In this study, the tunable properties of a bio-lens from a deep-sea shrimp were investigated for the first time using magnetic fields. The skin of the shrimp exhibited a brilliantly colored reflection of incident white light. The light reflecting parts and the oil droplets in the shrimp’s skin were observed in a glass slide sample cell using a digital microscope that operated in the bore of two superconducting magnets (maximum strengths of 5 and 13 T). In the ventral skin of the shrimp, which contained many oil droplets, some comparatively large oil droplets (50 to 150 μm in diameter) were present. A distinct response to magnetic fields was found in these large oil droplets. Further, the application of the magnetic fields to the sample cell caused a change in the size of the oil droplets. The phenomena observed in this work indicate that the oil droplets of deep sea shrimp can act as lenses in which the optical focusing can be modified via the application of external magnetic fields. The results of this study will make it possible to fabricate bio-inspired soft optical devices in future.

We performed numerical simulation of structure formation of magnetic particles under magnetic field toward anisotropic material development. In this study, we examined the unsteady process of the structure formation and its feature using magnetic particles with diameter of micrometers. This study evaluated the process of structure forming with various particle diameters and particle volume concentrations using the Non-dimensional Boundary Area (NBA). The structure formed by the magnetic particles does not depend on the particle diameter but depends on the particle volume concentration. In the case of particle volume concentration phi = 5 vol%, the bundle of chain-like cluster is not made and each chain-like cluster by magnetic particles is almost single chain. However, in the case of more than phi = 10 vol%, the bundle structure formed by contacts of multiple chain-like clusters is proceeding. On the process of structure formation by magnetic particles, firstly, the single particle rotates by itself with orienting the magnetic moment to the direction of the applied magnetic field. After then, particles connect with each other and the chain-like cluster is formed.

We are developing a superconducting magnet system to grow high-quality protein crystals. The gravity-controlled environment, based on magnetic forces, can suppress thermal convection and may give rise to a variety of additional effects on the protein crystal growth. To design suitable magnetic force conditions for protein crystal growth in protein solutions, we are studying a gravity-controlled environment by magnetic forces in the crystal growth process by computer simulations. In this study, we derived a modified Navier-Stokes equation with gravity and static magnetic force and numerically solved the equation. The obtained results show that the temperature dependence of the magnetization modifies the levitation condition and the magnetic force gives rise to an unexpected change of fluid motion.

Tilapia fish-scale type I atelocollagen hydrogels with aligned fibril structures were fabricated under a strong magnetic field of 6 or 12 T using two different methods. In the first method, a solution of acid-soluble collagen was neutralized with phosphate buffer saline and maintained in the magnetic field at 28°C for 3h. Under these conditions fibrogenesis occurs, and a hydrogel is formed. The hydrogel was subsequently crosslinked with ethyl-dimethylcarbodiimide (EDC). In the second method, the hydrogels were formed as described above, but in the absence of an applied magnetic field. Only after being crosslinked with EDC were these gels exposed to the magnetic field (28°C for 3h). Both methods led to alignment of the collagen fibrils perpendicular to the magnetic direction, the extent of which depended on the duration of magnetic treatment. Even after EDC treatment, collagen fibrils can align, indicating that crosslinking has taken place within fibrils. Both sorts of aligned hydrogels exhibited similar rheological properties with higher storage and loss moduli than were observed with unoriented gels. The hydrogels treated at 6 T had the best rheological properties. The decrease in tangent angle phase delta indicated that the ratio of elasticity to viscosity was greater in the crosslinked than in the non-crosslinked hydrogels. Atomic force microscopy images showed that magnetic treatment had no effect on the nanostructure of collagen fibrils. Differential scanning calorimetry measurements indicated that collagen hydrogels with and without magnetic treatment had the same denaturation temperature, 48°C, while EDC crosslinking increased the denaturation temperature to 62°C.

In bone tissue, two kinds of cells, osteoblast (OB) and osteoclast (OC), contribute to remodeling of bone. In the present study, a co-culture system of bone-forming cell (OB) and -dissolving cell (OC) was incubated in static magnetic fields of horizontal 14 T and vertical gradient 10 T. Effect of two kinds of magnetic fields was an inhibition of OC formation. Three kinds of mechanisms, magnetic orientation of OB, diamagnetic torque force acting on OC, and possible reduction of earth's gravity were discussed.

Fabrication of MgB2-based superconducting magnets has been attempted by a new approach using film coated on symmetric tubes. Superconducting MgB2 films have been prepared on iron substrates by electroplating in molten electrolytes. The critical current (Ic) of the MgB2 electroplating films at 4.2 K and at self-field was 15 A on the basis of 1 μV/cm of Ic criterion. A model calculation has shown that MgB2-based superconducting magnets based on MgB2 electroplating films have the potential to generate magnetic fields over 0.5 T.

