provide outstanding sensitivity. A nonlinear equivalent model is developed using the Euler–Bernoulli beam theory while accounting for the geometric and electrostatic nonlinearities. The sensor's dynamics are explored using a reduced-order model based on two-mode Galerkin discretization, which reveals the richness of the response. To demonstrate the proposed sensing scheme, the dynamic response of the weakly coupled resonator is investigated by tuning the stiffness and mass of the bridge and cantilever resonators, respectively. With its simple and scalable design, the proposed system shows great potential for intelligent multi-sensing detection in many applications. [ABSTRACT FROM AUTHOR]

We report on theoretical and experimental investigation of parametric amplification of acoustically excited vibrations in micromachined single-crystal silicon cantilevers electrostatically actuated by fringing fields. The device dynamics are analyzed using the Mathieu–Duffing equation, obtained using the Galerkin order reduction technique. Our experimental results show that omnidirectional acoustic pressure used as a noncontact source for linear harmonic driving is a convenient and versatile tool for the mechanical dynamic characterization of unpackaged, nonintegrated microstructures. The fringing field’s electrostatic actuation allows for efficient parametric amplification of an acoustic signal. The suggested amplification approach may have applications in a wide variety of micromechanical devices, including resonant sensors, microphones and microphone arrays, and hearing aids. It can be used also for upward frequency tuning.

Nanoresonators can be used in some engineering fields such as high quality factor filters for electronic signals and sensors. So, the main purpose of this paper is to analyze the nonlinear dynamic behavior of electrostatically actuated nanoresonators. In the framework of the Von Karman's theory and the Euler-Bernoulli beam model, the nonlinear governing equations of motion are developed using the Hamilton's principle. Also, the coupling of lateral and longitudinal vibrations is considered. The governing partial differential equations are discretized by means of the Galerkin’s method. The analytical and numerical solution are obtained using the multiple-scales method and Runge–Kutta method, respectively. The variation of natural frequencies and the response of the nanoresonator with the levels of the electrostatic load are investigated. The results show that the nonlinear frequency response curves are greatly affected by the gap distance and detuning frequency. A hardening behavior is observed in the nonlinear frequency responses of the nanoresonator. Also, through the comparison between the effect of gap distance and dc voltage, it is found that the natural frequencies of the nanoresonator are more sensitive to the variation of the dc voltage. So, this suggests a tunable resonator over a wide range of frequencies.

A new conceptual utilization of Silicon on Insulator (SOI) wafer is reported for bi-directional vertical electrostatic fringe field tuning of the Micro Electro Mechnical Systems (MEMS) micro accelerometer for compensating stress induced curling (up and down), sensitivity and mechanical dynamic response. The buried oxide (BOX) layer-based SOI wafer provides bi-directional electrodes for applying bias voltages independently. Residual stress induced curved deflection due to stress gradient is targeted for tuning and reducing its effects using fringe field electrode configuration in SOI wafer technology. Movable silicon structure is electrostatically (utilizing fringe field) brought back near to original mean position with softened stiffness (increase in sensitivity) and reducing drastically the effects of stress gradients. The simulations are carried out using COVENTORWARE and COMSOL Multiphysics software. The deflection results obtained by both software agree within 7.69% for maximum deviation. There is a deviation in change in capacitance (del C) of 5.89% when stress gradient of 0.1 MPa/μm and 17.62% when stress gradient of 4 MPa/μm is applied on the structure at 30 g. This deviation can be tuned by above mentioned Bi directional tuning. Additionally, non-linearity induced by stress gradient in sensitivity can also be tuned by electrostatic fringe field effectively upto 18.64% when higher stress gradient (4 MPa/μm) was affecting the structure. Maximum disagreement of 4.72% between analytical and simulated results promises the design of proposed tuning concept. The proposed tuning concept can be utilized for other MEMS devices suffering from stress gradient issues. [ABSTRACT FROM AUTHOR]

