Electric-field-based Poisson-Boltzmann theory: Treating mobile charge as polarization

Electroosmotic flow (EOF) has been widely used in various biochemical microfluidic applications, many of which use viscoelastic non-Newtonian fluid. This study numerically investigates the EOF of viscoelastic fluid through a 10:1 constriction microfluidic channel connecting two reservoirs on either side. The flow is modelled by the Oldroyd-B (OB) model coupled with the Poisson–Boltzmann model. EOF of polyacrylamide (PAA) solution is studied as a function of the PAA concentration and the applied electric field. In contrast to steady EOF of Newtonian fluid, the EOF of PAA solution becomes unstable when the applied electric field (PAA concentration) exceeds a critical value for a fixed PAA concentration (electric field), and vortices form at the upstream of the constriction. EOF velocity of viscoelastic fluid becomes spatially and temporally dependent, and the velocity at the exit of the constriction microchannel is much higher than that at its entrance, which is in qualitative agreement with experimental observation from the literature. Under the same apparent viscosity, the time-averaged velocity of the viscoelastic fluid is lower than that of the Newtonian fluid.

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On the Possibility of a Significant Increase in Semiconductors Photosensitivity Spatial Profiling Flux of Radiation.

10.46940/gjaap.02.1002 ◽

2020 ◽

pp. 1-6

Keyword(s):

Field Strength ◽

Electric Field ◽

Electric Field Strength ◽

Optical Radiation ◽

Charge Carriers ◽

Semiconductor Detectors ◽

Mobile Charge ◽

Abstract Theory ◽

Spatial Profiling ◽

Specific Profile

Abstract Theory-based, three new unknown photoelectric effects can be occurred in semiconductors under inhomogeneous optical illumination with specific profile shapes along electric field in semiconductor: self-amplification, self-quenching and sign self-inversion of photogeneration rate of mobile charge carriers. The general shapes of corresponding illumination profiles are calculated. The occurring effects cause by local photoexcited space charge (PSC). It is shown that profile shapes depend on parameters of semiconductor, dark electric field strength and temperature. Also, we determine general shapes of “neutral” profiles when local PSC although exists but does not affect the result of interaction of optical radiation with a semiconductor. In other words, calculations with such “neutral” profiles lead to the same result as with using quasi-neutrality approximation, which does not account PSC. The shape of “neutral” profile depends only on dark electric field strength, temperature and sample size along the electric field. Embodiments for all types of profiles are given. The results can be used in practice, first, to increasing significantly photoelectric response of semiconductor detectors of optical radiation.

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Effects of quantum vacuum fluctuations of the electric field on DNA condensation

Open Physics ◽

10.2478/s11534-010-0037-5 ◽

2011 ◽

Vol 9 (1) ◽

Author(s):

Alfredo Iorio ◽

Samik Sen ◽

Siddhartha Sen

Keyword(s):

Electric Field ◽

Casimir Energy ◽

Quantum Vacuum ◽

Many Body ◽

Classical Level ◽

Counter Ions ◽

Starting Point ◽

Dna Strands ◽

Poisson Boltzmann ◽

Poisson Boltzmann Equation

AbstractBy assuming that not only counter-ions but DNA molecules as well are thermally distributed according to a Boltzmann law, we propose a modified Poisson-Boltzmann equation, at the classical level, as a starting point to compute the effects of quantum fluctuations of the electric field on the interaction among DNA-cation complexes. The latter are modeled here as infinite one-dimensional wires (δ-functions). Our goal is to single out such quantum-vacuum-driven interaction from the counterion-induced and water-related interactions. We obtain a universal, frustration-free Casimir-like (codimension 2) interaction that extensive numerical analysis show to be a good candidate to explain the formation and stability of DNA aggregates. Such Casimir energy is computed for a variety of configurations of up to 19 DNA strands in a hexagonal array. It is found to be many-body.

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Effects of Hydrodynamic Slip on Rotating Magneto-Electro-Osmotic Flow through a Periodic Microfluidic System

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.409.67 ◽

2021 ◽

Vol 409 ◽

pp. 67-89

Author(s):

Mohammed Abdulhameed ◽

Dauda Gulibur Yakubu ◽

Garba Tahiru Adamu

Keyword(s):

Boltzmann Equation ◽

Electric Field ◽

Laplace Transform ◽

Electroosmotic Flow ◽

Numerical Procedure ◽

Flow Profile ◽

Micro Channel ◽

The Laplace Transform ◽

Poisson Boltzmann ◽

Poisson Boltzmann Equation

The study is concerned with the effects of slip velocity on a non-uniform rotating electroosmotic flow in a micro-channel. Electroosmotic driven fluid flow is obtained by the application of a potential electric field which describes the nonlinear Poisson-Boltzmann equation. The external electric potential is applied along the x and y directions which provides the necessary driving force for the electroosmotic flow. Two semi analytical techniques were employed to obtain the solution of the nonlinear Poisson-Boltzmann equation. The first method incorporates the complex normalized function into the Laplace transform and the second method is the combination of the Laplace transform and D’Alembert technique. Further, the complex normalized function became difficult to invert in closed form, hence we resort to the use of numerical procedure based on the Stehfest's algorithm. The graphical solutions to the axial velocities on both x and y components have been obtained and analyzed for the effects of the slip parameter and the amplitude of oscillation of the micro-channel walls. The solutions show that the rotating electroosmotic flow profile and the flow rate greatly depend on time, rotating parameter and the electrokinetic width. The results also indicate that the applied electric field and the electroosmotic force, play vital role on the velocity distribution in the micro-channel. The fact is that the solutions obtained in this study synthesize most of the solutions available in the previous studies. Finally, this study will be relevant in biological applications particularly in pumping mechanism to help transport substances within different parts of the systems.