The separation of biological materials by the magneto-Archimedes levitation technique is discussed in the present paper. Magneto-Archimedes levitation is a useful technique to levitate feeble magnetic materials by superconducting magnets of the 10 T class. Since the stable levitation position of matter is decided by the volume magnetic susceptibilities and densities of the object and the surrounding media, by utilizing the magneto-Archimedes levitation technique, a mixture of several materials can be spatially separated into each component. In a biological system, there are many materials with quite similar compositions or conformations. Even though the differences in their compositions or conformations are trivial, they may result in differences in their magnetic properties. Using magneto-Archimedes levitation, it seems possible to realize the fine separation of biological materials that have quite similar structures. The possibility of this novel fine separation technique for biological materials was evaluated using collagens as an example of a system with similar structures.

Using a two-dimensional closed vessel filled with an aqueous solution, we present triangle-lattice alignments with some spacing formed by interactions among magnetic dipoles induced in feeble magnetic substances under high magnetic fields. We conducted an experiment and a numerical simulation using Au particles with a 1mm diameter dispersed in a MnCl2 aqueous solution and compared their configurations quantitatively using a three-body distribution function. We confirmed that the numerical simulation demonstrates the formation of triangle-lattice alignments in a two-dimensional plane as obtained in the experiment and also verified that the interaction among induced magnetic dipoles is a significant force that governs the structure formed by feeble magnetic substances under high magnetic fields. On the basis of the results obtained in the experiment and the numerical simulation, it is clear that the distance among particles and the interaction force depend on the number of particle at a steady state and they are closely correlative with each other. The distance among particles can be estimated from the correlative relation.

The mechanism of the morphological effect of magnetic fields on electroless silver deposition was investigated through in situ microscopic observation by using a periscope system that was developed on the basis of a confocal scanning laser microscope. At the growth front of a silver dendrite, under a 12 T magnetic field applied perpendicularly to the sample plane, a silver branch was grown straightly for a while; then, a certain length of the branch at the neighbor of the tip started moving rapidly and was bent in an integrated manner. As a result of the process, a dense silver dendrite in the shape of a vortex was formed. When the sample space was narrowed, the branch did not bend due to the increase in the static friction between the branch and the glass plates. Judging from these observations, the mechanism of the formation of a dense vortex dendrite was thought to be the effect of a Lorentz force acting on the branch due to the electric current flowing through the branch itself accompanied by the silver deposition and the copper dissolution reactions.

Some ordered alignments of feeble magnetic particles were obtained utilizing magnetic dipole interactions. The interactions among feeble magnetic substances under magnetic fields, that is, interactions among magnetic dipoles induced in feeble magnetic substances have been believed too small to be observed. However, by controlling experimental conditions carefully, we confirmed that such interactions can be observed visually even in feeble magnetic substances. Furthermore, by applying the interactions to many-particle systems, ordered alignments were obtained such as chain-like alignments parallel to and triangle-lattice alignments perpendicular to magnetic fields. These results suggest that structures of feeble magnetic substances can be controlled by magnetic fields, and such application would be of use in materials processing.

We present visualization and measurement of the convection of water under a high magnetic field applied vertically to the fluid. The convection was either suppressed or enhanced depending on the direction of the magnetic force. The magnetic field effect was evaluated quantitatively by measuring the onset of convection, and discussed in terms of the Rayleigh number which includes the magnetic term. The results clearly show that the convection in a diamagnetic fluid such as water can be controlled using a common 10 T class magnet.

Two-dimensional crystallization of nonmagnetic gold spheres was achieved by the application of a high magnetic field. This phenomenon is based on the two different forces caused by a magnetic field; interactions between magnetic dipoles induced in the nonmagnetic spheres and magnetic force derived from field gradient. The former force is generally so weak and, hence, negligible. However, under an appropriate condition, we can achieve the subtle balance between the two forces. This phenomenon is a new class of self-assembling phenomena, and we believe that our achievement will be a milestone in the utilization of magnetic fields.

We introduce magneto-Archimedes separation and the induced magnetic dipole interaction in feeble magnetic materials as a novel method for utilizing high magnetic fields. Under the magneto-Archimedes levitation condition, stable levitation position is materials dependent since it is determined by the differences in volume magnetic susceptibilities and densities between objects and their surroundings. Using this feature, we have successfully demonstrated a novel magnetic separation technique. When powder mixtures composed of feeble magnetic materials were levitated, the initial mixture immediately underwent separation into its component particle aggregates. It was also confirmed that this method is sensitive to both material density and magnetic susceptibility. Interactions among induced magnetic dipoles were observed in the systems of feeble magnetic substances. Usually, such interactions are too small to be observed and have been so far neglected. However, we focused on the interactions and succeeded in observing them by using elaborate experiments. Furthermore, by introducing this interaction to many-particle systems, we obtained some peculiar alignments. These phenomena would be useful to control materials structures, and to bring new applications of magnetic fields into various processes.

