International Journal of Molecular Sciences

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14 pages, 2878 KiB

Open AccessArticle

Large Aberration Correction by Magnetic Fluid Deformable Mirror with Model-Based Wavefront Sensorless Control Algorithm

by Xiang Wei, Yuanyuan Wang, Zhan Cao, Dziki Mbemba, Azhar Iqbal and Zhizheng Wu

Int. J. Mol. Sci. 2019, 20(15), 3697; https://doi.org/10.3390/ijms20153697 - 28 Jul 2019

Cited by 7 | Viewed by 2788

Abstract

Magnetic fluid is a stable colloidal suspension of nano-sized, single-domain ferri/ferromagnetic particles dispersed in a liquid carrier. The liquid can be magnetized by the ferromagnetic particles aligned with the external magnetic field, which can be used as a wavefront corrector to correct the [...] Read more.

Magnetic fluid is a stable colloidal suspension of nano-sized, single-domain ferri/ferromagnetic particles dispersed in a liquid carrier. The liquid can be magnetized by the ferromagnetic particles aligned with the external magnetic field, which can be used as a wavefront corrector to correct the large aberrations up to more than 100 µm in adaptive optics (AO) systems. Since the measuring range of the wavefront sensor is normally small, the application of the magnetic fluid deformable mirror (MFDM) is limited with the WFS based AO system. In this paper, based on the MFDM model and the relationship between the second moment (SM) of the aberration gradients and the far-field intensity distribution, a model-based wavefront sensorless (WFSless) control algorithm is proposed for the MFDM. The correction performance of MFDM using the model-based control algorithm is evaluated in a WFSless AO system setup with a prototype MFDM, where a laser beam with unknown aberrations is supposed to produce a focused spot on the CCD. Experimental results show that the MFDM can be used to effectively compensate for unknown aberrations in the imaging system with the proposed model-based control algorithm. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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11 pages, 3891 KiB

Open AccessCommunication

Shape-Controlled Syntheses of Magnetite Microparticles and Their Magnetorheology

by Hiroya Abe, Takashi Naka, Kazuyoshi Sato, Yoshikazu Suzuki and Masami Nakano

Int. J. Mol. Sci. 2019, 20(15), 3617; https://doi.org/10.3390/ijms20153617 - 24 Jul 2019

Cited by 9 | Viewed by 3487

Abstract

Magnetic microspheres in a concentrated suspension can be self-assembled to form chain structures under a magnetic field, resulting in an enhanced viscosity and elasticity of the suspension (i.e., the magnetorheological (MR) effect). Recently, interest has been raised about the relationship between nonspherical particles, [...] Read more.

Magnetic microspheres in a concentrated suspension can be self-assembled to form chain structures under a magnetic field, resulting in an enhanced viscosity and elasticity of the suspension (i.e., the magnetorheological (MR) effect). Recently, interest has been raised about the relationship between nonspherical particles, such as octahedral particles and the MR effect. However, experimental studies have not made much progress toward clarifying this issue due to the difficulty associated with synthesizing microparticles with well-defined shapes and sizes. Here, we presented a method for the shape-controlled synthesis of magnetite (Fe₃O₄) microparticles and investigated the MR effects of two suspensions prepared from the two shape-controlled samples of Fe₃O₄ microparticles. Our method, which was based on the polyol method, enabled the preparation of spherical and octahedral Fe₃O₄ microparticles with similar sizes and magnetic properties, through a reduction of α-FeOOH in a mixed solvent of ethylene glycol (a polyol) and water. The water played an important role in both the phase transition (α-FeOOH to Fe₃O₄) and the shape control. No substantial difference in the MR effect was observed between an octahedral-particle-based suspension and a spherical-particle-based one. Therefore, in this study, the shape of the microparticles did not strongly influence the MR effect, i.e., the properties of the chain structures. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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37 pages, 20423 KiB

Open AccessArticle

Comparative Investigation of Phenomenological Modeling for Hysteresis Responses of Magnetorheological Elastomer Devices

by Yang Yu, Jianchun Li, Yancheng Li, Shaoqi Li, Huan Li and Weiqiang Wang

Int. J. Mol. Sci. 2019, 20(13), 3216; https://doi.org/10.3390/ijms20133216 - 30 Jun 2019

Cited by 34 | Viewed by 4268

Abstract

Magnetorheological elastomer (MRE) is a type of magnetic soft material consisting of ferromagnetic particles embedded in a polymeric matrix. MRE-based devices have characteristics of adjustable stiffness and damping properties, and highly nonlinear and hysteretic force–displacement responses that are dependent on external excitations and [...] Read more.

