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Magnetic nanofluid hyperthermia (MNFH) using colloidal superparamagnetic nanoparticles (SPNPs) has attracted considerable attentions as a potential treatment modality in cancer clinics due to its clinical efficacies including deep tissue penetration of AC magnetic heat induction power (specific loss power (SLP)) and prominently low side effect [1,2]. Accordingly, plenty of research activities were conducted to design and develop high-performance SPNPs with sufficient SLP for destroying tumors by cancer apoptosis or necrosis [3,4]. However, magnetic dipole coupling between the colloidal SPNPs depending on the concentration was regarded as a critical role in characterizing SLP in MNFH. Although the concentration-dependent SLP change behavior has been intensively investigated, the physical mechanism is still poorly understood, and some contradictory results have been recently reported [5,6].&lt;br/&gt;In this work, interparticle distance (&lt;i&gt;d&lt;sub&gt;c-c&lt;/sub&gt;&lt;/i&gt;)-dependent magnetic dipole coupling energy induced in nanofluids and their physical contribution to the SLP change behavior were investigated and analyzed by measuring the intrinsic/extrinsic magnetic parameters of nanofluids as a function of concentration. We first found and reported that the SLP of SPNP MNFH agent shows strong concentration-dependent oscillation behavior. According to the experimentally and theoretically analyzed results, the energy competition among the magnetic dipole interaction energy (&lt;i&gt;E&lt;sub&gt;dip&lt;/sub&gt;&lt;/i&gt;), magnetic potential energy (&lt;i&gt;E&lt;sub&gt;p&lt;/sub&gt;&lt;/i&gt;), and exchange energy (&lt;i&gt;E&lt;sub&gt;ex&lt;/sub&gt;&lt;/i&gt;), was revealed as the main physical reason for the oscillation behavior shown in Fig. 1. The empirically demonstrated new finding and physically established model on the concentration-dependent SLP oscillation behavior is expected to provide biomedically crucial information in determining the critical dose of an agent for clinically safe and highly efficient MNFH in cancer clinics.

MMM 2022

Concentration dependent Oscillation of Specific Loss Power in Magnetic Nanofluid Hyperthermia

Magnetic nanofluid hyperthermia (MNFH) using colloidal superparamagnetic nanoparticles (SPNPs) has attracted considerable attentions as a potential treatment modality in cancer clinics due to its clinical efficacies including deep tissue penetration of AC magnetic heat induction power (specific loss power (SLP)) and prominently low side effect [1,2]. Accordingly, plenty of research activities were conducted to design and develop high-performance SPNPs with sufficient SLP for destroying tumors by cancer apoptosis or necrosis [3,4]. However, magnetic dipole coupling between the colloidal SPNPs depending on the concentration was regarded as a critical role in characterizing SLP in MNFH. Although the concentration-dependent SLP change behavior has been intensively investigated, the physical mechanism is still poorly understood, and some contradictory results have been recently reported [5,6]. In this work, interparticle distance (dc-c)-dependent magnetic dipole coupling energy induced in nanofluids and their physical contribution to the SLP change behavior were investigated and analyzed by measuring the intrinsic/extrinsic magnetic parameters of nanofluids as a function of concentration. We first found and reported that the SLP of SPNP MNFH agent shows strong concentration-dependent oscillation behavior. According to the experimentally and theoretically analyzed results, the energy competition among the magnetic dipole interaction energy (Edip), magnetic potential energy (Ep), and exchange energy (Eex), was revealed as the main physical reason for the oscillation behavior shown in Fig. 1. The empirically demonstrated new finding and physically established model on the concentration-dependent SLP oscillation behavior is expected to provide biomedically crucial information in determining the critical dose of an agent for clinically safe and highly efficient MNFH in cancer clinics.

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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Please register for the MMM 2022 conference to join the event.

