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Transcranial Magnetic Stimulation (TMS) coils often are specific to deep brain or focal stimulation. A new technique is used which allows for deep and focal stimulation using temporal interference (TI). TI is a method that allows for steerability, focality, and depth of penetration. TI TMS operates based on the frequency difference of two different electric fields [1]. The TI stimulation frequencies would be in at 10kHz and is filtered by the brain’s inherent lowpass [4] behavior [2]. The frequency difference between the two induced electric fields results in an envelope which allows for a more focal stimulation. By using a coil assembly with several coils (as seen in figure 1), two areas of the brain could be selected and stimulated, focally for use in dual site TMS. Dual site TMS allows for the stimulation of two parts of the brain, which enforces or interferes with brain signals. Dual site TMS stimulation is currently done with two independent coils which are placed on the head and allows for error when placing [3]. The use of a single TI TMS coil for dual site stimulation could allow for a more focused and consistent stimulation for use with dual site TMS.

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2022 Joint MMM-INTERMAG

Temporal Interference for Dual Site Transcranial Magnetic Stimulation

The 15th Joint MMM-INTERMAG Conference (2022 Joint) is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a plenary session, and an evening session, with about 1500 presentations overall. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

The 2022 Joint Conference will offer both in-person and prerecorded on-demand content.

For tickets to the event, please register at the following link: https://magnetism.org/register

Please register for the Joint MMM-Intermag conference to join the event.

poster

The diagnosis and prevention of iron-steel infrastructure deterioration have become critical issues in recent years. To detect steel corrosion, a preliminary study of thickness measurement (extremely low-frequency eddy current testing : ELECT) using a magnetic sensor at extremely low-frequency ranges has been previously reported [1]. Iron-steel materials exhibit large variations in electromagnetic characteristics. In this study, the effect of electromagnetic characteristics on the magnetic thickness measurement was investigated to improve the thickness estimation. Four types of iron-steel plates (SS400, SM400A, SM490A, SMA400AW) with thickness ranging from 1 mm to 20 mm were measured via ELECT. The detected magnetic signal, consisting of a real and an imaginary component at each frequency, was plotted to obtain the magnetic spectrum. The differential magnetic vector between two appropriate frequencies is extracted from the magnetic spectrum, and the plate thickness is then estimated from the phase of the differential magnetic vector. For instance, the linearity of the calibration curves between the phase and thickness for each type of steel plate was obtained in the thickness range of 6–12 mm using a differential vector, which was obtained by subtracting the 3 Hz vector from the 5 Hz vector. However, the calibration curves for each type of steel plate did not coincide. To analyze the phase shift phenomenon, the electromagnetic characteristics (the permeability μ, the obtained magnetization curve, and the conductivity σ) of each type of steel plate were measured. The μσ magnitude relationship for each type of steel is as follows: SM400 &gt; SMA400AW &gt; SS400 &gt; SM490A. The parameter of σμ was correlated in each calibration curve shift, and the linearity region in the curve was shifted to the low-thickness region according to the increment of frequency. Therefore, the difference in calibration curve for each type of iron-steel could be explained by the difference in σμ parameter. In summary, this study clarified the relationship between the electromagnetic properties of various types of iron steel and the phase of detected magnetic signal in the thickness measurement.

Magnetic measurement for various types of iron steel thickness using magnetic sensor and the effect of their electromagnetic characteristics

Magnetic nanoparticles (MNPs) prepared as a stable colloidal suspension dispersed in water have attracted special interest for different applications in theranostics [1]. MNPs of maghemite obtained by a laser target evaporation (LTE) were shown to be excellent candidates for this purpose [2]. Magnetic suspension flowing through the blood vessel creates magnetic fields which can be detected by giant magnetoimpedance magnetic field sensor (GMI) [3]. In this work, we develop a computer model for calculation of the distribution of blood flow velocity V and magnetic fields H in the area of a blood vessel with stenosis. Finite element model (FEM) is used to analyze the properties of the model system reconstructed from the image obtained during routine examination of a patient using angiography. Figures show selected results of the studies. It was shown that the relative change of the magnetic field strength in the area inside the blood vessel doesn’t depend on the value of the external magnetic field He and the value of additional magnetic field connected to the blood flow is proportional to the concentration of MNPs. To describe the results obtained for a model of a real vessel, a model of a vessel in the form of a cylinder with different radius of curvature and thickness was studied. The results of calculations the flow of MNPs in the vessel showed that at 1.5 wt % of MNPs concentration (c=1.5 wt %) the relative change in the magnetic field in the area of stenosis is 0.43%, and in the area before stenosis is 0.33%. According to experimental data, the observed difference in the distribution of magnetic fields at a concentration of LTE MNPs from 0 to 2% can be measured using a thin-film detector of small magnetic fields GMI. This study was supported by the Ministry of Science and Higher Education of the Russian Federation (project No. FEUZ -2020-0051).

