Ferromagnetic Particles Research Articles

Match detection analysis on SentiMag® system and standard technique in SLNB of breast cancer

IntroductionIn breast cancer surgery, there are techniques for sentinel lymph node biopsy (SLNB) that do not require Nuclear Medicine, such SentiMag®, which uses ferromagnetic particles. The main purpose of this analysis is to study the degree of concordance in SLNB between SentiMag® and the standard method (Tc99 radiotracer). The secondary objective is to identify factors that impact in sentinel node detection rate and matching detection rate between both probes. MethodsObservational and retrospective study performed from January to December 2021 focused on patients undergoing breast surgery and SLNB who were injected with both tracers, the ferromagnetic SentiMag® and Tc99 radiotracer. Once the diagnostic accuracy tests were performed, a further evaluation of the detection rate for each probe and the concordance between probes were accomplished. After those results, a deeper analysis of differences in detection rates for each probe and concordance between probes were assessed for various factors: neoadjuvant therapy, BMI, mitotic index, and triple-negative immunohistochemical profile. ResultsThe clinical study had a sample size of 70 patients. The overall false-negative rate (FNR) was 4.3%. The detection rate was the same for each technique (85.7%). A total of 106 nodes were biopsied, with a concordance rate of 70.75%. Significant differences were found in concordant nodes according to neoadjuvant therapy (p-value 0.012). For the Ki-67 factor (<20 or ≥20), significant differences were found in detected nodes (p-value 0.031 gamma probe; p-value 0.124 SentiMag®). ConclusionsThe detection rates of SentiMag® and the gamma probe are equivalent. The application of the dual technique minimizes the FNR. A high mitotic index affects the detection rate of the gamma probe, and neoadjuvant therapy negatively impacts the concordance rate.

The Arrhenius law prefactor in permalloy mesoscale systems

The Arrhenius equation was used to describe the dynamics of two-state switching in mesoscale, ferromagnetic particles. Using square permalloy dots as an idealized two-state switching system, measurements of the prefactor of the Arrhenius law changed by 26 decades over barrier heights from 30 to 700 meV. Measurements of the prefactor ratios for a two well system revealed significant deviations from the common interpretation of the Arrhenius law. The anomalous Arrhenius prefactors and the prefactor ratios can be fitted to a modified model that includes entropic contributions to two-state transitions. Similar considerations are likely for the application of the Arrhenius law to other mesoscale systems.

Effect of isotropy and anisotropy: Toward understanding the fracture behavior of magnetoactive elastomers

Magnetoactive elastomers (MAEs) exhibit magneto-mechanical coupling and typically contain micron-sized spherical ferromagnetic particles embedded in an elastomeric matrix. Anisotropic particle arrangement in MAEs, achieved by curing the material in a magnetic field, offers tailored and enhanced magneto-mechanical coupling compared to isotropic configurations. While tunable MAE properties such as the effective modulus and vibrational response have been relatively well studied, a thorough understanding of their fracture mechanisms, particularly in MAEs with microstructural anisotropy or composites with similar structures remains almost completely unexplored. Here, we characterize the fracture mechanisms of anisotropic and isotropic unmagnetized MAEs using experiments and simulations, focusing on the effects of spherical particles in anisotropic chain-like configurations. Specifically, we experimentally measure the fracture toughness of MAEs containing different volume fractions of particles, and with particles arranged both randomly and aligned at 0°, 45°, and 90° to the loading direction. Results show that anisotropic MAEs with particle chains aligned with the load direction can improve fracture toughness by up to almost 600%, whereas isotropic MAEs increase the fracture toughness by only 420%, compared to the pure elastomer. Scanning electron microscopy of the post-fractured surface reveals toughening mechanisms at micro-scale, such as chain waviness, particle agglomeration, and particle distribution. Simulations using a finite element method-based decoupled phase field-cohesive zone model on simplified geometries qualitatively support imaging interpretations. Overall, this work explains how internal geometry, including waviness in particle chains, chain alignment, and particle agglomerations affects fracture of MAEs and generally soft composites with chain-like geometries of spherical particles. These results have engineering applications in improving fracture properties of smart soft composites relevant to soft robotics, tunable vibration absorbers, and noise attenuators.

