United States

Transcranial Magnetic Stimulation (TMS) coils are usually specialized for use in either deep brain or focal stimulation. One of the challenges in the development of TMS
therapy is the ability to deliver a focused magnetic field to the desires target in the brain. In the process of delivering a sufficiently strong H field to the target, surrounding areas of the brain
can be stimulated unnecessarily. A new technique is used here whereby deep and focal stimulation can be achieved using temporal interference (TI). TI is a method that allows for control
of steerability, focality, and depth of penetration. TI uses the frequency difference of two independent electric fields [1]. The TI stimulation frequencies in at 10kHz and is filtered by the
brain’s inherent lowpass [2] behavior [3]. The frequency difference between the two induced electric fields results in an envelope which allows improved focality of stimulation. By using a
coil assembly as shown in Figure 1, and using TI, the focality of the peak induced electric can be increased with respect to the surrounding area as shown inf Figure 2.. This focal point can
also be steered along the centerline between the two coils. Our current work involves using Sim4Life software on 50 unique head models derived from magnetic resonance imaging (MRI)
scans. We are investigating the focality of the induced electric field using our coil design with TI signals. The results will be compared with the commonly used figure-of-eight TMS coil
and the novel design Quadruple Butterfly Coil (QBC) [4].&lt;br&gt;

**References:**&lt;br&gt;

[1] M. Zaeimbashi, A. Khalifa, C. Dong, Y. Wei, S. Cash, and N. Sun, “Magnetic Temporal Interference For Noninvasive, High-resolution, and Localized Deep Brain
Stimulation: Concept Validation,” 2020.&lt;br&gt;
[2] B. Hutcheon and Y. Yarom, “Resonance, oscillation and the intrinsic frequency preferences of neurons,” Trends in Neurosciences, vol. 23, no. 5, pp. 216–222, 2000.&lt;br&gt;
[3] M. M. Sorkhabi, K. Wendt, and T. Denison, “Temporally Interfering TMS: Focal and Dynamic Stimulation Location,” 2020 42nd Annual International Conference of the IEEE
Engineering in Medicine &amp; Biology Society (EMBC), 2020.&lt;br&gt;
[4] P. Rastogi, “Novel coil designs for different neurological disorders in transcranial magnetic stimulation,” PhD Thesis, Iowa State University, Ames, IA, USA, 2019. Available:
https://lib.dr.iastate.edu/etd/17547
Brain Mapping, vol. 29, no. 1, pp. 82–96, 2007.&lt;br&gt;

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MMM 2022

Temporal Interference for Increased Focality of Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) coils are usually specialized for use in either deep brain or focal stimulation. One of the challenges in the development of TMS
therapy is the ability to deliver a focused magnetic field to the desires target in the brain. In the process of delivering a sufficiently strong H field to the target, surrounding areas of the brain
can be stimulated unnecessarily. A new technique is used here whereby deep and focal stimulation can be achieved using temporal interference (TI). TI is a method that allows for control
of steerability, focality, and depth of penetration. TI uses the frequency difference of two independent electric fields [1]. The TI stimulation frequencies in at 10kHz and is filtered by the
brain’s inherent lowpass [2] behavior [3]. The frequency difference between the two induced electric fields results in an envelope which allows improved focality of stimulation. By using a
coil assembly as shown in Figure 1, and using TI, the focality of the peak induced electric can be increased with respect to the surrounding area as shown inf Figure 2.. This focal point can
also be steered along the centerline between the two coils. Our current work involves using Sim4Life software on 50 unique head models derived from magnetic resonance imaging (MRI)
scans. We are investigating the focality of the induced electric field using our coil design with TI signals. The results will be compared with the commonly used figure-of-eight TMS coil
and the novel design Quadruple Butterfly Coil (QBC) [4]. 

