scholarly journals Rapid AC Electrokinetic Micromixer with Electrically Conductive Sidewalls

Micromachines ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 34
Author(s):  
Fang Yang ◽  
Wei Zhao ◽  
Cuifang Kuang ◽  
Guiren Wang
Keyword(s):  
Electric Field ◽  
Transverse Direction ◽  
Flow Direction ◽  
Conductivity Ratio ◽  
Mixing Length ◽  
Electrically Conductive ◽  
Electrokinetic Phenomena ◽  
Two Fluids ◽  
Conductivity Gradient ◽  
Lower Voltage

We report a quasi T-channel electrokinetics-based micromixer with electrically conductive sidewalls, where the electric field is in the transverse direction of the flow and parallel to the conductivity gradient at the interface between two fluids to be mixed. Mixing results are first compared with another widely studied micromixer configuration, where electrodes are located at the inlet and outlet of the channel with electric field parallel to bulk flow direction but orthogonal to the conductivity gradient at the interface between the two fluids to be mixed. Faster mixing is achieved in the micromixer with conductive sidewalls. Effects of Re numbers, applied AC voltage and frequency, and conductivity ratio of the two fluids to be mixed on mixing results were investigated. The results reveal that the mixing length becomes shorter with low Re number and mixing with increased voltage and decreased frequency. Higher conductivity ratio leads to stronger mixing result. It was also found that, under low conductivity ratio, compared with the case where electrodes are located at the end of the channel, the conductive sidewalls can generate fast mixing at much lower voltage, higher frequency, and lower conductivity ratio. The study of this micromixer could broaden our understanding of electrokinetic phenomena and provide new tools for sample preparation in applications such as organ-on-a-chip where fast mixing is required.

scholarly journals Численное моделирование субнаносекундного лавинного переключения кремниевых n-=SUP=-+-=/SUP=--n-n-=SUP=-+-=/SUP=--структур

2019 ◽  
Vol 53 (3) ◽  
pp. 401
Author(s):  
Н.И. Подольская ◽  
П.Б. Родин
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Voltage Pulse ◽  
Transverse Direction ◽  
Current Flow ◽  
Impact Ionization ◽  
Switching Time ◽  
Flow Direction ◽  
Initial Voltage ◽  
Simulation Results

AbstractThe simulations of recently discovered effect of subnanosecond avalanche switching of Si n ^+− n − n ^+-structures have been performed. The electric field in n ^+− n − n ^+-structure is shown to remain quasi-uniform along the current flow direction during the voltage rise stage and it reaches the effective threshold of impact ionization of ~200 kV/cm in the whole n-base. Comparing simulation results with experiments we argue that the field distribution is as well uniform in the transverse direction. Hense, the ultrafast avalanche transient develops quasi-uniformly in the whole n-base volume. The switching time is about ~150 ps. We compare numerical results obtained for various impact ionization models and estimate parameters of the initial voltage pulse that are required for ultrafast avalanche switching of n ^+− n − n ^+-structures.

Focusing of Proteins in a Horseshoe Microchannel

2008 ◽  
Author(s):  
Jaesool Shim ◽  
Prashanta Dutta ◽  
Cornelius F. Ivory
Keyword(s):  
Capillary Electrophoresis ◽  
Electric Field ◽  
Isoelectric Focusing ◽  
Ph Gradient ◽  
Complex Geometries ◽  
Electrokinetic Phenomena ◽  
Double Peaks ◽  
Zone Electrophoresis ◽  
Carrier Ampholytes ◽  
Ph Range

Ampholyte based isoelectric focusing (IEF) simulation was conducted to study dispersion of proteins in a horseshoe microchannel. Four model proteins (pls = 6.49, 7.1, 7.93 and 8.6) are focused in a 1 cm long horseshoe channel under an electric field of 300 V/cm. The pH gradient is formed in the presence of 25 biprotic carrier ampholytes (ΔpK = 3.0) within a pH range of 6 to 9. The proteins are focused at 380 sec in a nominal electric field of 300 V/cm. Our numerical results show that the band dispersions of a protein are large during the marching stage, but the dispersions are significantly reduced when the double peaks start to merge. This rearrangement of spreading band is very unique compared to linear electrokinetic phenomena (capillary electrophoresis, zone electrophoresis or electroosmosis) and is independent of channel position and channel shape. Hence, one can perform IEF in complex geometries without incorporating hyperturns.