Optical evidence of domain wall pinning in iron-garnet films by regular arrays of ferromagnetic particles

Control over the magnetic domain structure of garnet films is an important task that is attractive for a wide range of applications. One of the possible approaches here is based on the introduction of additional structured magnetic coverages interacting with the garnet layer. In this study, we demonstrate that arrays of asymmetric ferromagnetic cobalt particles regularly arranged on the surface of Lu,Bi-substituted iron garnet film influence the orientation and width of the stripe domains, as stems from the optical microscopy, magneto-optical and diffraction studies. We also show that triangular-shaped Co particles induce the asymmetry of the magnetic field dependence on the magneto-optical Kerr effect of the composite structure. We assert that the key effect here is the interaction of the residual magnetic moments of Co particles with the surface closure domains.

Pinning of domain walls in epitaxial garnet film patterned by surface arrays of ferromagnetic metal particles

Rare-earth iron garnet epitaxial films famous for their unique magnetic, microwave and optical properties consistently attract high interest. Domain structure of both bulk and interfaces of garnet films is closely connected with their magnetic properties and magnetization dynamics. In this work, we investigate the magnetic behaviour and domain structure of an epitaxial bismuth-substituted lutetium iron garnet film with a regular array of planar submicron particles made of Co film or Co/Pt multilayer on its surface. Optical polarization microscopy and magnetic force microscopy techniques used for the characterization of these composite structures confirm the mutual influence of the garnet and metal nanostructured layers on each other. On the one hand, dense ordered metal particles provide the pinning of the surface magnetic domains of the garnet film, which further affects the organization of the bulk stripe domains. On the other hand, we observed that the domain structure in the metallic pattern is governed by the domain structure of the garnet placed beneath it.

Microwaves in ferromagnetic composites Fe/Epoxy with aggregates of nanoparticles: Theory and experiment

Microwave transmission through plates of a composite material containing spherical Fe nanoparticles in an epoxyamine matrix and reflection from plates have been studied. Measurements were carried out at the frequencies from 26 to 32 GHz in the magnetic fields up to 12 kOe. The ferromagnetic resonance phenomenon in the composite has been investigated. The theory of electromagnetic waves transmitting through a composite material containing ferromagnetic particles, taking into account aggregating the particles, has been developed. A good agreement of calculation results and experimentally obtained field dependences of the transmission and reflection coefficients, as well as microwaves dissipation, has been achieved.

Multifunctional Magnetic Muscles for Soft Robotics

Despite recent advancements, artificial muscles have not yet been able to strike the right balance between exceptional mechanical properties and dexterous actuation abilities that are found in biological systems. Here, we present an artificial magnetic muscle that exhibits multiple remarkable mechanical properties and demonstrates comprehensive actuating performance, surpassing those of biological muscles. This artificial muscle utilizes a composite configuration, integrating a phase-change polymer and ferromagnetic particles, enabling active control over mechanical properties and complex actuating motions through remote laser heating and magnetic field manipulation. Consequently, the magnetic composite muscle can dynamically adjust its stiffness as needed, achieving a switching ratio exceeding 2.7 × 10³. This remarkable adaptability facilitates substantial load-bearing capacity, with specific load capacities of up to 1000 and 3690 for tensile and compressive stresses, respectively. Moreover, it demonstrates reversible extension, contraction, bending, and twisting, with stretchability exceeding 800%. We leverage these distinctive attributes to showcase the versatility of this composite muscle as a soft continuum robotic manipulator. It adeptly executes various programmable responses and performs complex tasks while minimizing mechanical vibrations. Furthermore, we demonstrate that this composite muscle excels across multiple mechanical and actuation aspects compared to existing actuators.