**References:** 

[1] M. Zaeimbashi, A. Khalifa, C. Dong, Y. Wei, S. Cash, and N. Sun, “Magnetic Temporal Interference For Noninvasive, High-resolution, and Localized Deep Brain
Stimulation: Concept Validation,” 2020. 
[2] B. Hutcheon and Y. Yarom, “Resonance, oscillation and the intrinsic frequency preferences of neurons,” Trends in Neurosciences, vol. 23, no. 5, pp. 216–222, 2000. 
[3] M. M. Sorkhabi, K. Wendt, and T. Denison, “Temporally Interfering TMS: Focal and Dynamic Stimulation Location,” 2020 42nd Annual International Conference of the IEEE
Engineering in Medicine & Biology Society (EMBC), 2020. 
[4] P. Rastogi, “Novel coil designs for different neurological disorders in transcranial magnetic stimulation,” PhD Thesis, Iowa State University, Ames, IA, USA, 2019. Available:
https://lib.dr.iastate.edu/etd/17547
Brain Mapping, vol. 29, no. 1, pp. 82–96, 2007. 

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poster

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

The Conference was held from October 31 to November 4 and offers both in-person and on-demand content.

MMM 2022 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 tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

In this in vivo study, we have used Magnetic Pen or MagPen (see Fig. 1(a)) to stimulate the rat sciatic nerve which led to the report of the dosage response curve for
micromagnetic stimulation (μMS). As reported earlier [1], the MagPen prototype consists of sub-mm size microcoil (μcoil) at its tip (see Fig. 1(b)). When driven by alternating current, this
μcoil generates a time-varying magnetic field, which induces an electric field on any conductor (here, the sciatic nerve) according to Faraday’s Law of electromagnetic induction. This
induced electric field activates the nerve. This work reports how the directionality of the magnetic μcoil plays a direct role in activating nerves directly observed in hind limb muscle
twitches. These limb twitches have been quantitatively characterized using electromyography (EMG) recordings. Furthermore, we have studied how on varying the amplitude and
frequency of the micromagnetic stimuli, alters hind limb muscle movements. Thereby, a dosage response curve for μMS was generated. The highlight of this dosage response curve is that,
at higher frequencies, significantly smaller amplitudes of MagPen stimuli can trigger limb twitches. This frequency-dependent nerve activation can be explained directly from Faraday’s
Law as the magnitude of the induced electric field used in neuromodulation is proportional to frequency. In our previous work of in vitro μMS of rat hippocampal slices [1], we explained
the frequency-dependent, low-power activation of μMS through numerical simulations. This work further corroborates the same concept through experiments. Implantable μMS is a novel
neuromodulation technique which is still in its infancy and aims to address the potential drawbacks of electrical implants in terms of MRI compatibility and biofouling. Since the induced
electric fields from these magnetic μcoils are not in galvanic contact with the nerve, μMS offers flexibility in applying waveforms to drive these magnetic implants (see Fig. 1(c)).
Fig 1. (a) Different directionalities of the MagPen prototype. Only Type V can activate the sciatic nerve. (b) Size of the sub-mm size μcoil implant compared to a rice grain. (c) The
waveform that activated the nerve. 

**References:** 

[1] Saha R., Faramarji S et al. (2022) Strength-frequency curve for micromagnetic neurostimulation (μMS) through EPSPs and numerical modeling. J. Neural Eng. 19 016018. 

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In vivo Micromagnetic Stimulation of the Rat Sciatic Nerve