This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

Modeling and computing heat transfer phenomena involving the magnetocaloric effect is of paramount importance for designing new heat management systems. The heatrapy python package has been used to compute heat transfer phenomena in magnetic refrigerators and heat pumps for the past 5 years [1-3]. It uses the finite difference method to solve the unidimensional heat conduction equation. So far, the package was downloaded over 50,000 times by the pip package manager [4]. A considerable share of devices can be modeled in one dimension. However, there are others where this is not sufficient. In those systems, at least two-dimensional approaches are required. Moreover, devices only relying on heat conduction require more complex heat transfer mechanisms, beyond the magnetocaloric effect, so that they can show functional behaviours, such as thermal phenomena involving phase transitions. To account for these issues, the heatrapy python package was upgraded aiming to add three new major features. The first is the extension to two-dimensional models. The second is to allow the live visualization of the computation. The third feature is to allow the incorporation of phase change transitions. Figure 1 shows an example for the computation of a magnetized structure made of aluminium and gadolinium. The detailed implementation is described, as well as minor updates.

Heatrapy 2.0: a two dimensional upgrade for computing dynamic heat transfer processes in Python involving non conventional phenomena

Due to their inherent characteristics regarding sensitivity and flexible design, Giant Magnetoresistance (GMR) based sensors are the preferred option for the measurement of low magnetic fields within small volumes (electronic compass, bio-magnetism, non-destructive testingâ€¦) [1]. In addition, GMR devices have demonstrated their compatibility with different standard technologies (such as CMOS) and other emerging ones (such as microfluidics) [2], so broadening their fields of application. For example, GMR sensors have been successfully used as currents sensors in integrated circuits and also as bio-detectors for different specimens in Lab-on-chip systems. More recently, GMR elements have been proposed as basic detectors in neuromorphicaly approached magnetic field imaging sensors, for potential applications in biotechnology and testing. The design and optimization of this kind of system demand electrical models which are compatible with conventional microelectronics design tools [3]. In this sense, partial solutions have been proposed, providing static, noise and thermal models, mainly for discrete components applications in electrical current sensing [4]. In this work, the development of a compact dynamic electrical model for GMR sensors is described. The Verilog-A high-level description language has been considered in order to provide a useful model for being used in conventional CMOS design tools, such as Cadence Virtuoso. The model includes the proper blocks for alternate current and transient analysis, which are mandatory by the high speed related to the design of neuromorphicaly approached imaging sensors. Functional parameters were obtained from specifically designed sensors including single resistors, voltage dividers and full bridges (see Fig. 1). The schematic of the model for the single resistor sensor is depicted in Fig. 1. Fig. 2 displays preliminary impedance results comparing experimental measurements with model-predicted behaviour for a frequency sweep in the range of interest. Fig. 2 also includes transient modelling for the voltage divider topology.

Electrical compact modelling of GMR devices for neuromorphically inspired sensors

Understanding the behavior of free-living marine organisms is pivotal for many conservation efforts (REF) and examining how to change, such as overfishing and climate variability, affect marine ecosystems [1]. For this, many researchers have turned to animal-attached tag technology [2] where study animals carry archival â€œsmartâ€ tags that record a suite of parameters to quantify particular aspects of their behavioral ecology or physiology. It was demonstrated that the Pelagic jellyfish blooms are increasing worldwide as a potential response to climate change. The results shown in [3] suggest an enhanced growth of the jellyfish in response to global warming, whereas low temperatures may set the limits for successful invasion of the jellyfish into colder water bodies. Therefore, we are developing an underwater reliable wireless marine monitoring system composed of a flexible magnet (NdFeB-PDMS) and an MTJ-based sensor as shown in Fig. 1 in order to count the number of the jellyfish contractions under different environmental conditions. The fabrication process of the NdFeB-PDMS composite magnet involves minimal complexity, has lower cost, and is highly versatile with respect to the shape of the magnets [4] which play the role of a monitor of any jellyfish movement that would be detected by our MTJ-based sensor over time as can be seen in Fig 2. The composite magnet is coated with Paralyne C to protect the composite from degradation, make the remanent magnetization constant, and provide resistance against corrosion and biofouling, flexibility, and biocompatibility. The results show the suitability of the composite magnets for marine applications. Our results provide a framework for understanding the physiological tolerance of Cassiopea under possible future climate changes, which can be better interpreted by statistical coming studies using a wireless marine monitoring system based on our MTJ sensors.