A Finemet-based microfluidic single-coil microsensor for monitoring oil condition

Wear is an unavoidable phenomenon that generates debris particles. i.e., ferromagnetic and non-ferromagnetic particles. If the system's condition is not monitored effectively, wear can lead to the breakdown of the system. Therefore, an inductive-resistance sensor was designed to monitor and detect debris particles. Moreover, Finemet (Fe73.5Si13.5B9Nb3Cu1) was applied to the sensor to improve its sensitivity. A comparison simulation and experiment examined the sensor's performance and Finemet's impact. The study shows that the induction mode has greater sensitivity in detecting ferromagnetic particles, while the resistance mode is more sensitive in detecting non-ferromagnetic particles. This study also demonstrates that the application of Finemet boosts the sensitivity of the sensors in both findings, indicating the significance of Finemet for the sensor's applications.

Dynamics of resonant magnetoelectric effect in a magnetoactive elastomer based cantilever: Magnetic field induced orientation transition and giant frequency tuning

Magnetoelectric (ME) effects in composite heterostructures containing mechanically coupled ferromagnetic and piezoelectric layers enable the mutual transformation of magnetic and electric fields and form the basis for the development of magnetic field sensors, actuators and energy harvesters. Promising materials for such composite structures are magnetoactive elastomers (MAE), which are silicone matrices with ferromagnetic particles uniformly distributed within them. The strong dependence of MAE properties on magnetic fields and their low rigidity enable contactless control of ME effects characteristics within such structures. In this work we have experimentally investigated the dynamics of resonant ME effects in a structure consisting of a MAE layer with carbonyl iron particles and a layer of polyvinylidene fluoride piezopolymer in a cantilever geometry. For the structure magnetized in a plane along the axis, the frequency tuning of the bending oscillations reached 360 % at the fields up to 2 kOe, and the maximum ME conversion coefficient was 1.74 V/(Oe·cm). For the structure magnetized perpendicular to the plane, an orientation transition was observed, which manifested itself as a jump-like bending of the structure to the angle up to ∼850 at magnetic field above the critical value. The frequency tuning by the magnetic field reached 185 %, and the maximum ME conversion coefficient was 135 V/(Oe·cm). A model has been developed that qualitatively describes the dynamics of ME effect in composite cantilever structures with a MAE layer for different orientations of the applied magnetic field.

Interdiffusion mechanism of hybrid interfacial layers for enhanced electrical resistivity and ultralow loss in Fe-based nanocrystalline soft magnetic composites

Soft magnetic composites (SMCs) composed of ferromagnetic particles and insulating binder are highly desired in energy-saving and high-efficiency devices for their high electrical resistivity and softer saturation characteristics. However, traditional insulation coatings are facing thermal instability, inhomogeneous distribution, and magnetic dilution, presenting a major challenge for the trade-off relationship between power loss and permeability. Here, the phosphate-coated FeSiBCuNb/SiO2 SMC is successfully fabricated by a unique interdiffusion effect in hybrid interfacial layers, which shows a combination of ultralow power loss of 135.8 kW/m3 (50 kHz/100 mT), high effective permeability of 80.6, and good temperature stability. The interdiffusion behavior between Si/O and Fe/P/O elements promotes the formation of ultrathin, uniform, and multilayer interface structure, which alleviates the magnetic dilution. Penetrating oxidation at the edge interface and elements interdiffusion effect contribute to a higher electrical resistivity induced by hot isostatic pressing with rapid quenching, leading to a low eddy current loss. Synergistic effect of isostatic pressures and rapid quenching facilitates the formation of high-density Cu clusters corresponding to ultrafine microstructure, which is beneficial for low coercivity and low hysteresis loss. This study involves the interdiffusion mechanism of hybrid interfacial layers and nanocrystalline behavior, providing a new strategy for the next-generation of high-performance SMCs.

