Fluid Mixing Control Inside a Y-Shaped Microchannel by Using Electrokinetic Instability

2007 ◽  
Author(s):  
Zheyan Jin ◽  
Hui Hu
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Fluid Mixing ◽  
Critical Voltage ◽  
Mixing Efficiency ◽  
Mixing Process ◽  
Static Electric Field ◽  
Electrokinetic Instability ◽  
Mixing Control ◽  
Static Electric Fields

An experimental study was conducted to further our understanding about the fundamental physics of electrokinetic instability (EKI) and to explore the effectiveness to enhance fluid mixing inside a Y-shaped microchannel by manipulating convective EKI waves. The dependence of the critical voltage of applied static electric field to trig EKI to generate convective EKI waves on the conductivity ratio of the two adjacent streams was quantified at first. The effect of the strength of the applied static electric field on the evolution of the convective EKI waves and fluid mixing process were assessed in terms of scalar concentration fields, shedding frequency of the convective EKI waves and scalar mixing efficiency. The effectiveness of manipulating the convective EKI waves by introducing alternative electric perturbations to the applied static electric fields was also explored for the further enhancement of the fluid mixing process inside the Y-shaped microchannel.

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.

Electrokinetic Instability Flow in Nanofilm-Coated Microfluidic Channels

2009 ◽  
Vol 60-61 ◽  
pp. 330-333
Author(s):  
Wei Chih Chen ◽  
Ting Fu Hong ◽  
Wen Bo Luo ◽  
Chang Hsien Tai ◽  
Chien Hsiung Tsai ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Flow Instability ◽  
Microfluidic Channels ◽  
Conductivity Ratio ◽  
Electrokinetic Instability ◽  
Two Samples ◽  
Significant Difference

This paper presented a parametric experimental study of electrokinetic instability phenomena in a cross-shaped configuration microfluidic device with varying channel depths and conductivity ratios. The flow instability is observed when applied electric field strength exceeds a certain critical value. The critical electric field strength is examined as a function of the conductivity ratio of two samples liquid, microchannel depth, and the treatment of microchannel wetted surface. It is found that the critical electric field strengths for the onset of electrokinetic instability are strongly dependent on the conductivity ratio of two samples liquid, and decrease as the channel depths increasing of microfluidic devices. In the present study, the surface inside microchannels is treated utilizing hydrophilic and hydrophobic organic-based SOG (spin-on-glass) nanofilms for glass-based microchips. The experimental results indicate that no significant difference for the critical electric fields for the onset of electrokinetic instability phenomena in both hydrophilic and hydrophobic SOG coating in the surface of microchannels. The critical electric fields for the onset of electrokinetic instability phenomena are slightly lower in both SOG coated cases in compare with that of the non-coated microchannel.

scholarly journals Fluid Mixing Control Inside a Y-shaped Microchannel by Using Electrokinetic Instability

2008 ◽  
Vol 3 (2) ◽  
pp. 260-273 ◽  
Author(s):  
Hui HU ◽  
Zheyan JIN ◽  
Abdulilah DAWOUD ◽  
Ryszard JANKOWIAK
Keyword(s):  
Fluid Mixing ◽  
Electrokinetic Instability ◽  
Mixing Control

scholarly journals Electric field assisted alignment of monoatomic carbon chains

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Stella Kutrovskaya ◽  
Igor Chestnov ◽  
Anton Osipov ◽  
Vlad Samyshkin ◽  
Irina Sapegina ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
X Ray Diffraction ◽  
Laser Ablation Process ◽  
Carbon Chains ◽  
High Resolution Tem ◽  
The Difference ◽  
A Chain ◽  
Quasi Crystals ◽  
Static Electric Fields

Abstract We stabilize monoatomic carbon chains in water by attaching them to gold nanoparticles (NPs) by means of the laser ablation process. Resulting nanoobjects represent pairs of NPs connected by multiple straight carbon chains of several nanometer lengths. If NPs at the opposite ends of a chain differ in size, the structure acquires a dipole moment due to the difference in work functions of the two NPs. We take advantage of the dipole polarisation of carbon chains for ordering them by the external electric field. We deposit them on a glass substrate by the sputtering method in the presence of static electric fields of magnitudes up to 105 V/m. The formation of one-dimensional carbyne quasi-crystals deposited on a substrate is evidenced by high-resolution TEM and X-ray diffraction measurements. The original kinetic model describing the dynamics of ballistically flowing nano-dipoles reproduces the experimental diagram of orientation of the deposited chains.

TWO-PHOTON-ABSORPTION SPECTRA OF QUANTUM-WELL EXCITONS IN STATIC ELECTRIC FIELDS

1991 ◽  
Vol 05 (17) ◽  
pp. 1133-1138
Author(s):  
KAZUHITO FUJII ◽  
AKIRA SHIMIZU ◽  
JOHAN BERGQUIST ◽  
SOTOMITSU IKEDA ◽  
TAKESHI SAWADA
Keyword(s):  
Electric Field ◽  
Quantum Well ◽  
Absorption Spectra ◽  
Electric Fields ◽  
Band Gap Energy ◽  
Photon Absorption ◽  
Static Electric Field ◽  
Quantum Well Structures ◽  
Two Photon Absorption ◽  
Two Photon

We have measured two-photon-absorption spectra of GaAs/Al 0.4 Ga 0.6 As quantum-well structures in a static electric field for photon energies near half the band gap energy, and found drastic field-induced-changes in the spectra. The two-photon-absorption peak at half the energy of the lowest light-hole exciton is induced by the static electric field normal to the quantum well layers, in agreement with a theory that takes account of quasi-two-dimensional exciton effects. With increasing the electric field, however, this peak grows more drastically than the theoretical prediction, and it approaches a large value predicted by another simplified theory based on a two-level model.

