K. I. Arai

Fabrication of magnetostrictive actuators using rare‐earth (Tb,Sm)‐Fe thin films (invited)

A new concept is proposed for the microactuation based upon magnetostriction. Magnetostrictive bimorph cantilever actuators and a traveling machine, composed of the magnetostrictive amorphous Tb‐Fe and Sm‐Fe thin films on a polyimide substrate, were fabricated. These actuators moved without power supply cables. The 3‐mm‐long cantilever actuator exhibited the large deflection above 100 μm in as low a magnetic field as 300 Oe and above 500 μm at resonant frequency in an alternating magnetic field of 300 Oe. Such unique characteristics suggest that magnetostriction is useful as the driving force of the microactuator.

Motion capture system of magnetic markers using three-axial magnetic field sensor

We have developed a magnetic motion capture system consisting of up to two magnetic markers (Nd-Fe-B magnet) and four three-axial sensors. The position and orientation of the magnetic markers (dipole) are detected by measuring the magnetic field of markers. Position accuracy of one marker is about 3 mm when a marker is located 150 mm from a sensor, position accuracy of two markers is about 20 mm when the markers are located 150 mm from sensors. The most common error source is crosstalk between the cores of three-axial sensors.

Effect of machine shape on swimming properties of the spiral-type magnetic micro-machine

The effect of machine shape on the swimming properties of a spiral-type magnetic micro-machine was examined by using a finite volume method. The optimum design of the blade shape was obtained by using the results of the simulation. According to the optimum design, the micro-machine was fabricated by stereolithography. The swimming properties of the machine agreed well with the analyzed results.

Spiral type magnetic micro actuators for medical applications

Magnetic micro actuators are characterized by their wireless operation. In this study, 3 types of magnetic micro actuators are fabricated. First, swimming micro actuator is described. The actuator could swim in the silicone oil. Second, on the basis of swimming actuator, a magnetic actuator running in a pigs liver was fabricated. Third, magnetic actuator for colonoscope navigation was fabricated. A motion test of the actuator was examined in a large intestine of living dog. All actuators indicate good performances and they have great potential for medical applications.

A high frequency carrier-type magnetic field sensor using carrier suppressing circuit

A highly sensitive high frequency carrier-type magnetic field sensor based on the giant magnetoimpedance effect has been developed. It has been combined with a high frequency carrier suppressing circuit to reduce carrier phase noise dramatically. Highly sensitive magnetic field resolution of 8.8/spl times/10/sup -7/ Oe (8.8/spl times/10/sup -11/ T) was demonstrated.

Development of multilayer planar flux sensing coil and its application to 1 MHz–3.5 GHz thin film permeance meter

Abstract We have developed a new planar flux sensing coil using multilayer printed wiring board fabrication technique. The coil is useful for high frequency magnetic flux sensing because the coil is sensitive to the magnetic field and insensitive to the electric field. A 1 MHz–3.5 GHz broad bandwidth thin-film permeance meter is developed by using parallel plates with short plate and shielded loop pickup coil combination. We investigated the upper frequency limit of permeance measurement is given by the minimum value of standing wave position at the center of pickup coil.

Noise analysis of a 1 MHz–3 GHz magnetic thin film permeance meter

We analyzed the permeability measurement error of a low permeance thin film. We clarified that the noise voltage was excited by a current loop which is composed of the coaxial cable and the ground plane. The current loop should be removed for high sensitivity of the permeameter. The permeability of a high electrical resistivity film (CoFeHfO) has been demonstrated 1 MHz–3.5 GHz.

Wireless Magnetic Position-Sensing System Using Optimized Pickup Coils for Higher Accuracy

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.

Fabrication of magnetic actuator for use in colon endoscope

Magnetic actuator for colonoscope navigation is fabricated. The actuator composed of tube-shape permanent magnet and spiral structure that made by rubber. The magnet is magnetized to the direction of its diameter. By applying the rotational magnetic field the machine rotate and moved in an intestine. The actuator is attached on an end of simulated endoscope. The actuator with flexible air tubes can move in small and large intestines of pig. This result suggests that the actuator have great possibility for colonoscope navigation.

Magnetic micromachines prepared by ferrite plating technique

By the sterolithography technique and the ferrite plating, we fabricated three types of magnetic micromachines which coated Fe3O4, Co0.39Fe2.61O4, and Co0.45Fe2.55O4, respectively. The stereolithography technique enables one to form the spiral-shape resinous templates and the ferrite plating enables one to coat the ferrites uniformly onto these templates from an aqueous solution. The total machine weight is light because a resin of the template body is almost the same density as water. We verified that the machines swim freely and wirelessly in water by applying a rotational magnetic field. As these machines coated with ferrites have the biocompatibility, there is the possibility of medical microrobots which swim in the human body for medical operations.