scholarly journals A Theoretical Analysis of Magnetic Particle Alignment in External Magnetic Fields Affected by Viscosity and Brownian Motion

2021 ◽  
Vol 11 (20) ◽  
pp. 9651
Author(s):  
Andrej Krafcik ◽  
Peter Babinec ◽  
Oliver Strbak ◽  
Ivan Frollo
Keyword(s):  
Magnetic Fields ◽  
Biomedical Applications ◽  
Molecular Mechanisms ◽  
Magnetic Particle ◽  
Fundamental Property ◽  
Oscillatory Behavior ◽  
Magnetic Flux Density ◽  
Inertial Torque ◽  
Particle Alignment ◽  
Viscous Torque

The interaction of an external magnetic field with magnetic objects affects their response and is a fundamental property for many biomedical applications, including magnetic resonance and particle imaging, electromagnetic hyperthermia, and magnetic targeting and separation. Magnetic alignment and relaxation are widely studied in the context of these applications. In this study, we theoretically investigate the alignment dynamics of a rotational magnetic particle as an inverse process to Brownian relaxation. The selected external magnetic flux density ranges from 5μT to 5T. We found that the viscous torque for arbitrary rotating particles with a history term due to the inertia and friction of the surrounding ambient water has a significant effect in strong magnetic fields (range 1–5T). In this range, oscillatory behavior due to the inertial torque of the particle also occurs, and the stochastic Brownian torque diminishes. In contrast, for weak fields (range 5–50μT), the history term of the viscous torque and the inertial torque can be neglected, and the stochastic Brownian torque induced by random collisions of the surrounding fluid molecules becomes dominant. These results contribute to a better understanding of the molecular mechanisms of magnetic particle alignment in external magnetic fields and have important implications in a variety of biomedical applications.

scholarly journals Optical Imaging of Magnetic Particle Cluster Oscillation and Rotation in Glycerol

2021 ◽  
Vol 7 (5) ◽  
pp. 82
Author(s):  
River Gassen ◽  
Dennis Thompkins ◽  
Austin Routt ◽  
Philippe Jones ◽  
Meghan Smith ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Particles ◽  
Magnetic Particle ◽  
Barium Hexaferrite ◽  
Optical Microscope ◽  
Simplified Model ◽  
Particle Cluster ◽  
Average Deviation ◽  
Cross Sectional

Magnetic particles have been evaluated for their biomedical applications as a drug delivery system to treat asthma and other lung diseases. In this study, ferromagnetic barium hexaferrite (BaFe12O19) and iron oxide (Fe3O4) particles were suspended in water or glycerol, as glycerol can be 1000 times more viscous than water. The particle concentration was 2.50 mg/mL for BaFe12O19 particle clusters and 1.00 mg/mL for Fe3O4 particle clusters. The magnetic particle cluster cross-sectional area ranged from 15 to 1000 μμm2, and the particle cluster diameter ranged from 5 to 45 μμm. The magnetic particle clusters were exposed to oscillating or rotating magnetic fields and imaged with an optical microscope. The oscillation frequency of the applied magnetic fields, which was created by homemade wire spools inserted into an optical microscope, ranged from 10 to 180 Hz. The magnetic field magnitudes varied from 0.25 to 9 mT. The minimum magnetic field required for particle cluster rotation or oscillation in glycerol was experimentally measured at different frequencies. The results are in qualitative agreement with a simplified model for single-domain magnetic particles, with an average deviation from the model of 1.7 ± 1.3. The observed difference may be accounted for by the fact that our simplified model does not include effects on particle cluster motion caused by randomly oriented domains in multi-domain magnetic particle clusters, irregular particle cluster size, or magnetic anisotropy, among other effects.