Maintenance of homoeostasis in human body is a very important indicator in all cell activities. Persistent acid-base imbalance leads to diseases such as metabolic and
respiratory acidosis or alkalosis. When exposed to a disease, various immune cells are activated due to the inflammatory response, and particularly T cells play a role in inducing apoptosis
of mutated cells such as tumor cells. When the activity of T cells is very low, infection by external invasion is easy, and on the contrary, excessive activation lead to chronic inflammation
caused by autoimmune diseases. Many clinical studies related to pulsed magnetic field (PMF) demonstrated its efficacy in reducing pain, improving blood circulation, as well as blood's
acid-base balance.[1-2] Therefore, our study has tried to investigate the influence of PMF on the regulation of acid-base homeostasis in EL4 cells, which are T cells formed through
lymphoma generated by inducing 9,10-dimethyl-1,2-benzanthrance to C57BL mice. In addition, we tried to explain the role of PMF on immune cell activity by measuring the level of proinflammatory
cytokines such as TNF-α and INF-γ in culture supernatants. EL4 cells were cultured in a DMEM medium supplemented with 10% FBS and 1% penicillin at a concentration
of 5.5 × 104 cells/ml in an incubator at 37 °C and 5% CO2 condition. Our PMF stimulator has the maximum intensity of 4700G at a transition time of 222 μs with pulse intervals of 1Hz.
The homoeostasis in pH was improved as the intensity of PMF increases.(Fig.1) Cell viability decreased by 32% after PMF stimulus of 4700G. It was observed that the concentration of
TNF-α and INF-γ, a cytokine related to inflammation, also decreased as the strength of PMF increased. These results suggest that PMF stimulus improves the anti-inflammatory effect,
therefore, it is thought to affect the immune system of the human body by balancing the activation and suppression of immune cells. For clinical use, our study might suggest non-invasive
PMF can be developed as a medical devices modulating immune system, although it is necessary to optimize the PMF conditions such as pulse shape, duration, or repetition rate. 

**References:** 

[1] N. M. Shupak, F. S. Prato & A. W. Thomas, Neurosci. Lett. Vol. 363, p.157–162(2004). 
[2] S. Bang & H. Lee, AIP Advances, 11(1), 015242(2021). 

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Effect of pulsed magnetic field in murine T lymphoma EL4 cells

The use of magnetic nanoparticles for cancer cell destruction is widely known due to their applications such as magnetic hyperthermia and magneto mechanical actuation
(MMA). Previously, we presented our results regarding a new type of magnetic particles (MPs), i.e. Fe-Cr-Nb-B MPs, prepared by wet milling of superferromagnetic precursor glassy
ribbons, designed for cancer treatment by MMA [1]. These MPs have an important shape anisotropy and a large saturation magnetization, which generates an improved torque in a rotating
magnetic field, producing important damages on the cellular viability of cancer cells. Inspired by these findings, we tested the possibility of using magnetic nanowires (NWs) that have a
higher shape anisotropy. Furthermore, the Fe-Co alloy that we propose has high saturation magnetization values. We prepared Fe64.5Co35.5 NWs with lengths of 4 microns by electrolytic
deposition in alumina membranes with a pore diameter of 200 nm.
The Fe-Cr-Nb-B MPs and Fe-Co nanowires were tested on human osteosarcoma cells (HOS) using various concentrations of particles and found that both are biocompatible in vitro.
Subsequently, we studied the effect of MMA in a rotating 80 Oe magnetic field and frequency of 2 Hz on the viability of HOS. We used MPs and NW with different concentrations, and
exposure time of 30 minutes, applied 24 hours after the introduction of the MPs and NWs into cell culture media. The results indicated that with a concentration of 1 mg/ml of MPs and 0.1
mg/ml of NWs, respectively, the cell viability decreased to about 6-7%. The concentration of NWs needed to induce cancer cell death is 10 times lower than the one needed for MPs. It is
worth mentioning that although NWs are more efficient when using low quantities, due to their higher magnetization and anisotropy, the magnetic nanoparticles are better internalized and
metabolized by cells. Therefore, MPs can be better targeted in tissues harder to reach than NWs. The latter are also harder to control, being more suitable for superficially-developed cancer
tissues.
Supported by (UEFISCDI) Contract no. PCE20/2021 (PN-III-P4-ID-PCE-2020-2381). 

