Numerical Simulation of Microscale Ion-Driven Air Flow

2003 ◽  
Author(s):  
Daniel J. Schlitz ◽  
Suresh V. Garimella ◽  
Timothy S. Fisher
Keyword(s):  
Electric Field ◽  
Charge Transport ◽  
Electric Fields ◽  
Air Flow ◽  
Maximum Velocity ◽  
Electronics Cooling ◽  
Pressure Head ◽  
Switching Frequency ◽  
Field Equations ◽  
Scale Motion

Ion-driven air flow is a novel method of pumping air at microscale dimensions using the concept of ion drag. The method employs a series of micro-fabricated electrodes to generate strong electric fields that pump unipolar ions through air. Ions collide repeatedly with neutral molecules, thus generating bulk motion of the gas. Meso-scale motion is obtained by changing the voltage of electrodes rapidly over time to create a nearly continuous force on the ions. One application of this technology involves generation of air flow through microchannels or other micro-featured surfaces to create compact, high flux heat sinks for electronics cooling. A numerical model of the fluid-ion-electric field interaction has been developed. The momentum and continuity equations are supplemented with equations for electric charge transport and for electric potential. The momentum equations are coupled through a body-force term to the charge transport and electric field equations, both of which are coupled to the momentum equations and to each other through source and convection terms. The model describes the one-dimensional, time-dependent flow of air and ions between evenly spaced microscale planar electrodes, of which the voltages are switched at frequencies on the order of 1 MHz. The flow is investigated to determine the effect of switching frequency on maximum velocity and pressure head.

Microscale Ion-Driven Air Flow Over a Flat Plate

Volume 4 ◽  
2004 ◽  
Author(s):  
Daniel J. Schlitz ◽  
Suresh V. Garimella ◽  
T. S. Fisher
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Air Flow ◽  
Electronics Cooling ◽  
Heat Sinks ◽  
Ion Current ◽  
Electrode Potentials ◽  
Bulk Motion ◽  
Generation Region ◽  
Ionized Air

A microscale air pump concept that uses ionized air molecules under the influence of an electric field is studied. The method employed is an extension of the corona wind concept and is referred to here as microscale ion-driven air flow. The two major differences are that the ions are created in a distinct generation region, and are then put in motion by a traveling electric field in the pumping region. The ions create bulk motion of the air because of ion drag. One application of this technology involves generation of air flow through microchannels or other micro-featured surfaces to create compact, high flux heat sinks for electronics cooling. This work focuses on the ion pumping aspect of the technology. A device was constructed and tested with an array of micro-fabricated electrodes that generate strong electric fields in the air. The electrode potentials were cycled to impart a unidirectional force to the ions over meso-scale distances. The microscale ion-driven air flow concept was demonstrated by electrical means, through the measurement of the ion current produced. A set of designed experiments were conducted that showed the electrode potential to be the most significant factor for sustaining an ion current. A two-dimensional numerical model of the ion motion has been developed and validated against the experimental results. The model describes the time-dependent ion flow induced over an array of evenly spaced microscale electrodes that are used to generate a translating electric field.

Research on Charge Transport in One-Dimensional Organic Semiconductors Material

2012 ◽  
Vol 531 ◽  
pp. 231-234 ◽  
Author(s):  
Wen Liu
Keyword(s):  
Electric Field ◽  
Charge Transport ◽  
Organic Semiconductors ◽  
Electric Fields ◽  
One Dimensional ◽  
Organic Semiconductor Materials ◽  
Insulator Metal Transition ◽  
The Family ◽  
High Electric Fields ◽  
Ssh Model

1D conjugated polymers belong to the family of organic semiconductor materials, in which the charge carriers are polarons or bipolarons. Charge transport in 1D organic semiconductors in the presence of high electric fields is studied within the SSH model. It is found that under a sufficiently high electric field, the polaron is dissociated into free-like electron. The electron performs Bloch oscillation (BO) in the organic semiconductors. By enhancing the electric field, BO will be destroyed and electrons can transit from the valence band to the conduction band, which is Zener tunneling in organic semiconductors. The results also indicate a field-induced insulator-metal transition.