Magnetophoresis Effects on the Flow Characteristics of Oil-Based Ferrofluids in Rectangular Enclosures

2015 ◽  
Vol 15 (10) ◽  
pp. 7451-7456
Author(s):  
Hyeon-Seok Seo ◽  
Jin-Hyo Boo ◽  
Youn-Jea Kim
Keyword(s):  
Magnetic Fields ◽  
Permanent Magnet ◽  
Flow Characteristics ◽  
Flow Fields ◽  
Working Fluid ◽  
Magnetic Flux Density ◽  
Magnetic Field Direction ◽  
Analysis Model ◽  
Rectangular Enclosure ◽  
Flow Phenomena

This study numerically investigated the flow characteristics in a rectangular enclosure filled with oil-based ferrofluid (EFH-1, Ferrotec.) under the influence of external magnetic fields. The rectangular enclosure contained obstacles with different shapes, such as a rectangle and a triangle mounted on the top and bottom wall surfaces. In order to generate external magnetic fields, a permanent magnet was located in the lower part of the rectangular enclosure, and its direction was selected to be either horizontal or vertical. Our results showed that the ferrofluid flow fields were affected by the applied external magnetic field direction and eddy flow phenomena in the working fluid were generated in the vicinity of high magnetic flux density distributions, such as at the edge of the permanent magnet. It was also confirmed that the magnetophoretic force distributions in the analysis model played a significant role in the development of the ferrofluid flow fields.

Characterization of Adaptive Magnetoelastic Metamaterials Under Applied Magnetic Fields

2016 ◽  
Author(s):  
Ryan L. Harne ◽  
Zhangxian Deng ◽  
Marcelo J. Dapino
Keyword(s):  
Magnetic Particle ◽  
Performance Metrics ◽  
Noise Control ◽  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
Structural Vibration ◽  
Dynamic Force ◽  
Particle Alignment ◽  
The Impact

Whether serving as mounts, isolators, or dampers, elastomer-based supports are common solutions to inhibit the transmission of waves and vibrations through engineered systems and therefore help to alleviate concerns of radiated noise from structural surfaces. The static and dynamic properties of elastomers govern the operational conditions over which the elastomers and host structures provide effective performance. Passive-adaptive tuning of properties can therefore broaden the useful working range of the material, making the system more robust to varying excitations and loads. While elastomer-based metamaterials are shown to adapt properties by many orders of magnitude according to the collapse of internal void architectures, researchers have not elucidated means to control these instability mechanisms such that they may be leveraged for on-demand tuning of static and dynamic properties. In addition, while magnetorheological elastomers (MREs) exhibit valuable performance-tuning control due to their intrinsic magnetic-elastic coupling, particularly with anisotropic magnetic particle alignment, the extent of their properties adaptation is not substantial when compared to metamaterials. Past studies have not identified means to apply anisotropic MREs in engineered metamaterials to activate the collapse mechanisms for tuning purposes. To address this limited understanding and effect significant performance adaptation in elastomer supports for structural vibration and noise control applications, this research explores a new concept for magnetoelastic metamaterials (MM) that leverage strategic magnetic particle alignment for unprecedented tunability of performance and functionality using non-contact actuation. MM specimens are fabricated using interrelated internal void topologies, with and without anisotropic MRE materials. Experimental characterization of stiffness, hysteretic loss, and dynamic force transmissibility assess the impact of the design variables upon performance metrics. For example, it is discovered that the mechanical properties may undergo significant adaptation, including two orders of magnitude change in mechanical power transmitted through an MM, according to the introduction of a 3 T free space external magnetic field. In addition, the variable collapse of the internal architectures is seen to tune static stiffness from finite to nearly vanishing values, while the dynamic stiffness shows as much as 50% change due to the collapsing architecture topology. Thus, strategically harnessing the internal architecture alongside magnetoelastic coupling is found to introduce a versatile means to tune the properties of the MM to achieve desired system performance across a broad range of working conditions. These results verify the research hypothesis and indicate that, when effectively leveraged, magnetoelastic metamaterials introduce remarkably versatile performance for engineering applications of vibration and noise control.

scholarly journals An adapted Coffey model for studying susceptibility losses in interacting magnetic nanoparticles