Pull-in potential of electrostatic actuation ohmic cantilever beam type RF MEMS switch is lowered by reducing stiffness constant of its cantilever beam. However, this design objective is highly interlinked to major criteria like its mechanical, RF performance parameters, materials used and fabrication constraints. The purpose of this study is to address the design methodology of such interdisciplinary complex phenomenon to obtain global optimum solution. A variable width cantilever beam design is proposed to lower its pull-in potential. The design optimisation methodology adopted in this study uses analytical model of stiffness constant, major interlinked criteria based on cantilever beam profile and geometric dimensions of the switch. This methodology is further identified as a multivariable constraint optimisation problem to be solved using evolutionary optimisation algorithm for various geometric dimensions of the switch. 3-D modelling, simulation of the optimised device for pull-in potential, mechanical and RF performance parameters is carried out using CAD tools. The results obtained from simulation and analytical models are in agreement. The proposed optimised design opens a new avenue in RF MEMS switch design as it satisfies additional essential performance parameters compared to the results of previous published designs concluding significance of design optimisation methodology adopted in this work. [ABSTRACT FROM AUTHOR]

MEMS resonators based on internal thermal-piezoresistive amplification are a suitable alternative for sensing applications since they enable high resonance frequencies and high Q-factors. In this work, the principle of operation of this amplification mechanism is modeled, using analytical and lumped methods, based on previous reports found in the literature. For a better understanding of the several domains involved in the principle of operation of the internal thermal-piezoresistive amplification mechanism, MEMS resonators with electrostatic actuation and piezoresistive readout and with single- or double-mass, were fabricated and experimentally characterized. This mechanism is quite sensitive to variations of the structure geometry or its environmental conditions. Moreover, despite several sources of error have been identified, the model for the single-mass resonator (SMR) fits quite well the experimental results. However, these errors prevented confirming whether the double-mass resonator (DMR) behaves according to the model developed. The DMR performed better than the SMR, achieving higher resonance frequency, higher Q-factor, and higher amplification in vacuum. This set of simulation and experimental results can be used to design novel high-frequency resonators for sensing applications with improved performance due to the Q-factor enhancement achieved by the internal thermal-piezoresistive amplification mechanism.

• Mathematical modeling of a three finger micro-tweezers. • Comparison of the gap distance of two and three-finger tweezers near pull-in voltage. • Validated results by comparing them with the available experimental data. • Fingers tip position for different applied voltage; simplified model and general model. • The impact of geometric parameters on the dynamic behavior using Taguchi method. For regenerative medicine and tissue engineering to advance, it has been necessary to develop technologies to handle microscopic biological samples such as cells and spheroids. One popular method for manipulating such samples in the fields of nano and biotechnology is the use of micro and nano-tweezers. This paper discusses the design and dynamic modeling of three-finger micro-tweezers, which are a type of nano-wire manufactured electromechanical tweezers. The article introduces an innovative technique for operating tweezers, which involves using high-frequency alternation to achieve symmetrical deformation of the arms. Due to the complexity of the technique, especially for an odd number of fingers, an analytical solution is not feasible, and a simplified simulation is presented instead. The system, crucially, is shown to seamlessly integrate with the COMSOL Multiphysics interfaces, a critical aspect that helps to generalize, stabilize, and streamline the implementation process. The simulation results are validated by comparing them with the available experimental data. Subsequently, the impact of geometric parameters on dynamic behavior is investigated. Finally, the behavior of the proposed nano-tweezers is compared to that of conventional two-armed tweezers. [Display omitted] [ABSTRACT FROM AUTHOR]

Micro-cantilever beam are now widely used in modern micro and nano devices. This device includes micro-switches and microscopes which are operated by atomic force. The dynamic analysis of cantilever beams is of critical prior to manufacturing of the beams. Dynamic analysis is carried out using an energy technique based on Galerkin method and pull-in parameters are to be found out for prismatic cantilever. In squeeze film damping the air present between movable beam and fixed beam behave as squeezed fluid and producing the damping effect which lead to reducing in displacement. In case of fringing field the line of action of electrostatic force do not remain perpendicular at the boundaries. The effect of damping due to Squeeze film and fringing field on dynamic performance of beam is studied and found out the pull-in factors and matched with the published outcomes. This area opens novel opportunities for structural optimization of electrostatic micro-beams. [ABSTRACT FROM AUTHOR]

