Capture Of Magnetic Particles Research Articles

Non-uniform magnetic particle capture based on single-fiber optical tweezers

In this study, single-fiber optical tweezers are used to capture polystyrene magnetic particles with non-uniform surfaces. By preparing the tip of the optical fiber probe in the shape of a protruding cone, the laser beam is highly converged at the tip of the fiber to form a strong focused light field, and the laser beam can pass through the gap between the inorganic magnetic particles on the surface of the magnetic particles and enter into the internal polystyrene to generate a gradient force and realize the stable capture of the magnetic particles. This method provides a feasible and effective solution for the capture of non-uniform polystyrene magnetic particles using optical fiber and opens up new possibilities for research in related fields.

Separation mechanism and experimental investigation of pulsating high gradient magnetic separation

Pulsating high gradient magnetic separation (PHGMS) has been widely used for separating magnetic minerals in the past decades. In practice, magnetic field and flow field are the main factors that affect the capture of magnetic particles by medium wires. Therefore, an insight into the magnetic field distribution and the flow field distribution around the matrix would provide a crucial foundation for understanding the separating mechanism. In this investigation, the magnetic field and the flow field in the PHGMS process are simulated. Furthermore, the capture of hematite on matrix and its dependence on the key parameters of the PHGMS separator, i.e., wire diameter of rod matrix, particle size, magnetic induction and flow velocity are analyzed. The results indicate that the slurry forms a roundabout flow around the wire and the fluid velocity around the magnetic wire’s left and right sides is far greater than that of the upper and lower sides; with the increase of distance from the magnetic wire surface, the magnetic induction intensity around the magnetic wire decreases gradually. It all proves that the magnetic particles are mostly captured on the upper and lower surface of the magnetic wires in the matrix. The optimized parameters obtained from pilot-scale, the rod diameter of 2 mm, particle size of 60%, magnetic field intensity of 0.9 T and re-cleaning magnetic field intensity of 1.1 T. When all the parameters are optimized, a full-scale PHGMS process produced a magnetic concentrate assaying 63.24% Fe with 93.67% recovery from the hematite feed assaying 49.22% Fe.

Model of Magnetic Particle Capture Under Physiological Flow Rates for Cytokine Removal During Cardiopulmonary Bypass.

The objective of this study is to design a physical model of a magnetic filtration system which can separate magnetic nanoparticle (MNP)-tagged cytokines from fluid at physiologically relevant flow rates employed during cardiopulmonary bypass (CPB) procedures. The Navier-Stokes equations for the pressure driven flow in the chamber and the quasistatic stray magnetic field produced by an array of permanent magnets were solved using finite element analysis in COMSOL Multiphysics for 2D and 3D representations of the flow chamber. Parameters affecting the drag and magnetic forces including flow chamber dimensions, high gradient magnet array configurations, and particle properties, were changed and evaluated for their effect on MNP capture. Flow chamber dimensions which achieve appropriate flow conditions for CPB were identified, and magnetic force within the chamber decreased with increased chamber height. A magnetic "block" array produced the highest magnetic force within the chamber. Polymeric microparticles loaded with MNPs were shown to have increased particle capture with increased hydrodynamic diameter. The model achieved a predicted efficiency up to 100% capture in a single-pass of fluid flowing at 1.75 L/min. This work is an important step in designing a magnetic flow chamber that can remove the magnetically tagged cytokines under high flow employed during CPB. Cytokines have been shown to stimulate the systemic inflammatory response (SIR) associated with CPB and are an established therapeutic target to mitigate the SIR. In the long term, this work aims to guide researchers in the more accurate design of magnetic separation systems.

Simulation of magnetic particle capture in the breast

New strategies, such as magnetic guidance of medicines, are used in cancer treatment. This work determined the topological characteristics of blood vessels in the breast with cancer. To remove the topology of the blood vessels mammogram imaging of cancer patients, image preprocessing was performed using conventional methods (Canny, Prewitt, and Sobel), with neural networks, and with light correction techniques, a 3D model was generated with finite element software to simulate velocity and blood flow, 700 nanoparticles of Magnetite were included, with a magnet of Neodymiun and the number of nanoparticles reaching the tumor was evaluated. The best results were obtained with the light correction method that improved the definition of blood vessels with the topology obtained and more particles were found to reach the magnetic field tumor compared when it is absent.

