Influence Of Non-uniform Electric Field Research Articles

Influence of nonuniform electric field due to a spherical collector on the particles dynamics in quiescent air

This study investigates particle dynamics impacting a charged spherical collector through experiments and simulations, revealing the influence of the collector’s non-uniform potential field. Electrostatic and drag forces govern trajectories, while gravity and dielectrophoretic forces play a minor role. Positive electrostatic and negative drag work are comparable, offering critical insights into particle energy budgets. Closer proximity to the collector center leads to a greater energy budget, causing uneven particle collection. Analysis of fractional energy loss indicates a critical point where electrostatic work dominates over viscous dissipation. This analysis is crucial for analyzing particle deposition behavior in non-uniform electric fields.

Electric-Field-Assisted Protein Crystallization in Continuous Flow

Crystallization is an attractive method for separation and purification of large biomolecules such as proteins due to inherent advantages related to product composition, stability, and process throughput. However, the lack of control over the nucleation and growth of protein crystals complicates design and operation. Electric fields have been used to improve control over the location and induction time of protein nucleation in small batches. To adopt electric-field-assisted protein crystallization as a separation and purification method, a novel device based on continuous flow is presented. The application of continuous flow allows for a large surface-to-volume ratio to be exploited for the electrode design and aligns with the current trend in the (bio)pharmaceutical industry toward continuous manufacturing. The device features millimeter-sized channels with coplanar electrodes to study the influence of nonuniform electric fields on protein crystallization in continuous flow. The results demonstrate that ...

Influence of Alternating Electric Fields on Protein Crystallization in Microfluidic Devices with Patterned Electrodes in a Parallel-Plate Configuration

Improved control over protein nucleation is important to advance the design and operation of protein separation and purification processes. The influence of nonuniform electric fields induced by patterned indium tin oxide (ITO) electrodes of various shapes and surface areas on protein nucleation in microfluidic devices with parallel electrodes is investigated experimentally. In particular, the impact of various electrode designs and electric-field properties on the solid-state form, induction time, nucleation rate, and the location of lysozyme crystals is described. The results demonstrate that both enhanced and inhibited protein crystallization can be observed depending on the specifics of electrode shape and surface area and electric-field properties. The nucleation location of crystals is found to be influenced by both the ITO layer as a template and the nonuniform electric field induced by specific designs of electrodes. The optimal electric-field conditions and electrode design for enhancement of lys...

Three-Dimensional Numerical Simulation of Bubble Dynamics in Microgravity under the Influence of Nonuniform Electric Fields

A three-dimensional VOSET method is used along with the adaptive mesh refinement (AMR) method to simulate the behaviors of a bubble departing from the outside wall of a horizontal square-cross-section tube in microgravity under the influence of nonuniform electric fields. The effects of gravity, electric field intensity, fluid permittivity, and bubble initial position on the bubble detachment and rising are investigated and analyzed. Computational results show that the gravity and electric fields have significant influences on the bubble detachment and rising velocity and rising trajectory. Decrease in gravity results in the decrease in the buoyancy exerted on the bubble, considerably mitigating the rising capability of the bubble and delaying the bubble detachment. Imposing a nonuniform electric field, which exhibits physically the strongest intensity in regions near the tube wall, can supply an additional driving force as a replacement of the buoyancy to accelerate the bubble detachment and rising. It is also shown that a larger electric field intensity or larger ratio of liquid permittivity to gas permittivity leads to a larger deformation, easier detachment, and larger rising velocity, of the bubble. The nonuniformity of the electric fields can also affect the bubble motion trajectory and result in the asymmetric deformation of the bubble.