**References:**
 1. H. Chiriac et al. Sci. Rep., 8.11538 (2018)

Cancer cell destruction by magneto mechanical actuation of nanowires compared with nano/micromagnetic particles

Nanosized magnetic materials form a single domain and, as a result, magnetic nanoparticles (MNPs) usually lose their ferromagnetic properties. However,
superparamagnetic NPs can generate sufficient heat to kill cancer cells under a weak magnetic field. In this study, NiFe2O4 NPs with particle sizes of 3–17 nm were prepared for
application in magnetic hyperthermia treatment (MHT), and their biocompatibility was improved by modification with polyethylene glycol (PEG). PEG is hydrophilic and is often used in
the medical field. Direct current (DC) magnetization measurements showed that all the samples exhibited no hysteresis or superparamagnetic behavior at 300 K. The temperature
dependence of the alternating current (AC) magnetic susceptibilities revealed that the peak temperature of the imaginary part of AC magnetic susceptibilities (χ") varied significantly with
particle size, and the 17 nm sample had a peak at approximately 310 K. It is known that χ" contributes significantly to heat generation owing to magnetic relaxation losses. The temperature
increase of the samples under an AC magnetic field (f = 15 kHz, h = 150 Oe) was measured. The sample with 17 nm particles showed a significant heating effect compared to the other
samples, reaching over 42.5 °C, which is sufficient to suppress cancer cells. Human breast cancer cells (MDA-MB-231) were cultured on a petri dish, and PEG-coated NiFe2O4 NPs were
added. The sample was heated using an AC magnetic field. Approximately 30% of cancer cells were successfully killed, and the magnetic hyperthermia effect was confirmed (Fig.1). To
evaluate the toxicity of PEG-coated magnetic NPs toward cancer cells, cell viability was observed for 24 h after the particles were dispersed in the culture dishes. PEG-coated NiFe2O4 NPs
successfully improved biocompatibility. Thus, NiFe2O4 NPs are expected to be useful agents for MHT. By using a zero-voltage switching (ZVS) circuit and generating an AC magnetic
field from a DC power source, a temperature rise two to eight times higher than that using conventional coils was achieved (Fig.2). 

**References:** 

P. Das, M. Colombo, D. Prosperi, Coll. Surf. B 174, 42 (2019) 

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Biocompatible Superparamagnetic NiFe2O4 Nanoparticles for Magnetic Hyperthermia Treatment using a ZVS Circuit

This work describes the use of magnetoresistive (MR) sensors coupled with a portable platform for the detection of dengue virus (DENV), a mosquito-borne infection
endemic to low- and middle-income countries, affecting 100-400 million people each year[1]. Nowadays, diagnosis relies on molecular or serological tests. Still, these tests remain discrete
(RNA vs. antibodies), and tend to be complex and/or expensive, requiring expert staff and fully equipped laboratories. As such, this work aims to combine both assays in a single analysis
by simultaneously detecting DENV RNA and anti-DENV antibodies using a portable platform[2,3]. A spin-valve based biochip was designed and functionalized with specific DNA oligo
probes and secondary antibodies (Fig1A)[4]. Extracted RNA and serum samples were provided by INSA-CEVDI and used as targets in molecular and serological assays, respectively. In
both assays, streptavidin coated 250 nm magnetic nanoparticles were used for biolabeling. The measurement output is represented by a voltage drop (dV/V) proportional to the number of
captured target molecules (Fig1B). However, to increase the dynamic range of the assays, the percentage difference of dV/V signals obtained using different immobilization
strategies/probes, was taken as the final output signal. Using the MR-platform, individual tests were carried out for the detection of DENV RNA and anti-dengue human antibodies. The
RNA target was detected down to a few hundreds of pM (Fig2A). For the serological response, a calibration curve with an LOD of 1.38 nM was achieved. Infected patients’ serum was also
tested for anti-DENV antibodies, obtaining a sensitivity of 100% and a specificity of 92%(Fig2B). Finally, simultaneous detection of antibodies and RNA was successfully achieved on the
same chip, showing no differences to the individual assays. To increase the multiplexing capability of the assay, a biochip with 144 sensors and multi-level contact layers was developed
and is under testing using DENV as a model disease. This chip design will allow the simultaneous discrimination of various viruses endemic in the same regions. 