The grand challenge toward the miniaturization of untethered robots is the lack of a proper actuation system that can effectively transform the limited onboard energy into an untethered movement of the whole body. Here, in this article, we present an insect scale, 5-mm-long, and 9.4 mg in body mass untethered crawling robot powered by a 37 mg onboard ceramic capacitor. With high electromechanical efficiency by utilizing self-excited electrostatic vibration, the prototype device can be directly powered by an onboard capacitor without any boost or frequency conversion circuitry, and forward movements have been achieved at an average moving speed of 5.9 mm/s for 1.68 s. The maneuverability of locomotion from solid ground to water and different moving directional controls via the leg designs have been demonstrated for the advancements in the field of millimeter-scale robotics research. [ABSTRACT FROM AUTHOR]

Abstract We present a method to fabricate planar metal layers to be used as micromachined mirrors. Released mirrors of pure metal involve severe stress and reveal specific challenges to obtain planar mirror structures. Introducing sub-structures generating corrugated patterns, the metal mirror layers can be mechanically stabilized and undesired mirror bending can be reduced. For our investigations we used different arrangements of line structures on our metal mirrors, such as a group of straight or curved lines oriented differently. Comparing all the implemented different designs, planar micromirrors were achieved via sub-structures with a combination of straight lines arranged orthogonally to a single line. These planar micromirrors allow steering of the incident light by reflection and adjustment of the window transmittance. The presented low-cost method is suitable for large area fabrication of micromirror arrays, but also can be customized for other applications, where planar free-standing metal layers are required.

Bifurcation-based sensors, implementing stability boundaries monitoring in bistable microstructures, may manifest higher sensitivity and robustness when compared to their statically operated counterparts. In the operation of these devices, two key questions arise: 1) how to reliably identify the critical events associated with the transition between two stable states; 2) what is the maximal sampling rate allowing to identify these critical events in a periodically actuated device. Motivated by the potential implementation as a bifurcation-based flow sensor, in this work we experimentally explore the transient snap-through (ST) and snap-back (SB) dynamics of a bistable initially curved ($500 \,\mu \text{m}$ long and $2.5\, \mu \text{m}$ wide) electrostatically actuated single-crystal Si microbeam. We employ a threshold-based approach for the ST and SB events detection and identify two mechanisms determining the maximal sampling frequency of the device: a phase lag between the voltage signal and the mechanical response and free decaying vibrations following the buckling event. In accordance with our experimental results and consistently with the reduced-order model predictions for the bistable beam operating at atmospheric pressure, at the actuation signal frequency of $\approx 0.6$ KHz, which is still much lower than the beam’s natural frequency of $\approx 110 $ KHz, the free oscillations engendered by one critical event (ST or SB) interfere with the consecutive one, preceding its emergence. On the other hand, an inherent phase lag ultimately hinders the abrupt ST and SB transitions at these actuating frequencies. [2021-0091] [ABSTRACT FROM AUTHOR]

Electro-responsive actuators (ERAs) hold great promise for cutting-edge applications in e-skins, soft robots, unmanned flight, and in vivo surgery devices due to the advantages of fast response, precise control, programmable deformation, and the ease of integration with control circuits. Recently, considering the excellent physical/chemical/mechanical properties (e.g., high carrier mobility, strong mechanical strength, outstanding thermal conductivity, high specific surface area, flexibility, and transparency), graphene and its derivatives have emerged as an appealing material in developing ERAs. In this review, we have summarized the recent advances in graphene-based ERAs. Typical the working mechanisms of graphene ERAs have been introduced. Design principles and working performance of three typical types of graphene ERAs (e.g., electrostatic actuators, electrothermal actuators, and ionic actuators) have been comprehensively summarized. Besides, emerging applications of graphene ERAs, including artificial muscles, bionic robots, human-soft actuators interaction, and other smart devices, have been reviewed. At last, the current challenges and future perspectives of graphene ERAs are discussed.