Characteristics of Voltage Holding Capability in Multi-stage Large Electrostatic Accelerator for Fusion Application

Voltage holding capability of a 500 kV, 22 A three-stage electrostatic accelerator, where large-area grids of 0.28 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and large fiberglass reinforced plastic (FRP) insulators of 1.8 m in diameter are used, was examined. High voltage was independently applied to each acceleration stage, where the voltage holding capabilities of 130 kV were obtained. To identify whether the breakdowns occur in the gaps between the grids or the FRP insulators, high voltages were applied to the accelerator with and without the grids. Breakdown voltages without grids, i.e., the FRP insulator itself reached 170 kV of design value for each stage. These results show that the breakdown voltage of the accelerator was mainly determined by the gaps between the large-area grids. In this paper, the influence of non-uniform electric field and multi-stage grids on the voltage holding capabilities was also discussed.

Bacterial handling under the influence of non-uniform electric fields: dielectrophoretic and electrohydrodynamic effects

This paper describes the modeling and experimental verification of a castellated microelectrode array intended to handle biocells, based on common dielectrophoresis. The proposed microsystem was developed employing platinum electrodes deposited by lift-off, silicon micromachining, and photoresin patterning techniques. Having fabricated the microdevice it was tested employing Escherichia coli as bioparticle model. Positive dielectrophoresis could be verified with the selected cells for frequencies above 100 kHz, and electrohydrodynamic effects were observed as the dominant phenomena when working at lower frequencies. As a result, negative dielectrophoresis could not be observed because its occurrence overlaps with electrohydrodynamic effects; i.e. the viscous drag force acting on the particles is greater than the dielectrophoretic force at frequencies where negative dielectrophoresis should occur. The experiments illustrate the convenience of this kind of microdevices to micro handling biological objects, opening the possibility for using these microarrays with other bioparticles. Additionally, liquid motion as a result of electrohydrodynamic effects must be taken into account when designing bioparticle micromanipulators, and could be used as mechanism to clean the electrode surfaces, that is one of the most important problems related to this kind of devices.

Nonuniform electric fields in pulse heated wires

The influence of nonuniform electric fields on the measurement of the electrical conductivity in pulse-heated wires is studied analytically. Two causes for nonuniformity are considered: switching-on of an external voltage source (transient skin effect) and temperature-dependent change of the electrical conductivity. This problem usually has two strictly different time scales: a short one, on which the transient skin effect takes place, and a long one, on which heat conduction happens. Here, the short time scale is considered.

Dielectrophoretic deposition in suspensions of macromolecules: Polyvinylchloride and sephadex G-50

The present work describes the influence of nonuniform electric fields (dielectrophoresis) on macromolecular suspensions of polyvinylchloride and Sephadex G-50. Experimental evidence was obtained of the existence of both positive and negative dielectrophoretic forces, according to whether the particles moved toward the electrodes or not. The dielectrophoretic yield of polyvinylchloride particles formed at the electrodes was seen to be a linear function of the alternating current applied, the concentration of particles in suspension, and square root of the collection time. Dielectrophoretic separation was also seen to be a function of the frequency and of the electrical conductivity of the medium, a maximum in this suspension being formed at about 1 MHz for an electrical conductivity of the medium of 4.0 × 10 −3 (Ωm) −1 . The addition of cations of different valencies affected dielectrophoretic separation. The experimental results suggest the presence of a dielectric relaxation phenomenon. In order to interpret the dielectrophoretic dispersion observed we suggest that an interfacial polarization of the Maxwell-Wagner mechanism, modified to include surface conduction properties, should be considered.

The action of a non-uniform electric field upon lossy dielectric systems-ponderomotive force on a dielectric sphere in the field of a point charge

The use of the Maxwell stress tensor method is shown to calculate forces and torques acting in non-homogeneous dielectric systems under the influence of non-uniform electric fields in the case of lossy dielectrics without confining the treatment to the dipole approximation, as usually made. The method is applied to the particular case of a lossy dielectric sphere subject to the field of a point charge and an analytical solution is obtained. The effects of the usual restrictive assumptions are pointed out and the dependence of force upon the electric properties of materials is shown.