scholarly journals AC electrohydrodynamic Landau–Squire flows around a conducting nanotip

2021 ◽  
Vol 925 ◽  
Author(s):  
Jyun-An Chen ◽  
Touvia Miloh ◽  
Watchareeya Kaveevivitchai ◽  
Hsien-Hung Wei
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Flow Characteristics ◽  
Flow Speed ◽  
Jet Flows ◽  
Driving Voltage ◽  
Ac Electric Fields ◽  
Measured Speed ◽  
Experimental Findings ◽  
Conical Electrode

Utilizing the joint singular natures of electric field and hydrodynamic flow around a sharp nanotip, we report new electrohydrodynamic Landau–Squire-type flows under the actions of alternating current (AC) electric fields, markedly different from the classical Landau–Squire flow generated by pump discharge using nanotubes or nanopores. Making use of the locally diverging electric field prevailing near the conical tip, we are able to generate a diversity of AC electrohydrodynamic flows with the signature of a 1/r point-force-like decay at distance r from the tip. Specifically, we find AC electrothermal jet and Faradaic streaming out of the tip at applied frequencies in the MHz and 102 Hz regimes, respectively. Yet at intermediate frequencies of 1–100 kHz, the jet flow can be reversed to an AC electro-osmotic impinging flow. The characteristics of these AC jet flows are very distinct from AC flows over planar electrodes. For the AC electrothermal jet, we observe experimentally that its speed varies with the driving voltage V as V3, in contrast to the common V4 dependence according to the classical theory reported by Ramos et al. (J. Phys. D: Appl. Phys, vol. 31, 1998, pp. 2338–2353). Additionally, the flow speed does not increase with the solution conductivity as commonly thought. These experimental findings can be rationalized by means of local Joule heating and double layer charging mechanisms in such a way that the nanotip actually becomes a local hotspot charged with heated tangential currents. The measured speed of the AC Faradaic streaming is found to vary as V3/2 logV, which can be interpreted by the local Faradaic leakage in balance with tangential conduction. These unusual flow characteristics signify that a conical electrode geometry may fundamentally alter the features of AC electrohydrodynamic flows. Such peculiar electrohydrodynamic flows may also provide new avenues for expediting molecular sensing or sample transport in prevalent electrochemical or microfluidic applications.

Effect of Microstructure on Lifetime Performance of Barium Titanate Ceramics Under DC and AC Electric Fields

2010 ◽  
Author(s):  
Jay Shieh
Keyword(s):  
Fatigue Strength ◽  
Barium Titanate ◽  
Electric Field ◽  
Electric Fields ◽  
Time To Failure ◽  
Electrical Loading ◽  
Ac Electric Fields ◽  
Lifetime Performance ◽  
Weibull Statistical Analysis ◽  
Dc Electric Field

Bulk barium titanate (BaTiO3 ) ceramic specimens with bimodal microstructures are prepared and their dielectric and fatigue strengths are investigated under an alternating current (AC) electric field and a direct current (DC) electric field. It is found that under AC electrical loading, both the dielectric and fatigue strengths decrease with increasing amount of coarse abnormal grains. The scatter of the AC fatigue strength is characterized with the Weibull statistics. The extent of scatter of the AC fatigue strength data correlates strongly with the size distribution of the coarse grains. Such correlation is resulted from the presence of intrinsic defects within the microstructure. For DC electrical loading, the time to failure of the specimens with coarse abnormal grains is significantly shorter than the lifetimes of the specimens with only small normal grains. It is found that under a DC electric field of 6 MVm−1, the BaTiO3 specimens would fail within 200 h when abnormal grains are present in the microstructure. However, the lifetimes of the specimens containing abnormal grains vary significantly from one to another. The Weibull statistical analysis indicates that the amount of abnormal grains has little influence on the lifetime performance of bulk BaTiO3 ceramics under large DC electric fields. In most of the failed BaTiO3 specimens under DC electrical loading, regardless of their lifetimes, large through-thickness round holes with recrystallization features are present. A mixed failure mode consisting of avalanche and thermal breakdowns is proposed for the failed specimens.

