Enhanced Capture of Magnetic Microbeads Using Combination of Reduced Magnetic Field Strength and Sequentially Switched Electroosmotic Flow—A Numerical Study

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Debarun Das ◽  
Marwan F. Al-Rjoub ◽  
Rupak K. Banerjee
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Magnetic Field Strength ◽  
Electric Fields ◽  
Electroosmotic Flow ◽  
Separation Technique ◽  
Target Cells ◽  
Magnetic Microbeads

Magnetophoretic immunoassay is a widely used technique in lab-on-chip systems for detection and isolation of target cells, pathogens, and biomolecules. In this method, target pathogens (antigens) bind to specific antibodies coated on magnetic microbeads (mMBs) which are then separated using an external magnetic field for further analysis. Better capture of mMB is important for improving the sensitivity and performance of magnetophoretic assay. The objective of this study was to develop a numerical model of magnetophoretic separation in electroosmotic flow (EOF) using magnetic field generated by a miniaturized magnet and to evaluate the capture efficiency (CE) of the mMBs. A finite-volume solver was used to compute the trajectory of mMBs under the coupled effects of EOF and external magnetic field. The effect of steady and time varying (switching) electric fields (150–450 V/cm) on the CE was studied under reduced magnetic field strength. During switching, the electric potential at the inlet and outlet of the microchannel was reversed or switched, causing reversal in flow direction. The CE was a function of the momentum of the mMB in EOF and the applied magnetic field strength. By switching the electric field, CE increased from 75% (for steady electric field) to 95% for lower electric fields (150–200 V/cm) and from 35% to 47.5% for higher electric fields (400–450 V/cm). The CE was lower at higher EOF electric fields because the momentum of the mMB overcame the external magnetic force. Switching allowed improved CE due to the reversal and decrease in EOF velocity and increase in mMB residence time under the reduced magnetic field strength. These improvements in CE, particularly at higher electric fields, made sequential switching of EOF an efficient separation technique of mMBs for use in high throughput magnetophoretic immunoassay devices. The reduced size of the magnet, along with the efficient mMB separation technique of switching can lead to the development of portable device for detection of target cells, pathogens, and biomolecules.

Effect of external magnetic field on lane formation in driven pair-ion plasmas

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Swati Baruah ◽  
U. Sarma ◽  
R. Ganesh
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Coupling Parameter ◽  
Critical Parameters ◽  
Coulomb Coupling ◽  
Lane Formation ◽  
Parameter Values

Lane formation dynamics in externally driven pair-ion plasma (PIP) particles is studied in the presence of external magnetic field using Langevin dynamics (LD) simulation. The phase diagram obtained distinguishing the no-lane and lane states is systematically determined from a study of various Coulomb coupling parameter values. A peculiar lane formation-disintegration parameter space is identified; lane formation area extended to a wide range of Coulomb coupling parameter values is observed before disappearing to a mixed phase. The different phases are identified by calculating the order parameter. This and the critical parameters are calculated directly from LD simulation. The critical electric field strength value above which the lanes are formed distinctly is obtained, and it is observed that in the presence of the external magnetic field, the PIP system requires a higher value of the electric field strength to enter into the lane formation state than that in the absence of the magnetic field. We further find out the critical value of electric field frequency beyond which the system exhibits a transition back to the disordered state and this critical frequency is found as an increasing function of the electric field strength in the presence of an external magnetic field. The movement of the lanes is also observed in a direction perpendicular to that of the applied electric and magnetic field directions, which reveals the existence of the electric field drift in the system under study. We also use an oblique force field as the external driving force, both in the presence and absence of the external magnetic field. The application of this oblique force changes the orientation of the lane structures for different applied oblique angle values.

Das toroidale schwachionisierte Magnetoplasma I

1967 ◽  
Vol 22 (12) ◽  
pp. 1890-1903
Author(s):  
F. Karger
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Transverse Electric ◽  
Refined Theory ◽  
Toroidal Plasma ◽  
Dc Discharge ◽  
Transverse Electric Fields

In a previous paper31 discrepancies between theory and experiment were found on investigating the positive column in a curved magnetic field. The approximation derived in 31 for the torus drift in a weakly ionized magnetoplasma is therefore checked here (Part I) with a refined theory which also yields the transverse electric field strength. Experimentally, both the transverse electric fields and the density profiles in the DC discharge were determined in addition to the longitudinal electric field strength.The discrepancies occurring in 31 are ascribed to the fact that the plasma concentrates at the cathode end of the magnetic field coils, this effect having a considerable influence on the form of the transverse density profile and on the stability behaviour. Part II later will show how the influence of this concentration can be eliminated and what effect in the current-carrying toroidal plasma causes a marked reduction of the charge carrier losses.

scholarly journals An experimental examination of the electrostatic behaviour of supraconductors.