**References:** 

[1] Who.int. 2022. Dengue and severe dengue. [online] Available at: <https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue> [Accessed 14 June 2022]. 
[2] J. Germano et al., Sensors 9, 4119 (2009). 
[3] V. C. Martins et al., Biosensors and Bioelectronics 24, 2690 (2009). 
[4] D. C. Albuquerque et al., Biosensors and Bioelectronics 210, 114302 (2022). 

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Portable Magnetoresistive Device for the Simultaneous Detection of Dengue RNA and Anti dengue Antibodies

Currently, the treatment of suppression of cytokine storm in severe COVID-19 patients includes cytokine receptor suppression and depletion of specific immune cells in
addition to steroid treatment. Monoclonal antibody therapy is also one of the methods for depleting specific immune cells. It is a monoclonal antibody therapy against CD3, one of the
important signaling molecules for T-cell receptor activation. Among others, T cells secrete interferon gamma (IFN-γ), a pro-inflammatory cytokine responsible for inducing inflammation.
Therefore, monoclonal antibody therapy againstis a therapy that specifically depletes IFN-γ-secreting T cells. However, intravenous injection of an anti-CD3 monoclonal antibody targeting
all T cells induces significant immunosuppression and has side effects such as high fever and chills. The purpose of this study is to prepare an optimized liquid phase as a CD3 antibodymagnetic
nanoparticle (Ab-MNP) conjugate to inhibit the overactivation of T cells. In current study, we aimed to check distribution of Fe after acute admistration of silica-conjugated
amine nanoparticles delivered by intravenous injection. Besides, the IFN- γ levels in serum and spleen homogenates will be analyzed. Finally, we will develop film-type microneedle patch
using pulse-type magnetic stimulation to control the amount of liquid passing through the skin. The reason for choosing the spleen from the mouse organ is that it stores MNPs with a
particle size of 50 nm administered in vivo. Therefore, the result is a difference in the concentration of Fe elements, which was 1.89×103 mg/kg in the spleen of a control mouse not
administered with MNPs, whereas increases significantly to 1.93×103 mg/kg in that of a mouse administered with MNPs as shown in Fig. 1(a) and 1(b). IFN-γ level in spleen tissue and
serum is increased after 10 days. Further, time kinetic analysis of biochemical and immunological parameters are required to confirm its suitability in bio-administration. 

**References:** 

[1] N. S. Remya, S. Syama, A. Sabareeswaran, and P. V. Mohanan, Toxicity, toxicokinetics and biodistribution of dextran stabilized Iron oxide Nanoparticles for biomedical
applications, International Journal of Pharmaceutics 511, 586-598 (2016). 
[2] F. Gao, An Overview of Surface-Functionalized Magnetic Nanoparticles: Preparation and Application for Wastewater Treatment, Chemistry Select 4, 6805-6811 (2019).<br<
[3] R. Q. Cron, R. Caricchio, and W. W. Chatham, Calming the cytokine storm in COVID-19, Nature Medicine 27, 1674–1675 (2021). 
[4] C. Kuhn and H. L. Weiner, Therapeutic anti-CD3 monoclonal antibodies: from bench to bedside, Immunotherapy 8, 889–906 (2016). 