Electric Conductance

1997 ◽  
Author(s):  
C. B. Li
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Colloidal Particles ◽  
Free Solution ◽  
Soil Particles ◽  
Electric Conductance ◽  
Variable Charge ◽  
Ac Electric Fields ◽  
The Difference ◽  
Variable Charge Soils

The migration of colloidal soil particles in an applied electric field has been discussed in Chapter 7. Soil particles carrying electric charges invariably adsorb equivalent amounts of ions of the opposite charge. Generally there is a certain amount of free ions present in soil solution. When an electric field is applied to a soil system, a phenomenon known as electric conductance occurs. As in the case for electrolyte solutions, soil particles and various ions interact with one another during their migration, and these interactions can affect the electric conductance of the system. Variable charge soils carry both positive and negative surface charges, and it can be expected that their interactions with various ions would be rather complicated during conductance. On the other hand, this makes the measurement of electric conductance an effective means in elucidating the mechanisms of interactions between variable charge soils and ions. Both direct-current (DC) electric fields and alternating-current (AC) electric fields can induce the migration of charged particles. In the latter case, the migration of these particles should be related to the frequency of the applied AC electric field. Therefore, in this chapter, after describing the principles of electric conductance of ions and colloids and the factors that affect the conductance of a soil, emphasis shall be placed on the interaction between variable charge soils and various ions as reflected by the frequency effect in electric conductance. For a colloidal suspension, the electric conductance may be regarded as the contribution of conductances of both charged colloidal particles and ions. These two parts may be called the electric conductance of colloidal panicles and the electric conductance of ions, respectively. However, in actual cases it is difficult to distinguish between these two parts. Therefore, it is a general practice to distinguish the electric conductance as that caused by colloidal particles plus their counterions from that caused by ions of the free solution. These may be called electric conductance of the colloid and electric conductance of the free solution. The former conductance is the difference between the electric conductance of the suspension and that of the free solution.

Dynamic Electromechanical Response of Multilayered Piezoelectric Composites From Room to Cryogenic Temperatures for Fuel Injector Applications

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Yasuhide Shindo ◽  
Takayoshi Sasakura ◽  
Fumio Narita
Keyword(s):  
Domain Wall ◽  
Electric Field ◽  
Electric Fields ◽  
Wall Motion ◽  
Domain Wall Motion ◽  
Cryogenic Temperatures ◽  
Fuel Injector ◽  
Temperature Dependent ◽  
Piezoelectric Composites ◽  
Ac Electric Fields

This paper studies the dynamic electromechanical response of multilayered piezoelectric composites under ac electric fields from room to cryogenic temperatures for fuel injector applications. A shift in the morphotropic phase boundary (MPB) between the tetragonal and rhombohedral/monoclinic phases with decreasing temperature was determined using a thermodynamic model, and the temperature dependent piezoelectric coefficients were obtained. Temperature dependent coercive electric field was also predicted based on the domain wall energy. A phenomenological model of domain wall motion was then used in a finite element computation, and the nonlinear electromechanical fields of the multilayered piezoelectric composites from room to cryogenic temperatures, due to the domain wall motion and shift in the MPB, were calculated. In addition, experimental results on the ac electric field induced strain were presented to validate the predictions.

