Mesh Coil Research Articles

Design and Development of a Planar Electromagnetic Conveyor for the Microfactory

This paper presents a planar electromagnetic conveyor for a microfactory. The uniqueness of the conveyor design lies in its arrangement of overlapped two-dimensional mesh coils in matrix configuration that enables to drive a mobile part over long strokes. The conveyor architecture includes a fixed part, which consists of 5×5 matrix design that has been fabricated on a multilayer printed circuit board. An analytical model that takes into account the electromagnetic and friction effects has been developed. A conveyor prototype has been fabricated and experimentally characterized in open-loop control. Linear and planar motions, positioning repeatability error, straightness error, and rotation have been experimentally measured. From experimental results, the proposed architecture enables long linear displacement strokes ( $\leqslant$ 70 mm) and rotation ( $\leqslant \pm$ 12.37 $^\circ$ ). In addition, a 12 mm/s speed can be achieved for the mobile part at a nominal current of 0.8 A.

Planar-type micro-electromagnetic actuators using patterned thin film permanent magnets and mesh type coils

In this paper, we propose several types of planar micro-electromagnetic actuator that can be applied in micro-pumps and micro-valves. The various types each consist of a thin film permanent magnet (TFPM), a micro-coil and, in some cases, a ferromagnetic layer. The magnetic properties of a TFPM with a multilayered structure, comprising 300nm thick NdFeB and 10nm thick Ta layers deposited sequentially, are as high as bulk NdFeB magnets. Conventional micro-electromagnetic actuators consist of a bulk permanent magnet and a spiral micro-coil, whereas the actuators proposed in this paper consist of segmented patterns of TFPM, such as line/space and chessboard patterns, and mesh coils surrounding the segmented patterns. The TFPMs are segmented in order to reduce the demagnetization effect and to generate a large flux density. The proposed micro-coils possess a 2D structure and are easy to fabricate compared with spiral type micro-coils. The results of simulation show that the electromagnetic forces generated by actuators with segmented TFPMs are several times higher than one without segmentation. Furthermore, the actuation force performance is enhanced by covering the TFPM pattern with a ferromagnetic layer of Ni55Fe45 permalloy. The electromagnetic actuators are fabricated by a fully integrated MEMS process. The measured magnetic flux densities generated by the patterned TFPMs agree with the simulated results. The electromagnetic force between the patterned TFPM and the micro-coil is measured by an electronic force balance. Due to alignment errors between the micro-magnet and micro-coil, the experimentally measured forces are from 70% to 90% of the simulated ones.

Design of a dynamic transcranial magnetic stimulation coil system.

To study the brain activity at the whole-head range, transcranial magnetic stimulation (TMS) researchers need to investigate brain activity over the whole head at multiple locations. In the past, this has been accomplished with multiple single TMS coils that achieve quasi whole-head array stimulation. However, these designs have low resolution and are difficult to position and control over the skull. In this study, we propose a new dynamic whole-head TMS mesh coil system. This system was constructed using several sagittal and coronal directional wires. Using both simulation and real experimental data, we show that by varying the current direction and strength of each wire, this new coil system can form both circular coils or figure-eight coils that have the same features as traditional TMS coils. Further, our new system is superior to current coil systems because stimulation parameters such as size, type, location, and timing of stimulation can be dynamically controlled within a single experiment.

Inspecting Printed Wiring by Using the Eddy-Current Testing Approach

Eddy-current testing (ECT) is used for inspecting cracks in metal structures. We propose a planar-type ECT probe consisting of a meander and a mesh coil, and discuss the possibility of using ways of this probe to inspect disconnections in printed wirings. This paper describes (1) finding disconnections in printed wiring and (2) discriminating between various patterns of printed wiring and disconnections. Experimental results confirm that it is possible in principle to use ECT for inspecting printed wiring.

プレーナ形渦電流探傷プローブの欠陥検出特性

This paper describes the detective characteristics of a planar-type eddy-current testing (ECT) probe for use in advanced ECT technology. The probe has a sandwich structure of meander and mesh coils. The key operation depends on the patterns of both meander and mesh coils for high-frequency excitation and sensing. The particular functions of the probe are the detection of (1)crack size and (2) its direction on the conducting plate. Experimental results confirm that the probe has detective characteristics, and sufficient sensitivity to detect cracks.

Eddy current testing probe composed of planar coils

This paper presents a new eddy-current probe composed of a micro-planar mesh coil and meander coil. The probe can be used to detect the existence and the size of cracks in metallic structures. Experimental results for the sensed output voltage of this device are presented. The output signal is shown to have a discrete nature. Also, the results show that the signal strength is weak and that an offset voltage exists. Improved probe characteristics are obtained by connecting two mesh coils in series, stacking the coils on top of each other and orienting the two coils 180/spl deg/ apart.

Improved longitudinal magnetic shielding by an amorphous FeSi steel composite panel

An improved magnetic shielding using the magnetic shaking technique with a planar mesh coil is applied to develop a composite shielding panel of Fe-based amorphous sheet and Si steel sheet. The mesh coil, sandwiched by the two ferromagnetic materials, makes a two-dimensional shaking field that enhances magnetic shielding. The composite panel annealed without field shows exceedingly high longitudinal shielding effectiveness. Fine and circular magnetic domains of amorphous Fe-based ribbons contribute to the magnetic shielding effectiveness for alternating fields at high frequencies.

電磁鋼・鉄基非晶質合金複合材料の磁気シールド特性

An improved magnetic shielding method using the magnetic shaking technique with a planar mesh coil was used to develop a composite shielding panel consisting of Fe-based amorphous sheets and Si-steel sheets. The mesh coil, sandwiched by the two ferromagnetic materials, creates a two-dimensional shaking field that enhances magnetic shielding. The composite panel, annealed without the application of a field, shows an exceedingly high shielding effectiveness of 470. The fine and circular magnetic domains of Fe-amorphous ribbons annealed without the application of a field contribute to the magnetic shielding effectiveness of alternating fields at high frequencies.

