Behavior Of Magnetic Particles Research Articles

Influence of Magnetic and Rheological Properties on a Leakage Channel in a Fluid Ring in Ferrofluid Seal

A ferrofluid ring can be compared to a liquid O-ring seal. This liquid ring is used in various applications, such as seals, valves, compressors, dampers, or thrust bearings. Its main advantage is that it maintains tightness and is held in a given place by a magnetic field. One of the main problems is the occurrence of leakage due to pressure differences. This affects the volume of liquid ejected outside the ferrofluid ring region and the value of the leakage itself. The research area of this publication is related to the recognition of how magnetic and rheological properties influence the mechanism of leakage channel formation in a single fluid ring. The purpose was to research basic parameters that characterize the leakage channel, such as the pressure jump value, the cross-sectional area, airflow, and leakage value. The results allow us to understand this problem better and provide insight into the behavior of magnetic particles in a colloid. Studies have shown that an increase in the number of magnetic nanoparticles increases the cross-sectional area of the leakage channel. The opposite effect is observed when a viscosity increase affects fluid resistance to deformation. The study also shows that the share of large particles does not significantly influence the leakage channel. However, the magnetic particles viscous drag affects the ability of particles to react to change.

An efficient magnetic approach for manipulating dispersed non-magnetic particles on surfaces and microchannels

Recently, there has been significant interest in understanding the behavior of magnetic particles in aqueous media under external excitations. The dynamics and self-organization of these systems, especially in the presence of time-dependent excitations, have been extensively studied due to their relevance in both fundamental physics and technological applications. In this study, we employ three Helmholtz coils to generate elliptically polarized fields. This configuration is utilized to manipulate micrometer-sized nickel and iron particles located at the bottom of a container filled with an aqueous medium. By analyzing video-microscopy images, we investigate the time-dependent displacement of these particles. Notably, we observe the formation of chain structures known as “rollers”, whose movement on the vessel’s bottom plane can be controlled through the applied magnetic field. Furthermore, we demonstrate that the introduction of glass microspheres results in induced motion due to the displacement and drag exerted by the magnetic structures. Exploiting this effect, we successfully control the movement of glass beads along microchannels. Our findings suggest potential applications for targeted cargo delivery using this simple approach.

Effects of magnet arrangement on the separation behavior of magnetic particles in high-concentration suspensions based on numerical simulations: Magnetic force induced eddies

ABSTRACT Particle-fluid dynamic behavior significantly influences the separation process of magnetic particles in open-gradient magnetic separation systems. In the present paper, a simplified model of the separation process of magnetic particles in an open-gradient magnetic separation system is developed based on a two-way particle-fluid coupling method. The effects of initial concentration and four magnet arrangements on the particle-fluid kinetic behavior and particle capture efficiency are investigated. The results show that the exclusion zone generated by the lateral concurrent arrangement can induce a double eddy structure and thus contribute to particle capture. This conclusion implies that the generation of eddy structures is not only related to the particle concentration but also to the distribution of the magnetic field. The results also show that the particle capture efficiency increases and then decreases with increasing initial concentration in the presence of a single magnet, i.e. there is an optimal capture concentration.

Numerical study on the effect of turbulence intensity on the separation behavior of magnetic particles under different magnet arrangements

ABSTRACT The crucial problem of magnetic separation is improving the ability to capture magnetic particles in complex fluid flow. This paper develops a numerical model of an open gradient magnetic separation (OGMS) system to study the capture process of magnetic particles in laminar flow and turbulent flow under four kinds of magnet arrangement modes. The particle capture efficiencies of four inlet turbulence intensities are analyzed and compared with that of laminar flow. The results show that the particle capture efficiency of turbulent flow is higher than that of laminar flow under the same inlet velocity distribution in a small Stokes number. Moreover, the particle capture efficiency of high turbulence intensity is significantly higher than that of low turbulence intensity. The results also indicate that the axial alternating arrangement (AAA) can provide a stronger magnetic field, which is beneficial to particle capture.