MTJ based Marine Sensor for Jellyfish Cassiopea Response to the Environmental Change

The real time non-destructive monitoring of stresses and temperature is one of the most demanded solutions in the field of sensor technologies. One of the most prospective technologies addressing this problem is a novel sensing technique for non-destructive monitoring utilizing ferromagnetic wire inclusions presenting the high frequency magnetoimpedance, MI, effect quite sensitive to tensile stress and magnetic field [1]. One of the advantages of this technology is that proposed free space microwave spectroscopy allows remote monitoring of external stimuli, like stress, magnetic field or temperature. The glass-coated microwires with typical diameters from 1 to 50 Î¼m can provide new functionalities such as improved mechanical and corrosive properties, adherence with polymeric matrices and biocompatibility [2]. In the present paper a novel sensing technique for direct non-destructive and non-contact monitoring of the composite polymerization utilizing ferromagnetic glass-coated microwire inclusions with magnetic properties sensitive to tensile stress and temperature is described. We provide in-situ studies of the evolution of the hysteresis loop of arrays consisting of Co- rich (Fe3.8Co65.4Ni1B13.8Si13Mo1.35C1.65) microwires during the composites matrix polymerization. We observed remarkable change of the hysteresis loops upon matrix polymerization: remarkable coercivity change and transformation of linear hysteresis loop into rectangular in the arrays with Co-rich microwires placed inside the matrix (see Fig.1a). Using the free space technique we observed considerable variation of the Transmission parameter of the microwires array in the range of 4-7 GHz upon the matrix polymerization (see Fig.1b). Observed dependencies are discussed considering heating during the matrix polymerization measured using a standard thermocouple (Fig.1c) and the matrix shrinkage and their influence on magnetic properties and MI effect of glass-coated microwires.

Novel Sensing Technique for Non Destructive Composites Monitoring

The amorphous magnetic wires are widely used as magnetic or magneto-mechanical sensors due to their very soft magnetic properties and high sensitivity to stress. [1-4]. A new design of a high sensitivity sensor with high capability to measure applied forces or load is proposed by this paper. The sensor consists in four pieces of high permeability Co68.18Fe4.32Si12.5B15 amorphous magnetic wire, 120 Î¼m in diameter, 20 mm in length, glued prestressed on a pcb board having 0.3 mm in thickness, 7 mm in width and 30 mm in length (Figure 1). The ends of each wire is soldered on the PCB to form a Wheatstone bridge circuit. The opposite arms of the bridge are placed on the same side of the pcb to increase the bridge unbalance when stressed. Also, all wires forming the bridge arms are parallel and close one to another to minimize the effect of the surrounding magnetic field. By using different PCB support for the bridge, it is possible to tailor the sensitivity and force measuring range. A special designed electronic device was built to power the bridge using a high frequency sinusoidal signal and to extract and amplify the unbalanced voltage of the bridge. The dependence of the output voltage/gain versus applied force, for a signal excitation frequency of 1 MHz, is shown is showin figure 2. The sensor shows linear behavior between Â± 0.15N and sensitivity of 43.7 mV/N, without gain, in the linear region. Financial support by the NUCLEU Program (PN 19 28 01 01) is gratefully acknowledged.