Dynamic capture and accumulation of multiple types of magnetic particles based on fully coupled multiphysics model in multiwire matrix for high-gradient magnetic separation

High-gradient magnetic separation (HGMS) effectively separates fine weakly magnetic minerals using a magnetic matrix. The basic principle of single-wire capture of magnetic particles in HGMS has received considerable attention. In practice, however, a real matrix is made of numerous magnetic wires. Transport of magnetic particles inside a multiwire matrix under various operating conditions has not been sufficiently investigated, and it is not clear whether single-wire and multiwire matrices differ significantly. A fully coupled multiphysics model based on the idealized capture model was developed to investigate the 2D capture and accumulation of multiple types of particles in single-wire and multiwire matrices. In this model, the properties of multiple types of particles were defined. Then, particle tracing via the fluid flow model was used to calculate the dynamic capture and accumulation of particles under the determined magnetic and flow fields. The time-dependent dynamic capture mode used in this study can reveal the details of particle capture and accumulation in single-wire and multiwire matrices. All the calculations and analyses indicate that single-wire and multiwire matrices both exhibit basically the similar capture tendency as the particle size, slurry feed velocity, and magnetic induction are gradually increased, and a single-wire matrix always has a much higher capture selectivity than a multiwire matrix. This difference in selectivity between the single-wire and multiwire matrices results mainly from magnetic coupling between magnetic wires in the multiwire matrix, where the fluid flow is also quite complicated. In addition, adjacent columns of wires are staggered vertically, increasing the probability of collisions between the particles and the wires; thus, intergrowth particles that are not captured by the upstream wires are more easily captured by the downstream wires. By comparing the experimental results with the simulation results, the correctness of the HGMS recovery and grade prediction results was verified.

Investigation on magnetization induced by tightly focused azimuthally polarized fractional vortex beam

All-optical magnetic recording based on the inverse Faraday effect has become a research hotspot in recent years due to its ultra-high storage density and ultra-fast magnetization reversal rate. Existing studies have shown that by optimizing the phase modulation or performing 4π tight focusing of azimuthally polarized vortex beams, high-resolution longitudinal magnetization fields with different axisymmetric intensity patterns can be generated. In order to meet the requirements of more complex all-optical magnetic recording and asymmetric magnetic particle capture and manipulation, it is particularly important to generate an asymmetric light-induced magnetization field with adjustable center position. Studies have shown that the fractional vortex phase could lead to the asymmetric focal field distribution generation under tight focusing conditions, which means that the tightly-focused azimuthally polarized light carrying the fractional vortex phase can produce a novel asymmetric light-induced magnetization field. As a new degree of freedom for the regulation of the magnetization field, the fractional topological charge will bring more new phenomena, new effects and new applications in the field of interaction between light and matter. In this work, for the first time to our knowledge, the magnetization induced by tightly focused azimuthally polarized fractional vortex beam is studied based on the Richard-Wolf vector diffraction theory and the inverse Faraday effect. The equivalent approximation of the magnetization induced by azimuthally polarized fractional vortex beam regarded as a weighted superposition of magnetization induced and crossly induced by a finite number of azimuthally polarized adjacent integer-order vortex beams, where the number of the equivalent terms is chosen by using the histogram intersection method of the intensity distribution image of the magnetization field. The magnetization field distribution under different values of <i>α</i> are also numerically simulated. Studies have shown that magnetization induced by the azimuthally polarized fractional vortex beam is asymmetrically distributed. When the fractional vortex topological charge α belongs to [0.5,1.5], as the vortex topological load increases, the splitting phenomenon of the transverse distribution of magnetization field appears with the magnetization spot position shift in the direction perpendicular to the optical axis. When <i>α</i> equals 0.5 or 1.5, the maximum offset of the center of the magnetization spot is 0.24<i>λ</i>. When the fractional vortex topological charge α belongs to [2,3], the transverse distribution of magnetization field splits two hot intensity spots with gradually growing outer ring diameter. When the fractional vortex topological charge <i>α</i> tends to be an integer 3, the transverse distribution of magnetization field also gets round and symmetrical. In particular, when the fractional vortex topological charge α is a half-integer, especially larger than 3. The number of hot spots (<inline-formula><tex-math id="M8">\begin{document}$\alpha - 0.5 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20200269_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20200269_M8.png"/></alternatives></inline-formula>) of the intensity of the magnetization field and the number of dark spots (<inline-formula><tex-math id="M9">\begin{document}$ \alpha - 1.5 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20200269_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20200269_M9.png"/></alternatives></inline-formula>) surrounded by them all have a positive correlation with the number of vortex order. The research in this paper is expected to have new applications in the fields of all-optical magnetic recording and the capture and manipulation of magnetic particles.

