Electrostatic Force Model Research Articles

Using finite element simulation to evaluate charge measurement precision for space inertial sensors

Non-contact measurement and control are essential for accumulated charges on the test mass (TM) of space inertial sensors, as these charges can worsen the sensitivity of space-based gravitational wave detection. However, it is a challenge to evaluate measurement precision due to the limitations of experimental methods. In this study, the charge measurement process is described using an electrostatic force model, and five influence factors in terms of measurement precision are quantitatively evaluated through finite element simulation. The results indicate that the main contributors to mean relative errors (MREs) are the geometric structure of inertial sensors and the charge distribution on the TM. By correcting the capacitance gradient coefficient in the measurement model, the MRE caused by geometric structure can be reduced from 48% to 2%. Furthermore, the rotational modulation scheme demonstrates lower MREs and relative standard deviations, making it a preferred scheme for charge measurement. This study provides a feasible approach to designing and evaluating the charge measurement scheme for space-based gravitational wave detection.

Modeling of Planar Hydraulically Amplified Self-Healing Electrostatic Actuators

With the advantages of high actuation strain and specific power and ability of self-healing after dielectric breakdown, the planar hydraulically amplified self-healing electrostatic (pHASEL) actuators are promising for extensive emerging applications of soft robots. However, the relationship between the output and the input of actuator should be quantified to provide precise driven behavior data for motion mechanism. Due to the interdependence of output length and force, we mainly investigate the voltage-length-force relationship of the pHASEL actuator in this paper. The output forces include electrostatic force, elastic force, and corrective elastic force, namely hydrostatic force. We deduce the electrostatic force model which is approximated to be an infinite parallel capacitor including three dielectric layers. The elastic force is produced by the main elastomer covered by electrode and the marginal elastomer, and they are predicted by Neo-Hookean model under biaxial condition. Since the aggregation of dielectric liquid used in pHASEL causes significant error in the electrostatic force prediction, we suggest calibrating the volume to reduce the error by nearly 50%. The influence by cambered shape elastomer is also deduced. To validate the proposed model, the output forces and the applied voltage under different sizes of pHASEL actuators are measured under different stretching lengths. The results demonstrate that the model can well describe the voltage-length-force relationship.

The Effect of Applied Normal Force on the Electrovibration.

Electrovibration has become one of the promising approaches for adding tactile feedback on touchscreen. Previous studies revealed that the normal force applied on the touchscreen by the finger affects significantly the electrostatic force. It is obvious that the normal force affects the electrostatic force if it changes the contact area between the finger and the touchscreen. However, it is unclear whether the normal force affects the electrostatic force when the apparent contact area is constant. In this paper, we estimated the electrostatic force via measuring the tangential force of the finger sliding on a 3M touchscreen at different normal forces under the constant apparent contact area. We found that the electrostatic force increases significantly as the normal force increases from 0.5 to 4.5N. We explained the experimental results using the most recently proposed electrostatic force model, which considers the effect of air gap. We estimated the averaged air gap thickness using the electrostatic force model. The results showed that the relationship between the air gap thickness and the normal force follows a power function. Our experiment suggests that the normal force has a significant effect on the air gap thickness, thus require consideration in the design of tactile feedback.

DelPhiForce web server: electrostatic forces and energy calculations and visualization.

Electrostatic force is an essential component of the total force acting between atoms and macromolecules. Therefore, accurate calculations of electrostatic forces are crucial for revealing the mechanisms of many biological processes. We developed a DelPhiForce web server to calculate and visualize the electrostatic forces at molecular level. DelPhiForce web server enables modeling of electrostatic forces on individual atoms, residues, domains and molecules, and generates an output that can be visualized by VMD software. Here we demonstrate the usage of the server for various biological problems including protein-cofactor, domain-domain, protein-protein, protein-DNA and protein-RNA interactions. The DelPhiForce web server is available at: http://compbio.clemson.edu/delphi-force. delphi@clemson.edu. Supplementary data are available at Bioinformatics online.