EXPERIMENTAL INVESTIGATION OF NEWLY DEVELOPED ELECTROLYTIC MAGNETIC ABRASIVE FINISHING SETUP WITH MULTIPLE POLE SYSTEM FOR FINISHING OF ALUMIUM WORKPIECE

The procedure of combining abrasion machining with chemical machining is the most demanding and crucial method of machining, because it guarantees higher levels of quality from the part. Combined procedure for machining are typically employed as the last step in the machining process, and their significance grows progressively crucial while a nano finished surface of the work piece material is necessary. The subject of nano surface finishing of materials via chemical machining and abrasion has advanced recently. Electrolytic magnetic abrasive finishing (EMAF) is a procedure that combines chemical and magnetic energy to achieve a desire finish. During the EMAF process, The work piece fits in the middle among two magnetic poles. A mixture of abrasives and ferromagnetic particles fills the gap between each pole and the workpiece. The electrode is positioned at a certain distance from the workpiece, and both are linked to a direct current (DC) power source. An electrolytic solution is circulated between the gap using a pump. The method offer a wide range of industrial applications because to its low specific energy consumption and enhanced surface finishing. This study presents the creation of a novel EMAF with multiple pole system. It further looks into the impact of different process attributes include machining time, rotational speed, size of the abrasive particles, electrolytic concentration and weight of the abrasive particles on the improved performance of material removal rate (MRR) and surface finishing (PISF).

Multifunctional Polymer Composites for Automatable Induction Heating with Subsequent Temperature Verification

Manipulating ferromagnetic particles using an alternating current (AC) magnetic field is a versatile method for quick, local, and on‐demand heat generation. These particles can be incorporated into various matrices as heating elements. Their heat release can be controlled by adjusting process or material parameters. Herein, a proof‐of‐concept for a flexible polymer composite with customizable magnetically triggered heat release due to prior object identification via fluorescence readout is presented. The maximum temperature resulting from this process can be determined through a second fluorescence readout ex post. This novel combination of functionalities results from the synergistic interaction of inductively heatable magnetic supraparticles (SPs) and luminescent communicating SPs in one polydimethylsiloxane composite. The surface of the composite can be heated to the maximum temperatures of choice in a range between 125 and 200 °C within 2 s. Heat release and temperature verification provide spatial resolution of millimeters. The identification signature and the working range of the temperature indication functionality of the composite are customizable by exploiting its modular material design. The temperature indication functionality of the composite offers spatial resolution and ex‐post readout at any point of interest, making it a versatile alternative to established optical thermometry methods.

Permanently magnetized elastomer rotating actuator using traveling waves

We report a soft actuator that generates continuous rotation of an object placed on it by electromagnetically exciting circular travelling waves in a soft disk. The disk, that serves as the stator, is made of a stretchable composite consisting of segments of silicone elastomer in which hard ferromagnetic particles are embedded. Inspired by piezoelectric traveling wave rotary actuators, the disk’s 16 sections are driven by underlying printed circuit board coils to create a flexural traveling wave on the disk’s surface. The rotor can be any object directly placed on the stator: the traveling wave in the stator leads by friction to the rotation of the rotor. Unlike conventional electromagnetic motors that rely on a precisely controlled gap between stator and rotor, a concept incompatible with soft robotics, our device exploits the contact between rotor and stator and the associated dry friction to generate torque. Rotation speeds of over 6 rpm were obtained for a partially rice-filled balloon, 30 cm diameter, weighing 17 g. We report detailed speed and performance metrics when rotating plastic disks. With this rotating actuator, we demonstrate an innovative way to transmit torques and rotations within soft structures.