Electrostatically actuated, bistable, curved micromechanical beams can exhibit latching, wherein the beams remain in two distinct stable states without an applied voltage. These structures could serve as building blocks in a variety of applications such as micromechanical logic elements, switches, non-volatile memories, and low power consumption sensors. However, the design of such devices is challenging since such structures are prone to symmetry breaking, which consequently inhibits latching. Generally, asymmetric responses may be circumvented by introducing a tailored axial compressive prestress. In this work we explore, both theoretically and experimentally, the influence of prestress on the single electrode, bidirectional dynamic switching of curved, latchable, single crystal Si $\approx 1000 \;\mu \text{m}$ long and $\approx 3.5\;\mu \text{m}$ wide beams. We use Joule heating to apply the necessary prestress required to eliminate symmetry breaking and ensure latching. In accordance with reduced-order model predictions, our experimental findings show that prestress plays a key role in the dynamic response of the beam. Our results demonstrate bidirectional operation using a single electrode, fostering a compact footprint device for tailoring the axial stress and dynamic conditions. [ABSTRACT FROM AUTHOR]

We present an electrostatically actuated rotary stage featuring liquid rings, which serve as both mechanical bearings and electric connections between the rotor and the substrate. The liquid rings are formed by confining a liquid inside hydrophilic grooves and repelling it from the superhydrophobic surfaces outside the grooves. Made of a fluid, the liquid-ring bearing avoids the dry friction of the solid bearings, significantly improving the reliability. Formed as rings, it avoids the resistance of contactangle hysteresis sliding over droplets, and hence dramatically reducing the static friction. Furthermore, surface tension facilitates the self-alignment of the rotor to the substrate and stator during the assembly and provides the stability against drift and shock during operation. Electrically, each liquid ring passes an independent electric signal, allowing a direct electrical path between the substrate and potential components on the rotor. A three-phase electrostatic rotary stage has been design, fabricated, and tested. The minimum torque to initiate the rotation is ∼2.5nṄm - hundreds of times smaller than droplet-based counterparts. The device has operated successfully by applying sequential voltages of 50V DC between the rotor and the stators. The electric transmission has been verified by powering an LED on a rotating rotor. This is the first report of an electrostatically actuated rotating microdevice with a liquid bearing and a direct power transmission. © 2013 IEEE.

The feasibility of using electrostatic forces to stabilize a close-proximity leader-follower formation is investigated. The leader craft is equipped with a set of affixed spheres whose charge is modulated to hold the charged follower craft along a proscribed trajectory to its nominal leader-relative position. This charge structure and the follower craft are constrained to remain in the plasma wake generated behind all LEO craft because the more-dense ambient plasma outside the wake prevents object charging and electric field propagation. Once the formation is achieved, a controlled electric field is generated by the leader to counter relative accelerations from perturbations like differential drag and solar radiation pressure, holding the follow near its nominal position. Two controllers are derived for the system described, incorporating Coulomb accelerations and linearized gravity and drag accelerations. Simulations are run under unmodeled perturbations and sensor noise for different scenarios, demonstrating the challenges and benefits associated with electrostatic actuation. [ABSTRACT FROM AUTHOR]

In this work, a microbeam model based on the Euler–Bernoulli beam theory and the nonlocal strain gradient theory was developed to study nonlinear vibration and stability of a functionally graded porous microbeam under electrostatic actuation. The electrostatic force is the driving force per unit length, resulting from electrostatic excitation. The material properties of the microbeam change continuously along thickness direction according to simple power-law distribution in terms of the fractions of constituents. Two cases of even and uneven porosity distributions are considered. The Hamilton principle is used to obtain the governing equations of the motion for the microbeam. The equation of motion for the microbeams is reduced to a nonlinear ordinary differential equation with rational restoring force by applying Galerkin method. The frequency–amplitude relationship is given in the closed form by employing He's Hamiltonian approach. The expression of the static pull-in voltage is also derived. Effects of the material length scale parameter, the nonlocal parameter, the power-law index, the porosity distribution factor, the applied voltage and the initial amplitude on nonlinear vibration and stability of the functionally graded porous microbeam are examined and discussed. [ABSTRACT FROM AUTHOR]