High gradient magnetic separation with involved Basset history force: Configuration with single axial wire

High gradient magnetic separation (HGMS) is an efficient and useful technique for the recovery of weakly magnetized microparticles. Usually the process of magnetic particle capture is considered to be governed by competition between the magnetic attraction of the particles to the magnetized wires, the Stokes viscous drag, and gravitational force on the particle. For the complete description of the motion of magnetic microparticles we have used the Maxey-Riley integro-differential equation containing also additional forces. We have therefore analysed the importance of these forces, especially the Basset history force and the added mass force, using an axial single wire HGMS filter with a bounded flow field. As has been found, magnitude of the Basset history force is largest in the close proximity to ferromagnetic wire, when the acceleration of microparticles is highest due to the large value of magnetic force. Including the Basset history force term into the description of the movement of a spherical magnetic particle in the moving fluid under the influence of the external magnetic force causes an expected deceleration of its movement. For example, relative capturing delay reaches values up to 10% (in absolute values few hundreds of microseconds). The obtained results clearly demonstrate the importance of these, usually neglected forces for the correct description of capture dynamics.

Centrifugal high gradient magnetic separation of fine ilmenite

High gradient magnetic separation (HGMS) has been an effective method for the concentration or removal of fine para-magnetic particles from suspension, but its powerful magnetic capture to magnetic particles results in the mechanical entrainment of non-magnetic particles in magnetic product, and thus reduces the separation selectivity. HGMS in centrifugal field (CHGMS) is proposed to improve the separation selectivity, and in this investigation a cyclic pilot-scale CHGMS separator was used to concentrate fine ilmenites from slurry. The theoretical descriptions on this CHGMS process indicate that the introduction of centrifugal field in the HGMS field has a promoting effect on the magnetic capture of matrix to magnetic particles and significantly improves the HGMS performance, and a minimum critical magnetic field force is required for the capture of magnetic particles in the centrifugal field. These theoretical descriptions were experimentally verified and the dependence of CHGMS performance on the key parameters such as centrifugal acceleration was determined. This CHGMS method has achieved a significantly improved separation selectivity and performance to the fine ilmenite, and thus provided a potential prospect in the development of CHGMS technology.

Simulation of dynamic magnetic particle capture and accumulation around a ferromagnetic wire

A new approach for modeling high gradient magnetic separation (HGMS)-type systems during the time-dependent capture and accumulation of magnetic particles by a ferromagnetic wire was developed. This new approach assumes the fluid (slurry) viscosity, comprised of water and magnetic particles, is a function of the magnetic particle concentration in the fluid, with imposed maxima on both the particle concentration and fluid viscosity to avoid unrealistic limits. In 2-D, the unsteady-state Navier-Stokes equations for compressible fluid flow and the unsteady-state continuity equations applied separately to the water and magnetic particle phases in the slurry were solved simultaneously, along with the Laplace equations for the magnetic potential applied separately to the slurry and wire, to evaluate the velocities and concentrations around the wire in a narrow channel using COMSOL Multiphysics. The results from this model revealed very realistic magnetically attractive and repulsive zones forming in time around the wire. These collection zones formed their own impermeable viscous phase during accumulation that was also magnetic with its area and magnetism impacting locally both the fluid flow and magnetic fields around the wire. These collection zones increased with an increase in the applied magnetic field. For a given set of conditions, the capture ability peaked and then decreased to zero at infinite time during magnetic particle accumulation in the collection zones. Predictions of the collection efficiency from a steady-state, clean collector, trajectory model could not show this behavior; it also agreed only qualitatively with the dynamic model and then only at the early stages of collection and more so at a higher applied magnetic field. Also, the collection zones decreased in size when the accumulation regions included magnetic particle magnetization (realistic) compared to when they excluded it (unrealistic). Overall, this might be the first time a mathematical model was shown to be capable of realistically predicting the dynamic nature of magnetic particle capture and accumulation around a wire in HGMS-type systems.