2015 ◽  
Vol 6 ◽  
pp. 2173-2182 ◽  
Author(s):  
Mihaela Osaci ◽  
Matteo Cacciola
Keyword(s):  
Relaxation Time ◽  
Magnetic Fields ◽  
Biomedical Applications ◽  
Tumor Therapy ◽  
Linear Response Theory ◽  
Orientation Model ◽  
Specific Loss Power ◽  
Acceptable Range ◽  
Nanoparticle System ◽  
Néel Relaxation

Background: Nanoparticles can be used in biomedical applications, such as contrast agents for magnetic resonance imaging, in tumor therapy or against cardiovascular diseases. Single-domain nanoparticles dissipate heat through susceptibility losses in two modes: Néel relaxation and Brownian relaxation. Results: Since a consistent theory for the Néel relaxation time that is applicable to systems of interacting nanoparticles has not yet been developed, we adapted the Coffey theoretical model for the Néel relaxation time in external magnetic fields in order to consider local dipolar magnetic fields. Then, we obtained the effective relaxation time. The effective relaxation time is further used for obtaining values of specific loss power (SLP) through linear response theory (LRT). A comparative analysis between our model and the discrete orientation model, more often used in literature, and a comparison with experimental data from literature have been carried out, in order to choose the optimal magnetic parameters of a nanoparticle system. Conclusion: In this way, we can study effects of the nanoparticle concentration on SLP in an acceptable range of frequencies and amplitudes of external magnetic fields for biomedical applications, especially for tumor therapy by magnetic hyperthermia.

scholarly journals An Analytical–Experimental Approach to Quantifying the Effects of Static Magnetic Fields for Cell Culture Applications

2020 ◽  
Vol 10 (2) ◽  
pp. 531
Author(s):  
Pablo Ferrada ◽  
Sebastián Rodríguez ◽  
Génesis Serrano ◽  
Carol Miranda-Ostojic ◽  
Alejandro Maureira ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Permanent Magnets ◽  
Bubbly Flow ◽  
Scenedesmus Obliquus ◽  
Relative Difference ◽  
Magnetic Flux Density ◽  
The South ◽  
Nannochloropsis Gaditana ◽  
Static Magnetic Fields ◽  
The North

This work aimed to study the effects of static magnetic fields (SMFs) on cell cultures. A glass flask was filled with a liquid medium, which was surrounded by permanent magnets. Air was introduced through a tube to inject bubbles. Two magnet configurations, north and south, were used as perturbation. Scenedesmus obliquus and Nannochloropsis gaditana, growing in Medium 1 and 2, were subjected to the bubbly flow and SMFs. Differences between media were mainly due to conductivity (0.09 S/m for Medium 1 and 4.3 S/m for Medium 2). Joule dissipation ( P ) increased with the magnetic flux density ( B 0 ), being 4 orders of magnitude higher in Medium 2 than in 1. Conversely, the time constant ( τ P ) depended on B 0 , being nearly constant for Medium 1 and decreasing at 449 s/T for Medium 2. Dissipation occurred with the same τ P (235 s) in Medium 1 and 2 at B 0 = 0.5 T. In Species 1, the SMF effect was inhibitory. For Species 2, a higher enzymatic activity was observed. For superoxide dismutase, the relative difference was 78% with the north and 115% with the south configuration compared to the control values. For the catalase, differences of 29% with the north and 23% with the south configuration compared to control condition were obtained.

scholarly journals The biology, function, and biomedical applications of exosomes

Science ◽  
2020 ◽  
Vol 367 (6478) ◽  
pp. eaau6977 ◽  
Author(s):  
Raghu Kalluri ◽  
Valerie S. LeBleu
Keyword(s):  
Amino Acids ◽  
Extracellular Vesicles ◽  
Intercellular Communication ◽  
Biomedical Applications ◽  
Molecular Mechanisms ◽  
Biological Fluids ◽  
Average Diameter ◽  
Cell Of Origin ◽  
Intracellular Vesicles ◽  
Cellular Components

The study of extracellular vesicles (EVs) has the potential to identify unknown cellular and molecular mechanisms in intercellular communication and in organ homeostasis and disease. Exosomes, with an average diameter of ~100 nanometers, are a subset of EVs. The biogenesis of exosomes involves their origin in endosomes, and subsequent interactions with other intracellular vesicles and organelles generate the final content of the exosomes. Their diverse constituents include nucleic acids, proteins, lipids, amino acids, and metabolites, which can reflect their cell of origin. In various diseases, exosomes offer a window into altered cellular or tissue states, and their detection in biological fluids potentially offers a multicomponent diagnostic readout. The efficient exchange of cellular components through exosomes can inform their applied use in designing exosome-based therapeutics.