Numerical and experimental analysis of terminal settling velocity in the presence of magnetic field aligned with gravity for ferro-magnetite particles using coupled CFD+DPM method

ABSTRACT Based on the previous investigations, in the presence of a magnetic field aligned with the gravity, the terminal settling velocity (TSV) of magnetic particles is improved compared to that of non-magnetic particles. In this paper, the effects of magnetic fields with intensities of 0.03 and 0.05 T on the TSVs of spherical magnetite particles and steel balls of different sizes were simulated using combined computational fluid dynamics and discrete phase methods (CFD + DPM). Simulations showed that the application of a magnetic field with the mentioned intensities increased the TSVs of the steel balls and the magnetite spherical particles up to 16.16% and 13.88%, respectively. To validate simulation outputs, using synthetic samples and a Magneto-Gravity Settling Device (MGSD) designed and fabricated by the authors, a series of lab settling tests were performed under the same operational conditions as those of simulations. The results of the test work concluded that in the presence of magnetic fields of 0.03 and 0.05 T intensities, steel balls and spherical magnetite particles settled faster by 8.84% and 7.41%, respectively. This shows that, with an acceptable error, CFD + DPM simulation methods can well predict the influence of the magnetic field on the settling behaviour of magnetic particles.

Improved in-vivo airway gene transfer via magnetic-guidance, with protocol development informed by synchrotron imaging

Gene vectors to treat cystic fibrosis lung disease should be targeted to the conducting airways, as peripheral lung transduction does not offer therapeutic benefit. Viral transduction efficiency is directly related to the vector residence time. However, delivered fluids such as gene vectors naturally spread to the alveoli during inspiration, and therapeutic particles of any form are rapidly cleared via mucociliary transit. Extending gene vector residence time within the conducting airways is important, but hard to achieve. Gene vector conjugated magnetic particles that can be guided to the conducting airway surfaces could improve regional targeting. Due to the challenges of in-vivo visualisation, the behaviour of such small magnetic particles on the airway surface in the presence of an applied magnetic field is poorly understood. The aim of this study was to use synchrotron imaging to visualise the in-vivo motion of a range of magnetic particles in the trachea of anaesthetised rats to examine the dynamics and patterns of individual and bulk particle behaviour in-vivo. We also then assessed whether lentiviral-magnetic particle delivery in the presence of a magnetic field increases transduction efficiency in the rat trachea. Synchrotron X-ray imaging revealed the behaviour of magnetic particles in stationary and moving magnetic fields, both in-vitro and in-vivo. Particles could not easily be dragged along the live airway surface with the magnet, but during delivery deposition was focussed within the field of view where the magnetic field was the strongest. Transduction efficiency was also improved six-fold when the lentiviral-magnetic particles were delivered in the presence of a magnetic field. Together these results show that lentiviral-magnetic particles and magnetic fields may be a valuable approach for improving gene vector targeting and increasing transduction levels in the conducting airways in-vivo.

Effects of particle morphology and magnetocrystalline anisotropy on < 111 > orientation and magnetostriction of sintered Tb-Dy-Fe/DyCu compacts