1936 ◽  
Vol 155 (884) ◽  
pp. 102-110 ◽  
Author(s):  
Heinz London ◽  
Frederick Alexander Lindemann
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Magnetic Field Strength ◽  
Current Density ◽  
Experimental Examination ◽  
Characteristic Constant

In previous papers of F. and H. London supraconductivity has been described as a phenomenon, in which the current density is not connected with the electric field, as in normal conductors, but depends on magnetic field strength according to the equation Λ c curl J = - H with B = H and with Λ = m / ne 2, a new characteristic constant which contains the number n of supraconducting electrons. the behaviour of the electric field is not completely determined by this equation. Using Maxwell's induction law one can conclude from (1) only that Λ c curl j = c curl E or Λj = E + grand μ, where the physical signifance of grad μ is yet unknown.

Regulation Behavior of Microwave Reflectivity in Magnetorheological Fluids

2011 ◽  
Vol 413 ◽  
pp. 213-216
Author(s):  
Ji Jun Fan ◽  
Nan Hui Yu
Keyword(s):  
Magnetic Field ◽  
Experimental Study ◽  
External Magnetic Field ◽  
Field Strength ◽  
Internal Structure ◽  
Magnetic Field Strength ◽  
Particle Concentration ◽  
Microwave Frequency ◽  
Microwave Reflection ◽  
The Given

In this paper, experimental study of the microwave reflection behavior in MRF was carried out. The results showed that at the same frequency the microwave reflectivity of MRF decreased with the increasing of magnetic field strength; and with the increasing of particle concentration, microwave reflectivity decreased, monotonously. Under the given magnetic field, with the increasing of microwave frequency, it first decreased, there is a lowest point at 9.2GHz, and then it increased. Usually, it is considered that the change of internal structure of MRF under external magnetic field is the main reason for the regulation behavior of microwave reflectivity.

The Effect of Low-Intensity Static Magnetic Field on Ni-P-PTFE Electroless Composite Plating Coatings

2016 ◽  
Vol 717 ◽  
pp. 112-117
Author(s):  
Jun Ying Hou ◽  
Hong Jiang Gao ◽  
Xiao Lin Liu ◽  
Yu Jiao ◽  
Li Liu
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Composite Coating ◽  
Magnetic Field Strength ◽  
Composite Coatings ◽  
Magnetic Field Direction ◽  
Composite Plating ◽  
External Magnetic Field Strength ◽  
New Processing

A new processing concept has been developed to produce Ni-P-PTFE electroless composite coating. This method combines magnetic field and electroless composite plating techniques to prepare high-quality Ni-P-PTFE electroless composite coating. The influence of magnetic on composite plating process and coatings performance by changing some factors such as the plating time, magnetic field strength, magnetic field direction. The results indicate that the external magnetic field improved deposition rate and the PTFE particles content of composite coatings, meanwhile, some performances of composite coating like thickness, corrosion resistance, were effected by external magnetic field strength. Therefore, the method combines magnetic field and electroless completing techniques had a wide application prospect in the aspect of improving the properties of electroless composite coating.

Photomagnetic Medium as Weak Magnetic Field Sensor

2015 ◽  
Vol 230 ◽  
pp. 285-290
Author(s):  
Oleksandr Tychko
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Weak Magnetic Field ◽  
Magnetic Field Sensor ◽  
Strength Measurement ◽  
Field Sensor

Photoinduced nucleation in an external magnetic field is investigated. A possibility of a week magnetic field strength measurement is showed.