scholarly journals Visualization of an Accelerated Electrochemical Reaction under an Enhanced Electric Field

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Chen Cui ◽  
Rong Jin ◽  
Dechen Jiang ◽  
Jianrong Zhang ◽  
Junjie Zhu
Keyword(s):  
Electric Field ◽  
Charge Transport ◽  
Electric Fields ◽  
Electrochemical Reaction ◽  
Ruthenium Complex ◽  
Electron Transfer Mechanism ◽  
Heterogeneous Interfaces ◽  
Electrochemical Mechanism ◽  
High Electric Fields ◽  
First Time

Locally enhanced electric fields produced by high-curvature structures have been reported to boost the charge transport process and improve the relevant catalytic activity. However, no visual evidence has been achieved to support this new electrochemical mechanism. Here, accelerated electrochemiluminescence (ECL) reactions emitting light are visualized for the first time at the heterogeneous interfaces between microbowls and the supporting electrode surface. The simulation result shows that the electric intensity at the interface with a high curvature is 40-fold higher than that at the planar surface. Consequently, local high electric fields concentrate reactive species to the heterogeneous interfaces and efficiently promote the charge transport reactions, which directly leads to the enhancement of ECL emission surrounding the microbowls. Additionally, the potential to induce visual ECL from a ruthenium complex drops to 0.9 V, which further illustrates the promotion of an electrochemical reaction with the aid of an enhanced electric field. This important visualization of electric field boosted electrochemical reactions helps to establish the proposed electron transfer mechanism and provide an alternative strategy to improve electrocatalytic efficiency.

Effect of Electric Field on a 3D Rising Bubble in Viscous Fluids

2013 ◽  
Author(s):  
Qingzhen Yang ◽  
Yang Liu ◽  
Ben Q. Li ◽  
Yucheng Ding
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Phase Field Model ◽  
Coupled Model ◽  
Viscous Force ◽  
Field Equations ◽  
Navier Stokes Equation ◽  
Dielectric Fluids ◽  
Rising Bubble

Understanding of a rising bubble in fluid with the presence of external fields is of fundamental importance in boiling heat transfer and gas-liquid flows. In this paper, a computational methodology is presented for a modeling study of hydrodynamic behavior of a bubble rising in fluid subject to an applied electric field. The computational model is developed by solving the Navier-Stokes equation coupled with the phase field model and electric field equations. The coupled model is capable of predicting the evolution of electric field, bubble motion and deformation and the medium fluid. Numerical simulations were conducted to study the combined effect of coupled electrical force, gravity, surface tension and viscous force on the deformation and motion of a bubble as it ascends through the liquid. The liquid and gas are considered as the dielectric fluids and both vertical and horizontal electric fields are studied. The in-house Fortran code was developed to enable the simulation, and numerical results are presented showing that the deformation and rising speed of the bubble are affected by the applied electric field in both magnitude and direction.

scholarly journals Observation of an inner magnetosphere electric field associated with a BBF-like flow and PBIs

2009 ◽  
Vol 27 (4) ◽  
pp. 1489-1500
Author(s):  
T. Johansson ◽  
J. W. Bonnell ◽  
C. Cully ◽  
E. Donovan ◽  
J. Raeder ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Electric Fields ◽  
Plasma Flow ◽  
Maximum Velocity ◽  
Inner Magnetosphere ◽  
Ion Flow ◽  
Field Activity ◽  
The Magnetic Field

Abstract. Themis E observed a perpendicular (to the magnetic field) electric field associated with an Earthward plasma flow at XGSM=−9.6 RE on 11 January 2008. The electric field observation resembles Cluster observations closer to Earth in the auroral region. The fast plasma flow shared some characteristics with bursty bulk flows (BBFs) but did not meet the usual criteria in maximum velocity and duration to qualify as one. Themis C observed the same flow further downtail but Themis D, separated by only 1 RE in azimuthal direction from Themis E, did not. At the time of the electric field and ion flow event, the all-sky imager and ground-based magnetometer at Rankin Inlet observed Poleward Boundary Intensifications (PBIs) and a negative bay signature. None of the other Themis ground-based observatories recorded any significant auroral or magnetic field activity, indicating that this was a localized activity. The joint Themis in situ and ground-based observations suggest that the two observations are related. This indicates that auroral electric fields can extend to regions much farther out than previously seen in Cluster observations.