A Planar Labyrinth Micromixer

2010 ◽  
Author(s):  
Jeremy T. Cogswell ◽  
Peng Li ◽  
Mohammad Faghri
Keyword(s):  
Soft Lithography ◽  
Lab On A Chip ◽  
Fluorescein Isothiocyanate ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Mixing Length ◽  
Two Fluids ◽  
Curved Channels ◽  
Passive Mixing ◽  
Important Challenge

Rapid mixing of two fluids in microchannels has posed an important challenge to the development of many integrated lab-on-a-chip systems. In this paper, we present a planar labyrinth micromixer (PLM) to achieve rapid and passive mixing by taking advantage of a synergistic combination of the Dean vortices in curved channels, a series of perturbation to the fluids from the sharp turns, and an expansion and contraction of the flow field via a circular chamber. The PLM is constructed in a single soft lithography step and the labyrinth has a footprint of 7.32 mm × 7.32 mm. Experiments using fluorescein isothiocyanate solutions and deionized water demonstrate that the design achieves fast and uniform mixing within 9.8 s to 32 ms for Reynolds numbers between 2.5 and 30. Compared to the mixing in the prevalent serpentine design, our design results in 38% and 79% improvements on the mixing efficiency at Re = 5 and Re = 30 respectively. An inverse relationship between mixing length and mass transfer Pe´clet number (Pe) is observed, which is superior to the logarithmic dependence of mixing length on Pe in chaotic mixers. Having a simple planar structure, the PLM can be easily integrated into lab-on-a-chip devices where passive mixing is needed.

scholarly journals Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability

2013 ◽  
Vol 31 (9) ◽  
pp. 1535-1541 ◽  
Author(s):  
K.-I. Nishikawa ◽  
P. Hardee ◽  
B. Zhang ◽  
I. Duţan ◽  
M. Medvedev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Magnetic Fields ◽  
Electric Field ◽  
Flow Direction ◽  
Transverse Magnetic ◽  
Velocity Shear ◽  
Helmholtz Instability ◽  
Magnetic Field Generation ◽  
Relativistic Jet

Abstract. We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin–Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin–Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (γj = 1.5) is larger than for a relativistic jet case (γj = 15).

MEASUREMENT OF LEAKAGE CURRENTS AND QUASI-STATIONARY ELECTRIC FIELD IN THE SURFACE AREA OF THE ISS RS IN THE EARTH'S IONOSPHERE

2021 ◽  
pp. 5-21
Author(s):  
Yury V. LISAKOV ◽  
Olga V. LAPSHINOVA ◽  
Nikolay M. PUSHKIN ◽  
Viktor P. KONOSHENKO ◽  
Nikolay V. MATVEEV ◽  
...  
Keyword(s):  
Electric Field ◽  
Spatial Configuration ◽  
Flow Direction ◽  
Electrical Measurements ◽  
Leakage Currents ◽  
Current Leakage ◽  
Stationary Electric Field ◽  
Charged Component ◽  
Stage 1 ◽  
Orbital Data

The paper presents the results of analysis of electrical measurements performed in the space experiment "Impulse (stage 1)" on the Service module of the ISS RS. This experiment investigated the effects of the interaction of the charged component of the ionosphere to the surface of large KA, which is the ISS. This paper analyses the measurement of quasi-stationary electric field and current leakage, was, respectively, sensors of the vibration type and flat probes from the Complex control electrophysical parameters (CCEP), developed by SPJ MT. To study the dependence of measurements from the ionosphere flow direction to the surface of the ISS RS was installed two sets of sensors with the direction of the angle of "visibility" in the Nadir (towards the Earth) and to "satellite footprint " (against the velocity vector of the ISS). Carried out analysis of common regularities measurements depending on the sun-shadow environment on orbit ISS motions and depending on current geophysical dynamics of the ionosphere. Massive the measurements including more than 170 telemetric sessions were analyzed. More than 11000 hours of measurements current of leakage (or runoff current) and measurements of quasi-stationary electric field with discretization 1s and UT binding to each point were analysed. The data measurements, geophysical and orbital data were collected in an electronic album. It is shown that experimental data correlate with the crossing time of the ISS boundaries known geophysical structures: the noon Meridian, the Main ionospheric failure (MIF), the boundaries diffuse intrusion (BDI), the Equatorial Geomagnetic anomaly (EA). In this regard, despite the specificity of the ISS (the spacecraft super big sizes, the most complex spatial configuration) similar measurements, nevertheless, are quite suitable for monitoring researches of some features of an ionosphere at the level of F2 layer with a temporary scale from 1s and can be used for more detailed study of the geophysical structures and related effects in the ionosphere. In addition, the results obtained can be used for the analysis of disturbances of electromagnetic conditions near the surface of the ISS RS, for monitoring potential and currents of leakage on the surface of the ISS. Keywords: electrophysical measurements, sensors of the vibration type, flat probes, electric field, current leakage, geophysical structure, ionosphere