Influence of Mechanical Pressure and External Field on Dynamic Interactions in Segnetomagnetics

2010 ◽  
Vol 168-169 ◽  
pp. 89-92
Author(s):  
M.K. Kharrasov ◽  
I.R. Kyzyrgulov ◽  
I.F. Sharafullin
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
External Field ◽  
Electric Field ◽  
External Electric Field ◽  
Electric Fields ◽  
Mechanical Pressure ◽  
Dynamic Interactions ◽  
Magnetoelectric Interaction

The interaction of spin, ferroelectric and elastic subsystems is investigated in antisegnetoantiferromagnetic crystal depending on the magnetic and electric fields, and also on an external mechanical pressure. It is shown that the magnitude of the magnetoelectric interaction increases with the rise of an external magnetic field and decreases with increasing external electric field.

scholarly journals Flow behavior of cementitious-like suspension with nano-Fe3O4 particles under external magnetic field

2021 ◽  
Vol 54 (6) ◽  
Author(s):  
Dengwu Jiao ◽  
Karel Lesage ◽  
Mert Yücel Yardimci ◽  
Caijun Shi ◽  
Geert De Schutter
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
High Magnetic Field ◽  
Apparent Viscosity ◽  
Flow Behavior ◽  
Limestone Powder ◽  
Powder Suspension ◽  
The Magnetic Field

AbstractThe flow behavior of cementitious-like (limestone powder) suspension containing nano-Fe3O4 particles at constant shear rate of 10 s−1, characterized by the evolution of apparent viscosity over time, is investigated under various magnetic fields. Results show that the limestone powder suspension at flow-state exhibits remarkable magneto-rheological responses, reflected by a significant increase in the apparent viscosity after applying an external magnetic field. A higher field strength corresponds to a more rapid and pronounced response. The apparent viscosity experiences a sudden alteration with the stepwise change of the magnetic field due to the formation or disintegration of magnetic clusters. Linearly increasing magnetic field strength at low ranges (e.g. 0 T–0.3 T) shows less influences on the evolution of apparent viscosity, while at relatively high magnetic field, the apparent viscosity gradually increases with the magnetic field strength and the increase rate is comparable to that obtained under constant high magnetic field of 0.75 T. When the magnetic field is removed, the apparent viscosity exhibits a sharp reduction. If the magnetic field strength linearly decreases to zero, however, the apparent viscosity continuously increases until reaching a peak and then gradually decreases. This research shows in different ways how a desired apparent viscosity level of a cementitious-like suspension can be reached by means of an external magnetic field.

scholarly journals Isolated electrostatic structures observed throughout the Cluster orbit: relationship to magnetic field strength

2004 ◽  
Vol 22 (7) ◽  
pp. 2515-2523 ◽  
Author(s):  
J. S. Pickett ◽  
L.-J. Chen ◽  
S. W. Kahler ◽  
O. Santolík ◽  
D. A. Gurnett ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Magnetic Field Strength ◽  
Local Magnetic Field ◽  
Unexpected Result ◽  
Time Duration ◽  
Waveform Data ◽  
Negative Peak ◽  
The Magnetic Field

Abstract. Isolated electrostatic structures are observed throughout much of the 4RE by 19.6RE Cluster orbit. These structures are observed in the Wideband plasma wave instrument's waveform data as bipolar pulses (one positive and one negative peak in the electric field amplitude) and tripolar pulses (two positive and one negative peak, or vice versa). These structures are observed at all of the boundary layers, in the solar wind and magnetosheath, and along auroral field lines at 4.5-6.5RE. Using the Wideband waveform data from the various Cluster spacecraft we have carried out a survey of the amplitudes and time durations of these structures and how these quantities vary with the local magnetic field strength. Such a survey has not been carried out before, and it reveals certain characteristics of solitary structures in a finite magnetic field, a topic still inadequately addressed by theories. We find that there is a broad range of electric field amplitudes at any specific magnetic field strength, and there is a general trend for the electric field amplitudes to increase as the strength of the magnetic field increases over a range of 5 to 500nT. We provide a possible explanation for this trend that relates to the structures being Bernstein-Greene-Kruskal mode solitary waves. There is no corresponding dependence of the duration of the structures on the magnetic field strength, although a plot of these two quantities reveals the unexpected result that with the exception of the magnetosheath, all of the time durations for all of the other regions are comparable, whereas the magnetosheath time durations clearly are in a different category of much smaller time duration. We speculate that this implies that the structures are much smaller in size. The distinctly different pulse durations for the magnetosheath pulses indicate the possibility that the pulses are generated by a mechanism which is different from the mechanism operating in other regions.

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