Electrokinetic Dispersion in Field Amplified Sample Stacking

2018 ◽  
Author(s):  
Kaushlendra Dubey ◽  
Amit Gupta ◽  
Supreet Singh Bahga
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Body Force ◽  
Vital Role ◽  
Scaling Analysis ◽  
Unstable Flow ◽  
Sample Stacking ◽  
Concentration Enhancement ◽  
High Electric Fields ◽  
Conductivity Gradient

In this work, we performed an experimental study of electrohydrodynamic effects on the dispersion of sample ions in field amplified sample stacking (FASS). A typical FASS experiment involves a streamwise electrical conductivity gradient collinear to the applied electric field to enhance the sample stacking. Earlier studies on FASS have focused on how the conductivity gradient sets a non-uniform electro-osmotic flow which causes the dispersion. However, the coupling of the electric field with conductivity gradient leads to a destabilizing electric body force and generates unstable flow. This work demonstrates that generated body force influences the dynamics of FASS. We present a scaling analysis to show that at high fields, electrohydrodynamic effects play a vital role in sample dispersion. To justify our scaling arguments, we performed experiments at varied electric fields which shows that at high electric fields maximum concentration enhancement is lowered significantly. To ensure the EHD effects on the dynamics of FASS, we have also performed experiments with suppressed EOF conditions.

scholarly journals Dynamics of Field Amplified Sample Stacking

2001 ◽  
Author(s):  
Rajiv Bharadwaj ◽  
Juan G. Santiago
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Concentration Field ◽  
Initial Step ◽  
Step Function ◽  
Buffer Concentration ◽  
Sample Stacking ◽  
Sample Concentration ◽  
Concentration Enhancement ◽  
Channel Configuration

Abstract We present an analysis and an experimental study of field amplified sample stacking. The analysis consists of a one dimensional, unsteady electromigration model of the concentration fields in sample stacking. The model predicts that the sample concentration develops as a non-linear concentration wave with a peak concentration increasing with time that reaches a maximum value determined by ratio of electric fields in the sample and the buffer region. The experimental work is a preliminary study of the effects of electroosmotic flow on sample stacking for a single fluid-fluid interface within a glass microchannel. Using a simple cross-channel configuration a high-gradient initial step-function in the buffer concentration field was established which causes an unsteady sample concentration process. The experimental results qualitatively confirm the wave-like profile of the stacked analyte predicted by the analytical model. Experiments also provide evidence of internal pressure generation due to mis-matched electroosmotic velocities during stacking. The effect of electric field strength and sample-to-background buffer concentration ratio, γ, are also presented. Stacked sample concentration at γ = 4 is found to initially increase with increasing electric field but saturates at higher electric fields. Stacking rates at higher γ ratios indicate that concentration enhancement is quickly limited by dispersion due to internally generated pressure gradients.

Electrokinetic instability due to streamwise conductivity gradients in microchip electrophoresis

2021 ◽  
Vol 925 ◽  
Author(s):  
Kaushlendra Dubey ◽  
Sanjeev Sanghi ◽  
Amit Gupta ◽  
Supreet Singh Bahga
Keyword(s):  
Electric Field ◽  
Numerical Simulations ◽  
Electric Fields ◽  
Quantitative Measure ◽  
Underlying Mechanism ◽  
Scaling Analysis ◽  
Recirculating Flow ◽  
Electrokinetic Instability ◽  
Spatial Features ◽  
Proper Orthogonal Decomposition Technique

We present an experimental and numerical investigation of electrokinetic instability (EKI) in microchannel flow with streamwise conductivity gradients, such as those observed during sample stacking in capillary electrophoresis. A plug of a low-conductivity electrolyte solution is initially sandwiched between two high-conductivity zones in a microchannel. This spatial conductivity gradient is subjected to an external electric field applied along the microchannel axis, and for sufficiently strong electric fields an instability sets in. We have explored the physics of this EKI through experiments and numerical simulations, and supplemented the results using scaling analysis. We performed EKI experiments at different electric field values and visualised the flow using a passive fluorescent tracer. The experimental data were analysed using the proper orthogonal decomposition technique to obtain a quantitative measure of the threshold electric field for the onset of instability, along with the corresponding coherent structures. To elucidate the physical mechanism underlying the instability, we performed high-resolution numerical simulations of ion transport coupled with fluid flow driven by the electric body force. Simulations reveal that the non-uniform electroosmotic flow due to axially varying conductivity field causes a recirculating flow within the low-conductivity region, and creates a new configuration wherein the local conductivity gradients are orthogonal to the applied electric field. This configuration leads to EKI above a threshold electric field. The spatial features of the instability predicted by the simulations and the threshold electric field are in good agreement with the experimental observations and provide useful insight into the underlying mechanism of instability.