Magnetorheological elastomer (MRE) is a type of magnetic soft material consisting of ferromagnetic particles embedded in a polymeric matrix. MRE-based devices have characteristics of adjustable stiffness and damping properties, and highly nonlinear and hysteretic force–displacement responses that are dependent on external excitations and applied magnetic fields. To effectively implement the devices in mitigating the hazard vibrations of structures, numerically traceable and computationally efficient models should be firstly developed to accurately present the unique behaviors of MREs, including the typical Payne effect and strain stiffening of rubbers etc. In this study, the up-to-date phenomenological models for describing hysteresis response of MRE devices are experimentally investigated. A prototype of MRE isolator is dynamically tested using a shaking table in the laboratory, and the tests are conducted based on displacement control using harmonic inputs with various loading frequencies, amplitudes and applied current levels. Then, the test results are used to identify the parameters of different phenomenological models for model performance evaluation. The procedure of model identification can be considered as solving a global minimization optimization problem, in which the fitness function is the root mean square error between the experimental data and the model prediction. The genetic algorithm (GA) is employed to solve the optimization problem for optimal model parameters due to its advantages of easy coding and fast convergence. Finally, several evaluation indices are adopted to compare the performances of different models, and the result shows that the improved LuGre friction model outperforms other models and has optimal accuracy in predicting the hysteresis response of the MRE device. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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10 pages, 2670 KiB

Open AccessArticle

Chain Structure in a Cross-Linked Polyurethane Magnetic Elastomer Under a Magnetic Field

by Mayuko Watanabe, Yoshihiro Takeda, Takayuki Maruyama, Junko Ikeda, Mika Kawai and Tetsu Mitsumata

Int. J. Mol. Sci. 2019, 20(12), 2879; https://doi.org/10.3390/ijms20122879 - 13 Jun 2019

Cited by 22 | Viewed by 2963

Abstract

The morphology of magnetic particles with a size of 7.0 μm was observed for magnetic elastomers with a concentration of magnetic particles of 70 wt% using an X-ray microscope remolded into high resolution. Computed tomography images revealed that magnetic particles were distributed isotopically [...] Read more.

The morphology of magnetic particles with a size of 7.0 μm was observed for magnetic elastomers with a concentration of magnetic particles of 70 wt% using an X-ray microscope remolded into high resolution. Computed tomography images revealed that magnetic particles were distributed isotopically in the absence of a magnetic field, but they formed a chain structure in the polyurethane network under a magnetic field of 270 mT. It was also established, by image analysis, that magnetic elastomers had an anisotropic structure under the magnetic field. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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15 pages, 6464 KiB

Open AccessArticle

Theoretical Analysis for Wireless Magnetothermal Deep Brain Stimulation Using Commercial Nanoparticles

by Tuan-Anh Le, Minh Phu Bui and Jungwon Yoon

Int. J. Mol. Sci. 2019, 20(12), 2873; https://doi.org/10.3390/ijms20122873 - 12 Jun 2019

Cited by 16 | Viewed by 5342

Abstract

A wireless magnetothermal stimulation (WMS) is suggested as a fast, tetherless, and implanted device-free stimulation method using low-radio frequency (100 kHz to 1 MHz) alternating magnetic fields (AMF). As magnetic nanoparticles (MNPs) can transduce alternating magnetic fields into heat, they are targeted to [...] Read more.

A wireless magnetothermal stimulation (WMS) is suggested as a fast, tetherless, and implanted device-free stimulation method using low-radio frequency (100 kHz to 1 MHz) alternating magnetic fields (AMF). As magnetic nanoparticles (MNPs) can transduce alternating magnetic fields into heat, they are targeted to a region of the brain expressing the temperature-sensitive ion channel (TRPV1). The local temperature of the targeted area is increased up to 44 °C to open the TRPV1 channels and cause an influx of Ca²⁺ sensitive promoter, which can activate individual neurons inside the brain. The WMS has initially succeeded in showing the potential of thermomagnetics for the remote control of neural cell activity with MNPs that are internally targeted to the brain. In this paper, by using the steady-state temperature rise defined by Fourier’s law, the bio-heat equation, and COMSOL Multiphysics software, we investigate most of the basic parameters such as the specific loss power (SLP) of MNPs, the injection volume of magnetic fluid, stimulation and cooling times, and cytotoxic effects at high temperatures (43–44 °C) to provide a realizable design guideline for WMS. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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13 pages, 2134 KiB