In a framework of 1D membrane MEMS theory, we consider the MEMS boundary semi-linear elliptic problem with fringing field u ′ ′ = - λ 2 (1 + δ | u ′ | 2) (1 - u) 2 in Ω , u = 0 on ∂ Ω , where λ 2 and δ are positive parameters, Ω = [ - L , L ] ⊂ R , and u is the deflection of the membrane. In this model, since the electric field E on the membrane is locally orthogonal to the straight line tangent to the membrane at the same point, | E | , proportional to λ 2 / (1 - u) 2 , is considered locally proportional to the curvature of the membrane. Thus, we achieve interesting results of existence writing it into its equivalent integral formulation by means of a suitable Green function and applying on it the Schauder–Tychonoff fixed point theory. Therefore, the uniqueness of the solution is proved exploiting both Poincaré inequality and Gronwall Lemma. Then once the instability of the only obtained equilibrium position is verified, an interesting limitation for the potential energy dependent on the fringing field capacitance is obtained and studied. [ABSTRACT FROM AUTHOR]

This paper presents a compact reconfigurable elliptical shaped fractal patch (ESFP) antenna with elliptical shaped RF MEMS switch is used for satellite applications at X-band. The proposed work involves the incorporation of RF MEMS switches loaded using parasitic elements with ease of simpler implementation without using DC bias lines. The proposed antenna is integrated with two MEMS switches and reconfigurability is obtained for varying the capacitance of the switch by actuating the switch to ON and OFF states. The elliptical shape is considered for the proposed microstrip patch antenna is to attain large flexibility in the design and attain good return loss, radiation patterns, gain and bandwidth of the antenna. The proposed antenna is designed on flexible polyamide substrate and resonating frequency is obtained at 9.07 GHz frequency with − 43 dB return loss with gain of 6.05 dB. When the proposed switch is integrated on to the elliptical patch fractal antenna it resonates at four different operating frequencies. Among all the four states the state-4 resonates at 9.02 GHz frequency with − 52.8 dB return loss with gain of 6.36 dB. The ESFP antenna has perform four operating frequencies with two RF-MEMS switches for reconfigurability applications. The simulated results are in good agreement between the measured results. A small deviation is observed between simulated and measured results. [ABSTRACT FROM AUTHOR]

Universal logic gates NAND and NOR along with NOT and XOR are successfully implemented using graphene cantilever structures. Three-dimensional (3D) modeling of different graphene cantilever structures is carried out using the COMSOL Multiphysics software. The high electrical conductivity of graphene makes it a better choice for the cantilever beams in this study. A very low actuation voltage of 1.57 V is obtained for a 2-µm-long, 0.2-µm-wide, and 5-nm-thick graphene cantilever beam. For all the cantilever-based logic gates, the switching speed is 45 ns. The simulated cantilever-based logic gates could enable the implementation of different digital circuits. [ABSTRACT FROM AUTHOR]

Previous work has shown that optomechanical resonators are particularly well suited to the design of ultrasensitive mass sensors. They present an extremely low noise level, very high optical quality factor (Q > 105), excellent integration density and can resonate both in a gaseous and liquid environment. In order to reduce the long measurement time due to their small particle-capture area, several such resonators must be integrated onto the same chip. However, bulky laboratory equipment currently used to read a single optomechanical resonator cannot be practically scaled up to a large array of transducers. It is then required to design and eventually integrate a read-out interface that can process tens to thousands of resonators. To ease the design of such a circuit, this article presents a compact analytical model of an electrostatically actuated optomechanical resonator implemented in Verilog A. The proposed model includes both the optical and mechanical behaviors, as well as optomechanical coupling and thermo-optical effect. It was simulated in the Cadence Virtuoso environment and is consistent with the measured results. [ABSTRACT FROM AUTHOR]

An approach for gas flow velocity measurement at two different closely located points using a simple device incorporating only one thermal sensing element, is introduced and the feasibility to determine different velocities is experimentally demonstrated. An electrostatically actuated initially curved bistable microbeam heated by an electric current and convectively cooled by airflow is switched between two stable locations through the snap-through (ST) and snap-back (SB) buckling mechanisms. The velocities of an air flow at these positions are obtained by measuring the critical ST and SB values of the actuation voltage. In the experiments, our $500~\mu \text{m}$ long, $2~\mu \text{m}$ wide single-crystal Si beam with $\approx \, 2.5\,\mu \text{m}$ nominal initial elevation demonstrated sensitivity of $S_{\text {ST}} \approx 0.25$ V/(m/s) and $S_{\text {SB}} \approx 0.84$ V/(m/s) at the ST and SB points, respectively. In the present device, the distance between the two measurement points is $\approx 10~\mu \text{m}$. Our experimental results indicate that the suggested approach can be used for the velocity gradient measurements. The sensing principle relying on a single bistable sensing element opens new opportunities for measurement of gas flow velocity and velocity gradients at scales significantly smaller than the state-of-the-art multi hot-wire sensors. [ABSTRACT FROM AUTHOR]