Sintered Tb-Dy-Fe materials prepared by the compression molding method have higher relative density and energy density than powder-bonded composites. However, due to the low magnetocrystalline anisotropy and the cubic symmetry of the Laves structure, the orientation degree of sintered materials is relatively low and not beneficial for obtaining large magnetostriction. We prepared the sintered Tb-Dy-Fe/DyCu compacts with preferred <111 > orientation by applying magnetically oriented powder metallurgy. The dependence of orientation degree and magnetostriction of oriented Tb-Dy-Fe/DyCu sintered compacts on different particle morphology and Tb/Dy ratios were studied. The oriented Tb-Dy-Fe/DyCu sintered compacts prepared from the milled single crystal Tb-Dy-Fe powders gained a higher <111 > orientation due to the small rotational resistance when magnetic particles move in a magnetic field, achieving improved magnetostriction. Magnetocrystalline anisotropy which determines the rotational torque caused by the magnetic field is one of the important factors affecting the rotation behavior of magnetic particles in a magnetic field. We designed Tb-Dy-Fe alloys with different Tb/Dy ratios which have different magnetocrystalline anisotropy, and prepared the sintered Tb-Dy-Fe/DyCu compacts under the same process parameters. The magnetocrystalline anisotropy constant K1 of TbxDy1-xFe1.95 (x = 0.27, 0.30, 0.33, 0.50) alloys increased from 0.66 × 106 J/m3 to 3.85 × 106 J/m3 by raising the Tb/Dy ratios, and the <111 > orientation degree of sintered Tb-Dy-Fe/DyCu compacts was promoted simultaneously. The oriented Tb0.33Dy0.67Fe1.95/DyCu sintered compact achieved the highest <111 > orientation degree of 56.6%, resulting in the largest magnetostriction of 1326 ppm and the d33 peak value of 6.81 nm/A.

Vector-Controlled Wheel-Like Magnetic Swarms With Multimodal Locomotion and Reconfigurable Capabilities.

Inspired by the biological collective behaviors of nature, artificial microrobotic swarms have exhibited environmental adaptability and tasking capabilities for biomedicine and micromanipulation. Complex environments are extremely relevant to the applications of microswarms, which are expected to travel in blood vessels, reproductive and digestive tracts, and microfluidic chips. Here we present a strategy that reconfigures paramagnetic nanoparticles into a vector-controlled microswarm with 3D collective motions by programming sawtooth magnetic fields. Horizontal swarms can be manipulated to stand vertically and swim like a wheel by adjusting the direction of magnetic-field plane. Compared with horizontal swarms, vertical wheel-like swarms were evaluated to be of approximately 15-fold speed increase and enhanced maneuverability, which was exhibited by striding across complex 3D confinements. Based on analysis of collective behavior of magnetic particles in flow field using molecular dynamics methods, a rotary stepping mechanism was proposed to address the formation and locomotion mechanisms of wheel-like swarm. we present a strategy that actuates swarms to stand and hover in situ under a programming swing magnetic fields, which provides suitable solutions to travel across confined space with unexpected changes, such as stepped pipes. By biomimetic design from fin motion of fish, wheel-like swarms were endowed with multi-modal locomotion and load-carrying capabilities. This design of intelligent microswarms that adapt to complicated biological environments can promote the applications ranging from the construction of smart and multifunctional materials to biomedical engineering.

Numerical simulation for magnetic field analysis and magnetic adsorption behavior of ellipse magnetic matrices in HGMS: Prediction magnetic adsorption behavior via numerical simulation

Magnetic matrices are the core components of HGMS systems. In this study, the induced magnetic field distribution characteristics of ellipse magnetic matrices are investigated via numerical simulation. Besides, the effects of magnetic matrices structure parameters and magnetic field distribution characteristics on the cumulative adsorption behavior of magnetic particles are also discussed. First, the numerical simulation results indicated that compared with the simulation results of a single magnetic matrix, the multi-matrix composite system simulation results demonstrate that an interaction of the induced magnetic fields generated by the superposition of magnetic fields is enhanced with the increase in the long axis size or the decrease in the gap between the matrices, heightening the magnetic induction but leading to the magnetic field gradient and magnetic field forces to significantly decrease near the surface of the matrix. And the rapid reduction of the magnetic field forces around the single matrix leads to a reduction in the range of action. However, to a certain extent, the interaction of the induced magnetic fields also will make the scope of the magnetic field force expand with the decrease in the gap between the matrices. The magnetic cumulative adsorption tests prove that it is feasible to infer the adsorption behavior of magnetic particles through the numerical simulation and theoretical calculations. The adsorption morphology of magnetic particles on the surface of magnetic matrices show that the repulsive region of magnetic particles is perpendicular to the direction of magnetic field, and the adsorption region of magnetic particles is parallel to the direction of magnetic field and with the increase of the size of magnetic matrices, the effective adsorption area of magnetic particles on the surface of magnetic matrices decreases gradually. Besides, with the increase of the horizontal gap between adjacent magnetic matrices, the adsorption thickness of magnetic particles on the surface of magnetic matrices decreases. Moreover, with the expansion of the horizontal gap between the adjacent magnetic matrices, the adsorption amount of the magnetic particles gradually decreases due to the decrease of the adsorption area and fill rate. The adsorption amount of magnetic particles will decrease as the long axis size increases when the fill rate of the magnetic matrices is similar.