QUANTITATIVE EVALUATION OF FORMATION PERMEABILITY FROM ACOUSTIC AND ELECTRIC STONELEY WAVES

2010 ◽  
Vol 02 (03) ◽  
pp. 585-615 ◽  
Author(s):  
BORIS D. PLYSHCHENKOV ◽  
ANATOLY A. NIKITIN
Keyword(s):  
Electric Field ◽  
Quantitative Evaluation ◽  
Pressure Field ◽  
Plane Waves ◽  
Stoneley Wave ◽  
Axial Component ◽  
Electrokinetic Phenomena ◽  
Stoneley Waves ◽  
Complex Valued ◽  
Analytical Expressions

Numerical experiments based on Pride's model of electrokinetic phenomena have shown that electromagnetic Stoneley waves as well as pressure Stoneley waves are most sensitive to permeability variations. A new way for quantitative evaluation of any value of formation permeability is presented. It is based on simultaneous measurement of pressure field and axial component of electric field excited by an acoustic source in fluid-filled borehole with help from a set of receivers in borehole. Frequency dependence of ratio of the complex-valued amplitudes of the electric Stoneley wave to the pressure Stoneley wave obtained as a result of plane waves decomposition of pressure field and mentioned component of electric field carries important information about permeability. The ratio of the real part of this ratio to its imaginary part is very sensitive to permeability variations. The approximate analytical expressions for this ratio derived for open and sealed pores on borehole wall are base for construction of a new way of quantitative evaluation of formation permeability.

scholarly journals Three-Dimensional Couette Flow of a Second-Grade Fluid Along Periodic Injection/Suction

Coatings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 553 ◽  
Author(s):  
Muhammad Afzal Rana ◽  
Yasar Ali ◽  
Babar Ahmad ◽  
Muhammad Touseef Afzal Rana
Keyword(s):  
Transverse Direction ◽  
Flow Direction ◽  
Three Dimensional ◽  
Analytic Solutions ◽  
Main Flow ◽  
Second Grade ◽  
Second Grade Fluid ◽  
Suction Velocity ◽  
Grade Fluid ◽  
Main Flow Direction

This work explores the three-dimensional laminar flow of an incompressible second-grade fluid between two parallel infinite plates. The assumed suction velocity comprises a basic steady dispersal with a superimposed weak transversally fluctuating distribution. Because of variation of suction velocity in transverse direction on the wall, the problem turns out to be three-dimensional. Analytic solutions for velocity field, pressure and skin friction are presented and effects of dimensionless parameters emerging in the model are discussed. It is observed that the non-Newtonian parameter plays dynamic part to rheostat the velocity component along main flow direction.

STUDY ON ELECTROHYDRODYNAMIC CAPILLARY INSTABILITY OF VISCOELASTIC FLUIDS IN PRESENCE OF AXIAL ELECTRIC FIELD

2012 ◽  
Vol 04 (03) ◽  
pp. 1250027 ◽  
Author(s):  
D. K. TIWARI ◽  
MUKESH KUMAR AWASTHI ◽  
G. S. AGRAWAL
Keyword(s):  
Electric Field ◽  
Flow Analysis ◽  
Critical Value ◽  
Deborah Number ◽  
Wave Number ◽  
Conductivity Ratio ◽  
Ohnesorge Number ◽  
Capillary Instability ◽  
Axial Electric Field ◽  
Linear Viscoelastic

Linear viscoelastic potential flow analysis of capillary instability in presence of axial electric field has been studied. A dispersion relation is derived for the case of axially imposed electric field and stability is discussed in terms of various parameters such as electric field, Deborah number, Ohnesorge number, permittivity ratio and conductivity ratio etc. Stability criterion is given in the terms of critical value of wave number as well as critical value of applied electric field. The system is unstable when electric field is less than the critical value of electric field, otherwise it is stable. It has been found that in presence of the electric field the growth rates for viscoelastic fluid are higher than viscous fluid. Various graphs have been plotted for growth rate and critical electric field.

Spectral Method for Analyzing Motions of Ellis Fluid Over Corrugated Boundaries

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
M. Fazel Bakhsheshi ◽  
J. M. Floryan ◽  
P. N. Kaloni
Keyword(s):  
Boundary Conditions ◽  
Spectral Method ◽  
Transverse Direction ◽  
Flow Direction ◽  
Immersed Boundary ◽  
Computational Domain ◽  
Physical Domain ◽  
Planar Channel ◽  
Spectral Accuracy ◽  
Fourier Expansions

A spectral method for solving the steady flow of a shear-thinning Ellis fluid is discussed for the case of a planar channel with corrugated boundaries. Polynomial approximations are employed for the velocity and viscosity distributions in the regions around singularities. The proposed algorithm employs a fixed computational domain with the physical domain of interest submerged inside the computational domain. The flow boundary conditions are imposed using the concept of immersed boundary conditions. The method, thus, eliminates the need for grid generation. The algorithm relies on Fourier expansions in the flow direction and Chebyshev expansions in the transverse direction. Various tests confirm spectral accuracy of the algorithm.

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