![](https://assets.underline.io/uploads/markdown_image/1/image/c3552b4a706a15d7f35085e81cea29cb.jpg)

Fig.1. Velocity distribution in a blood vessel with stenosis. The inset shows the value along the cross-section indicated by horizontal red line.

![](https://assets.underline.io/uploads/markdown_image/1/image/826311968a42b753a82900dafb6fb368.jpg)

Fig.2. Magnetic field (H) distribution in a blood vessel with stenosis. The inset shows the value along the cross-section indicated by horizontal red line. He = 5 Oe and is directed from left to right, c=1.5 wt %.

The Modeling of Magnetic Detection of Iron Oxide Nanoparticles in the Stream of Patient-Specific Coronary Artery with Stenotic Lesion: the Effects of Vessel Geometry and Particle Concentration

Introduction: Simulation based transcranial magnetic stimulation (TMS) studies have demonstrated the importance of anatomical variations in TMS treatments [1]. Most of the studies use magnetic resonance image (MRI) derived heterogeneous head models but lack anisotropy in their electrical and magnetic properties. Our objective was to use modeling and simulation techniques to determine the effect of neuroanatomy on resting motor thresholds (RMT) recorded from the first dorsal interosseous (FDI). Experimental Details: TMS was performed on 10 healthy patients using a Magstim BiStim2 and 70mm figure-of-eight coil and RMT values were collected using electromyography signals as a percentage of the maximum stimulator output (%MSO) [2]. MRI scans including diffusion tensor imaging (DTI) were used for fiber tract extraction (Fig 1), where individual fiber tract surface areas and tract fiber counts for the FDI were determined. T1 and T2 weighted images were taken from the MRI scans for segmentation and creation of anatomically accurate head models using SimNIBS pipeline [1]. Brain scalp distance (BSD) was measured at the point of stimulation in the models. TMS of the head models was simulated using finite element analysis to calculate cortical peak electric fields using Sim4Life (Fig 2) [3]. A linear mixed effects model was used to assess the effects of these parameters on RMT. Results: Peak induced electric fields were in the range of 90.5-147 V/m with a mean of 118.9 V/m at the cortical hotspot. Electric field and RMT are correlated, dependent on fiber tract surface area (p = 0.036) and tract fiber count (p = 0.004), but not on BSD (p = 0.423). Conclusion: The relationship between RMT and electric field intensity depended on both fiber tract surface area and tract count, emphasizing the effect of site-specific cortical architecture. The induced electric field at the hotspot region of the grey matter depended on the stimulator output (i.e. current in the coil). We found that MRI modeling techniques relate to the empirically collected data, suggesting an MRI based approach may be predictive of dosage determination and TMS outcomes.

![](https://assets.underline.io/uploads/markdown_image/1/image/69f60456d51bb65ffad9ae0005c0a087.jpg)

Fig. 1 Fiber tracts extracted from DTI [4].

![](https://assets.underline.io/uploads/markdown_image/1/image/ac2c26188bc7225953ab57da364583e9.jpg)

Fig. 2 M1 region peak electric field intensity.

Effect of Fiber Tracts on Resting Motor Thresholds During Transcranial Magnetic Stimulation

Various magnetic robots have been widely investigated as a possible means to replace conventional biomedical technologies [1, 2]. The use of multi-modular helical magnetic millirobots (MHMMs), such as the one shown in Fig. 1, has especially attracted attention since an MHMM can increase the number of modules by simply attaching additional modules along the longitudinal direction of the body without changing their radial dimensions [3]. Thus, an MHMM may employ multiple functional modules to perform complex tasks within a confined tubular environment such as the human blood vessel. In this research, we analytically and experimentally investigated the locomotive characteristics of the MHMM with respect to a different number of modules. It was seen that the MHMM becomes geometrically more suitable to navigate in a curved and narrow tube as the number of modules increases, even when the overall length of the MHMM does not change. We established a condition to calculate the least required number of modules to make the MHMM navigate in a given tubular condition. It was also seen that the nonlinear characteristics of the MHMM’s rotational movement transmission derived from the universal joint mechanism used to connect modules decreases as the number of modules increases. Therefore, an MHMM composed of a large number of modules can navigate in a tube with a relatively harsh condition in a steady manner. In this research, we constructed prototype MHMMs with a different number of modules, as shown in Fig. 2, and demonstrated various navigating motions to show the validity of the proposed structure. Results showed that the MHMM composed of the largest number of modules (5) can navigate in a more confined tubular environment (high curvature and small diameter) compared to other MHMMs. This research can contribute to the development of multifunctional intravascular robots with high locomotive characteristics for various biomedical applications.