Tuning the Electric Field Response of MOFs by Rotatable Dipolar Linkers

2019 ◽  
Author(s):  
Johannes P. Dürholt ◽  
Babak Farhadi Jahromi ◽  
Rochus Schmid
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Structural Changes ◽  
Dielectric Behavior ◽  
Two Dimensions ◽  
Dielectric Constants ◽  
Electric Response ◽  
Dipole Strength ◽  
Metal Organic ◽  
Dynamics Simulations

Recently the possibility of using electric fields as a further stimulus to trigger structural changes in metal-organic frameworks (MOFs) has been investigated. In general, rotatable groups or other types of mechanical motion can be driven by electric fields. In this study we demonstrate how the electric response of MOFs can be tuned by adding rotatable dipolar linkers, generating a material that exhibits paralectric behavior in two dimensions and dielectric behavior in one dimension. The suitability of four different methods to compute the relative permittivity κ by means of molecular dynamics simulations was validated. The dependency of the permittivity on temperature T and dipole strength μ was determined. It was found that the herein investigated systems exhibit a high degree of tunability and substantially larger dielectric constants as expected for MOFs in general. The temperature dependency of κ obeys the Curie-Weiss law. In addition, the influence of dipolar linkers on the electric field induced breathing behavior was investigated. With increasing dipole moment, lower field strength are required to trigger the contraction. These investigations set the stage for an application of such systems as dielectric sensors, order-disorder ferroelectrics or any scenario where movable dipolar fragments respond to external electric fields.

scholarly journals Meta-Deflectors Made of Dielectric Nanohole Arrays with Anti-Damage Potential

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 107
Author(s):  
Haichao Yu ◽  
Feng Tang ◽  
Jingjun Wu ◽  
Zao Yi ◽  
Xin Ye ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Laser Cutting ◽  
High Complexity ◽  
Damage Potential ◽  
Optical Components ◽  
Nanohole Arrays ◽  
Intense Light ◽  
Polarization Of Light ◽  
Air Hole

In intense-light systems, the traditional discrete optical components lead to high complexity and high cost. Metasurfaces, which have received increasing attention due to the ability to locally manipulate the amplitude, phase, and polarization of light, are promising for addressing this issue. In the study, a metasurface-based reflective deflector is investigated which is composed of silicon nanohole arrays that confine the strongest electric field in the air zone. Subsequently, the in-air electric field does not interact with the silicon material directly, attenuating the optothermal effect that causes laser damage. The highest reflectance of nanoholes can be above 99% while the strongest electric fields are tuned into the air zone. One presentative deflector is designed based on these nanoholes with in-air-hole field confinement and anti-damage potential. The 1st order of the meta-deflector has the highest reflectance of 55.74%, and the reflectance sum of all the orders of the meta-deflector is 92.38%. The optothermal simulations show that the meta-deflector can theoretically handle a maximum laser density of 0.24 W/µm2. The study provides an approach to improving the anti-damage property of the reflective phase-control metasurfaces for intense-light systems, which can be exploited in many applications, such as laser scalpels, laser cutting devices, etc.

scholarly journals Integrating flexible electronics for pulsed electric field delivery in a vascularized 3D glioblastoma model

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Marie C. Lefevre ◽  
Gerwin Dijk ◽  
Attila Kaszas ◽  
Martin Baca ◽  
David Moreau ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Flexible Electronics ◽  
Soft Tissues ◽  
Multiphoton Microscopy ◽  
Membrane Integrity ◽  
Tumor Model ◽  
Pulsed Electric Fields ◽  
In Ovo ◽  
Cell Membrane Integrity