Optimization of an endovascular magnetic filter for maximized capture of magnetic nanoparticles.

To computationally optimize the design of an endovascular magnetic filtration device that binds iron oxide nanoparticles and to validate simulations with experimental results of prototype devices in physiologic flow testing. Three-dimensional computational models of different endovascular magnetic filter devices assessed magnetic particle capture. We simulated a series of cylindrical neodymium N52 magnets and capture of 1500 iron oxide nanoparticles infused in a simulated 14mm-diameter vessel. Device parameters varied included: magnetization orientation (across the diameter, "D", along the length, "L", of the filter), magnet outer diameter (3, 4, 5mm), magnet length (5, 10mm), and spacing between magnets (1, 3mm). Top designs were tested in vitro using 89Zr-radiolabeled iron oxide nanoparticles and gamma counting both in continuous and multiple pass flow model. Computationally, "D" magnetized devices had greater capture than "L" magnetized devices. Increasing outer diameter of magnets increased particle capture as follows: "D" designs, 3mm: 12.8-13.6%, 4mm: 16.6-17.6%, 5mm: 21.8-24.6%; "L" designs, 3mm: 5.6-10%, 4mm: 9.4-15.8%, 5mm: 14.8-21.2%. In vitro, while there was significant capture by all device designs, with most capturing 87-93% within the first two minutes, compared to control non-magnetic devices, there was no significant difference in particle capture with the parameters varied. The computational study predicts that endovascular magnetic filters demonstrate maximum particle capture with "D" magnetization. In vitro flow testing demonstrated no difference in capture with varied parameters. Clinically, "D" magnetized devices would be most practical, sized as large as possible without causing intravascular flow obstruction.

Computational Study of Kinematics of Capture of Magnetic Particles by Stent: 2-D Model

This paper presents a simple 2-D model to study the kinematics of capture of 1 $\mu \text{m}$ diameter magnetic particles (MPs) by a periodic array of magnetic wires, which are aligned perpendicularly to Poiseuille flow in a rectangular 2-D channel in order to suggest improvements in the design of stent-assisted drug-targeting systems. The model examines the following: 1) the kinematics of particles near the wires; 2) the distribution of captured particles across the array of wires; and 3) the final position of particles that are not captured. An external homogenous magnetic field is applied perpendicularly to the axis of the wires and either perpendicular to or along the flow in order to magnetize the particles and the wires to saturation. The trajectories of MPs are determined using the first-order stiff ordinary differential equations that are solved numerically using MATLAB. These trajectories reveal that regardless of the orientation of external magnetizing field, it is always the first wire that captures the MPs. In addition, the particles that are not captured are found to be repelled to the center of the channel when compared with their starting position. This is an unexpected phenomenon indicating that the repulsive effect of the magnetic stent is stronger than the attractive effect, and the simplicity of our model allowed us to expose this previously undiscovered effect.

Dynamics of Magnetic Nanoparticles in Newly Formed Microvascular Networks Surrounding Solid Tumours: A Parallel Programming Approach

In this paper we extend a previous 2D parallel implementation of a continuous-discrete model of tumour-induced angiogenesis. In particular, we examine the transport and capture of magnetic nanoparticles through a newly formed vascular network of blood vessels. We demonstrate how our models can be used to describe the dynamics of magnetic nanoparticles in a microvasculature and observe that the orientation of the blood vessels with respect to the magnetic force crucially affects particle capture rates leading to heterogeneous particle distributions. In addition, efficiency of magnetic particle capture depends on the ratio between the magnetic velocity and blood vessel aspect ratio. Such simulations allow a more detailed understanding of the use of magnetic nanoparticles as a mechanism for targeted anti-cancer drug delivery.

Investigation of the Capture of Magnetic Particles From High-Viscosity Fluids Using Permanent Magnets.

