Distributed Current Source Method for Modeling of Magnetic and Eddy-Current Fields in Sensing System Design

This paper presents a distributed current source (DCS) method for modeling the eddy current (EC) fields induced in biological or non-ferrous metallic objects in two-dimensional axisymmetric and three-dimensional Cartesian coordinates. The EC fields induced in the objects, magnetic flux density (MFD) in space, and magnetic flux (MF) of the sensing coils are formulated in state-space representation. The harmonic responses of the eddy current fields and electromotive force (EMF) of the sensing coil are formulated in closed-form solutions. The proposed DCS method is applied to design two eddy current sensing systems. The Bio-Differential Eddy Current (BD-EC) sensor distinguishes biological objects, and the Metal-Coaxial Eddy Current (MC-EC) sensor classifies non-ferrous metallic objects. The simulated EC field and EMF are numerically verified by comparing results with finite element analysis. An example is utilized to illustrate the advantage of the DCS method for calculating the MFD, MF, and EMF contributed from the induced ECD in the objects directly, and the EMF generated from each material. The proposed method, along with a prototype of the BD-EC sensor, has been experimentally evaluated on sweep frequency analysis for detecting meat and bone.

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Nanoflowers Versus Magnetosomes: Comparison Between Two Promising Candidates for Magnetic Hyperthermia Therapy

Magnetic Fluid Hyperthermia mediated by iron oxide nanoparticles is one of the most promising therapies for cancer treatment. Among the different candidates, magnetite and maghemite nanoparticles have revealed to be some of the most promising candidates due to both their performance and their biocompatibility. Nonetheless, up to date, the literature comparing the heating efficiency of magnetite and maghemite nanoparticles of similar size is scarce. To fill this gap, here we provide a comparison between commercial Synomag Nanoflowers (pure maghemite) and bacterial magnetosomes (pure magnetite) synthesized by the magnetotactic bacterium Magnetospirillum gryphiswaldense of ⟨D⟩≈ 40 –45 nm. Both types of nanoparticles exhibit a high degree of crystallinity and an excellent degree of chemical purity and stability. The structural and magnetic properties in both nanoparticle ensembles have been studied by means of X–Ray Diffraction, Transmission Electron Microscopy, X–Ray Absorption Spectroscopy, and SQUID magnetometry. The heating efficiency has been analyzed in both systems using AC magnetometry at several field amplitudes (0–88 mT) and frequencies (130, 300, and 530 kHz).

Published in the IEEE Magnetics Society Section within IEEE Access.

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Design and Fabrication of Magnetic System Using Multi-Material Topology Optimization

This paper presents the design and fabrication schemes of a magnetic system consisting of segmented permanent magnet (PM) blocks, back-iron and frame structures. Here, a frame structure aims to bind PM blocks and iron structure. Non-intuitive design of segmented PMs and back-iron are obtained using multi-material topology optimization formulation. Subsequently, a non-magnetic frame structure is designed through a post-processing procedure, which is proposed using the smoothed fields of optimized PM and back-iron densities. Final design results are converted into computer-aided design (CAD) models and fabricated using conventional or additive manufacturing techniques. Segmented PM blocks, and back-iron structures are processed using water-jet cutting and wire electrical discharge machining, respectively. A frame structure is fabricated by additive manufacturing using a multi-jet printing machine. Using the proposed schemes, two magnetic systems are successfully designed and fabricated, respectively, for maximizing the magnetic field inside a rectangular cavity, and maximizing the magnetic force generated with a C-core electromagnet.

Published in the IEEE Magnetics Society Section within IEEE Access.

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