Scale-dependent pull-in instability of functionally graded carbon nanotubes-reinforced piezoelectric tuning nano-actuator considering finite temperature and conductivity corrections of Casimir force

A scale-dependent analytical model is presented to solve the nonlinear pull-in instability of functionally graded carbon nanotubes (CNTs) reinforced nano-actuator with piezoelectric layer considering high order-corrected electrostatic pressure and finite temperature and conductivity corrections of Casimir force. Based on Eringen’s nonlocal elasticity theory considering the long range forces among atoms, and geometrical nonlinearity, the electro-thermo-mechanical coupling governing equation of nano-actuator is derived, and solved by utilizing natural mode function and Galerkin’s decomposition method. The higher-order corrected model of electrostatic force with fringing field effect accounting for large gap and geometrical nonlinearity is employed. The results indicate that pull-in voltage decreases with increase of positive piezoelectric effect but increases with increment of negative piezoelectric effect. Pull-in voltage declines as the piezoelectric layer thickness of nano-actuator increases. Casimir force appears in more significant effect on the pull-in voltage of nano-actuator than that of van der Waals force, which shows that the analysis of nanoscale devices cannot neglect the influences of intermolecular forces within sub-micron separations. Finally, the coupling influences of van der Waals force and Capillary force on pull-in voltage are compared.

Modeling and analysis of dynamics for spacecraft relative motion actuated by inter-satellite non-contacting force

With the recent flurry of research on spacecraft relative motion actuated by inter-satellite non-contacting force, i.e., electrostatic force, electromagnetic force and magnetic flux-pinned force, the need has become apparent for dynamic modeling and dynamics analysis that capture the characteristics of this generic force. Based on the basic derivation of electrostatic force model and some theorems, the actuations of electrostatic force, electromagnetic force/torque and magnetic flux-pinned force/torque are unified and the corresponding mathematic models are derived. And then, with a general notation of this inter-satellite non-contacting force, the dynamic models are developed with respect to several assumptions of circular orbit, elliptical orbit and general Keplerian orbit pertaining to the motion of center of mass of the spacecraft cluster. A detailed dynamics analysis based on these derived models are carried out, including constraints of the relative motion dynamics, the special characteristics of applications to the near-Earth relative orbit motion and the deep space relative motion, and then a case with co-rotating pair of satellites subject to the previously mentioned inter-satellite non-contacting forces was simulated to validate the dynamic modeling and dynamics analysis. At last, some useful conclusions follow.

Analytical model of electrostatic force generated by edge effect of a Kelvin capacitor based on conformal transformation

We present a new realization of weak electrostatic force based on Kelvin capacitor, which, compared with the conventional realization, simplifies the mechanical design without synchronously moving the central and guard-ring electrodes. However, a residual force due to the edge effect of the capacitor should be accurately known. In this paper, an analytic model of the electrostatic force generated from the edge effect is presented based on conformal transformations. The accuracy of the model is verified by the finite element calculation based on a micro-Newton weak force generation.

Investigation of Flux Decline in Tortuous Pore Structures via Three-Dimensional Simulation of Cross-Flow Microfilter Fouling

This paper presents a fluid dynamic-based approach to the prediction of the flux decline due to partial and complete pore blocking in the microfiltration process. The electrostatic force model includes both particle–particle (PP) and particle–membrane (PM) electrostatic forces. The addition of such forces was shown to affect particle trajectories in a tortuous three-dimensional microfilter membrane geometry. The model was validated by comparing experimental flux decline data with simulation flux decline data. A design of experiments was conducted to investigate the effects of transmembrane pressure, PM- and PP-zeta potential on flux decline. The simulation experiments revealed that low flux decline was associated with relatively low transmembrane pressures and near-zero values of PP- and PM-zeta potential; and relatively high transmembrane pressures and more-negative values of PP- and PM-zeta potential. The amount of flux decline was shown to be correlated to the specific nature of partial and complete pore blocking in the pore structure.