Effects of particle surface modification on magnetic behavior of soft magnetic Fe@SiO2 composites and Fe compacts

The study aims to evaluate the influence of surface modification of Fe powder on the magnetic behavior of soft magnetic compacts and composites that can possibly enhance their properties. The smoothing of ferromagnetic particle surfaces led to a decrease in the total energy loss as the most evident positive impact in all investigated classes (max. by 11% for small, 63–125 μm particle-based annealed Fe compacts, at max. induction 0.5 T and frequency 100 Hz) and to a partial increase in specific electrical resistivity (max. by 47% for small particle-based Fe@SiO2 composites) and resonant frequency (max. by 48% for large, 200–400 μm particle-based Fe@SiO2 composites) as well as partial decrease in coercivity (max. by 14% for small particle-based annealed Fe compacts). Removing surface irregularities negatively affected the maximum total permeability (max. drop by 28% for large particle-based Fe@SiO2 composites) due to increased inner demagnetizing fields. Applying the Bertotti theory for loss separation, we obtained parameters of loss components and assumed the domain structure using simultaneously active magnetic objects as predictors. The total loss decrease observed after the smoothing process originates from the significantly increased numbers of active magnetic objects, facilitating AC magnetization reversal so that domain wall displacements are accompanied by lower energy loss, manifested as a decrease in the excess loss component (max. by 61% for small particle-based Fe@SiO2 composites).

Magneto-Acoustic Theranostic Approach: Integration of Magnetomotive Ultrasound Shear Wave Elastography and Magnetic Hyperthermia.

Although magnetically induced hyperthermia has shown great efficiency in the treatment of solid tumors, it is still a challenge to avoid incomplete ablation or overtreatment. In this study, we applied magnetomotive ultrasound shear wave elastography (MMUS-SWE) as a tool for real-time image guidance and feedback in the magnetic hyperthermia (MH) process. We called this new method as magneto-acoustic theranostic approach (MATA). In MATA, a ferromagnetic particle (fMP) was simultaneously used as a thermoseed for MH and a shear wave source for MMUS-SWE. The fMP was excited by a high-frequency magnetic field to induce the heating effect for MH. Meanwhile, the fMP was stimulated by a pulsed magnetic field to generate shear wave propagation for MMUS-SWE. Thus, the changes in elastic modulus surrounding fMP can be used to estimate the therapy effect of MH. The phantom and in vitro experiments were conducted to verify the feasibility of MATA, which has good performance in magnetothermal conversion and treatment efficacy feedback. The shear wave speed of the isolated pork liver changed significantly after the MH process, which varied from about 1.36 to 4.85 m/s. Preliminary results proved that changes in elastic modulus could be useful to estimate the therapy effect of MH. We expect that MATA, which is the integration of MMUS-SWE and MH, will be a novel theranostic method for clinical translation.

Oil wear debris sensor with temperature compensation

In this paper, in response to the problem that oil temperature changes will affect the detection results of the inductive wear debris sensor, a Wheatstone bridge-type oil wear debris sensor was designed using two two-wire helical tube coils, precision potentiometers, precision resistors, and a conditioning circuit with differential, phase-locked, and amplification functions were designed. Through practical tests, 72–400 μm iron particles were detected under the water bath's heating condition from 20℃ to 70℃. It proves that the designed Wheatstone bridge sensor and conditioning circuit can detect ferromagnetic particles in multiple temperature oil. The de-signed sensor and conditioning circuit effectively solves the problem of temperature drift of the detected signal under high-temperature conditions, improving the signal-to-noise ratio of wear debris detection under multiple temperatures. The sensor is suitable for lubricant detection systems with varying or constant high oil temperatures. The work presented in this paper provides significant reference value for the practical operation of oil sensors in real-world environments.

