Rotation of Magnetization Derived from Brownian Relaxation in Magnetic Fluids of Different Viscosity Evaluated by Dynamic Hysteresis Measurements over a Wide Frequency Range

Ota, Satoshi; Kitaguchi, Ryoichi; Takeda, Ryoji; Yamada, Tsutomu; Takemura, Yasushi

doi:10.3390/nano6090170

Cited by 38 publications

(34 citation statements)

References 29 publications

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“…As discussed in the Supporting Information, physical rotation is expected to dominate the magnetization response of relatively large IONPs and strongly magnetically interacting aggregates suspended in a liquid, [18,31] making Brownian relaxation most relevant to the ferrofluids studied here. For low applied fields, the value of its time constant is approximated by [18,32,33]…”

Section: τ ω ≈mentioning

confidence: 99%

Living, Self‐Replicating Ferrofluids for Fluidic Transport

Mirkhani

Christiansen

Schuerle

2020

Adv Funct Materials

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Magnetic actuation offers a means to wirelessly control flow in ferrofluids for applications including microfluidic pumping and targeted drug delivery. Despite the promise of these concepts, practical use of synthetic ferrofluids as actuators of flow frequently requires high concentrations and is hindered by low ferrohydrodynamic coupling efficiency and inhomogeneous flow fields. Inspired by the magnetic properties and hydrodynamic forms displayed by magnetotactic bacteria (MTB), this work studies the use of these microbes as a living, self‐replicating ferrofluid for improved fluidic transport via magnetically coerced rotation. Using multicore iron oxide nanoparticles as a performance benchmark, MTB under rotating magnetic fields are shown to produce more homogeneous and efficient flow. Coupling is enhanced whether the comparison is made in terms of volume of magnetic material or total volume fraction. To clarify the mechanistic role of interactions with boundaries in transport, a computational model is developed and validated experimentally. Applying this model, two distinct and feasible magnetic control strategies are predicted: a rotating gradient field that generates directional flow despite boundaries that promote flow in opposing directions and a magnetostatic gating field that enables spatially selective actuation. The advantageous properties identified for MTB open a design space for these strategies to be realized.

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Section: τ ω ≈mentioning

confidence: 99%

Living, Self‐Replicating Ferrofluids for Fluidic Transport

Mirkhani

Christiansen

Schuerle

2020

Adv Funct Materials

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“…On the other hand, SAR characterization is usually conducted in colloidal samples, very often with different viscosities, where MNPs can spin around fast and/or rotate toward the AC magnetic field lines. These mechanical effects greatly influence the magnetic dynamics and accordingly the SAR [39,40]. Given that particles' mobility is usually highly suppressed within biological environments, a simple characterization in aqueous colloid can lead to overestimate the heating capacity of samples.…”

Section: Introductionmentioning

confidence: 99%

Exploring the potential of the dynamic hysteresis loops via high field, high frequency and temperature adjustable AC magnetometer for magnetic hyperthermia characterization

Rodrigo

Castellanos-Rubio

Garaio

et al. 2020

International Journal of Hyperthermia

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Aim: The Specific Absorption Rate (SAR) is the key parameter to optimize the effectiveness of magnetic nanoparticles in magnetic hyperthermia. AC magnetometry arises as a powerful technique to quantify the SAR by computing the hysteresis loops' area. However, currently available devices produce quite limited magnetic field intensities, below 45mT, which are often insufficient to obtain major hysteresis loops and so a more complete and understandable magneticcharacterization. This limitation leads to a lack of information concerning some basic properties, like the maximum attainable (SAR) as a function of particles' size and excitation frequencies, or the role of the mechanical rotation in liquid samples. Methods: To fill this gap, we have developed a versatile high field AC magnetometer, capable of working at a wide range of magnetic hyperthermia frequencies (100 kHz-1MHz) and up to field intensities of 90mT. Additionally, our device incorporates a variable temperature system for continuous measurements between 220 and 380 K. We have optimized the geometrical properties of the induction coil that maximize the generated magnetic field intensity. Results: To illustrate the potency of our device, we present and model a series of measurements performed in liquid and frozen solutions of magnetic particles with sizes ranging from 16 to 29 nm. Conclusion: We show that AC magnetometry becomes a very reliable technique to determine the effective anisotropy constant of single domains, to study the impact of the mechanical orientation in the SAR and to choose the optimal excitation parameters to maximize heating production under human safety limits.

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“…The subtraction of magnetization curves is a validated method in extracting specific magnetization dynamics from superposed complex dynamics [ 29 ]. The AC magnetization curves and their dependence on frequency shown in the figure are quite similar to those of the magnetic iron oxide nanoparticles [ 30 , 31 ]. The magnetization curves obtained under the applied DC field or AC field at the low frequency of 1 kHz exhibit approximately no remanent magnetization.…”

Section: Discussionmentioning

confidence: 69%

Magnetization Characteristics of Oriented Single-Crystalline NiFe-Cu Nanocubes Precipitated in a Cu-Rich Matrix

et al. 2020

Self Cite

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In this study, we evaluated the magnetization properties of a magnetic alloy with single-crystalline cubic nanostructures, in order to clarify its magnetocrystalline anisotropy. Upon applying a specific annealing treatment to the CuNiFe base material, the precipitated magnetic particles grew into cubic granules, resulting in the formation of nanometric cubic single crystals of magnetic CuNiFe in a nonmagnetic Cu-rich matrix. The cubic nanostructures of CuNiFe were oriented along their crystallographic axis, in the <100> direction of the face-centered-cubic structure. We evaluated the static magnetization properties of the sample, which originated primarily from the CuNiFe nanocubes precipitated in the Cu-rich matrix, under an applied DC magnetic field. The magnetocrystalline anisotropy was readily observed in the magnetization curves. The <111> axis of the CuNiFe was observed to be the easy axis of magnetization. We also investigated the dynamic magnetization properties of the sample under an AC magnetic field. By subtracting the magnetic signal induced by the eddy current from the magnetization curves of the sample, we could obtain the intrinsic AC magnetization properties of the CuNiFe nanocubes.

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Rotation of Magnetization Derived from Brownian Relaxation in Magnetic Fluids of Different Viscosity Evaluated by Dynamic Hysteresis Measurements over a Wide Frequency Range

Cited by 38 publications

References 29 publications

Living, Self‐Replicating Ferrofluids for Fluidic Transport

Living, Self‐Replicating Ferrofluids for Fluidic Transport

Exploring the potential of the dynamic hysteresis loops via high field, high frequency and temperature adjustable AC magnetometer for magnetic hyperthermia characterization

Magnetization Characteristics of Oriented Single-Crystalline NiFe-Cu Nanocubes Precipitated in a Cu-Rich Matrix

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