Mixing Behaviors of Granular Materials in Gas Fluidized Beds with Electrostatic Effects

The discrete element method combined with computational fluid dynamics was coupled to an electrostatic force model for computational studies of mixing behaviors in gas fluidized bed systems with electrostatic effects. Due to the presence of strong electrostatic forces between particles and walls, there was a high tendency for particles to be adhered to the walls or other particles near the walls within the fluidized bed, resulting in less vigorous fluidization. This in turn resulted in lower mixing efficiencies in comparison with fluidization in the presence of weaker electrostatic effects. Particle–wall electrostatic forces were on average stronger than both fluid drag forces and particle–particle collision forces when strong electrostatic effects were present, and this accounted for the difficulty with which particles adhered to walls could be removed and transferred to other locations within the bed. Such transfers of particles were necessary for mixing to occur during fluidization but required strong electrostatic forces to be overcome.

Experimental and Numerical Investigation on the Interaction Between Ar Flow Channel and Ar Plasma Jet at Atmospheric Pressure

In this paper, the interaction between Ar flow channel and atmospheric pressure plasma jet (APPJ) is investigated quantitatively by combining 3-D species transport simulation and optical schlieren observation together. The turbulence model, gravity force, and electrostatic force model are included into the Ar flow channel simulation. It is found that, with the increment of the Ar flow rate, the plasma plume reaches the maximum length at 3.5 L/min and then decreases sharply, which is corresponding to the Ar flow status. The simulations of the Ar flow channel show good agreement with the captured schlieren images. At small flow rates, the Ar flow channel bends downward due to the gravity. Under laminar flow, the high Ar mole fraction region near the axis of the Ar flow channel increases with the flow rate. However, the Ar flow presents as twist and radial diffusion, and the Ar mole fraction decreases rapidly when the Ar flow transits into turbulence, which leads the length of the Ar plasma plume to decrease sharply correspondingly. The plasma plume bestows the Ar flow channel a forward momentum, which decreases the curvature of bending downward and reinforces the twist and instability of the Ar flow channel under turbulence flow. By coupling the optical emission spectra and flow channel investigation together, it is revealed that Ar APPJ propagates along the core of the conelike flow channel. The Ar mole fractions at the head of the plasma plume are about 0.985 and 0.45 under laminar and turbulence flow, respectively.

Orbit Boosting Maneuvers for Two-Craft Coulomb Formations

This paper investigates the effectiveness of using active electrostatic charging to perform orbit altitude adjustments of a nominally circular orbit. Coulomb forces are employed to gently pull a charged object, such as space debris or a satellite being repositioned, in the along-track direction. In contrast to prior work, this study uses an enhanced position-dependent electrostatic force model. The charge at a fixed absolute potential is a function of separation distance, size, and charge of the neighboring object. The pulling configuration at a given voltage is shown to provide larger electrostatic forces over a pushing configuration. Further, the pulling configuration provides relative dynamics that are easier to stabilize. Variational equations are employed to estimate the resulting semimajor axis changes. Numerical sweeps are performed illustrating that kilovolt levels of potential are sufficient to achieve kilometer-level radius changes per orbit for geosynchronous orbit regimes. A key new insight is that, with a linear mass to effective radius scaling of the tugged object, a critical mass always exists beyond which the increased capacitance dominates over the mass increase. As a result, using the electrostatic tractor on a multiton geosynchronous orbit object can become easier if the object is larger than this critical mass.

Voltage-assisted polymer wafer bonding

Polymer wafer bonding is a widely used process for fabrication of microfluidic devices. However, best practices for polymer bonds do not achieve sufficient bond strength for many applications. By applying a voltage to a polymer bond in a process called voltage-assisted bonding, bond strength is shown to improve dramatically for two polymers (Cytop™ and poly(methyl methacrylate)). Several experiments were performed to provide a starting point for further exploration of this technique. An optimal voltage range is experimentally observed with a reduction in bonding strength at higher voltages. Additionally, voltage-assisted bonding is shown to reduce void diameter due to bond defects. An electrostatic force model is proposed to explain the improved bond characteristics. This process can be used to improve bond strength for most polymers.