Motion and trapping of micro- and millimeter-sized particles on the air–paramagnetic-liquid interface

Understanding the motion of particles on an air-liquid interface can impact a wide range of scientific fields and applications. Diamagnetic particles floating on an air-paramagnetic-liquid interface are previously known to have a repulsive motion from a magnet. Here, we show a motion mechanism where the diamagnetic particles floating on the air-paramagnetic-liquid interface are attracted and eventually trapped at an off-center distance from the magnet. The behavior of magnetic particles has been also studied and the motion mechanisms are theorized in a unified framework, revealing that the motion of particles on an air-paramagnetic-liquid interface is governed not only by magnetic energy, but as an interplay of the curvature of the interface deformation created by the nonuniform magnetic field, the gravitational potential, and the magnetic energy from the particle and the liquid. The attractive motion mechanism has been applied in directed self-assembly and robotic particle guiding.

Thermal Analysis of Crosslinking Reactions in Epoxy Nanocomposites Containing Polyvinyl Chloride (PVC)-Functionalized Nickel-Doped Nano-Fe3O4

This work reports on the thermal analysis of epoxy containing polyvinyl chloride (PVC) surface-functionalized magnetic nanoparticles (PVC–S/MNP) and its bulk-modified nickel-doped counterpart (PVC–S/MNP/Bi–B). Nanoparticles were synthesized through the cathodic electro-deposition method. The morphology of particles was imaged on a field-emission scanning electron microscope (FE-SEM), while X-ray diffraction analysis and Fourier-transform infrared spectroscopy (FTIR) were used to detect changes in the structure of nanoparticles. The magnetic behavior of particles was also studied by vibrating sample magnetometry (VSM). In particular, we focused on the effect of the bulk (Ni-doping) and surface (PVC-capping) modifications of MNPs on the thermal crosslinking of epoxy using nonisothermal differential scanning calorimetry (DSC) varying the heating rate. The cure labels of the prepared nanocomposites were assigned to them, as quantified by the cure index. The good cure state was assigned to the system containing PVC–S/MNP/Bi–B as a result of excessive ring opening of epoxy. Cure kinetics parameters of PVC–S/MNP/Bi–B incorporated epoxy was obtained by the use of isoconversional methodology. The activation energy of epoxy was decreased upon addition of 0.1 wt% of PVC–S/MNP/Bi–B due to the reaction of Cl− of PVC by the functional groups of resin.

Evolution Strategy-Based Many-Objective Evolutionary Algorithm Through Vector Equilibrium

In recent years, numerous many-objective evolutionary algorithms (MaOEAs) have been developed to search for well-diversified and well-converged Pareto optimal solutions for high-dimensional many-objective optimization problems (MaOPs). However, existing MaOEAs have to tackle some daunting challenges, including the emergence of dominance resistance solutions, effective diversity preservation scheme, management of a large population size, extremely high computational complexity, sensitivity to the shape of Pareto front (PF), and overly relying on high-quality reference points. In this article, we present an evolution strategy (ES) for solving MaOPs, called MaOES, which can solve these challenges efficiently and effectively. Inspired by the Vector Equilibrium phenomenon in magnetic fields, isotropic magnetic particles would automatically repel from each other, keep the uniform distance from the nearest neighbors, and extend the entire magnetic fields as far as possible, all at the same time. In the proposed algorithm, an efficient self-adaptive Precision-Controllable Mutation operator is designed for individuals to explore and exploit the decision space. In addition, the Maximum Extension Distance strategy, which emulates the isotropic magnetic particle behavior in a magnetic field, is developed to guide individuals to keep uniform distance and extension to approximate the entire PF. As a result, the MaOES can obtain a well-converged and well-diversified PF with much less population size and far lower computational complexity. The larger the number of individuals, the sharper the contour the resulting approximate PF will be. Finally, the proposed algorithm is evaluated by the scalable MaOPs test suites on DTLZ and WFG. The experimental results have been demonstrated to provide a competitive and oftentimes better performance when compared against some chosen state-of-the-art MaOEAs.