4D printing of magnetic smart structures based on light-cured magnetic hydrogel

In recent years, with the development of materials science, various new materials that can sense external stimuli and respond have emerged. This ability to respond to external stimuli enables these materials to empower other materials or structures, greatly promoting the development of soft robots. In recent years, many 4D printed magnetic silicon gels have appeared, while 4D printing of magnetic hydrogels is still a blank slate. Here, we have developed a light-curable magnetic hydrogel that can be 4D printed. Unlike traditional methods of thickening hydrogels for 3D printing, we added bentonite to thicken the printing ink and controlled its rheological properties to make it suitable for printing. During the printing process, we used capacitive momentary discharge to generate a strong magnetic field to program the printing ink, eliminating the need for pre-treatment of the printing ink. We also studied the influence of the content of ferromagnetic particles and the size of the external magnetic field on its responsiveness. Finally, we printed and programmed the hydrogel on a silicone sheet to empower the silicone sheet. Based on this, we have created a variety of different types of soft actuators to achieve different movements and functions.

Synthesis of CS-Fe3O4/GO nanocomposite for adsorption of heavy metal in aqueous environment

In this study, magnetic material based on graphene oxide (GO) was developed for enhanced adsorption capacity for heavy metals. The Fe3O4 nanoparticles were combined with the GO material using a chitosan (CS) binder to obtain the CS-Fe3O4/GO nanocomposite. The adsorption capacity of this nanocomposite was evaluated by removing heavy metals including Ni2+ ions. When GO was composed with Fe3O4 and CS, the GO films were densely covered with ferromagnetic particles, which were bound and densely distributed on the GO film surface due to the interaction between GO and CS. The optimal conditions for the complexation of Ni2+ and 4-(2-pyridyl azo)-rezoxine (PAR) are 1 ml Ni2+, 2 ml PAR 100 mg l−1, pH = 6 (adjusted with 0.7 ml of the 0.1 M K2HPO4 solution) and a complexation time of 20 min. After 50 min of adsorption, the Ni2+ removal efficiency of the CS-Fe3O4/GO nanocomposite reached 81.21% and the corresponding adsorption capacity was 2.03 mg g−1 . The Ni2+ removal process followed the first-order model and Freundlich isotherm. This process was spontaneous (ΔG o < 0) and an exothermic process (ΔH o = −1128.875 J·mol−1). In addition, the factors affecting this process were investigated, including the pH solution, the dosage of the CS-Fe3O4/GO nanocomposite and the initial Ni2+ concentration. The CS-Fe3O4/GO nanocomposite showed a potential adsorption capacity in removing Ni2+ at low concentrations from wastewater.

Activation of Zeolite in a Magnetic Fluidized Bed

The influence of the phase composition of zeolite rocks and their modification under the influence of an electromagnetic field in an environment of ferromagnetic particles on the physical properties and sorption of heavy metals has been studied. The results of water purification from heavy metals using activated zeolite in a magnetic fluidized bed are presented.

The Design and Study of a Four-Coil Oil Multi-Pollutant Detection Sensor

The operating environment of large mechanical equipment on ships is extremely harsh. Under such harsh conditions, it is necessary to effectively monitor and assess the health status of machinery and equipment and to take appropriate maintenance measures to ensure the normal operation of the ship and the safety of the lives and property of the crew. However, currently used methods are less effective in detecting non-ferromagnetic abrasive particles and non-metallic contaminants and may not be able to respond to certain emergencies promptly. Therefore, in this paper, a quad-solenoid coil multi-contaminant oil detection sensor is proposed to detect metallic abrasive particles and non-metallic contaminants using the voltage–capacitance dual mode. We provide an analytical expression for the magnetic field strength of the present sensor and develop a corresponding mathematical model. In order to verify its accuracy, we compared the model results with finite element analysis and verified them experimentally. Analysis of the experimental results shows that by switching the detection mode of the sensor, ferromagnetic metal particles, non-ferromagnetic metal particles, and non-metallic contaminants in the oil can be identified according to the different experimental signal curves. The sensor recognizes ferromagnetic particles over 70 μm in diameter, non-ferromagnetic particles over 220 μm in diameter, water droplets over 100–110 μm in diameter, and air bubbles over 180–190 μm in diameter. By comparing the sensor with existing sensors, the sensor can provide accurate information about various pollutants, help maintenance personnel to develop a reasonable maintenance program, and reduce the maintenance cost of ship machinery.