Erratum to CFD Modeling of Electrostatic Forces in Gas-Solid Fluidized Beds [1] (Pp.189–205)

Erratum to CFD Modeling of Electrostatic Forces in Gas-Solid Fluidized Beds [1] (Pp.189–205)

A new power series solution on the electrostatic pull-in instability of nano cantilever actuators

In this paper, a power series solution is used to study the deflection and pull-in instability of nano cantilever electromechanical switches using a distributed parameter model. In the modeling of intermolecular force the Casimir force and in the modeling of electrostatic force, the fringing field effect is taken into account. A closed form power series solution basis on symbolic computation is introduced to obtain a semi analytical solution for the distributed parameter model. The minimum initial gap and the detachment length of the actuator that does not stick to the substrate due to the Casimir attractions, as an important parameter in pull-in instability of a nano cantilever actuator, is calculated by obtained power series. Furthermore, the present method is capable of determining stress distribution of the nano beam actuator at the onset of instability. It is seen that the Casimir effect significantly reduce the maximum value of stress resultants at the onset of instability. The obtained results are compared with numerical results and the Adomian decomposition method. The obtained solution in compare with the Adomian decomposition method represents a remarkable accuracy.

CFD Modeling of Electrostatic Forces in Gas-Solid Fluidized Beds

Electrostatic charges in gas-solid fluidized beds are known to influence the bed dynamics, bubble shape and size, particle agglomeration, segregation and entrainment. In practice, accumulation of electrostatic charges in fluidized beds can lead to operational issues. The present work focuses on the modeling of electrostatics in gas-solid fluidized beds. The particles are assumed to carry a prescribed size-dependent charge, and charge generation and dissipation are not modeled. To consider the effects of bi-polar charging the polarity of the charge carried by fine particles is taken opposite to that of coarse particles. The magnitude of particle charges is approximated to realistic charges reported in the literature. The principal objective is to develop a multi-fluid Euler-Euler model that can describe electrostatic forces on charged particles in gas-solid fluidized beds. The multi-fluid model is solved in a commercial CFD code (ANSYS Fluent 6.3) and uses the kinetic theory of granular flow for calculating solids pressure and viscosity. The electric field, generated by the presence of charged particles, is solved for at every time step in the time-dependent simulation. The electrostatic forces, proportional to the gradient of the electric field and the particle charge, lead to charge-dependent forces on the particles. The electrostatic model has been developed and applied to a two-dimensional fluidized bed. Charge-dependent segregation is found to vary with the polarity and magnitude of the charge on the solid phase as a function of the particle size.

Forcing mechanisms in supersonic flow actuation achieved by direct-current surface glow discharge plasma

Forcing mechanisms in aerodynamic flow actuation in Mach 3 supersonic flow provided by a direct-current surface discharge are investigated experimentally and computationally. High-speed flow actuation is achieved by creating a near-wall ionization region produced by striking a discharge between two bare round electrodes which are flush mounted on a ceramic actuator plate. Flow actuation which is signatured by the occurrence of a weak oblique shock originating from the ionization region is observed with a lower power ( ∼ 10 's W ) diffuse discharge which exhibits a volumetric ionization region above the cathode. This actuation effect is achieved when the cathode is placed upstream of the anode while no actuation is detected for the opposite case albeit with the same power input. Gas heating effect on flow actuation is evaluated by estimating gas (rotational) temperature using optical emission spectroscopy and numerical simulation. Significant gas heating as high as 400 K (free stream temperature is about 110 K) is observed near the cathode and numerical simulation confirms that gas heating is effective in supersonic flow actuation. However, the fact that the peak magnitude and spatial profile of gas temperature is similar for both cathode-upstream and cathode-downstream cases implies similar gas heating effect on supersonic flow actuation even though the actuation effect is different. Electrohydrodynamic (EHD) effect on flow actuation is emphasized by experimental results whose effect has been ignored in supersonic flow actuation and is supported by phenomenological modeling of electrostatic force. Analytic estimate of electrostatic forcing and corresponding computational result propose the potential role of EHD effect on supersonic flow actuation explaining the absence of flow actuation in the cathode downstream case.

