Author
Ken Ichi Arai
Other affiliations: NEC, Nagasaki University, Missouri University of Science and Technology
Bio: Ken Ichi Arai is an academic researcher from Tohoku University. The author has contributed to research in topics: Magnetic field & Inductor. The author has an hindex of 31, co-authored 268 publications receiving 3856 citations. Previous affiliations of Ken Ichi Arai include NEC & Nagasaki University.
Papers published on a yearly basis
Papers
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TL;DR: In this article, two types of one-dimensional photonic crystals composed of magnetic and dielectric materials (magnetophotonic crystals) driven by Kerr (reflection) and Faraday (transmission) modes were constructed.
Abstract: Two types of one-dimensional photonic crystals composed of magnetic and dielectric materials (magnetophotonic crystals) driven, respectively, by Kerr (reflection) and Faraday (transmission) modes were constructed. Their optical and magneto-optical (MO) properties were studied in detail to confirm our theoretical results showing the large Kerr and Faraday effects of the media originating in the localization of light. For the Kerr-mode operation, films with (SiO2/SiN)×k/Co/(SiN/SiO2)×k (k: number of layers) structures were fabricated, while for the Faraday-mode operation, films with (SiO2/Ta2O5)×k/Bi:DyIG/(Ta2O5/SiO2)×k structures were formed. Excellent agreement between the theoretical and experimental results was obtained, where large enhancement in both Kerr and Faraday rotations appeared originating in the localization of light in the vicinity of the magnetic layers. Since the localized state of light can be controlled artificially, the one-dimensional magnetophotonic crystals will impact for various MO...
315 citations
TL;DR: In this article, the magneto-optical (MO) Faraday effect of one-dimensional photonic crystals (1D-PCs) composed of Bi-substituted yttrium-iron-garnet films and dielectric films such as SiO2 and TiO2 films was studied theoretically.
Abstract: The magneto-optical (MO) Faraday effect of one-dimensional photonic crystals (1D-PCs) composed of Bi-substituted yttrium–iron–garnet films and dielectric films such as SiO2 and TiO2 films were studied theoretically. Because of considerable localization of light, these media exhibit a very large MO effect. For instance, when the film structure is chosen to be appropriate for supporting the localization of light, the 1D-PC films can possess a huge Faraday rotation angle reaching to −28 deg/μm at λ=1.15 μm. The analysis reveals that the MO characteristics of the 1D-PC films are almost governed by the degree of localization of light, which can be controlled by varying the number of reflection layers in the films.
250 citations
TL;DR: In this article, a new type of micro swimming mechanism was proposed for microrobots working in water, which is composed of a small magnet attached to a spiral wire, and an external alternating magnetic field causes the magnet to rotate due to magnetic torque.
Abstract: A new type of micro swimming mechanism is proposed for microrobots working in water. It is composed of a small magnet attached to a spiral wire. An external alternating magnetic field causes the magnet to rotate due to magnetic torque. As a result, the mechanism can swim propelled by waves traveling along the spiral. The swimming velocity increases linearly with increasing excitation frequency, and the increasing rate depends on the shape of the spiral. The experimental velocity agrees with the calculation result based upon Lighthill's theory (1975, 1976).
218 citations
TL;DR: In this paper, a thin-film inductor for 1 GHz-drive mobile communication handset application has been demonstrated in a 370 μm×370 μm square four turn spiral of line/space with 0.1-μm-thick slitted Fe61Al13O26 film with Cr underlayer.
Abstract: Thin-film inductors for 1 GHz-drive mobile communication handset application has been demonstrated. This is the possible practical application of soft magnetic films in 1 GHz range. Fe61Al13O26 with Ms=1.2 T, ρ=500 μΩ cm, fr=2 GHz were used for the inductors. L=7.6 nH, R=6.5 Ω, and Q=7.4 were obtained at 1 GHz in a 370 μm×370 μm square four turn spiral of line/space=11 μm/11 μm covered with 0.1-μm-thick slitted Fe61Al13O26 film with Cr underlayer. The L was increased over the flux saturated inductor by 8.6% without any degrade of quality factor.
163 citations
TL;DR: Magnetic micro-machines capable of swimming through liquid or gel were fabricated as mentioned in this paper, and they were driven by an external rotating magnetic field and featured a screw-shaped structure and permanent magnet.
Abstract: Magnetic micro-machines capable of swimming through liquid or gel were fabricated. The micro-machines were driven by an external rotating magnetic field and featured a screw-shaped structure and permanent magnet. The machines could swim under condition of a Reynolds number ( Re ) of 10 −7 , and were able to run through agar or a bovine tissue sample using the same principle. Their running behavior was dependent on the frequency and strength of the external field, and on the surrounding media. These machines have great potential for medical applications in the human body.
144 citations
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TL;DR: In this paper, the authors describe photonic crystals as the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures, and the interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
2,722 citations
01 Sep 1955
TL;DR: In this paper, the authors restrict their attention to the ferrites and a few other closely related materials, which are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present.
Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.
2,659 citations
TL;DR: The aim of this review is to provide a comprehensive survey of the technological state of the art in medical microrobots, to explore the potential impact of medical micRORobots and inspire future research in this field.
Abstract: Microrobots have the potential to revolutionize many aspects of medicine. These untethered, wirelessly controlled and powered devices will make existing therapeutic and diagnostic procedures less invasive and will enable new procedures never before possible. The aim of this review is threefold: first, to provide a comprehensive survey of the technological state of the art in medical microrobots; second, to explore the potential impact of medical microrobots and inspire future research in this field; and third, to provide a collection of valuable information and engineering tools for the design of medical microrobots.
1,580 citations
TL;DR: The construction and operation of chiral colloidal propellers that can be navigated in water with micrometer-level precision using homogeneous magnetic fields are reported.
Abstract: For biomedical applications, such as targeted drug delivery and microsurgery, it is essential to develop a system of swimmers that can be propelled wirelessly in fluidic environments with good control Here, we report the construction and operation of chiral colloidal propellers that can be navigated in water with micrometer-level precision using homogeneous magnetic fields The propellers are made via nanostructured surfaces and can be produced in large numbers The nanopropellers can carry chemicals, push loads, and act as local probes in rheological measurements
1,122 citations
TL;DR: ABF swimmers represent the first demonstration of microscopic artificial swimmers that use helical propulsion and are of interest in fundamental research and for biomedical applications.
Abstract: Inspired by the natural design of bacterial flagella, we report artificial bacterial flagella (ABF) that have a comparable shape and size to their organic counterparts and can swim in a controllable fashion using weak applied magnetic fields. The helical swimmer consists of a helical tail resembling the dimensions of a natural flagellum and a thin soft-magnetic “head” on one end. The swimming locomotion of ABF is precisely controlled by three orthogonal electromagnetic coil pairs. Microsphere manipulation is performed, and the thrust force generated by an ABF is analyzed. ABF swimmers represent the first demonstration of microscopic artificial swimmers that use helical propulsion. Self-propelled devices such as these are of interest in fundamental research and for biomedical applications.
1,040 citations