AbstractGlioblastoma is a highly aggressive brain tumor, very invasive and thus difficult to eradicate with standard oncology therapies. Bioelectric treatments based on pulsed electric fields have proven to be a successful method to treat cancerous tissues. However, they rely on stiff electrodes, which cause acute and chronic injuries, especially in soft tissues like the brain. Here we demonstrate the feasibility of delivering pulsed electric fields with flexible electronics using an in ovo vascularized tumor model. We show with fluorescence widefield and multiphoton microscopy that pulsed electric fields induce vasoconstriction of blood vessels and evoke calcium signals in vascularized glioblastoma spheroids stably expressing a genetically encoded fluorescence reporter. Simulations of the electric field delivery are compared with the measured influence of electric field effects on cell membrane integrity in exposed tumor cells. Our results confirm the feasibility of flexible electronics as a means of delivering intense pulsed electric fields to tumors in an intravital 3D vascularized model of human glioblastoma.

scholarly journals Electro-Optic Control of Lithium Niobate Bulk Whispering Gallery Resonators: Analysis of the Distribution of Externally Applied Electric Fields

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 298
Author(s):  
Yannick Minet ◽  
Hans Zappe ◽  
Ingo Breunig ◽  
Karsten Buse
Keyword(s):  
Lithium Niobate ◽  
Electric Field ◽  
Electric Fields ◽  
Frequency Comb ◽  
Parametric Oscillation ◽  
Pockels Effect ◽  
Optical Mode ◽  
Cylindrical Resonator ◽  
Whispering Gallery ◽  
Electro Optic

Whispering gallery resonators made out of lithium niobate allow for optical parametric oscillation and frequency comb generation employing the outstanding second-order nonlinear-optical properties of this material. An important knob to tune and control these processes is, e.g., the linear electro-optic effect, the Pockels effect via externally applied electric fields. Due to the shape of the resonators a precise prediction of the electric field strength that affects the optical mode is non-trivial. Here, we study the average strength of the electric field in z-direction in the region of the optical mode for different configurations and geometries of lithium niobate whispering gallery resonators with the help of the finite element method. We find that in some configurations almost 100% is present in the cavity compared to the ideal case of a cylindrical resonator. Even in the case of a few-mode resonator with a very thin rim we find a strength of 90%. Our results give useful design considerations for future arrangements that may benefit from the strong electro-optic effect in bulk whispering gallery resonators made out of lithium niobate.

scholarly journals Double layers in the downward current region of the aurora

2003 ◽  
Vol 10 (1/2) ◽  
pp. 45-52 ◽  
Author(s):  
R. E. Ergun ◽  
L. Andersson ◽  
C. W. Carlson ◽  
D. L. Newman ◽  
M. V. Goldman
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Phase Space ◽  
Electric Field ◽  
Electric Fields ◽  
Double Layers ◽  
Parallel Electric Field ◽  
Electrostatic Waves ◽  
Current Region ◽  
Decisive Evidence

Abstract. Direct observations of magnetic-field-aligned (parallel) electric fields in the downward current region of the aurora provide decisive evidence of naturally occurring double layers. We report measurements of parallel electric fields, electron fluxes and ion fluxes related to double layers that are responsible for particle acceleration. The observations suggest that parallel electric fields organize into a structure of three distinct, narrowly-confined regions along the magnetic field (B). In the "ramp" region, the measured parallel electric field forms a nearly-monotonic potential ramp that is localized to ~ 10 Debye lengths along B. The ramp is moving parallel to B at the ion acoustic speed (vs) and in the same direction as the accelerated electrons. On the high-potential side of the ramp, in the "beam" region, an unstable electron beam is seen for roughly another 10 Debye lengths along B. The electron beam is rapidly stabilized by intense electrostatic waves and nonlinear structures interpreted as electron phase-space holes. The "wave" region is physically separated from the ramp by the beam region. Numerical simulations reproduce a similar ramp structure, beam region, electrostatic turbulence region and plasma characteristics as seen in the observations. These results suggest that large double layers can account for the parallel electric field in the downward current region and that intense electrostatic turbulence rapidly stabilizes the accelerated electron distributions. These results also demonstrate that parallel electric fields are directly associated with the generation of large-amplitude electron phase-space holes and plasma waves.

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