Undercut Removal of Micrometer-Scale Particles from Surfaces

Effective removal of particulate contaminants from wafer surfaces during semiconductor manufacturing is essential for high-yield processing. To improve cleaning effectiveness, experimental and theoretical evaluations of undercut cleaning were conducted. A model system of polystyrene latex (PSL) spheres being removed from a tetraethyl ortho-silicate (TEOS)-sourced silicon dioxide surface was examined. 7 and PSL particles were spray deposited on wafer surfaces and allowed to settle for . Undercutting was then carried out using 20:1 buffered hydrofluoric acid to etch the silicon dioxide under nonflow conditions. Pre- and postetch scans of the wafer surface were obtained using a Tencor SP1 Surfscan in the laboratories of SEZ America in Phoenix, AZ. The percentage of particles that remained adhered to the surface after etching for varying lengths of time was monitored. A model for undercut removal of particles from surfaces was proposed. Chemical etching of the silicon dioxide surface was assumed to cause a reduction in the particle-wafer contact area. Undercut removal was hypothesized to occur due to a subsequent reduction in the van der Waals force of adhesion and an increase in the area over which repulsive electrostatic forces were dominant. Interactions between the PSL and the silicon dioxide were calculated based on computer simulation of a van der Waals adhesion model and an electrostatic force model. Particle and surface morphology, mechanical properties, and geometry were included in the van der Waals calculation, and the electrostatic force calculation considered the particle and silicon dioxide zeta potentials and local separation distance. The model and experiments agreed to within 10%.

ワイヤ放電加工の加工精度に関する基礎的研究 （第６報） 仕上げ加工の加工条件とサーボ特性の検討

Unsuitable EDM conditions for the finish cut on wire EDM result in a concave or a convex wall straightness of the workpiece. It takes a long time to determine the proper EDM conditions for the finish cut because many test cuts of the workpiece are required. In this study, we investigate and discuss the EDM conditions and servo feed functions of the finish cut, by examining relationships between the wire behaviors and the wall straightness of the workpiece. A method of determining EDM conditions for the finish cut is described, based on a balance model of electrostatic force and discharge force acting on the wire. A servo feed function responding to the variation of skimmed depth is investigated. Control methods for responding to the height variation of the workpiece at the finish cut are discussed.

Brownian Dynamics Simulation of Protein–Protein Diffusional Encounter

Protein association events are ubiquitous in biological systems. Some protein associations and subsequent responses are diffusion controlledin vivo.Hence, it is important to be able to compute bimolecular diffusional association rates for proteins. The Brownian dynamics simulation methodology may be used to simulate protein–protein encounter, compute association rates, and examine their dependence on protein mutation and the nature of the physical environment (e.g., as a function of ionic strength or viscosity). Here, the theory for Brownian dynamics simulations is described, and important methodological aspects, particularly pertaining to the correct modeling of electrostatic forces and definition of encounter complex formation, are highlighted. To illustrate application of the method, simulations of the diffusional encounter of the extracellular ribonuclease, barnase, and its intracellular inhibitor, barstar, are described. This shows how experimental rates for a series of mutants and the dependence of rates on ionic strength can be reproduced well by Brownian dynamics simulations. Potential future uses of the Brownian dynamics method for investigating protein–protein association are discussed.

Adhesive Force acting on Micro Objects.

In this paper, the adhesive force acting on micro objects is discussed. The origin of the adhesion is generally considered to be van der Waals force, surface tension force, and electrostatic force. We found that electrostatic force due to native charge dominates the adhesion of small metal particles at the humidity of 25%. Furthermore, the relationship between surface roughness and electrostatic force is measured by micro force measurement system. The model of electrostatic force acting on rough surface is also shown.