Modeling of Nanoparticle-Mediated Electric Field Enhancement Inside Biological Cells Exposed to AC Electric Fields

2009 ◽  
Vol 48 (8) ◽  
pp. 087001 ◽  
Author(s):  
Pawan K. Tiwari ◽  
Sung Kil Kang ◽  
Gon Jun Kim ◽  
Jun Choi ◽  
A.-A. H. Mohamed ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Field Enhancement ◽  
Biological Cells ◽  
Electric Field Enhancement ◽  
Ac Electric Fields

UNDERSTANDING ELECTRIC INTERACTIONS IN SUSPENSIONS IN GRADIENT AC ELECTRIC FIELDS I: EXPERIMENTAL

2011 ◽  
Vol 25 (07) ◽  
pp. 919-925
Author(s):  
YAN SHEN ◽  
ZHIYONG QIU ◽  
SHIGERU TADA
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Corn Oil ◽  
Electrode Array ◽  
Ac Electric Fields ◽  
Ac Electric Field ◽  
Alpha Olefin ◽  
Dilute Suspensions ◽  
Spatially Periodic ◽  
Neutrally Buoyant

When neutrally buoyant poly alpha olefin particles in corn oil were exposed to a gradient ac electric field generated by a spatially periodic electrode array, these particles experienced the negative dielectrophoresis and instability in all the suspensions of concentration range from 0.01% to 5% (v/v). One critical particle concentration was experimentally determined as 1% (v/v) below which the particles in corn oil were segregated to form island-like structures in the lower electric field regions; and above which, particles only formed straight stripes. The island-like structure was suspended in the lowest electric field area. Specially designed experiments with a suspension of 1.126% (v/v) confirmed that there exists particle instability. Anisotropic properties of electric interactions are responsible for particle instability in all the suspensions of different concentrations and island-like structures were formed only in the dilute suspensions in which the particle instability has enough space to be developed.

Precise morphology control and fast merging of a complex multi-emulsion system: the effects of AC electric fields

Soft Matter ◽  
2019 ◽  
Vol 15 (28) ◽  
pp. 5614-5625 ◽  
Author(s):  
Yi Huang ◽  
Shuai Yin ◽  
Wen Han Chong ◽  
Teck Neng Wong ◽  
Kim Tiow Ooi
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Morphology Control ◽  
Emulsion System ◽  
Contact Type ◽  
Ac Electric Fields ◽  
Ac Electric Field

We showed a full morphology control over complex emulsions through an AC electric field by non-contact type of electrodes.

CONVERGING AND DIVERGING FLOW OF ELECTRORHEOLOGICAL FLUID IN MINUTE CHANNELS

2001 ◽  
Vol 15 (06n07) ◽  
pp. 723-730 ◽  
Author(s):  
TAKATSUNE NARUMI ◽  
TAKASHI HAYASHIBE ◽  
TOMIICHI HASEGAWA ◽  
YOSHINOBU ASAKO
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Flow Rate ◽  
Flow Direction ◽  
Particle Diameter ◽  
Flow Characteristics ◽  
Electrorheological Fluid ◽  
Rectangular Pulse ◽  
Parallel Channel ◽  
Converging Channel

We have examined ER effects in very small parallel and non-parallel gaps utilizing conventional ER suspensions. The flow rate reduction due to the electric field applied is measured as the ER effect for parallel, converging, diverging and combined channels. The test with the parallel channel under AC or rectangular pulse wave electric fields shows that the ER fluids are helpful for the flow rate control even in a narrow gap with the size about 10 times of particle diameter. In comparison between a converging channel and a diverging one, the former has advantages in magnitude and stability of ER effect. Moreover, the converging channel generates larger ER effect than that of the parallel channel with same flow characteristics under no electric field. It is considered that a small area with a higher electric field in the non-parallel channel makes it easy to control the flow rate. Further, the multiplier effect of the converging flow of particles and the increase in electric field along the flow direction generates a larger and stable ER effect. We have also examined with a combined converging and diverging channel and confirmed the similar enhancement in ER effect to the single converging one without the unsymmetrical ER effect due to the flow direction.

scholarly journals Electrical Behavior and Microstructural Features of Electric Field-Assisted and Conventionally Sintered 3 mol% Yttria-Stabilized Zirconia