After developing a magnetically actuated microshutter array sub-system, which acts as a field object selector for the James Webb Space Telescope (JWST), our team at the NASA Goddard Space Flight Center (GSFC) focused on the development of electrostatically actuated microshutter arrays – the Next Generation Microshutter Arrays (NGMSA). This letter describes the first NGMSA array that performed shutter operations for telescope imaging and spectroscopy in space. The carrier telescope, the Next-Generation Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy (NG-FORTIS) was produced by Prof. Stephan McCandliss and his team at Johns Hopkins University and launched into space successfully. [2020-0226] [ABSTRACT FROM AUTHOR]

To induce snap-through (ST) switching in an electrostatically actuated bistable latchable curved microbeam, a close gap electrode facing the concave surface of the beam is commonly used. In the framework of an alternative architecture considered here, the electrode is placed in front of the convex (backward), rather than concave (forward) side of a beam. The initially curved stress free beam is activated by an electrostatic force pulling it quasistatically in the backward direction, away from the desired buckled configuration. Once the voltage is turned off, the accumulated strain energy is released, and the beam is catapulted toward the buckled state, similarly to an arrow fired by a bow. In the case where the beam exhibits latching, the device may remain in its buckled state indefinitely under zero voltage. The beam can also be snapped back (released), by applying a voltage to the same electrode. In this article, the efficiency of this bow-like actuation is estimated. By means of a reduced order model, it is shown that due to the nonlinearity of the electrostatic force, the suggested operation scenario may lead to a 54 ${\%}$ reduction in the ST switching voltage, when compared to the traditional forward actuation. As a result, the device allows bidirectional switching by using a single electrode, and can be viewed as a micromechanical realization of a toggle flip-flop element. [ABSTRACT FROM AUTHOR]

Electrostatic actuation is one of the most commonly used methods for excitation and measurement in micro and nanoscale resonators. In the dynamical behavior analyses of such systems, the resonating beam is often assumed to be a perfect conductor. In this paper, the effect of electrical resistivity on the vibrational response of these systems, including the natural frequency and damping, is investigated. The governing coupled nonlinear partial differential equations of motion are derived and a new finite element method formulation is presented by developing a new electromechanical element. The numerical natural frequencies are compared with experimental measurements and the achieved correlation is better than that in the prior studies. Results indicate that there is a jump in the frequency and damping of the system at a critical resistivity. As the system size decreases and the applied voltage approaches the pull-in voltage, the electrical resistivity completely dominates the response nature of the system. An experiment is also conducted, and good agreement with the theory is observed regarding the effect of electrical resistivity. [ABSTRACT FROM AUTHOR]

Thermal switches are a type of heat control devices widely used in electronics, engineering machinery, and other applications. Electrostatically driven thermal switches (EDTS) have received wide attention due to their high specific mass density, precise control of heat flow, and flexibility. However, most of the actuating components of EDTS are made of polymers with a poor thermal conductivity, which seriously affects the effectiveness of the thermal switch. This paper presents a highly efficient, reliable, and easy-to-implement EDTS with a mini-channel cooling, which combines the convective cooling with the electrostatic actuation by adding a cooling module to the radiator. The proposed EDTS controls its ON/OFF state using the electric field, and the water is used as the cooling fluid for absorbing the heat generated from the heat source. The experimental results demonstrated that the proposed EDTS achieves a switch ratio of 2964 ± 135 and a coefficient of performance (COP) of 11.6, indicating that it can effectively regulate the heat flow in the hot path. It demonstrates the prospect of becoming widely used in the thermal management of engineering machinery and electronic devices. [ABSTRACT FROM AUTHOR]