Feasibility of the multi-particle collision dynamics method as a simulation technique for a magnetic particle suspension

ABSTRACTWe have elucidated the feasibility of the multi-particle collision dynamics (MPCD) method as a technique for the simulation of a magnetic particle suspension, by addressing the dependence of the translational and rotational Brownian motion of the magnetic particles on the parameters that characterise a MPCD simulation. A reasonable level of activation of the Brownian motion is indispensable for simulating the aggregate structures of the magnetic particles because their internal structure is strongly dependent on particle Brownian motion. In the present study, we have employed a diffuse reflection model for treating the interaction between the fluid and the magnetic particles. The diffuse reflection model gives rise to the tendency that the translational Brownian motion of the magnetic particles is more significantly activated than the rotational Brownian motion. If a scaling coefficient is introduced for modifying the interaction between the fluid and the magnetic particles, a more accurate solution may be obtained in regard to the aggregate structures of the magnetic particles. We may conclude that the MPCD method with the diffuse reflection model is a promising simulation technique for analysing the behaviour of magnetic particles in a suspension.

Magnetic Accumulation of SPIONs under Arterial Flow Conditions: Effect of Serum and Red Blood Cells.

Magnetic drug targeting utilizes an external magnetic field to target superparamagnetic iron oxide nanoparticles (SPIONs) and their cargo to the diseased vasculature regions. In the arteries, the flow conditions affect the behavior of magnetic particles and the efficacy of their accumulation. In order to estimate the magnetic capture of SPIONs in more physiological-like settings, we previously established an ex vivo model based on human umbilical cord arteries. The artery model was employed in our present studies in order to analyze the effects of the blood components on the efficacy of magnetic targeting, utilizing 2 types of SPIONs with different physicochemical characteristics. In the presence of freshly isolated human plasma or whole blood, a strong increase in iron content measured by AES was observed for both particle types along the artery wall, in parallel with clotting activation due to endogenous thrombin generation in plasma. Subsequent studies therefore utilized SPION suspensions in serum and washed red blood cells (RBCs) at hematocrit 50%. Interestingly, in contrast to cell culture medium suspensions, magnetic accumulation of circulating SPION-3 under the external magnet was achieved in the presence of RBCs. Taken together, our data shows that the presence of blood components affects, but does not prevent, the magnetic accumulation of circulating SPIONs.

Aggregation and flow behavior of magnetic particles in microchannel flow governed by a transverse magnetic field

Magnetic particles (MPs) can be used as carriers for intentionally transporting medium with the effect of external magnetic field. To reveal the aggregation and transportation regularity of magnetic particles in microchannel flow, the three-dimensional (3D) and two-phase lattice Boltzmann method combined by both the immersed boundary method and the discrete element method is established and the investigation on the evolution of chain-like structure composed of MPs in a microchannel flow governed by transverse uniform magnetic field is investigated. It is revealed MPs can maintain the chain-like structure in the channel flow due to the magnetic dipole force, and the final postures of MP chains are determined by the coupling effect of the base fluid and the chains. The average velocity of the MPs moving in the form of chains is smaller than that moving as discrete elements and the velocity of near-wall fluid is increased. Being a cohesive force, if magnetic dipole force is not large enough, the chain-like structure will be broken due to the push of base fluid with velocity gradient. It is also found that there exists a critical value of the intensity of magnetic dipole force for MPs to maintain the chain-like structure in a microchannel flow with the given inlet velocity. This work demonstrates that, under transverse uniform magnetic field, the discrete MPs can be transported as an entirety in microchannel flow on the promise that the magnetic dipole force is large enough to hold the MPs in the flow field with velocity gradient.