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Analysis of Fe element and interferon gamma in serum and spleen homogenates after injection of silica coated magnetic nanoparticles (SiO2 Fe3O4)

In this work, we have displayed an easy way to produce monodisperse spinel nanoparticles (NPs), as well as the antifungal activity of CoFe2O4, Co0.5Zn0.5Fe2O4 and
ZnFe2O4 nanostructures. Firstly, the structural, morphological and magnetic properties of each NP were fully investigated through x-ray diffraction (XRD), Transmission Electron
Microscopy (TEM) and Vibrating Sample Magnetometer (VSM). The XRD data showed diffraction peaks related to the crystalline spinel phase. No additional phase was observed, which
evidences the purity of the nanostructure synthesized. The TEM micrographs displayed monodisperse NPs with spherical morphology. The average sizes of CoFe2O4, Co0.5Zn0.5Fe2O4
and ZnFe2O4 NPs were found to be 6.87 ± 0.05 nm, 5.18 ± 0.01 nm and 11.52 ± 0.09 nm, respectively. The VSM data indicated the nanostructures are superparamagnetic at room
temperature. Afterwards, the antifungal properties of the Co/Zn-based ferrite NPs against Botrytis cinerea were tested. So, the inhibition of mycelial growth by different concentrations (45
– 360 ppm) of NPs was measured. The most effective nanostructure was found to be CoFe2O4 with an EC50 value of 265 ppm. To go further and elucidate how the NPs are affecting B.
cinerea, reactive oxygen species (ROS) production was measured. The results indicated that the CoFe2O4 monodisperse NPs are able to induce a burst of ROS in B. cinerea, promoting
damage cellular. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/acd208162929898417ff9472572af142.png)

Easy synthesis of monodisperse Co/Zn based ferrite nanoparticles and their antifungal activities on Botrytis cinerea

Magnetic nanomaterials such as magnetite (Fe3O4) are sought after for their promising applications in sensing, drug delivery, tissue engineering and are also used as
contrast agents in magnetic resonance imaging [1 ].Synthesis of these nanomaterials with good uniformity in size and shape is imperative for their use in different applications.
Microfluidic-based synthesis in designed reactors is a new technology which controls the mixing of fluids within a fixed channel dimension (ranging from 10-100 μm), offers efficient mass
transport in channels and also reduces reaction time.[2,3] Herein, we present a new synthesis strategy which utilizes 3D-printing technique to develop a microfluidic device for synthesis of
Fe3O4 nanoparticles by droplet-based method.[4] The droplet-based method uses oil as a continuous medium which confines the reactants in a droplet, and each droplet functions as an
individual reactor thereby providing high level of control on synthesis conditions. This strategy overcomes the limitations of conventional glassware-based synthesis such as polydispersity
and batch-to-batch variability in nanoparticles. Enhanced magnetism and monodispersity in Fe3O4 nanoparticles were controlled by application of AC voltage across the electrodes placed
beneath the reaction chamber of the device. The present device can be used for synthesing metal nanoparticles. 

**References References:** 

1. A. H. Lu, E. Salabas, F. Schüth (2007) Magnetic nanoparticles: synthesis, protection, functionalization, and application. Angew. Chem. 119:1242-1266; Angew. Chem. Int. Ed. 46:
1222-1244 
2. G. M. Whitesides (2006) The origins and the future of microfluidics. Nature 442:368–373 
3. K. Ren, J. Zhou, H. Wu (2013) Materials for Microfluidic Chip Fabrication. Acc. Chem. Res. 46:2396–2406 
4. V. Singh, R. Singh (2022) Voltage-Driven Microfluidic Synthesis of Magnetite and Gold Nanomaterials. J Flow Chem. DOI: 10.1007/s41981-022-00231-3. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/28425bfc6bdbba3234ada2a178e6f9e5.png)

