Influence Of Uniform Electric Field Research Articles

Electro-kinetically driven route for highly sensitive blood pathology on a paper-based device.

Enhancing the sensitivity of colorimetric detection in paper-devices is a quintessential step in achieving frugal diagnosis. Here, we demonstrate an effective way of improving the detection sensitivity of paper-based devices, as mediated by electro-kinetic mechanisms. By directly employing blood plasma, we investigate the electro-kinetic clustering of glucose, a neutral molecule in paper devices. Under the influence of uniform electric field, dispersed glucose gets accumulated in the paper strips. Due to the combination of EOF and electrophoretic migration, we achieve twofold increase in the colour intensity for both normal and diabetic samples. This approach is robust and possesses better sensitivity than conventional colorimetric assays and can be easily extended to other body fluid based diagnosis. These results may turn out to be of profound importance in improving the quality of pathological diagnosis in low-cost paper-based point-of-care devices deployed in resource-limited settings.

Surface Discharges and Flashover Voltages in Nanocomposite XLPE Samples

DC cable insulation is a field of intensive research activity. Special attention is being given to polymer nanocomposites, as promising insulation for such cables. Relatively little is known regarding surface discharges and flashover voltages for the aforementioned materials. In this paper, a comparison is made between samples of cross-linked polyethylene insulation with added MgO nanofillers and samples of pure polyethylene w.r.t. the behavior of surface discharges and flashover voltages in arrangements of water droplets of various conductivities on the said polymeric surfaces under the influence of uniform electric fields. Experimental evidence indicates that the flashover voltages of XLPE with MgO nanofillers are higher that the ones obtained with pure PE.

Drop deformation and emulsion rheology under the combined influence of uniform electric field and linear flow

Electrohydrodynamics of a leaky dielectric suspended drop subjected to the combined influence of a uniform electric field and linear velocity field is analysed analytically and numerically. In the limit of small charge convection and small shape deformation, an analytical solution is obtained for the deformed drop shape when the imposed linear flow is of uniaxial extensional type with the extensional component aligned in the direction of the electric field. This perturbation approach is then applied towards obtaining the effect of a uniform electric field on the effective extensional rheology of a dilute emulsion. Key results indicate that the magnitude and sense of drop deformation not only depends on the material properties of the drop and medium but is also governed by the strength of the applied electric field relative to the applied flow field. The interfacial charge convection is found to increase or decrease the drop deformation depending on the direction of electrohydrodynamic flow and relative strength of electric field. The electrohydrodynamic flow and drop deformation modulates the effective extensional viscosity of the emulsion. Importantly, the presence of the electric field leads to strain-rate-dependent effective extensional viscosity of the emulsion. The emulsion is found to exhibit strain-rate thinning/thickening behaviour depending on the drop to medium charge relaxation time scale. The analytically obtained drop shape and deformation are in excellent agreement with numerical simulations for the small deformation ranges.

Effect of uniform electric field on the drop deformation in simple shear flow and emulsion shear rheology

Electrohydrodynamic deformation and orientation of a neutrally buoyant, leaky dielectric, Newtonian drop suspended in another immiscible, leaky dielectric, Newtonian medium is analyzed under the combined influence of uniform electric field and simple shear flow. Application of uniform electric field, perpendicular to the direction of shear flow, not only deforms the drop but also modifies the rheological behavior of a dilute emulsion. In the creeping flow limit, an analytical solution for the deformed drop shape is obtained when the drop shape remains nearly spherical and the surface charge convection is weak. The effective shear rheology is obtained for a dilute emulsion of non-interacting drops by calculating the one-particle contribution to the emulsion stress. The results show that the combined influence of uniform electric field and shear flow is not a simple linear superposition of the independent contributions from electric field and shear flow. Application of uniform electric field always leads to larger drop deformation with drop inclination more towards the direction of velocity gradient for the particular case of perfectly dielectric drops. Presence of surface charge convection for a leaky dielectric drop can increase or decrease the drop deformation with the drop inclination more towards either the direction of shear flow or velocity gradient. The effective shear viscosity and normal stress differences are found to be independent of shear rate. These quantities are significantly affected by the surface charge convection and shape deformation. Shape deformation always increases the effective viscosity of a dilute emulsion composed of perfectly dielectric drops. Interestingly, for a dilute emulsion composed of leaky dielectric drops, results show that the combined influence of charge convection and shape deformation can augment or decrease the effective shear viscosity.