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Effects of Externally Applied Electric Field on the Electric Double Layer Formed in an Electrolyte Layer and its Contribution Towards Joule Heating

Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B ◽

10.1115/imece2011-63329 ◽

2011 ◽

Author(s):

Neeraj Sharma ◽

Gerardo Diaz ◽

Edbertho Leal-Quiros

Keyword(s):

Electric Field ◽

Double Layer ◽

Joule Heating ◽

Electric Potential ◽

Applied Electric Field ◽

Electric Double Layer ◽

Potential Distribution ◽

Electrolyte Layer ◽

Poisson Boltzmann ◽

Poisson Boltzmann Equation

Joule heating of liquid films in the presence of an externally applied electric field is influenced by the formation of the electric double layer. The thickness and charge distribution inside the electric double layer determine the extent of interaction of the charge in the electric double layer with the externally applied electric field and the Joule heating of the electrolyte layer. For this reason, the effects of externally applied electric field (both parallel and along the normal to the surface) on the electric double layer are being studied in the present paper. In the absence of the externally applied electric field, the distribution of the electric potential in the double layer is given by Poisson equation. Assuming Boltzmann distribution for the ionic concentration in the double layer, one arrives at Poisson-Boltzmann equation for the electric potential distribution. The externally applied electric field changes this electric potential distribution. Hence, the contribution of the externally applied electric field is studied by including it in the Poisson-Boltzmann equation.

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Resolution in photoelectron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086593 ◽

1991 ◽

Vol 49 ◽

pp. 458-459

Author(s):

G. F. Rempfer

Keyword(s):

Electron Microscopy ◽

Electric Field ◽

Ultraviolet Light ◽

Uniform Field ◽

Virtual Image ◽

Lens System ◽

Photoemission Electron Microscopy ◽

Planar Electrode ◽

Electron Lens ◽

Photoemission Electron

In photoelectron microscopy (PEM), also called photoemission electron microscopy (PEEM), the image is formed by electrons which have been liberated from the specimen by ultraviolet light. The electrons are accelerated by an electric field before being imaged by an electron lens system. The specimen is supported on a planar electrode (or the electrode itself may be the specimen), and the accelerating field is applied between the specimen, which serves as the cathode, and an anode. The accelerating field is essentially uniform except for microfields near the surface of the specimen and a diverging field near the anode aperture. The uniform field forms a virtual image of the specimen (virtual specimen) at unit lateral magnification, approximately twice as far from the anode as is the specimen. The diverging field at the anode aperture in turn forms a virtual image of the virtual specimen at magnification 2/3, at a distance from the anode of 4/3 the specimen distance. This demagnified virtual image is the object for the objective stage of the lens system.

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Current Status of Solid-State X-Ray Systems

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117789 ◽

1985 ◽

Vol 43 ◽

pp. 158-161

Author(s):

Martin Peckerar ◽

Anastasios Tousimis

Keyword(s):

Solid State ◽

Electric Fields ◽

Spectral Lines ◽

Current Status ◽

Mobile Charge ◽

Electron Hole ◽

X Ray ◽

Sensing Systems ◽

Transmission Electron ◽

Electron Microscopes

Solid state x-ray sensing systems have been used for many years in conjunction with scanning and transmission electron microscopes. Such systems conveniently provide users with elemental area maps and quantitative chemical analyses of samples. Improvements on these tools are currently sought in the following areas: sensitivity at longer and shorter x-ray wavelengths and minimization of noise-broadening of spectral lines. In this paper, we review basic limitations and recent advances in each of these areas. Throughout the review, we emphasize the systems nature of the problem. That is. limitations exist not only in the sensor elements but also in the preamplifier/amplifier chain and in the interfaces between these components.Solid state x-ray sensors usually function by way of incident photons creating electron-hole pairs in semiconductor material. This radiation-produced mobile charge is swept into external circuitry by electric fields in the semiconductor bulk.

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Field-assisted ionization theory for microscopists

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100171833 ◽

1994 ◽

Vol 52 ◽

pp. 820-821

Author(s):

Patrick P. Camus

Keyword(s):

Electric Field ◽

Electron Tunneling ◽

Ionization Probability ◽

Critical Distance ◽

Tunneling Probability ◽

Field Ionization ◽

Radius Of Curvature ◽

Field Evaporation ◽

A Value ◽

Ion Emission

The theory of field ion emission is the study of electron tunneling probability enhanced by the application of a high electric field. At subnanometer distances and kilovolt potentials, the probability of tunneling of electrons increases markedly. Field ionization of gas atoms produce atomic resolution images of the surface of the specimen, while field evaporation of surface atoms sections the specimen. Details of emission theory may be found in monographs.Field ionization (FI) is the phenomena whereby an electric field assists in the ionization of gas atoms via tunneling. The tunneling probability is a maximum at a critical distance above the surface,xc, Fig. 1. Energy is required to ionize the gas atom at xc, I, but at a value reduced by the appliedelectric field, xcFe, while energy is recovered by placing the electron in the specimen, φ. The highest ionization probability occurs for those regions on the specimen that have the highest local electric field. Those atoms which protrude from the average surfacehave the smallest radius of curvature, the highest field and therefore produce the highest ionizationprobability and brightest spots on the imaging screen, Fig. 2. This technique is called field ion microscopy (FIM).

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