Simple Synthesis of Magnetic Nanomaterials by Microfluidics Process

Magnetic fluids have a unique combination of magnetic properties, fluidity and colloidal stability, which has allowed them to find applications in a variety of technical
devices, such as shock absorbers and sensors. One of the features of this smart material is the ability to control its physical properties using various combinations of magnetic influences. In
this work, the dynamics of a magnetic fluid volume levitating in an uniform magnetic field of an electromagnet undergoing oscillatory shear is investigated. The samples with different
physical parameters were considered, the dependence of magnetoviscous effect was investigated. It is shown that the microstructure of the sample and the presence of large magnetic
particles have the greatest influence on the dynamics of the magnetic fluid undergoing oscillatory shear and magnetoviscous effect. The results of the work can be used to develop a method
for express testing of magnetic fluid samples, as well as to develop acceleration and vibration sensors based on magnetic fluids [1].
The dependences of the viscosity for samples MF-1 – MF-4 are plotted, shown in Figure 1. The obtained dependences of the viscosity show an increase in its value by a factor of 5 for the
MF-1 sample, with an increase in the field to 1000 kA/m, which can be explained by interparticle interactions and the formation of weakly bound aggregates in the near-wall layer in a
more concentrated initial MF-1 sample. In a more diluted sample MF-2, such an increase in viscosity is not observed. The images MF-3, MF-4 are characterized by the presence of an
excess free surfactant, which negatively affects the magnetoviscous effect.
The work was carried out the part of the implementation of the program of strategic academic leadership "Priority-2030" (Agreements No. 075-15-2021-1155 and No. 075 -15-2021-1213)
and as part of the implementation of the state task (No 0851-2020-0035). 


**References:** 1. Ryapolov P. A., Polunin V. M., Shel'deshova E. V, JMMM 496, 165924 (2020). 

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Dynamics of magnetic fluids and bidisperse magnetic systems undergoing oscillatory shear

Various biomedical magnetic robots have been widely investigated as a possible means to replace conventional invasive regimens [1-3]. In our previous research, we
proposed a self-assembled magnetic millirobot with a multi-modular ring-like chain structure (SAMR) that can change its equilibrium formations under different conditions [4]. The SAMR
is composed of several arc-shaped modules serially connected by a pin joint, and a magnet is inserted into each module (Fig. 1). Due to the interactive magnetic forces and torques within
the modules, the SAMR can be self-assembled into a ring formation without a magnetic field or disassembled into a straight formation under an applied magnetic field. In this research, we
further investigated the wireless manipulation abilities of the SAMR’s mechanical motions. Based on the mechanical conditions of the SAMR shown in Fig. 1, we established a method that
can generate and maneuver the SAMR’s various mechanical movements, including self-assembly, disassembly, tumbling, crawling, and cargo trapping motions simply via the control of an
external magnetic field. Since such motions allow the low-invasive manipulation of the SAMR during the access to a target area and the performance of functions in the area, as shown in
Fig. 1, these motion abilities can significantly improve the SAMR’s usefulness as a minimally invasive device. In an experiment to verify the effectiveness of the proposed motion control
method, the SAMR initially disassembled and loaded inside the medical syringe successfully self-assembled into a ring formation. The SAMR then sequentially showed tumbling,
crawling, and cargo trapping and delivery motions actuated by different magnetic fields. This research can contribute to developing minimally invasive biomedical magnetic robots. 

**References** 

[1] M. Sitti, H. Ceylan, W. Hu, J. Giltinan, M. Turan, S. Yim, and E. Diller, “Biomedical Applications of Untethered Mobile Milli/Microrobots,” Proc. IEEE, vol. 103, no. 2,
pp. 205-224, 2015. 
[2] S. Yim and M. Sitti, “SoftCubes: Stretchable and self-assembling three-dimensional soft modular matter,” Int. J. Rob. Res., vol. 33, no. 8, pp. 1083–1097, 2014. 
[3] H. Lee and S. Jeon, “A Study on the Self-Assembly and Disassembly Abilities of a Multi- Modular Magnetic Millirobot,” J. Inst. Cont., Rob. Sys.,” vol. 25, no. 3, pp. 235-240, 2019. 
[4] H. Lee and S. Jeon, “An intravascular helical magnetic millirobot with a gripper mechanism performing object delivery and collecting motions actuated by precession rotating magnetic
fields,” AIP Adv., vol. 11, pp. 025236, 2021. 

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