Influence of Uniform Electric Field in Bioremediation of Oil-Contaminated Soils

Electrokinetic remediation is an effective technology to enhance bioremediation of oil-contaminated soil as the transport process of non-polar organic contaminants in soil was promoted under low-power direct current electric fields. In this study three treatments including the application of electric field treatment alone, inoculation treatment alone, and combination of the application of electric field and inoculation treatment were carried out. The results indicated that highest removal efficiency was 83% in couple of the application of electric field and inoculation treatment. TPH concentration decreased from 6000 mg.kg-1 to 2000 mg.kg-1 when a 30 voltage direct current electric field was applied to oil-contaminated soil for 10 min after 4 days. It was observed that dehydrogenase activity had no increase after application direct current electric field. However, the TPH degradation efficiency was 52% higher than the control treatment. GC analysis showed that n-alkanes (C14-C31) were preferentially degraded, and soil remaindered more low quality compounds after the application of electric field treatment applied 52 days. These results indicated that the application of electric field improved degradation of inoculated bacteria through promoting the transport of nutrients, such as nitrogen and phosphorous and electron acceptors.

A Study of the Behaviour of Water Droplets Under the Influence of Uniform Electric Field in Epoxy Resin Samples

A Study of the Behaviour of Water Droplets Under the Influence of Uniform Electric Field in Epoxy Resin SamplesWater droplets on the surface of epoxy resin samples were investigated under the influence of uniform electric fields. Several parameters of water droplets were investigatedwrtthe flashover voltage of the epoxy resin samples, such as water conductivity, droplet volume, number of droplets as well as the positioning of the droplets regarding the electrodes. The droplet behavior is affected by the above mentioned parameters. Perhaps the most striking conclusion is that the flashover voltage depends more on the positioning of the dropletswrtthe electrodes than on the droplet volume and/or number of droplets.

CREEPING MOTION OF A BUBBLE WITH FIXED SURFACE CHARGE IN A UNIFORM ELECTRIC FIELD

Approximate solutions of the shape function and the electrophoretic movement of a bubble in an aqueous medium with ionized detergent and a small number of electrolytes under the influence of uniform electric field are derived. Specifically, a bubble that has the interface saturated and densely packed with detergent molecules is considered, and the charges were deemed to be fixed provided the position change among the detergent molecules is hindered relative to the free molecule. The surface tension at the interface is weakened with the addition of the detergent, and the deformation can be significant. The variation of the shape of the bubble was represented by the Legendre polynomial and the perturbed velocity profile was used to derive the drag force for the deformed bubble. The speed and size of the bubble was assumed to be very small so that the flow around it is in the creeping flow regime. The shape of the bubble with fixed surface charge undergoes a prolate deformation with axial symmetry around the axis parallel to the direction of the electric field and exhibits asymmetry with respect to the plane that goes through the center of the bubble and is perpendicular to the axis. But this asymmetry is not significant unless the surface charge density and the electric field are very large. Only symmetric deformation governs the movement, and, consequently, the drag force is not dependent on the sign of surface charge. As the bubble becomes more slender with deformation, the movement is enhanced.

Electrohydrodynamic behaviour of a drop subjected to a steady uniform electric field at finite electric Reynolds number

The electrohydrodynamic flow associated with a fluid drop in an electric field is a consequence of the tangential electric stress at the fluid interface. The tangential viscous stress due to the electrohydrodynamic flow arises to just balance the tangential electric stress at the fluid interface so that the traction boundary condition is satisfied. Influenced by both the local electric stress and viscous stress, the drop interface may exhibit various shapes. The presence of fluid flow also leads to charge convection phenomena. The relative significance of the charge convection effect is usually measured in terms of the electric Reynolds number, Re E , defined as the ratio of the timescales of charge convection by flow and that for charge relaxation by ohmic conduction. This work presents a quantitative analysis of the charge convection effects in a framework of the leaky dielectric model at finite Re E , which has not been considered in previous investigations. Axisymmetric steady flows driven by an applied uniform electric field about a deformable fluid drop suspended in an immiscible fluid are studied by computational means of the Galerkin finite–element method with supplementary asymptotic analysis. The results of finite–element computations are in general agreement with the prediction by the asymptotic analysis for spherical drops at vanishingly small Re E . A common effect of charge convection is found to reduce the intensity of electrohydrodynamic flow. As a consequence, oblate drops are predicted to be less deformed in an electric field when charge convection is taken into account. The prolate drops are often associated with an equator–to–pole flow, which convects charges toward the poles to form a charge distribution resembling that in a highly conducting drop immersed in an insulating medium. Therefore, charge convection tends to enhance the prolate drop deformation. In many cases, charge convection effects are found to be significant even at apparently small Re E , corresponding to the charge relaxation time–scale about 10 −3 s, suggesting that many experimental results reported in the previous publications could have been influenced by charge convection effects.

Influence of a uniform electric field on the intraband Faraday effect

AbstractThe quantum theory of the complex dielectric tensor εij(ω, q), which has been developed in [6], is extended to the case of crossed electric and magnetic fields. The quasi‐classical approximation is considered and the results are compared with earlier papers [6 to 9]. The expression for the complex conductivity tensor δij(ω, q) is used for studying the influence of the external uniform electric field on the intraband Faraday effect in semiconductors with simple band structure in two cases: the classical magnetic field and quantum limit. A brief discussion of the results is given.