Effect of a High Electric Field on the Thermal and Phase Change Characteristics of an Impacting Drop

2019 ◽  
Author(s):  
Abhishek Basavanna ◽  
Prajakta Khapekar ◽  
Navdeep Singh Dhillon
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Phase Change ◽  
Electric Fields ◽  
High Speed ◽  
Impact Behavior ◽  
Liquid Drops ◽  
Active Interest ◽  
Post Impact ◽  
High Electric Fields

Abstract The effect of applied electric fields on the behavior of liquids and their interaction with solid surfaces has been a topic of active interest for many decades. This has important implications in phase change heat transfer processes such as evaporation, boiling, and condensation. Although the effect of low to moderate voltages has been studied, there is a need to explore the interaction of high electric fields with liquid drops and bubbles, and their effect on heat transfer and phase change. In this study, we employ a high speed optical camera to study the dynamics of a liquid drop impacting a hot substrate under the application of high electric fields. Experimental results indicate a significant change in the pre- and post-impact behavior of the drop. Prior to impact, the applied electric field elongates the drop in the direction of the electric field. Post-impact, the recoil phase of the drop is significantly affected by charging effects. Further, a significant amount of micro-droplet ejection is observed with an increase in the applied voltage.

OBIC Analysis of Different Edge Terminations of Planar 1.6 kV 4H-SiC Diodes

2007 ◽  
Vol 556-557 ◽  
pp. 1007-1010 ◽  
Author(s):  
Christophe Raynaud ◽  
Daniel Loup ◽  
Phillippe Godignon ◽  
Raul Perez Rodriguez ◽  
Dominique Tournier ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Breakdown Voltage ◽  
High Voltage ◽  
Semiconductor Devices ◽  
Optical Beam ◽  
Induced Current ◽  
Bipolar Diodes ◽  
High Electric Fields ◽  
Optical Beam Induced Current

High voltage SiC semiconductor devices have been successfully fabricated and some of them are commercially available [1]. To achieve experimental breakdown voltage values as close as possible to the theoretical value, i.e. value of the theoretical semi-infinite diode, it is necessary to protect the periphery of the devices against premature breakdown due to locally high electric fields. Mesa structures and junction termination extension (JTE) as well as guard rings, and combinations of these techniques, have been successfully employed. Each of them has particular drawbacks. Especially, JTE are difficult to optimize in terms of impurity dose to implant, as well as in terms of geometric dimensions. This paper is a study of the spreading of the electric field at the edge of bipolar diodes protected by JTE and field rings, by optical beam induced current.

Calculations of Some Transport Coefficients in Simple Semiconductors at Low Temperatures and High Electric Fields

1971 ◽  
Vol 49 (7) ◽  
pp. 876-880 ◽  
Author(s):  
Jyoti Kamal ◽  
Satish Sharma
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Low Temperatures ◽  
Transport Coefficients ◽  
Drift Mobility ◽  
Temperature Dependent ◽  
Hall Constant ◽  
The Difference ◽  
High Electric Fields ◽  
Model Semiconductor

In this paper the authors have calculated Hall mobility, drift mobility, and Hall constant for a non-degenerate simple model semiconductor at low temperatures for an arbitrary electric field strength. Following Paranjape the modified distribution of phonons has been taken into account. The difference between the calculations of transport coefficients made by taking into account the modified phonon distribution and by not taking it into account is quite appreciable at high electric field. Calculations also show that for Ne = 1016/cm3 the mobility of electrons remains temperature dependent.