scholarly journals Body Water-Mediated Conductivity Actualizes the Insect-Control Functions of Electric Fields in Houseflies

Insects ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 561 ◽  
Author(s):  
Yoshihiro Takikawa ◽  
Takeshi Takami ◽  
Koji Kakutani
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Arc Discharge ◽  
Body Water ◽  
The Body ◽  
Static Electric Field ◽  
Free Electrons ◽  
Water Conductivity ◽  
Control Functions ◽  
Negative Pole

In the present study, the relationship between body water loss and conductivity was examined in adult houseflies (Musca domestica). The events an insect experiences in an electric field are caused by the conductive nature of the insect body (i.e., movement of electricity within or its release from the insect). After houseflies were dehydrated, rehydrated, refrigerated, and frozen and thawed, they were placed in static and dynamic electric fields. Untreated houseflies were deprived of their free electrons to become positively charged and then attracted to the insulated negative pole in the static electric field and were exposed to corona and arc discharge from non-insulated negative pole in the dynamic electric field. There was no current in the bodies of dehydrated and frozen flies; hence, there was no attractive force or discharge exposure. In the remaining insects, the results were identical to those in the untreated control insects. These results indicated that the reduction of body water conductivity inhibited the release of electricity from the body in the static electric field and the discharge-mediated current flow through the body in the dynamic electric field. The insect was affected by the electric fields because of its conductivity mediated by body water.

scholarly journals Quasi-static electric fields phenomena in the ionosphere associated with pre- and post earthquake effects

2008 ◽  
Vol 8 (1) ◽  
pp. 101-107 ◽  
Author(s):  
M. Gousheva ◽  
D. Danov ◽  
P. Hristov ◽  
M. Matova
Keyword(s):  
Pacific Ocean ◽  
Electric Field ◽  
Electric Fields ◽  
Seismic Data ◽  
Seismic Activity ◽  
Vertical Component ◽  
Satellite Orbits ◽  
Static Electric Field ◽  
Earthquake Zone ◽  
Earthquake Effects

Abstract. To prove a direct relationship between the quasi-static electric field disturbances and seismic activity is a difficult, but actual task of the modern ionosphere physics. This paper presents new results on the processing and analysis of the quasi-static electric field in the upper ionosphere (h=800–900 km) observed from the satellite INTERCOSMOS-BULGARIA-1300 over earthquakes' source regions (seismic data of World Data Center, Denver, Colorado, USA). Present research focuses on three main areas (i) development of methodology of satellite and seismic data selecting, (ii) data processing and observations of the quasi-static electric field (iii) study and accumulation of statistics of possible connection between anomalous vertical electric fields penetrating from the earthquake zone into the ionosphere, and seismic activity. The most appropriate data (for satellite orbits above sources of forthcoming or just happened seismic events) have been selected from more than 250 investigated cases.The increase of about 5-10-15 mV/m in the vertical component of the quasi-static electric field observed by INTERCOSMOS-BULGARIA-1300 during seismic activity over Southern Ocean, Greenland Sea, South-Weat Pacific Ocean, Indian Ocean, Central America, South-East Pacific Ocean, Malay Archipelago regions are presented. These anomalies, as phenomena accompanying the seismogenic process, can be considered eventually as possible pre-, co- (coeval to) and post-earthquake effects in the ionosphere.

scholarly journals Controlling turbulent drag across electrolytes using electric fields

2017 ◽  
Vol 199 ◽  
pp. 159-173 ◽  
Author(s):  
Rodolfo Ostilla-Mónico ◽  
Alpha A. Lee
Keyword(s):  
Electric Field ◽  
Numerical Method ◽  
Electric Fields ◽  
Planck Equation ◽  
Transition To Turbulence ◽  
Navier Stokes ◽  
Hydrodynamic Friction ◽  
Turbulent Drag ◽  
In Operando ◽  
Static Electric Fields

Reversible in operando control of friction is an unsolved challenge that is crucial to industrial tribology. Recent studies show that at low sliding velocities, this control can be achieved by applying an electric field across electrolyte lubricants. However, the phenomenology at high sliding velocities is yet unknown. In this paper, we investigate the hydrodynamic friction across electrolytes under shear beyond the transition to turbulence. We develop a novel, highly parallelised numerical method for solving the coupled Navier–Stokes Poisson–Nernst–Planck equation. Our results show that turbulent drag cannot be controlled across dilute electrolytes using static electric fields alone. The limitations of the Poisson–Nernst–Planck formalism hint at ways in which turbulent drag could be controlled using electric fields.

Spontaneous electric fields in solid carbon monoxide

2015 ◽  
Vol 17 (44) ◽  
pp. 30177-30187 ◽  
Author(s):  
Jérôme Lasne ◽  
Alexander Rosu-Finsen ◽  
Andrew Cassidy ◽  
Martin R. S. McCoustra ◽  
David Field
Keyword(s):  
Carbon Monoxide ◽  
Infrared Spectroscopy ◽  
Electric Field ◽  
Electric Fields ◽  
Solid Carbon ◽  
Static Electric Field ◽  
Reflection Absorption Infrared Spectroscopy

Reflection–absorption infrared spectroscopy (RAIRS) is shown to provide a means of observing the spontelectric phase of matter, the defining characteristic of which is the occurrence of a spontaneous and powerful static electric field within a film of material.

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