Open AccessArticle

Magnetodielectric Response of Soft Magnetoactive Elastomers: Effects of Filler Concentration and Measurement Frequency

by Sergei A. Kostrov, Mikhail Shamonin, Gennady V. Stepanov and Elena Yu. Kramarenko

Int. J. Mol. Sci. 2019, 20(9), 2230; https://doi.org/10.3390/ijms20092230 - 7 May 2019

Cited by 17 | Viewed by 2983

Abstract

The magnetodielectric response of magnetoactive elastomers (MAEs) in its dependence on filler concentration, magnetic field, and test frequency is studied experimentally. MAEs are synthesized on the basis of a silicone matrix filled with spherical carbonyl iron particles characterized by a mean diameter of [...] Read more.

The magnetodielectric response of magnetoactive elastomers (MAEs) in its dependence on filler concentration, magnetic field, and test frequency is studied experimentally. MAEs are synthesized on the basis of a silicone matrix filled with spherical carbonyl iron particles characterized by a mean diameter of 4.5 µm. The concentration of the magnetic filler within composite materials is equal to 70, 75, and 80 mass%. The effective lossless permittivity ε′ as well as the dielectric loss tanδ grow significantly when the magnetic field increases. The permittivity increases and the dielectric loss decreases with increasing filler concentration. In the measurement frequency range between 1 kHz and 200 kHz, the frequency hardly affects the values of ε′ and tanδ in the absence of a magnetic field. However, both parameters decrease considerably with the growing frequency in a constant magnetic field. The more strongly the magnetic field is applied, the larger the change in permittivity and loss tangent at the same test frequency is observed. An equivalent circuit formulation qualitatively describes the main tendencies of the magnetodielectric response. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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14 pages, 4439 KiB

Open AccessArticle

Simulation of Magnetodielectric Effect in Magnetorheological Elastomers

by Danil Isaev, Anna Semisalova, Yulia Alekhina, Liudmila Makarova and Nikolai Perov

Int. J. Mol. Sci. 2019, 20(6), 1457; https://doi.org/10.3390/ijms20061457 - 22 Mar 2019

Cited by 23 | Viewed by 3395

Abstract

We present the results of numerical simulation of magnetodielectric effect (MDE) in magnetorheological elastomers (MRE)—the change of effective permittivity of elastomer placed under the external magnetic field. The computer model of effect is based on an assumption about the displacement of magnetic particles [...] Read more.

We present the results of numerical simulation of magnetodielectric effect (MDE) in magnetorheological elastomers (MRE)—the change of effective permittivity of elastomer placed under the external magnetic field. The computer model of effect is based on an assumption about the displacement of magnetic particles inside the elastic matrix under the external magnetic field and the formation of chain-like structures. Such displacement of metallic particles between the planes of capacitor leads to the change of capacity, which can be considered as a change of effective permittivity of elastomer caused by magnetic field (magnetodielectric effect). In the literature, mainly the 2D approach is used to model similar effects. In this paper, we present a new approach of magnetorheological elastomers simulation—a 3D-model of the magnetodielectric effect with ability to simulate systems of

10^{5}

particles. Within the framework of the model, three types of particle size distributions were simulated, which gives an advantage over previously reported approaches. Lognormal size distribution was shown to give better qualitative match of the modeling and experimental results than monosized type. The developed model resulted in a good qualitative agreement with all experimental data obtained earlier for Fe-based elastomers. The proposed model is useful to study these novel functional materials, analyze the features of magnetodielectric effect and predict the optimal composition of magnetorheological elastomers for further profound experimental study. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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19 pages, 3739 KiB

Open AccessArticle

Thermal Stability and Rheological Properties of Epoxidized Natural Rubber-Based Magnetorheological Elastomer

by Nurul Azhani Yunus, Saiful Amri Mazlan, Ubaidillah, Siti Aishah Abdul Aziz, Salihah Tan Shilan and Nurul Ain Abdul Wahab

Int. J. Mol. Sci. 2019, 20(3), 746; https://doi.org/10.3390/ijms20030746 - 10 Feb 2019

Cited by 26 | Viewed by 4673

Abstract

Determination of the thermal characteristics and temperature-dependent rheological properties of the magnetorheological elastomers (MREs) is of paramount importance particularly with regards to MRE applications. Hitherto, a paucity of temperature dependent analysis has been conducted by MRE researchers. In this study, an investigation on [...] Read more.