Tailorable force sensor based on stress magneto

With the rapid advancement in electronics systems, there is a high demand for components that achieve size, weight, power, and cost reductions (SWaP+C). This need for greater miniaturization has contributed to a dramatic increase in heat generation within these systems, resulting in compromised performance, sacrificed reliability, and reduced device lifecycle.1 In addition, with ever-increasing spectral congestion and since electronic products incorporate faster components operating at higher frequencies than ever before, electromagnetic interference is becoming challenging to mitigate, posing a major concern for human health and the environment.2 It is therefore highly critical to develop high-performance material systems that can concurrently mitigate the detrimental effects of thermal and EM radiation while maintaining the highly desired SWaP+C configurations. To this effect, we have developed an innovative synthesis strategy involving melt blending, vacuum impregnation, and magnetic-field assisted spin coating to fabricate flexible multicomposite films comprising of FeSi particles (~30-50 Î¼m) and graphene nanoflakes (200-300 nm) confined in a shape-stabilized phase change material (PCM) matrix. In this multifunctional material, the PCM enables efficient heat absorption via the phase change process, the graphene flakes enhance the thermal conductivity to facilitate heat dissipation, and the FeSi particles enhance electromagnetic absorption in the X and Ku bands due to their high magnetization and magnetic anisotropy. With the synergistic effect of graphene and FeSi, the resulting composite displays a thermal conductivity of 0.60-0.75 W/mK, latent heat of 110-120 J/g at 70 Â°C, and excellent EM shielding effectiveness (SE) in the range of 10-60 dB depending on thickness in the range 200 Î¼m to 2 mm (an example is shown in Fig 1). Processing-structure-property correlations of the multifunctional films will be discussed in the context of their percolation threshold. Research supported by the Commonwealth Cyber Initiative (Grants HV-2Q22-003 and HV-4Q21-002).

Multifunctional Phase Change Composites for Passive Thermal Management and Electromagnetic Shielding of High Frequency Devices

Positioning systems with high resolution are in a high demand for robotics, operating in a wide scales of positioning ranges from tens of meters in heavy machine industry, down to few nanometers in high-precision electronics. A promising approach for a robust positioning at nanoscale is integration of magnetic field sensors into the positioning electronics and detection of magnetized objects by their induced magnetic fields. In this work, we introduce an approach for magnetic-based positioning, in which the displacement of a magnetized micro-object is detected by magnetic field sensor, as a variation of magnetic field, associated with this displacement. For the purpose to have higher resolution in positioning, magnetic sensor was composed of an array of magnetic tunnel junctions, having magnetoresistance of ~ 170 percent, whereas the geometry of the magnetized object was optimized to have a higher gradient of magnetic field along the positioning direction. The magnet-sensor configuration was optimized as follows: i) magnetization direction in the magnetized object, as well as the displacement direction were varied in respect to field sensing direction of the MTJ sensor, to achieve high linearity of the sensor signal variations with the displacements of the object, ii) the shape of the magnetized object was optimized to improve sensitivity of the MTJ sensor array to positioning displacements of this object, iii) the distance between the MTJ sensor array and the magnetized object was optimized to have largest dynamic range of MTJ output voltage variations, without oversaturating the sensor, iv) the lateral and transversal dimensions of the MTJ sensor array were optimized to improve sensitivity to gradient of magnetic field, induced by the micromagnet. With the optimized configuration the positioning sensitivity of the sensor platform was tested with a micromagnet, placed on a nano-positioning piezo-stage, operating in a closed-loop feedback mode with 10 nm step resolution. The tests in open environment demonstrate robust operation of the magnetic tunnel junction sensor-based platform as a positioning sensor for displacements of magnetized objects with a resolution down to 100 nm.