This paper investigates the practicality of using a small, permanent magnet to capture magnetic particles out of high-viscosity biological fluids, such as synovial fluid. Numerical simulations are used to predict the trajectory of magnetic particles toward the permanent magnet. The simulations are used to determine a "collection volume" with a time-dependent size and shape, which determines the number of particles that can be captured from the fluid in a given amount of time. The viscosity of the fluid strongly influences the velocity of the magnetic particles toward the magnet, hence, the collection volume after a given time. In regards to the design of the magnet, the overall size is shown to most strongly influence the collection volume in comparison to the magnet shape or aspect ratio. Numerical results showed good agreement with in vitro experimental magnetic collection results. In the long term, this paper aims to facilitate optimization of the collection of magnetic particle-biomarker conjugates from high-viscosity biological fluids without the need to remove the fluid from a patient.

Magnetic particle capture for biomagnetic fluid flow in stenosed aortic bifurcation considering particle–fluid coupling

Magnetic nanoparticles drug carriers continue to attract considerable interest for drug targeting in the treatment of cancer and other pathological conditions. Guiding magnetic iron oxide nanoparticles with the help of an external magnetic field to its target is the basic principle behind the Magnetic Drug Targeting (MDT). It is essential to couple the ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD) principles when magnetic fields are applied to blood as a biomagnetic fluid. The present study is devoted to study on MDT technique by particle tracking in the presence of a non uniform magnetic field in a stenosed aortic bifurcation. The present numerical model of biomagnetic fluid dynamics (BFD) takes into accounts both magnetization and electrical conductivity of blood. The blood flow in the bifurcation is considered to be incompressible and Newtonian. An Eulerian–Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow using ANSYS FLUENT two way particle–fluid coupling. An implantable infinitely long cylindrical current carrying conductor is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Results concerning the velocity and temperature field indicate that the presence of the magnetic field influences the flow field considerably and the disturbances increase as the magnetic field strength increases. The insert position is also varied to observe the variation in flow as well as temperature field. Parametric investigation is conducted and the influence of the particle size (dp), flow Reynolds number (Re) and external magnetic field strength (B0) on the “capture efficiency” (CE) is reported. The difference in CE is also studied for different particle loading condition. According to the results, the magnetic field increased the particle concentration in the target region. Analysis shows that there exists an optimum regime of operating parameters for which deposition of the drug carrying magnetic particles in a target zone on the partly occluded vessel wall can be maximized. The results provide useful design bases for in vitro set up for the investigation of MDT in stenosed blood vessels.

On Computational Fluid Dynamics Study of Magnetic Drug Targeting

Magnetic drug targeting is continuing to draw attention as a potential technique for cancer and tumour treatment. This paper focuses on the development of computational fluid dynamic models for magnetic drug targeting. Magnetic particle capture has been simulated in a 90o coronary artery bend of circular tube for a range of different particle sizes. The magnetic field is produced by a current carrying wire. It has been found that increasing the sizes of magnetic particles increases the capture of particles. Extensions are made on the model to include the effects of non-Newtonian fluid and the pulsating nature of blood flow. These extensions improved the basic model by simulating a more physiologically accurate application of magnetic drug targeting. A reduction of the particle capture efficiency is experienced based on this physiologically accurate model. Time of injection over the flow cycle of the pulsating nature of blood flow greatly influences the particle capture efficiency.

Effect of non-Newtonian characteristics of blood on magnetic particle capture in occluded blood vessel

Abstract Magnetic nanoparticles drug carriers continue to attract considerable interest for drug targeting in the treatment of cancer and other pathological conditions. Magnetic carrier particles with surface-bound drug molecules are injected into the vascular system upstream from the desired target site, and are captured at the target site via a local applied magnetic field. Herein, a numerical investigation of steady magnetic drug targeting (MDT) using functionalized magnetic micro-spheres in partly occluded blood vessel having a 90° bent is presented considering the effects of non-Newtonian characteristics of blood. An Eulerian–Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow using ANSYS FLUENT. An implantable infinitely long cylindrical current carrying conductor is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Parametric investigation is conducted and the influence of the insert configuration and its position from the central plane of the artery ( z offset ) , particle size ( d p ) and its magnetic property ( χ ) and the magnitude of current (I) on the “capture efficiency” (CE) is reported. Analysis shows that there exists an optimum regime of operating parameters for which deposition of the drug carrying magnetic particles in a target zone on the partly occluded vessel wall can be maximized. The results provide useful design bases for in vitro set up for the investigation of MDT in stenosed blood vessels.