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 Corona at Large Coated Electrodes

2018 ◽  
Author(s):  
Mats Larsson ◽  
Olof Hjortstam ◽  
Håkan Faleke ◽  
Liliana Arevalo ◽  
Dong Wu ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Negative Polarity ◽  
Electrode Geometry ◽  
Positive Polarity ◽  
Electrical Fields ◽  
Insulating Material ◽  
Air Gaps ◽  
High Electric Fields ◽  
Coated Electrodes

<p>In geometries relevant form HVDC applications where large electrodes and large air gaps are utilized, the observed corona can be quite different from geometries studied in the literature where needles or wires are used as high voltage electrodes. Corona discharges at large electrodes often initiates when the electric field on the electrode surface appears lower than the critical electric field strength, 2.4 kV/mm. Surface contamination of the electrode has been pointed out as the reason for such discharge events. Our experimental results indicate that one possible way to prevent such corona is to coat the electrode with an insulating material, such as epoxy or oxide layers. It seems that the layer separates any corona inducing particle from the electrode, which in turn hinders the corona to form. However, as the layer breaks down and gets punctured, the corona preventing propertied disappears and corona forms easily. We conclude that as long as the layer doesn’t get punctured, coating electrodes with insulating material is preventing corona to initiate at electrical fields below the critical electric field, as given by the electrode geometry. In contrast to positive polarity, for negative polarity the epoxy coating could withstand high electric fields without breaking down.</p>

Driftgeschwindigkeit und Beweglichkeit von Elektronen in Silicium bei 4,2 °K in Abhängigkeit vom elektrischen Feld / Driftvelocity and Mobility of Electrons in Silicon at 4.2 °K in Dependence of Electric Field

1972 ◽  
Vol 27 (1) ◽  
pp. 26-30
Author(s):  
P. Deimel
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Silicon Surface ◽  
Surface Barrier ◽  
Surface Barrier Detector ◽  
Direct Information ◽  
Fully Depleted ◽  
Barrier Detector ◽  
High Electric Fields ◽  
Silicon Surface Barrier Detector

Abstract The pulse rise times of an n-type silicon surface barrier detector were measured at 4.2 °K. At this temperature the detector was fully depleted even at very low bias and the measured pulse rise times gave direct information about the driftvelocity and the mobility. Instead of E-0.5, an E-0.8 dependence of the mobility at moderate electric fields was found. At high electric fields agreement exists with theory.

Magnitude of Intrinsic Electrocaloric Effect in Pb(Zr1-xTix)O3 at High Electric Fields

2013 ◽  
Vol 700 ◽  
pp. 7-10
Author(s):  
Wen Jiang Feng ◽  
Zhi Guo Zhang ◽  
Chuang Wu ◽  
Hao Chen
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Structural Transition ◽  
Strong Electric Field ◽  
Zero Field ◽  
Electrocaloric Effect ◽  
Structure Transition ◽  
First Order ◽  
High Electric Fields ◽  
Curie Temperatures

The structure transition and electrocaloric effect in PbZr1-xTixO3withx=0.5 and 0.6 were MV/m can make the structural transition be a continuous one. In addition, whenx=0.5 and 0.6 at the zero field, the first order structural transition occurs atT0=665 and 691 K, respectively. The first order structural transition comes to the second one upon the strong electric field, which leads to lower the change of specific hea. The structural transition temperature is shifted at high temperature with increasing electric field. The maximum electrocaloric effect is present at about 200 K above their corresponding Curie temperatures.

Moleküldissoziation durch hohe elektrische Felder

1964 ◽  
Vol 19 (1) ◽  
pp. 71-83 ◽  
Author(s):  
H. D. Beckey
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Charge Ratio ◽  
Mass Spectrometers ◽  
Basic Model ◽  
Internal Interaction ◽  
High Electric Fields ◽  
Very High ◽  
Field Dissociation ◽  
Positively Charged

It has been shown by different experiments using field ion mass spectrometers that molecules may be dissociated by very high electric fields (several 107 - 108 V/cm) immediately after field ionization. The large variety of field dissociation processes observed in field ion mass spectrometers is treated systematically. This is done by assuming a basic model underlying the effect of field dissociation. The rules derived from the model are confirmed experimentally by the field ion mass spectra of homologous series of organic substances.After derivation of the model it is shown that field dissociation of organic ions is dependent on factors such as: Charge distribution in the molecule rearranged by the electric field, interaction of the positively charged parts of the molecule with the external electric field, internal interaction of the field dissociating parts of the molecule.Each of these main factors in turn is dependent on further factors which will be discussed, the most important ones being the mass to charge ratio and the electronic structure of both the field ionized molecule and the subsequently formed fragments.

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