Ceramics ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Sabrina Carvalho ◽  
Eliana Muccillo ◽  
Reginaldo Muccillo
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Vacancy Concentration ◽  
Chemical Species ◽  
Oxygen Vacancy Concentration ◽  
Electrical Behavior ◽  
Boundary Conductivity ◽  
Ac Electric Fields ◽  
Ac Current ◽  
Field Assisted Sintering

ZrO2: 3 mol% Y2O3 (3YSZ) polycrystalline pellets were sintered at 1400 °C and by applying an alternating current (AC) electric field at 1000 °C. An alumina sample holder with platinum wires for connecting the sample to a power supply was designed for the electric field-assisted sintering experiments. The apparent density was evaluated with the Archimedes technique, the grain size distribution by analysis of scanning electron microscopy images, and the electrical behavior by the impedance spectroscopy technique. Sintering with the application of AC electric fields to 3YSZ enhances its ionic conductivity. An explanation is proposed, based on the dissolution back to the bulk of chemical species, which are depleted at the grain boundaries, leading to an increase in the oxygen vacancy concentration. For the enhancement of the grain boundary conductivity, an explanation is given based on the diminution of the concentration of depleted chemical species, which migrate to the bulk. This migration leads to a decrease of the potential barrier of the space charge region, known to be responsible for blocking the oxide ions through the intergranular region. Moreover, the heterogeneity of the distribution of the grain sizes is ascribed to the skin effect, the tendency of the AC current density to be largest near the surface, decreasing towards the bulk.

scholarly journals In-flight calibration of double-probe DC electric field measurements on Cluster

2014 ◽  
Vol 4 (1) ◽  
pp. 85-107
Author(s):  
Y. V. Khotyaintsev ◽  
P.-A. Lindqvist ◽  
C. M. Cully ◽  
A. I. Eriksson ◽  
M. André
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Field Measurements ◽  
Calibration Procedure ◽  
Double Probe ◽  
Ac Electric Fields ◽  
Dc Electric Field ◽  
Electric Field Measurements

Abstract. Double-probe electric field instrument with long wire booms is one of the most popular techniques for in situ measurement of DC and AC electric fields in plasmas on spinning spacecraft platforms, which have been employed on a large number of space missions. Here we present an overview of the calibration procedure used for the EFW instrument on Cluster, which involves spin fits of the data and correction of several offsets. We also describe the procedure for the offset determination and present results for the long-term evolution of the offsets.

scholarly journals Reaction-free concentration gradient generation in spatially non-uniform AC electric fields

2022 ◽  
Author(s):  
Ran An ◽  
Adrienne Minerick
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Concentration Gradient ◽  
Electrochemical Techniques ◽  
Hafnium Dioxide ◽  
Ion Concentration ◽  
Concentration Gradients ◽  
Free Concentration ◽  
Bulk Fluid ◽  
Ac Electric Fields

The ability to generate stable, spatiotemporally controllable concentration gradients is critical for both electrokinetic and biological applications such as directional wetting and chemotaxis. Electrochemical techniques for generating solution and surface gradients display benefits such as simplicity, controllability, and compatibility with automation. Here, we present an exploratory study for generating micro-scale spatiotemporally controllable gradients using a reaction-free electrokinetic technique in a microfluidic environment. Methanol solutions with ionic Fluorescein isothiocyanate (FITC) molecules were used as an illustrative electrolyte. Spatially non-uniform alternating current (AC) electric fields were applied using hafnium dioxide (HfO2) coated Ti/Au electrode pairs. Results from spatial and temporal analysis, along with control experiments suggest that the FITC ion concentration gradient in bulk fluid (over 50 µm from the electrode) was established due to spatial variation of electric field density, and was independent of electrochemical reactions at the electrode surface. The established ion concentration gradients depended on both amplitudes and the frequencies of the oscillating AC electric field. Overall, this work reports a novel approach for generating stable and spatiotemporally tunable gradients in a microfluidic chamber using a reaction-free electrochemical methodology.

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