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![](https://assets.underline.io/uploads/markdown_image/1/image/95675a398c69cfb84924c7db950380d1.jpg)

A Study on the Locomotive Advantages of a Multi-Modular Helical Magnetic Millirobot in Curved and Narrow Blood Vessels

A Study on the Locomotive Advantages of a Multi-Modular Helical Magnetic Millirobot in Curved and Narrow Blood Vessels

Implantable drug delivery system is a prevailing approach for the drug administration [1]. The main challenge of implantable drug delivery systems is reliable implementation of a low power actuation device and a micropump with an accurate flow rate. Here we introduce a low flow rate implantable micropump fabricated using 3D printing, based on a low-power electromagnetic actuating system. We have designed the micropump structure shown in Fig. 1(a), made from polydimethylsiloxane (PDMS). The top membrane, which is 100 μm thick, was created using the spin coating. The cylindrical NdFeB magnet was placed on the membrane. The micropump structure and the membrane were bonded by 20 s of oxygen plasma. A solenoid with 2000 turns was applied as the actuator for the micropump, and it was located 2mm above the micropump as Fig. 1(b) depicts. Fig. 1(c) shows how we use the diffuser-nozzle element to achieve valveless one-direction flow. The electromagnetically actuated field could provide a periodic force on the membrane, so this top layer could deflect downward and upward. During the upward motion, negative relative pressure would be created inside the chamber and there will be more liquid drawn into the pump chamber through the inlet. On the contrary, during the membrane’s downward motion, the pressure inside the chamber rises thus more liquid exit through the nozzle than the diffuser. Therefore, a net volume of liquid would be transferred from the diffuser to the nozzle for every period [2]. Under the actuation of a varying magnetic field generated by the electromagnet, micropump can produce a flow rate of 6±0.21 μl/s, which is close to previously simulated work [3]. The fabricated micropump is shown in Fig. 1(d). In summary, we successfully designed and fabricated an implantable drug delivery system, with high precision drug release [4]. The valveless unidirectional flow is achieved by using the diffuser-nozzle structure. More studies will be performed to implement a miniaturized, fully automatic and comfortable system for daily injection applications.

![](https://assets.underline.io/uploads/markdown_image/1/image/b7fc911ea854a9ba203ad4d87fa786ce.jpg)

3D Printed Electromagnetics Micropump for Implantable Drug Delivery

3D Printed Electromagnetics Micropump for Implantable Drug Delivery

Introduction: Transcranial magnetic stimulation (TMS) is extensively used in research and clinical applications pertaining to psychiatric and neurological disorders [1]. The current TMS treatments are all single-focus treatments. To satisfy the requirements of clinical treatment and improve the understanding of the synergies among different brain regions [2,3], researchers are investigating TMS that can stimulate multi brain regions. However, it is not clear whether the TMS can also develop multiple stimulation focal points in the deep brain region. Purpose: The purpose of this study is to investigate whether is it possible to use TMS for multi-focus deep brain stimulation Methods: We first established a mathematical relationship between the multi-focus electric field distribution and the winding of the TMS coil, thereby realizing the stream-function-based inverse design algorithm that can automatically generate the TMS coil winding pattern by setting the target E-field. Thereafter, we fixed the offset distance between the two-focal points of target electric fields and generated the corresponding coils by setting the focal points at different depths, thereby verifying whether the TMS coil can achieve multi-focus E-field to the deep target. Results: When the distance between the two focal points was set to 5 cm, through different depth settings and appropriate parameter selection, we theoretically found that the TMS coil can be developed for a depth that is several times the distance between the two focal points. Moreover, after further verification of the electric field generated by these coils, we found that they all meet the conditions for generating multiple focal points in the deep brain regions. Therefore, we theoretically confirmed that it is possible to use TMS for multi-focus deep brain stimulation.

![](https://assets.underline.io/uploads/markdown_image/1/image/e36c6a4ee603254bec558c7ce93578d4.jpg)

Fig.1 Generation of multi-focus TMS winding when the distance between the two focal points is fixed at 5 cm and are at different depths.