Effects of Lidocaine and Verapamil on Defibrillation in Humans

Abstract Patients with automatic defibrillators frequently require chronic antiarrhythmic drug therapy or receive acute therapy with the onset of symptoms. The effects on energy requirements for defibrillation of lidocaine hydrochloride and verapamil hydrochloride, two commonly used antiarrhythmic agents, were examined in 20 successive patients undergoing corrective arrhythmia surgery. The minimum energy requirement for ventricular defibrillation before and 5 minutes after the administration of 150 mg of lidocaine intravenously (n = 8), or 10 minutes after 10 mg of verapamil intravenously (n = 12), were determined. Each patient was assigned to receive either verapamil or lidocaine. Three mesh coil defibrillating electrodes (Medtronic 6891, 6892) were sutured to the epicardium of the right and left ventricles. Ventricular fibrillation was induced using alternating current. After a minimum of 10 seconds of fibrillation, the minimum energy for defibrillation was established using sequential pulse defibrillation. The preselected drug was then infused and the ventricular defibrillation energy was again determined after 5 or 10 minutes circulation time. Lidocaine did not alter the minimum energy for defibrillation (3.0 ± 1.4 J vs. 3.0 ± 1.8 J, mean ± SD), despite plasma levels of lidocaine that averaged 13.2 ± 1.9 μmol/l. In contrast, verapamil significantly increased (3.9 ± 2.2 J vs. 6.5 ± 2.9 J) the minimum energy necessary for defibrillation. The difference in defibrillation energy was significantly correlated to the fall in systolic blood pressure induced by verapamil administration (r = 0.72). These data reinforce the necessity for determining efficacy of defibrillation when medication changes are instituted. Verapamil should be used with caution in patients with automatic defibrillators and marginal defibrillation threshold.

An improved mesh shaking coil and its application to a magnetic shielding panel

An improved structure for a mesh shaking coil with finite area is presented by which shielding performance of ferromagnetic shielding is enhanced while suppressing unwanted leakage of the shaking field. A surrounding conductor is added in series to a finite mesh coil in order to cancel the edge effect which deteriorates the multipole distribution of the shaking field. Cancellation of the edge effect is confirmed by experiment and calculation. The improved mesh coil is applied to develop a magnetic shielding panel with a magnetic sheet/coil/magnetic sheet sandwich structure. The shielding factor of a 20-cm/sup 2/ shielding panel of 6.5% Si-Fe steel was enhanced about three times to 152 by magnetic shaking using the mesh shaking coil.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of lidocaine and verapamil on defibrillation in humans

Patients with automatic defibrillators frequently require chronic antiarrhythmic drug therapy or receive acute therapy with the onset of symptoms. The effects on energy requirements for defibrillation of lidocaine hydrochloride and verapamil hydrochloride, two commonly used antiarrhythmic agents, were examined in 20 successive patients undergoing corrective arrhythmia surgery. The minimum energy requirement for ventricular defibrillation before and 5 minutes after the administration of 150 mg of lidocaine intravenously (n = 8), or 10 minutes after 10 mg of verapamil intravenously (n = 12), were determined. Each patient was assigned to receive either verapamil or lidocaine. Three mesh coil defibrillating electrodes (Medtronic 6891, 6892) were sutured to the epicardium of the right and left ventricles. Ventricular fibrillation was induced using alternating current. After a minimum of 10 seconds of fibrillation, the minimum energy for defibrillation was established using sequential pulse defibrillation. The preselected drug was then infused and the ventricular defibrillation energy was again determined after 5 or 10 minutes circulation time. Lidocaine did not alter the minimum energy for defibrillation (3.0 +/- 1.4 J vs. 3.0 +/- 1.8 J, mean +/- SD), despite plasma levels of lidocaine that averaged 13.2 +/- 1.9 mumol/l. In contrast, verapamil significantly increased (3.9 +/- 2.2 J vs. 6.5 +/- 2.9 J) the minimum energy necessary for defibrillation. The difference in defibrillation energy was significantly correlated to the fall in systolic blood pressure induced by verapamil administration (r = 0.72). These data reinforce the necessity for determining efficacy of defibrillation when medication changes are instituted. Verapamil should be used with caution in patients with automatic defibrillators and marginal defibrillation threshold.

Planar inductors with a new coil configuration (abstract)

High-frequency (f≥1 MHz) magnetic power devices are key elements for developing compact and low-profile switching power supplies. Planar inductors with a flat coil are investigated,1–3 however, a problem arising from the use of a flat coil is not addressed. The problem is that normal components to the magnetic plate inevitably exist in the exciting fields from a flat coil and that those components induce severe in-plane eddy currents. The problem is most typical in the case of a spiral coil. In this paper, a new flat coil is proposed (see Fig. 1) for planar inductors which greatly improves the problem because paths of eddy currents are chopped up corresponding to the mesh size of the coil. It is obvious that density of eddy currents becomes small when the mesh size becomes fine. Sandwich planar inductors with a proposed coil (mesh coil) and a meander one were prepared for preliminary tests using pairs of Metglas 2705M amorphous ribbons of 50×50 mm2 and 100-μm copper wires, where the mesh size was 3 mm, equal to the pitch of the meander coil. Inductances at 1 MHz were 1.85 μH for the mesh coil and 2.25 μH for the meander one, whereas Qmax=5 at 6 MHz for the mesh coil and 4.5 at 2 MHz for the meander one. Advantages of the mesh coil may further become clear when it is made on the magnetic plates with thin insulating layer in between by IC or thick-film process.