A novel magnetic separation method, which utilizes the magneto-Archimedes levitation, has been introduced and applied to separation of biological materials. By using the feature that the stable levitation position under a magnetic field depends on the density and magnetic susceptibility of materials, we have successfully separated biological materials such as hemoglobin, fibrinogen, cholesterol, and so on. So far, the difference of magnetic properties was not utilized for the separation of biological materials. Magneto-Archimedes separation seems to be a potential way in biological materials separation.

Interactions among induced magnetic dipoles were observed in the systems of feeble magnetic substances. Usually, such interactions are too small to be observed, and have been neglected so far. However, we focused on the interactions, and succeeded in observing the interactions through elaborate experiments. Furthermore, by applying this interactions to many-particle systems, some peculiar alignments were obtained. These phenomena would be of use as a control of materials structures, and bring new applications of magnetic fields in various processing.

The effect of a magnetic field on the unidirectional solidification process of the high-Tc superconductor Bi2Sr2CaCu2Oy (Bi-2212) was studied. The apparatus used in this study was a high-frequency heating furnace located in the room-temperature bore of a superconducting magnet. A sinterad rod of Bi-2212 was put into an alumina tube, then moved parallel to the applied magnetic field direction through the high-frequency coil. The magnetic field intensity was about 7 T in the molten zone. After solidification, the initial and later parts of the samples thus obtained ware cut into blocks, and X-ray diffraction and magnetization measurements were performed to evaluate their orientations. When a conventional unidirectional solidification process such as the floating-zone method is used, Bi-2212 crystals tend to grow with their c-axes perpendicular to the direction of motion. On the other hand, when a high magnetic field is applied during the solidification process, samples with their c-axes parallel to the direction of motion were obtained. This phenomenon was due to the paramagnetic anisotropy of Bi-2212 crystals. It can be said therefore that a magnetic field can be used to control the grain orientations in melt-solidification processes of even feeble magnetic substances.

Magnetic-field simulations have been carried out to attain efficient magnetic shielding from high and static magnetic fields. A stray field created by a 10 T solenoid superconducting magnet with a φ100 mm room-temperature bore was assumed. As a shielding material, plate-, cylindrical-, and the combination of a plate- and framework-shaped irons were selected. To investigate the effect of the iron shield, the shielding factors were evaluated systematically by changing the shape, size, thickness, etc. of the shield emphasizing the area around 2 m apart from the field center in the axial direction. Various simulations led us to conclude that the shielding factor becomes high because of the use of large iron plates and not because of either the thickness or the number of layered plates. Then, the combination of a iron plate and framework was suggested and examined as a way of efficient shielding. On the other hand, when the shield was placed in the radial direction, the larger and the thicker the shield became, the higher the shielding factor. In designing magnetic shields, it is important to consider what to be shielded from and where to be shielded from stray fields. In this respect, an easy method to reduce stray fields in one direction was obtained.

Magnetic fields up to 10T have been applied on various substances composed of non-magnetic liquids, solids and/or gases. It has turned out that the magnetic fields of this range do produce various visible effects on the equilibrium shape, relative distribution of the substances or kinetic processes of the systems. The phenomena observed are due to the magnetization force that becomes non-significant in determining the mechanical balance of the system. The effects manifest themselves through the deformation of the equilibrium shape of the liquid interfaces, through the change in the effective weight which determines the relative positions occupied in the space by the substances involved and through the creation of convection in a non-uniform gas or liquid phase in terms of the magnetic susceptibility. Some of the processes seem to be utilized for practical purposes.

The effect of a magnetic field on the gas dissolution process into degassed water was studied. Under magnetic fields up to 10T, the equilibrium concentration of paramagnetic oxygen gas was not changed, whereas the dissolution rate was significantly accelerated. The mechanism was found to be based on magnetically induced convection in water due to the non-uniformity of magnetic susceptibility created by the dissolution of oxygen into the water phase. This paper presents a theoretical discussion of the mechanism in terms of the hydrodynamics on the analogy of thermal convection. To confirm this argument, two kinds of experiments were carried out. The degree of acceleration of oxygen dissolution depended on the product of the magnetic field intensity and its gradient, B . dB/dz. The maximum acceleration occurred at the maximum position of B . dB/dz on the bore axis of the magnet. In contrast, the dissolution of diamagnetic carbon dioxide gas was not accelerated by the magnetic field. However, under the coexistence of oxygen gas, the dissolution rate of carbon dioxide became fast. These observations support the proposed mechanism.