Is it possible to use transcranial magnetic stimulation for multi-focus deep brain stimulation?

Electrical and magnetic stimulation are used for neuromodulator therapies. Electrical stimulation is applied through an electrode in the brain, which is very focal while magnetic stimulation done transcranially, is non-invasive, highly permeable through tissues but not focal. Implantable micromagnetic stimulation (µMS) was pioneered by Bonmassar et al.[1] in 2012 by using commercially available sub-mm sized μcoils to stimulate neurons. As per Faraday’s law of electromagnetic induction, a time-varying magnetic field induces an electric field which is spatially asymmetric. This induced electric field supports selective activation of neurons. Therefore, focal stimulation with magnetic fields may activate different populations of neurons than electrical stimulation and has the advantage that it doesn’t require an electrochemical interface. This creates many safety limitations in the waveforms that can be applied to drive these devices. In this work, we have studied the neuromodulation with solenoidal μcoils of dimensions 1 mm × 0.5 mm × 0.6 mm with 21 turns. By solving a modified version of T-Ω formulation of Maxwell’s equations on ANSYS-Maxwell software, the electromagnetic (EM) field calculations were then integrated to a NEURON model reported by Pashut et al.[2] to detect any possible elicitation of neuron response. Our results indicate that solenoidal μcoils can trigger action potential in neurons locally. Furthermore, excitatory post synaptic (EPSP) experiments performed on rat hippocampal slices for the same μcoils further corroborates our modeling results. This technology, despite its unique advantages is still in its infancy which is in ardent need of a protocol. Hence to fill this research gap, we further validated the EPSPs if they were biological, using a neurotoxin, named tetrodotoxin (TTX) which blocks the sodium channels on the neurons. We have successfully shown that on application of TTX to slices, we see no neuron response to magnetic stimulation; whereas, on washing out TTX, the neuron response from magnetic stimulation reappears.

![](https://assets.underline.io/uploads/markdown_image/1/image/57f4105642049be550632ab01f384a75.jpg)

(a) The μcoil set-up(b) Image of sub-mm sized μcoils(c) The schematic of the driving circuitry(d) Schematic of the rat hippocampal slice(e) The neuron recording set-up.

Implantable Magnetic Microcoils (μcoils) for Neuromodulation

The COVID-19 pandemic has hit and drastically changed the world during the last months. The severe consequences reveal the necessity of new tools and procedures to reduce the impact of future emergencies. Lateral flow immunoassays (LFA), better known as “rapid tests”, have been used to detect the infection. Now, when vaccination is the goal, they can be used to detect the body's immune response. Both immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies are produced against protein S, one of COVID-19 antigens. IgM is produced in the early stages of the infection whereas IgG takes longer but is more durable and could be the key to lasting immunity (Figure 1A-B). In this work, we propose a magnetic rapid serological test to detect and quantify the COVID-19 IgM and IgG antibodies in the blood (Figure 1C). Two different LFA have been designed to separate the antibodies against the RBD (a fragment of protein S). We tagged anti-human IgM and anti-human IgG with magnetic nanoclusters based on ferrite nanoparticles to make them detectable. These will produce a signal in the inductive sensor, specially designed to read LFA out [1][2]. The mapping technique uses an impedance analyzer synchronized with a micropositioner. The microstructural properties of the magnetic nanoparticles have been investigated by XRD, TEM, and AFM techniques while the magnetic properties have been assessed through NMR measurements and SQUID magnetometry. The detection and quantification of IgG and IgM are promising not only to identify exposed individuals but to generate quick data for rapid decision making. The authors would like to thank IEEE Magnetics Society for funding.

![](https://assets.underline.io/uploads/markdown_image/1/image/715779147c9702ba564970a9c9ec0ab7.jpg)

Figure 1. A) SARS-COVID-2 structure and amplification of protein S. B) Serology response: IgM and IgG production. C) Schematic LFA with its components. D) Schematic configuration of the tests designed to quantify the IgM (left) and IgG (right). Created with BioRender.com.

![](https://assets.underline.io/uploads/markdown_image/1/image/96c25f688cef533e93cd0c970f09d5f9.jpg)

Figure 2. Inductive measurement setup to accurately quantify the IgG and IgM.

