Search

An analysis of the dynamic characteristics of pull-in for parallel-plate and torsional electrostatic actuators is presented. Traditionally, the analysis for pull-in has been done using quasi-static assumptions. However, it was recently shown experimentally that a step input can cause a decrease in the voltage required for pull-in to occur. We propose an energy-based solution for the step voltage required for pull-in that predicts the experimentally observed decrease in the pull-in voltage. We then use similar energy techniques to explore pull-in due to an actuation signal that is modulated depending on the sign of the velocity of the plate (i.e., modulated at the instantaneous mechanical resonant frequency). For this type of actuation signal, significant reductions in the pull-in voltage can theoretically be achieved without changing the stiffness of the structure. This analysis is significant to both parallel-plate and torsional electrostatic microelectromechanical systems (MEMS) switching structures where a reduced operating voltage without sacrificing stiffness is desired, as well as electrostatic MEMS oscillators where pull-in due to dynamic effects needs to be avoided. [1256] Index Terms--Electrostatic devices, microactuators, microelectromechanical systems (MEMS), microresonators, nonlinear systems, switches.

Several electrostatic discharge (ESD) protection device options, focusing on improvement in Q are explored. It is shown that SiGe diodes are preferred over SiGe n-p devices and a detailed analysis of experimental results is provided.

The electrostatic discharge (ESD) characteristics of a three-body problem comprised of a charged human body approaching an electronic system with an interposed guard electrode are investigated. Capacitance coefficients were measured for various three conductor arrangements; for an assumed charge on the human body, body potentials were calculated and the relative effectiveness of different guard electrode geometries to control the ESD event compared. The results provide a better understanding of the fundamental principles involved in the ESD event involving three bodies and have application in the design of interfaces between the charged human body and electronic systems. Index Terms--Control, electrostatic discharge (ESD), human body.

This work concerns the alleviation of friction in a novel design of multistator electrostatic wobble motor. The output torque and the kinematic accuracy of this device are limited by the sliding friction between the rotor and the top surface of the bearing. A solution for an axial bearing has been developed using an advanced LIGA technique to integrate polymethylmethacrylate (PMMA) cylinders into nickel micro structures. A new version of the micromotor has been fabricated, utilizing an axial electrostatic field to hold the rotor against an engineered sliding surface. The integrated bearing stabilizes the rotor and potentially permits operation in liquid environments by sealing the stator electrodes. [334] Index Terms - Electrostatic bearing, electrostatic motor, LIGA process, micromotor, wobble motor.

Pull-in study of an electrostatic microactuator is essential for making the electrostatic actuation more effective. In this paper, pull-in analysis is presented for an electrostatic torsion microactuator. The torsion microactuator can be used as a microtorsion mirror. A polynomial algebraic equation for the pull-in voltage and pull-in angle of a torsion microactuator is derived. Two types of microactuators fabricated using bulk micromachining are presented. Measurements done on the fabricated microactuators are reported, showing deviations within 1% error from the calculations. [325] Index Terms - Electrostatic, microactuator, micromirror, pull-in, torsion.

Problems in the calibration of electrostatic probes used for measuring the surface charge on dielectrics are illustrated by a calibration error. The use of the probe response theorem to achieve better experimental results is proposed. The calibration error resulted in an excess of experimental probe charge densities over the Faraday pail values in the test data. Assessing the nonuniformity and linearity of data difference patterns in a practical situation will require a multi-point scanning procedure.

Based on the conception of optimum estimation and AIC criterion, the time-varying coefficient autoregressive (AR) model is established for the random drift rate of the electrostatic suspended gyro (ESG) by recursive algorithm. The time-varying coefficient with its canonical standard error and mode's residual variance are then discussed. According to the variant of the coefficient and its canonical standard error, we distinguish whether or not there is singular signal (or failure).

An electrostatic orrery for studying Keplerian orbits has been constructed in which one or more negatively charged hollow glass microparticles orbit a 9.5-mm-diam metal sphere at +8-kV potential in a vacuum. The device is similar to an earlier cylindrical orrery in which particles orbit a rod [Biewer et al., Am. J. Phys. 62(9), 821-827 (1994)]. Electrically biased cylinders covering the rod supporting the sphere give nearly spherical potential surfaces inside the trap. Additional electrodes at the boundary are used to reduce the perturbation of gravity and to prevent motion resulting in collisions with the supporting rod. Orbits last approximately 10 min or about [10.sup.4] revolutions. The orbiters are illuminated with a slide projector and can be seen with the naked eye as well as videotaped. The trap has been used to observe orbital precession, interparticle collisions, and the effects of time-independent perturbations. This apparatus provides an opportunity for the study and demonstration of orbital motion in a laboratory.