Effects of particle–fluid coupling on particle transport and capture in a magnetophoretic microsystem

A numerical analysis is presented of the effects of particle–fluid coupling on the transport and capture of magnetic particles in a microfluidic system under the influence of an applied magnetic field. Particle motion is predicted using a computational fluid dynamic CFD-based Lagrangian–Eulerian approach that takes into account dominant particle forces as well as two-way particle–fluid coupling. Two dimensionless groups are introduced that characterize particle capture, one that scales the magnetic and hydrodynamic forces on the particle and another that scales the distance to the magnetic field source. An analysis is preformed to parameterize capture efficiency with respect to the dimensionless numbers for both one-way and two-way particle–fluid coupling. For one-way coupling, in which the flow field is uncoupled from particle motion, correlations are developed that provide insight into system performance towards optimization. The difference in capture efficiency for one-way versus two-way coupling is analyzed and quantified. The analysis demonstrates that one-way coupling, in the dilute limit, provides a conservative estimate of capture efficiency in that it overpredicts the magnetic force needed to ensure particle capture as compared with a more rigorous fully coupled analysis. In two-way coupling there is a cooperative effect between the magnetic force and a particle-induced fluidic force that enhances capture efficiency. Thus, while one-way coupling is useful for rapid parametric screening of particle capture performance, more accurate predictions require two-way particle–fluid coupling. This is especially true when considering higher capture efficiencies and/or higher particle concentrations.

Integration of a zero dead-volume PDMS rotary switch valve in a miniaturised (bio)electroanalytical system

This work features the design, fabrication and characterisation of a miniaturised electroanalytical lab on a chip that allows the performance of a complete bioassay, from the capture of magnetic particles through their functionalisation and sample incubation to the detection of electroactive reaction products. The system is built using mainly polymeric materials such as PMMA and PDMS and fast prototyping techniques such as milling and moulding. The system also includes a set of microelectrodes, photo-lithographed on a silicon chip. The novelty lies in the design of the rotary microvalve, which contains a microreactor so that various reaction and incubation steps can be carried out in isolation from the detection event with zero dead volume. This avoids contamination and fouling of the electrodes by proteins or other organic matter, and extends the useful lifetime of the detector. The system operation is demonstrated by a model example, consisting in the functionalisation of streptavidin-coated magnetic particles with biotinylated beta-galactosidase over periods ranging from 5 to 15 min, at which point the particles saturate. Although the system is intended for the development of enzyme-based electrochemical bioassays, the concept of its rotary microreactor can be applied more broadly.

Computational Simulations of Magnetic Particle Capture in Arterial Flows

The aim of Magnetic Drug Targeting (MDT) is to concentrate drugs, attached to magnetic particles, in a specific part of the human body by applying a magnetic field. Computational simulations are performed of blood flow and magnetic particle motion in a left coronary artery and a carotid artery, using the properties of presently available magnetic carriers and strong superconducting magnets (up to B ≈ 2 T). For simple tube geometries it is deduced theoretically that the particle capture efficiency scales as eta sim sqrt{{Mn}_{rm p}}, with Mn p the characteristic ratio of the particle magnetization force and the drag force. This relation is found to hold quite well for the carotid artery. For the coronary artery, the presence of side branches and domain curvature causes deviations from this scaling rule, viz. η ∼ Mn pβ, with β > 1/2. The simulations demonstrate that approximately a quarter of the inserted 4 μm particles can be captured from the bloodstream of the left coronary artery, when the magnet is placed at a distance of 4.25 cm. When the same magnet is placed at a distance of 1 cm from a carotid artery, almost all of the inserted 4 μm particles are captured. The performed simulations, therefore, reveal significant potential for the application of MDT to the treatment of atherosclerosis.

Diffusive Capture of Magnetic Particles by an Assemblage of Random Cylindrical Collectors

We develop an effective medium model describing the capture of ultra-fine magnetic particles (diameter much less than 1 µm) by an assemblage of parallel magnetic cylinders, randomly distributed in static fluid. The continuity equation describing the dynamics of concentration is solved numerically to obtain the concentration in various regions around the collector. The concentration contours are generated and the saturation, accumulation, and depletion regions are indicated. The effect of varying collector packing fractions appears significantly in regions close to the outer boundary of the representative cell where the build-up features of ultra-fine particles near the collector surface are similar for packing fractions in range 5–10%.