119 Elucidation of the Behavior of Magnetic Particles in an Alternating Magnetic Field for Application to Magnetic Hyperthermia

119 Elucidation of the Behavior of Magnetic Particles in an Alternating Magnetic Field for Application to Magnetic Hyperthermia

Investigation of magneto-optical properties of ferrofluids by laser light scattering techniques

Investigation of magnetooptical characteristics of ferrofluids is an important task aimed at the development of novel optoelectronic systems. This article reports on the results obtained in the experimental studies of the factors that affect the intensity and spatial distribution of the laser radiation scattered by magnetic particles and their agglomerates in a magnetic field. Laser correlation spectroscopy and direct measurements of laser radiation scattering for studies of the interactions and magnetooptical properties of magnetic particles in solutions were employed. The objects were samples of nanodispersed magnetite (Fe3O4) suspended in kerosene and in water. Our studies revealed some new behavior of magnetic particles in external magnetic and light fields, which make ferrofluids promising candidates for optical devices.

LBM-IBM-DEM modelling of magnetic particles in a fluid

A lattice Boltzmann method-immersed boundary method-discrete element method (LBM-IBM-DEM) scheme was presented to simulate the behavior of magnetic particles in a fluid with external magnetic field. In the present scheme, the flow field was solved by the LBM, the DEM with the consideration of the magnetic force was used to describe the particle behavior and the flow field was computed by the momentum exchange-based IBM. Numerical simulations of fluid-particle interactions with uniform magnetic fields in different directions (vertical magnetic field and transverse magnetic field) were carried out to study the particle motion and hydrodynamic behavior in details. The numerical results indicated that the external magnetic force has a significant influence on the particle behavior, where some fragmented chains along the direction are formed and these chain-like clusters continue to lengthen, align, and approach an almost steady state. In addition, we also studied the effect of the magnetic field strength on the motion of magnetic particles showing that in the same particle system, stronger magnetic field brings magnetic particles greater kinetic energy than the low density magnetic field does.

Targeting Behavior of Magnetic Particles Under Gradient Magnetic Fields Produced by Two Types of Permanent Magnets

Fully understanding the dynamics of particles induced by magnetic fields with considering particle-particle interaction is an interesting and important issue for delivering magnetic particles to a target site with a high efficiency. For this purpose, permanent magnets with horizontal and vertical magnetization directions respectively have been taken for generating two types of gradient magnetic fields, which are applied to produce similar gradient magnetic forces while with different magnetic interaction forces between particles. On this basis, the distributions of particles under the two gradient magnetic fields are investigated and compared using Monte Carlo simulations. The results show that the concentrated particles have chainlike structures and their distributions are configuration dependent with the magnetization direction of permanent magnets: parallel and perpendicular to the bottom line for horizontal and vertical magnetization directions, respectively. Above all, a detailed microscopy study reveals that the movement trajectories of magnetic particles are affected by both transport and aggregation behavior of particles and the microscopic visualizations of particle distributions in the target region are in agreement with simulation predictions.

Simulations of behavior of magnetic particles in magnetic functional fluids using a hybrid method of lattice Boltzmann method, immersed boundary method and discrete particle method

Abstract The microstructure formation of magnetic particles in magnetorheological (MR) fluids has an important role on the macroscopic properties such as viscosity. To simulate the behavior and microstructure formation of magnetic particles, hybrid simulations were conducted by combining the lattice Boltzmann, immersed boundary and discrete particle methods, and by taking account of magnetic interactions between magnetic particles under an external magnetic field. The microstructure formation of magnetic particles in an MR fluid between two parallel plates, where one plate moves with constant velocity and the plate remains stationary, is calculated. A sheet-like structure appears when relatively strong shear and strong magnetic field are applied. In contrast, a fibrous-like structure moves in the flow when the shear is small.