Various models are used to simulate the electrostatic discharge (ESD) event associated with semiconductor devices; these include the human body model (HBM), the charged device model (CDM), and the field induced charged device model (FCDM). Maxwell's method is used to analyze these models to determine device potentials and the transfer of charge during typical discharges; existing test methods are also examined. A charge injection test method is introduced which provides control of the charge transferred to the device under test; it is proposed as a means to study charge related phenomena due to ESD.

Numerical simulations are used in the investigation of the quality and the pumping of an electron beam by means of inhomogeneous electrostatic fields at the anode aperture. The numerical simulation uses the specially developed relativistic particle-in-cell code. The longitudinal velocity spread and pitch ratio of the beam electrons are also determined as functions of different aperture radii and cathode-aperture distances. The operation of high power cyclotron resonance masses with sharpened cathode and anode aperture is also effected by this method.

A distributed electrostatic micro actuator (DEMA) has been proposed. The actuator has many small driving units which consist of two wave-like insulated electrodes. Both ends of insulated electrodes are connected to each other, and the driving unit has narrow gap for deformation caused by electrostatic forces. The driving units have large area of electrodes and are distributed in series and in parallel. So, a strong electrostatic force can be obtained, and the deformation and the generated force of the actuator would be large. Macro model of the DEMA was fabricated with polyimide films, and the deformation of the actuator was measured. When the applied voltage was 200 V, the deformation ratio was 36%. A micro actuator was fabricated by use of photolithography and electroplating. The displacement of 28 micrometer was observed when applied voltage was 160 V. Experimental results of the micro actuator were compared with the results simulated by finite element method (FEM) analysis.

This paper presents the theory, simulation results, and experimental study of the levitating force (normal to the substrate) associated with interdigitated capacitor (electrostatic comb) lateral actuators. For compliant suspensions, normal displacements of over 2 micrometer for a comb bias of 30 V are observed. This phenomenon is due to electrostatic attraction induced on top of the suspended structure. By electrically isolating alternating drive-comb fingers and applying voltages of equal magnitude and opposite sign, levitation force can be reduced by an order of magnitude, while reducing the lateral drive force by less than a factor of 2. The levitation theory incorporates electrostatic simulation results, and agrees well with experimental data.

The effect of electrostatic coupling is investigated using numerical simulation, between a quantum point contact (QPC) detector of various geometries and a planar quantum double dot in a few-electron quantum dot circuit.

An approach, referred to as the hybrid BIE/Poisson/Schrodinger approach, for electrostatic analysis of nanoelectrochemical device and system (NEMS) is proposed. The approach resulted in reduced computational cost and higher accuracy of the solution.

Two-dimensional electrostatic particle simulation is used for studying the results of a weak transverse magnetic field on negative ion extraction in a negative ion source. Weak transverse magnetic field may lead to an improvement in the extraction of the negative ions.

An experimental work leading to the determination of the optimal glass blend and to the optimal electrode pattern in order to maximize the exploitable forces is presented. The measurements and models presented constitute a tool to design electrostatic glass actuators such as, for example, a miniature disk drive, which is presented as one of several promising applications.

Recent success of microelectromechanical systems (MEMS) in projection displays have raised similar expectation for an efficient, low power, affordable, full-page and pneumatic tactile display. Such design has not been achieved by the conventional technology but could bring significant improvement to current refreshable Braille displays. This paper demonstrates a novel bulk-micromachined electrostatic microvalve suitable for a pneumatic tactile display. The microvalve, a silicon perforated diaphragm juxtaposed to a silicon inlet orifice, requires relatively low closing voltage against a large supply differential pressure and flow rate, i.e., 72.9 V-rms for 19.3 kPa and 86 mL/min. Such an attractive characteristic is due to its unique curved-compliant structure that has, unlike other electrostatic microvalves, no tolerance for any initial air gap between its electrodes. As a design tool, a mechanical model of the microvalve is introduced based on the lubrication theory and large plate deflection theory. The model is established on a steady-state coupled field problem of a fluid-solid mechanics. Reynolds and von-Karman equations were simultaneously solved for the microvalve geometry by finite difference approximation and double Fourier series expansion. The results of the model and experiments are compared and found to be in good agreement with a relative error less than 10%. [557] Index Terms--Coupled field, curved-compliant, electrostatic, lubrication, microvalve, tactile display.

The configurational entropy and the free energy of two charged disks neutralized by mono-and divalent counterions are calculated by using (N, V, T) Monte Carlo simulations. All ion-ion, ion-disk, disk-disk interactions described in the framework of the Primitive model includes intrinsic correlations responsible for long range attractions between colloids under high electrostatic coupling conditions.

