We investigated the behaviors and sensitivity of thin-film magnetoimpedance elements having an easy axis angle of 0°-45° when applying dc bias current directly to the elements. All elements show ...symmetric impedance profiles with respect to the impedance axis without dc bias current, while their profiles become asymmetric with dc bias current. This appearance of the asymmetric property on the impedance profiles indicates that the shape of cross section of the element has asymmetric configuration. On the other hand, when the easy axis angle is relatively small, the sensitivity for field detection is enhanced with a small dc bias level, while a stronger bias level is required for the element with a larger easy axis angle. The obtained results show a potential to optimize the sensor properties by dc bias current with small intensity in case that design properties are not obtained in the fabrication process.
The magnetic flux density change ΔB caused by the inverse magnetostrictive effect is key for achieving high-performance vibration power generation. As the magnetization curve of the polycrystalline ...Fe–47.6 at. % Co–2.3 at. % V (Fe–Co–V) alloy became easier to magnetize by applying tensile stresses, the value of ΔB estimated from the magnetization curves depended significantly on magnetic fields. Hence, the vibration power generation of a U-shaped unimorph device using a polycrystalline Fe–Co–V alloy core was demonstrated under various bias magnetic fields. As a result of bias magnetic field adjustment, the open-circuit voltage induced by the vibration of the device improved to ∼7.0 V. Such superior performance is attributable to a large ΔB of 1.1 T in the Fe–Co–V alloy core. Therefore, adjustment of bias magnetic fields is essential for obtaining large ΔB in Fe–Co–V alloys, which are promising inverse magnetostrictive materials for high-performance vibration power generation.
Various magnetic micro-robots driven by an external magnetic field have recently been suggested for bio-medical application. The main benefit of control using an external magnetic field that it is ...wireless and the robot is battery-free. Most locomotion methods of magnetic micro-robots depend on swimming method using an alternatiing magnetic field. In addition, a rotating magnetic field has been used for the spiral swimming method. In this paper, we propose a new locomotion method and mechanism within the rotating magnetic field using a three-axis Helmholtz coil. The proposed mechanism is based on snake-like skeletal motion that consists of an NdFeB spherical magnet, artificial spine, and ribs. This structure creates an undulatory motion based on dynamic rotation of both roll and yaw motions by magnetic torque. The proposed mechanism and driving method shows excellent mobility in various environments.
With the aim of improving the detection accuracy of a wireless magnetic position-sensing system using an LC resonant magnetic marker, a pickup coil with an optimal size (10 mm in diameter × mm ...thick), as calculated by a previous simulation study, was used and tested in this paper. Our study confirmed that positional errors were reduced to a submillimeter order in the area within y =120 mm from the pickup coil array. On the contrary, in the area outside y =130 mm from the pickup coil array, the errors increased by about 0.5-2 mm compared to the results for the previous pickup coil size (25 mm in diameter × 2 mm thick). Regardless of the size of the pickup coil, however, compensation can be made for these positional deviations, including the influence of the mutual inductance between the LC marker and the exciting coil. After application of the compensation process, the detection results were corrected approximately to the actual positions of the LC marker.
This paper presents a magnetic centrifugal pump, driven by an external rotating magnetic field, for use in artificial heart-assist blood pumps. The magnet rotor in the pump is synchronized to a ...rotating magnetic field, which then causes the fabricated impeller to produce a centrifugal force in the pump. Because the pump is driven by the direct application of an external rotating magnetic field, the proposed pump does not require a shaft or mechanical bearings. Thus, the proposed mechanism and external driving source give the pump the advantages of compact size; wireless, battery-free operation; heat-free operation; and minimal risk of bacterial infections. The pump weight, length, and diameter are 34 g, 35 mm, and 20 mm, respectively. The compact size and performance make the device suitable for use in pediatric cardiac assistance pumps.
Abstract Therapeutic drug monitoring (TDM) and subsequent dosage adjustment for individual patients in the treatment with tacrolimus are required after liver transplantation to prevent rejection and ...over-immunosuppression, which leads to severe infection and adverse reactions including nephrotoxicity. The purpose of this study was to evaluate the analytical performance among commercially available immunoassay methods, which were microparticle enzyme immunoassay (MEIA), chemiluminescent enzyme immunoassay (CLIA), and affinity column-mediated immunoassay (ACMIA), compared with an assay using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In addition, the flow injection assay (FIA-MS/MS) was also evaluated to determine whether it could be available as a new method of analysis in tacrolimus therapy. The blood tacrolimus concentrations in samples from liver transplant recipients (n = 102) were measured using MEIA, CLIA, ACMIA, and LC-MS/MS. Additional blood samples from liver transplant recipients (n = 54) were analyzed using both FIA-MS/MS and LC-MS/MS. Because the assay performance and characteristics of MEIA, CLIA, ACMIA, and FIA-MS/MS are relatively different, the measured data should be carefully considered depending on the methodology.
In this paper, we present a pushing force mechanism in a magnetic spiral-type machine for use in therapy and diagnosis. Non of the current spiral-type machines can create a pushing force. Thus, their ...locomotion or tasks are controlled by magnetic field strength and driving frequency. However, the proposed mechanism increases the thrust force on the robot itself in the working space without field controls. The developed pushing force mechanism uses a magnetic suspension structure based on two magnets between the two spiraltype machines. Through this mechanism, the two spiral-type machines act independently via a rotating magnetic field. Thus, the different thrust forces between the two machines create a variation of the magnetic repulsive force in the magnetic suspension. Therefore, the combination of the two thrust forces and the magnetic repulsive force become a total propulsive force. The prototype of the mechanism increased the total thrust force by approximately 3.6 times for locomotion and generated a maximum pushing force of 0.345 N.
We investigated the effects of controlling the distribution of the demagnetizing field on the impedance profiles of stepped giant magnetoimpedance elements. Elements with an ellipsoidal shape were ...adopted to improve the properties in discontinuous impedance jumps, as the demagnetizing field is expected to be uniform in an ellipsoid. The impedance jumps in the ellipsoidal elements became sharper and more abrupt, and the height ratio improved by 3-4 times compared with the ratio of the conventional rectangular elements. The observed domain structures propagated from the edge to the center in the rectangular elements, which is explained on the basis of the calculated distribution of the demagnetizing factor. On the other hand, all the domains appeared or disappeared in the ellipsoidal elements, indicating that the demagnetizing factor is nearly constant in the elements. The results contribute to a miniaturization of the element in order to keep the abrupt discontinuous impedance.
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