Magnetic particle inspection and EMF Directive 2013/35/EU

2020 ◽  
Vol 62 (2) ◽  
pp. 69-72
Author(s):  
H Bibby ◽  
J Hinsley
Keyword(s):  
Risk Assessment ◽  
Electromagnetic Fields ◽  
Magnetic Particle ◽  
Computer Modelling ◽  
Successful Outcome ◽  
Magnetic Flux Density ◽  
Field Exposure ◽  
Limit Values ◽  
Magnetic Particle Inspection ◽  
The Uk

EMF Directive 2013/35/EU [1] was transposed into legislation in EU member states in 2016. In the UK, the Health and Safety Executive (HSE) produced the Control of Electromagnetic Fields at Work (CEMFAW) Regulations 2016 [2] . It is the first piece of legislation in the UK that is specific to electromagnetic fields (EMFs) and requires all employers to perform an EMF risk assessment. For many this is a relatively easy process, as most workplaces do not contain equipment capable of producing high fields. However, any piece of equipment that uses a high level of electrical current is capable of generating a high magnetic field and, in the case of magnetic particle inspection (MPI), it is an intended output. As the operator is often required to stand close to the generated field, exposure levels can be relatively high. Magnetic flux density measurements have shown that the action levels (ALs) used as the basis for exposure assessment can be exceeded. In some instances this can be mitigated by some instruction or training, while in others it may be necessary to prove compliance with exposure limit values (ELVs). Proving compliance with ELVs is more complicated than proving compliance with ALs. It is by no means impossible, however, as computer modelling can be employed. The regulations also list categories of worker considered to be at particular risk. Pregnant workers and workers with active medical devices, such as pacemakers, or passive implants, for example artificial joints, pins, plates, screws or stents, are all considered to be at particular risk. To perform a risk assessment for such workers, reference levels contained in EU Council Recommendation 1999/519/EC [3] are used. These are much more stringent than ALs and compliance is more difficult, but a pragmatic approach can be employed to achieve a successful outcome. Fundamentally, the purpose of the regulations is not to place obstacles in the way of industry but to make employers and equipment manufacturers aware of their obligations and the possible routes that can be taken to achieve compliance.

Effects and molecular mechanisms of the biological action of weak and extremely weak magnetic fields

BIOPHYSICS ◽  
2010 ◽  
Vol 55 (4) ◽  
pp. 565-572 ◽  
Author(s):  
V. V. Novikov ◽  
V. O. Ponomarev ◽  
G. V. Novikov ◽  
V. V. Kuvichkin ◽  
E. V. Yablokova ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Molecular Mechanisms ◽  
Biological Action ◽  
Weak Magnetic Fields

Strong vortical flows generated by the collective motion of magnetic particle chains rotating in a fluid cell

Lab on a Chip ◽  
2015 ◽  
Vol 15 (1) ◽  
pp. 351-360 ◽  
Author(s):  
Yang Gao ◽  
Jasper Beerens ◽  
Alexander van Reenen ◽  
Martien A. Hulsen ◽  
Arthur M. de Jong ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Magnetic Particle ◽  
Collective Motion ◽  
Vortical Flow ◽  
Rotating Magnetic Fields ◽  
Magnetic Microparticles ◽  
Biochemical Assays ◽  
Magnetic Capture ◽  
Particle Chains ◽  
Fluid Cell

Magnetic microparticles suspended in a microfluidic cell exhibit coherent collective motion when actuated with rotating magnetic fields, creating strong vortical flow and enhancing biochemical assays with magnetic capture particles.

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