Magnetic tunnel junctions for positioning systems with down to 100 nm resolution

Airborne particulate matter (PM) have been significantly increasing over the past two decades carrying significant health risks such as premature death, damage to the lungs, heart tissue, and even cancer. PM2.5 is the main concern as it has the most harmful health effects while being more difficult to detect [1]. Moreover, these magnetic nanoparticles are readily absorbed into the bloodstream causing neurodegenerative diseases such as Alzheimerâ€™s and cancerous tumors [2]. Therefore, it is essential to monitor the magnetic portion of PM and its adverse effects on health [3], [4]. This work focuses on developing, modeling, and simulation of a new kind of magnetic sensor that can count and localize these magnetic nanoparticles. Additionally, we have fabricated a novel low-noise and high-precision readout circuit for tunneling magnetoresistive (TMR) array to evaluate the bio-magnetic measurement platformâ€™s suitability for detecting weak bio-magnetic fields. The proposed sensors could help to prevent these nanoparticles from the polluted environment and undoubtedly reduce their adverse risks to humans. The modeled magnetic system consists of a TMR sensor array, a conducting line, and the detected magnetite nanoparticles as shown in Fig. 1(a). The localization and quantization of these Fe3O4 nanoparticles (characterized in Fig. 1(b)) can be achieved by analyzing total output voltages from the TMR sensor array. The Fe3O4 magnetite is injected inside the small closed chamber and they are exerting an external magnetic field that is aligned or opposed to the pinning field, which results in shifting the MTJ curve as seen in Fig. 1(c). After applying a current in the conducting line and creating an external field, the magnetite gets polarized and approaches the MTJ sensors. This technique can detect 50-200 nm magnetic particles compared to existing commercial monitoring solutions that are limited to 1-3Âµm particles.

High performance MTJ

Early cancer detection greatly enhances the prognosis and allows for higher treatment success. Cancer metastasis, which occurs in later stages, is believed to cause more than 90% of cancer-related deaths [1]. In earlier cancer stages, circulating tumor cells (CTCs) may be detected in the blood of cancer patients, which can correlate with patient survival rate. Accurate, non-invasive separation of these cells allows for early detection of cancer and aids in increasing therapeutic efficacy [2]. This work provides an integrated on-chip quantitative cell sorting platform that separates and counts magnetically labeled cells through a microfluidic channel. First, an immunomagnetic assay is utilized to label CTCs with highly selective magnetic nanoparticles. Then, magnetically labeled cells are separated and guided through the microfluidic channel by electromagnetics and ferromagnetic strips [3]. After cell separation, magnetically labeled biomarkers are detected by the magnetic tunnel junction (MTJ) sensor that measures stray fields surrounding the labeled CTCs, generating an electrical signal for each passing particle. Additionally, biomarkers with different sizes, such as CTCs and protein-based cancer biomarkers, can be detected and quantified as they move through the microfluidic channel at different speeds, yielding distinct peaks at the MTJ output [3][4]. This work demonstrates a highly selective platform that actively sorts magnetically labeled biomarkers by combining magnetophoresis-based cell sorting and MTJ-based flow cytometry allowing for highly sensitive quantitative on-chip cell sorting.

On chip Quantitative Cell sorting based on High Performance Magnetic Tunnel Junction

Flow cytometry is a powerful technique that enables cell quantification and analysis. As a result, it has become an essential instrument in biomedical research and clinical testing for disease diagnosis or treatment monitoring. However, the current technique is large and expensive, driving research into smaller, cheaper, and more efficient flow cytometers [1]. One approach to tackle this problem can be with the application of spintronic sensors such as giant magnetoresistance sensors for cell quantification [1][2]. In this work, we report a highly sensitive flow cytometer based on magnetic tunnel junction (MTJ) technology. After external labeling of cells with magnetized beads placed above the MTJ sensor to measure stray magnetic field surrounding the beads. When labeled cells pass through the sensitive area, a signal peak will be generated at the output of the MTJ sensor [3]. Alternatively, magnetic flow cytometers can evaluate the efficacy of certain cancer immunotherapies where cancer cell membranes coat magnetic nanoparticles to activate a specific natural killer (KT) cell response [4]. One of the cytometer applications is Live/dead cancer cells discrimination. This cytometer can detect the presence of these magnetic nanoparticles to ensure proper activation of KT cells and thorough removal of the modified magnetic particles. This result demonstrates a novel MTJ-based, highly sensitive flow cytometer design for quantifying magnetically labeled cells and cancer therapy involving magnetic nanoparticles. Using our suggested device, we can distinguish and separate between cancer cells and prove Live/dead cancer cells discrimination.

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Concentration dependent Oscillation of Specific Loss Power in Magnetic Nanofluid Hyperthermia

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Heatrapy 2.0: a two dimensional upgrade for computing dynamic heat transfer processes in Python involving non conventional phenomena

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