Determination of the thermal characteristics and temperature-dependent rheological properties of the magnetorheological elastomers (MREs) is of paramount importance particularly with regards to MRE applications. Hitherto, a paucity of temperature dependent analysis has been conducted by MRE researchers. In this study, an investigation on the thermal and rheological properties of epoxidized natural rubber (ENR)-based MREs was performed. Various percentages of carbonyl iron particles (CIPs) were blended with the ENR compound using a two roll-mill for the preparation of the ENR-based MRE samples. The morphological, elemental, and thermal analyses were performed before the rheological test. Several characterizations, as well as the effects of the strain amplitude, temperature, and magnetic field on the rheological properties of ENR-based MRE samples, were evaluated. The micrographs and elemental results were well-correlated regarding the CIP and Fe contents, and a uniform distribution of CIPs was achieved. The results of the thermal test indicated that the incorporation of CIPs enhanced the thermal stability of the ENR-based MREs. Based on the rheological analysis, the storage modulus and loss factor were dependent on the CIP content and strain amplitude. The effect of temperature on the rheological properties revealed that the stiffness of the ENR-based MREs was considered stable, and they were appropriate to be employed in the MRE devices exposed to high temperatures above 45 °C. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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9 pages, 3420 KiB

Open AccessCommunication

Elastic Properties of Magnetorheological Elastomers in a Heterogeneous Uniaxial Magnetic Field

by Takehito Kikuchi, Yusuke Kobayashi, Mika Kawai and Tetsu Mitsumata

Int. J. Mol. Sci. 2018, 19(10), 3045; https://doi.org/10.3390/ijms19103045 - 6 Oct 2018

Cited by 10 | Viewed by 2860

Abstract

Magnetorheological elastomers (MREs) are stimulus-responsive soft materials that consist of polymeric matrices and magnetic particles. In this study, large-strain response of MREs with 5 vol % of carbonyl iron (CI) particles is experimentally characterized for two different conditions: (1) shear deformation in a [...] Read more.

Magnetorheological elastomers (MREs) are stimulus-responsive soft materials that consist of polymeric matrices and magnetic particles. In this study, large-strain response of MREs with 5 vol % of carbonyl iron (CI) particles is experimentally characterized for two different conditions: (1) shear deformation in a uniform magnetic field; and (2), compression in a heterogeneous uniaxial magnetic field. For condition (1), dynamic viscoelastic measurements were performed using a rheometer with a rotor disc and an electric magnet that generated a uniform magnetic field on disc-like material samples. For condition (2), on the other hand, three permanent magnets with different surface flux densities were used to generate a heterogeneous uniaxial magnetic field under cylindrical material samples. The experimental results were mathematically modeled, and the relationship between them was investigated. We also used finite-element method (FEM) software to estimate the uniaxial distributions of the magnetic field in the analyzed MREs for condition (2), and developed mathematical models to describe these phenomena. By using these practicable techniques, we established a simple macroscale model of the elastic properties of MREs under simple compression. We estimated the elastic properties of MREs in the small-strain regime (neo–Hookean model) and in the large-strain regime (Mooney–Rivlin model). The small-strain model explains the experimental results for strains under 5%. On the other hand, the large-strain model explains the experimental results for strains above 10%. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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Review

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17 pages, 3563 KiB

Open AccessReview

Magnetoferritin: Process, Prospects, and Their Biomedical Applications

by Le Xue, Dawei Deng and Jianfei Sun

Int. J. Mol. Sci. 2019, 20(10), 2426; https://doi.org/10.3390/ijms20102426 - 16 May 2019

Cited by 27 | Viewed by 5044

Abstract

Ferritin is a spherical iron storage protein composed of 24 subunits and an iron core. Using biomimetic mineralization, magnetic iron oxide can be synthesized in the cavity of ferritin to form magnetoferritin (MFt). MFt, also known as a superparamagnetic protein, is a novel [...] Read more.

Ferritin is a spherical iron storage protein composed of 24 subunits and an iron core. Using biomimetic mineralization, magnetic iron oxide can be synthesized in the cavity of ferritin to form magnetoferritin (MFt). MFt, also known as a superparamagnetic protein, is a novel magnetic nanomaterial with good biocompatibility and flexibility for biomedical applications. Recently, it has been demonstrated that MFt had tumor targetability and a peroxidase-like catalytic activity. Thus, MFt, with its many unique properties, provides a powerful platform for tumor diagnosis and therapy. In this review, we discuss the biomimetic synthesis and biomedical applications of MFt. Full article

(This article belongs to the Special Issue Magnetic Soft Materials)

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