A rapid magnetic serological test for COVID-19

Magnetic nanoparticles have been drawn much attention and discussion for their biomedical applications. Previously, we reported the relationship between AC magnetic susceptibilities and significant hyperthermia effect of several kind of magnetic nanoparticles [1,2]. However, in order to utilize biomedical treatment, biocompatibility and dispersibility are important factors. In this study, we prepared Ni-ferrite nanoparticles with diameter between 3 nm and 17 nm when magnetic properties were first investigated. Then several sizes of polyethylene glycol (PEG) were modified to magnetic nanoparticles to solve the above problems. Effective heat dissipation for magnetic hyperthermia treatment in AC field depends on the magnetic relaxation parameters. AC magnetic measurements were performed in order to estimate the heating effect of MNPs for hyperthermia treatment. The particle size of the samples were varied and examined. Fig.1 shows the temperature increase of PEGylated Ni-ferrite nanoparticles in a 150 Oe, 15 kHz field. As expected by magnetic measurements, the 17 nm- sample showed significant heating effect than other samples. The temperature rose to more than 42.5 degrees Celsius, a temperature at which cancer cells are greatly supressed. Using human breast cancer cells, toxicity of PEGylated magnetic nanoparticles and without modified particles was investigated. The PEGylated samples showed a 30% increase in cell viability, confirming the improved biocompatibility of PEG modification. Furthermore, PEG has hydrophilic property, and the hydrodynamic diameter in water was measured to be about one order of magnitude smaller (Fig.2). Thus, the improvement of dispersibility in water was confirmed. Thus, we successfully developed highly biocompatible and dispersible magnetic Ni-ferrite nanoparticles and these particles were expected to be agents for hyperthermia treatment.

![](https://assets.underline.io/uploads/markdown_image/1/image/8c03f65d99bad85130e5bdfb4866d428.jpg)

Fig1. Increase in temperature of various particle sizes of PEGylated Ni-ferrite nanoparticles.

![](https://assets.underline.io/uploads/markdown_image/1/image/edde948e51fcce79c14a886ea2f45b3d.jpg)

Fig.2 Water dispersibility of samples with varying amounts of PEG modification.

Development of Biocompatible Ni-ferrite Nanoparticles for Magnetic Hyperthermia

With the ongoing global pandemic of coronavirus disease 2019 (COVID-19), there is an increasing quest for more accessible, easy-to-use, rapid, inexpensive, and high accuracy diagnostic tools. Traditional disease diagnostic methods such as qRT-PCR (quantitative reverse transcription-PCR) and ELISA (enzyme-linked immunosorbent assay) require multiple steps, trained technicians, and long turnaround time that may worsen the disease surveillance and pandemic control. In sight of this situation, a rapid, one-step, easy-to-use, and high accuracy diagnostic platform will be valuable for future epidemic control especially for regions with scarce medical resources. Herein, we report a magnetic particle spectroscopy (MPS, see Fig.1) platform for detection of SARS-CoV-2 biomarkers: spike and nucleocapsid proteins.[1]This technique monitors the dynamic magnetic responses of magnetic nanoparticles (MNPs) and uses their higher harmonics as a measure of the nanoparticles’ binding states.[2,3] By anchoring polyclonal antibodies (pAbs) onto MNP surfaces, these nanoparticles function as nanoprobes to specifically bind to target analytes (SARS-CoV-2 spike and nucleocapsid proteins in this work) and form nanoparticle clusters. This binding event causes detectable changes in higher harmonics and allows for quantitative and qualitative detection of target analytes in liquid phase.[4] We have achieved detection limits of 1.56 nM (equivalent to 125 fmole) and 3.13 nM (equivalent to 250 fmole) for detecting SARS-CoV-2 spike and nucleocapsid proteins, respectively, as shown in Fig.2. This MPS platform combined with one-step, wash-free, nanoparticle clustering-based assay method is intrinsically versatile and allows for the detection of a variety of other disease biomarkers by simply changing the surface functional groups on MNPs.

![](https://assets.underline.io/uploads/markdown_image/1/image/3d37e47db5c2cfb0d72184dca1783bf1.jpg)

Fig.1. (a) Photograph of the MPS portable device with a smartphone application. The overall dimensions of device are 212 mm (L) × 84 mm (W) × 72 mm (H). (b) Photograph of the internal structures of the MPS device. (c) and (d) are the 3D models of the device.

![](https://assets.underline.io/uploads/markdown_image/1/image/1a1a222a873ba044453a3c65d935768d.jpg)

Fig.2. Concentration-response profiles of SARS-CoV-2 (a) spike and (b) nucleocapsid proteins.

Temporal Interference for Dual Site Transcranial Magnetic Stimulation

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