In electrostatic comb drive-based sensors and actuators, often there is a possibility of nonparallel motion or bending in individual comb which considerably affects the device performance including pull-in characteristic. In this paper, we have presented a theoretical and experimental investigation to reduce such undesired beam bending in gap closing-type comb drive actuator. It has been envisaged that three key parameters, responsible for beam bending, are spring stiffness, beam stiffness, and number of actuation beams. Subsequently, a design guideline has been proposed to reduce the undesired bending by appropriate selection of these parameters. A specific comb drive actuator having multiple actuation regions with varying number of beams is designed, simulated, and analyzed using a semianalytical approach and FEM tool. Further, the structure is fabricated by establishing a silicon-on-insulator (SOI)-based single mask fabrication process and tested with an in-house experimental setup. The theoretical predictions are validated with the experimental results to demonstrate how the undesired beam bending can be reduced significantly by suitable selection of number of actuation combs for a given ratio of spring and beam stiffness. The proposed guidelines enable the micro-electromechanical system (MEMS) designers to cautiously choose the key parameters while designing in order to avoid the undesired comb bending and operate the device safely. [ABSTRACT FROM AUTHOR]

Experimental and computational approaches are utilized to investigate the influence of electrostatic fields on the binding force between human coagulation protein thrombin and its DNA aptamer. The thiolated aptamer was deposited onto gold substrate located in a liquid cell filled with binding buffer, then the thrombin-functionalized atomic force microscopy (AFM) probe was repeatedly brought into contact with the aptamer-coated surface under applied electrical potentials of −100, 0, and 100 mV respectively. Force drops during the pull-off process were measured to determine the unbinding forces between thrombin and aptamer in a range of loading rates spanning from ~3 × 102 to ~1 × 104 pN/s. The results from experiments showed that both of the binding strength and propensity of the complex are drastically diminished under positive electrode potential, whereas there is no influence on the molecular binding from negative electrode potential. We also used a theoretical analysis to explain the nature of electrostatic potential and field inside the aptamer-thrombin layer, which in turn could quantify the influence of the electrostatically repulsive force on a thrombin molecule that promotes dissociation from the aptamer due to positive electrode potential, and achieve good agreement with the experimental results. The study confirms the feasibility of electrostatic modulation upon the binding interaction between thrombin and aptamer, and implicates an underlying application perspective upon nanoscale manipulation of the stimuli responsive biointerface. [ABSTRACT FROM AUTHOR]

In this paper, we report a novel laterally actuated Radio Frequency (RF) Microelectromechanical Systems (MEMS) switch, which is based on a combination of electrothermal actuation and electrostatic latching hold. The switch takes the advantages of both actuation mechanisms: large actuation force, low actuation voltage, and high reliability of the thermal actuation for initial movement; and low power consumption of the electrostatic actuation for holding the switch in position in ON state. The switch with an initial switch gap of 7 µm has an electrothermal actuation voltage of 7 V and an electrostatic holding voltage of 21 V. The switch achieves superior RF performances: the measured insertion loss is −0.73 dB at 6 GHz, whereas the isolation is −46 dB at 6 GHz. In addition, the switch shows high reliability and power handling capability: the switch can operate up to 10 million cycles without failure with 1 W power applied to its signal line.

Increasing interests have been directed toward the exploitation of origami techniques in developing biomimetic soft robots. There is a need for effective design solutions to exploit the properties of origami structure with simplified assembly and improved robotic mobility. In this study, inspired by human long-standing jumps, we present a soft electrostatically driven legged accordion fold actuator made by turning a flat paper into hollow polyhedron structure with a spring like rear and capable of electrostatic pad-assisted steering and carrying loads. Without the need for integration of external actuators, the actuator is composed of the electrostatic origami actuator itself supported by a single-fold leg with fast response, easy fabrication process, and low cost. Initiated by periodic deformation around the folding hinges caused by alternating current voltage and ground reaction forces, the actuators exhibit a unique jump-slide movement outperforming other existing soft electrostatic actuators/robots in terms of relative speed. We examined the effect of different geometric and external factors on the relative speed and highlighted the significance of body scale and short-edge panels as the elastic elements, as well as operating at resonance frequency in producing effective performances. Theoretical locomotion models and finite element analysis were carried out to interpret the working principle and validate experimental results.