Reduced-order dynamic macromodels are an effective way to capture device behavior for rapid circuit and system simulation. In this paper, we report the successful implementation of a methodology for automatically generating reduced-order nonlinear dynamic macromodels from three-dimensional (3-D) physical simulations for the conservative-energy-domain behavior of electrostatically actuated microelectromechanical systems (MEMS) devices. These models are created with a syntax that is directly usable in circuit- and system-level simulators for complete MEMS system design. This method has been applied to several examples of electrostatically actuated microstructures: a suspended clamped beam, with and without residual stress, using both symmetric and asymmetric positions of the actuation electrode, and an elastically supported plate with an eccentric electrode and unequal springs, producing tilting when actuated. When compared to 3-D simulations, this method proves to be accurate for non-stress-stiffened motions, displacements for which the gradient of the strain energy due to bending is much larger than the corresponding gradient of the strain energy due to stretching of the neutral surface. In typical MEMS structures, this corresponds to displacements less than the element thickness. At larger displacements, the method must be modified to account for stress stiffening, which is the subject of part two of this paper. [448] Index Terms--Basis-function methods, computer-aided design, electrostatic actuation, energy methods, macromodels, modal analysis, reduced-order models.

The electrostatic wafer chuck is the most preferable handling method in advanced semiconductor manufactures. Even in a vacuum environment, it enables not only the ability to retain a wafer flat, but also to enhance heat transfer through the whole surface area because of firm contact. We have investigated the fundamental characteristics of an electrostatic chuck consisting of a pair of comb-type electrodes and a thin polymer film as a dielectric layer. In order to prevent breakdown between electrodes, the air gap between electrodes was filled with sealing material. The electrostatic force acting on the 4-in silicon wafer is measured. Several types of insulating sealants and dielectric films were examined. The attractive force increased with the square of the applied voltage in the region of lower applied voltage and gradually saturated at higher voltage. The maximum force obtained in our experiments was approximately 30 N. These experimental results proved the high potentiality in actual use of the electrostatic chuck for silicon wafer handling. However, a few problems have to be overcome. Although the higher electrostatic force can be gained with the thinner dielectric layer, the thin polymer film is easily deformed and torn by tension when the object starts moving. Index Terms--Dielectric layer, electrostatic force, silicon wafer, wafer handling.

This paper presents an analytical solution to the electrostatic actuation of an asymmetric combdrive in out-of-plane and torsional motions. The exact solutions to force in the out-of-plane motion and the integral for torque in the torsional motion are obtained. The dependence of the peak force on the thickness of the movable fingers and the amount of overlap of the combs is given in closed form. Using our model, the shift of the natural resonant frequency due to a dc bias is analyzed. Furthermore, our solution also applies to the in-plane motion of an in-plane interdigitated combdrive. We found that an in-plane interdigitated combdrive generates a constant force within 0.1% when the minimum initial engagement length of the combs is twice the separation gap. [454] Index Terms--Asymmetric combdrive, electric field, electrostatic force, in-plane interdigitated combdrive, torque.

The pull-in instability limits the travel distance of elastically suspended parallel-plate electrostatic microactuators to about 1/3 of the undeflected gap distance. In this paper, we examine the 'leveraged bending' and 'strain-stiffening' methods for extending the travel range of electrostatic actuators. The leveraged bending effect can be used to achieve full gap travel at the cost of increased actuation voltage. The strain-stiffening effect can be used to minimize actuation voltage for a given travel range. An analytical approximation shows that the strain-stiffening effect can be used to achieve a stable travel distance up to about 3/5 of the gap. A tunable reflective diffraction grating known as the polychromator has been designed using these actuation techniques, and selected designs have been fabricated and tested for actuation behavior. Gratings with 1024 fiat, closely packed grating-element actuators have been fabricated with over 1-cm-long mirrors, achieving stable vertical travel distances of more than 1.75 [micro]m out of a 2-[micro]m gap. [407] Index Terms--Electrostatic positioning, electrostatic pull-in effect, microelectromechanical actuators, nonlinear stiffness, optical diffraction gratings.

An electrostatic system that reduces airborne dust and microorganisms in poultry houses could also help sterilize Salmonella and other pathogenic bacteria in the dust, USDA Agricultural Research Service scientists report. [...]

Hydrodynamic Measurement of Double-Layer Repulsion Between Colloidal Particle and Flat Plate THE ELECTROSTATIC INTERACTION of charged bodies across electrolyte solutions is profoundly different from the interaction across a vacuum. The [...]