T. Honda

Micro swimming mechanisms propelled by external magnetic fields

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 Lighthills theory (1975, 1976).

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.

Dependence of magnetostriction of sputtered Tb-Fe films on preparation conditions

Amorphous Tb-Fe thin films prepared by the sputtering method in the compositional range Tb/sub x/Fe/sub 1-x/ (x=0-0.5) are investigated in view of their potential for use in electromagnetic thin film actuators. The magnetostriction and the coercive force for the Tb-Fe films are examined for different sputtering conditions to obtain both soft magnetic properties and large magnetostriction in this system. As a result, Tb-Fe thin films having large magnetostrictions (180*10/sup -6/ at 1 kOe) and low coercive force (60-70 Oe) are obtained. These films are prepared under the conditions of the composition of 45-50 at.% Tb, Ar gas pressure of 4 mTorr, RF input power of 200 W and using water cooled substrates. A trial actuator using magnetostrictive thin films is also reported. >

Fabrication of small flying machines using magnetic thin films

A small flying machine based upon a new mechanism was realized. The flying machine driven by magnetic torque had hard magnetic films as wings and a soft magnetic wire as a body, respectively. The wing has two hinges, which create different drag during up and down strokes, and produced lifting force. Shape magnetic anisotropy of the body stabilized the attitude. The flying machine flew without power supply cables and guides when an alternating magnetic field of more than 400 Oe around 12 Hz was applied.

Growth and Characterization of Bulk Si–Ge Single Crystals

Si–Ge single crystals, 7 mm in diameter and about 20 mm long with compositions ranging from 0 to 50 at.% Si were grown by the traveling solvent method. The compositions of the crystals were shown to be uniform parallel and perpendicular to the growth axis using EPMA measurement. Raman spectra indicated that the ratio of the numbers of Si–Ge and Ge–Ge bonds agreed with that expected for a random distribution of Si and Ge atoms. The band gap energy of the alloy increased linearly up to 15 at.% Si and increased gradually above 15 at.% Si. From photoluminescence measurements done under uniaxial stress along the direction, it was shown that the dependence of excitonic no-phonon spectrum on the stress changed at about 15 at.% Si. These results indicated that the position of the conduction band minimum of Si–Ge alloy in the k-space changed at about 15 at.% Si.

Fabrication of actuators using magnetostrictive thin films

A new concept of the microactuation driven by magnetostriction is proposed. We fabricated two kinds of cantilever actuators and a travelling machine, composed of the magnetostrictive thin films on a polyimide film. Amorphous Tb-Fe and Sm-Fe thin films were used as the magnetostrictive materials. These actuators moved without power supply cable and the cantilever actuators exhibited the large deflection in low magnetic fields. Such unique characteristics suggest that the magnetostriction is suitable for the driving force of the microactuator.

Recrystallization and magnetic properties of purified 3% silicon steels

The effect of impurities on the tertiary recrystallization and magnetic properties of the thin (10 to 100 μm) silicon steels was investigated. For purification, the conventional grain oriented silicon steels, which were used as starting materials with a thickness of 0.30 mm were pre‐annealed at 1200u2009°C in a vacuum of 1×10−3 Pa before cold rolling. In sheets without pre‐annealing, the tertiary recrystallization was observed after annealing for at least 3 h over 1200u2009°C in a vacuum. On the other hand, in pre‐annealed sheets, the tertiary recrystallization was completed within 10 min at an annealing temperature of 1150u2009°C in a vacuum. Through recrystallization, B8 increased to 1.95 T. Even in sheets annealed at 1050u2009°C, the B8 increased with increasing the annealing time, and became 1.95 T after anneals of 2 h. The pre‐annealed sheets were also annealed in hydrogen atmosphere. In this case, at annealing temperatures over 1100u2009°C, the tertiary recrystallization was completed in less than 1 h. Using the purifi...

Magnetic Small Flying Machines

A small flying machine driven by magnetic torque was realized. The flying machine had hard magnetic films as wings and a soft magnetic wire as a body, respectively. Magnetic torque flapped the wing. Shape magnetic anisotropy of the body stabilized the attitude. The wing with two hinges made a difference of drag during up and down strokes and produced lifting force over 2.5 mgf. The flying machine flew without any power supply cables or contact guides when the alternating magnetic field of more than 400 Oe around 12 Hz was applied.

A theory for analyzing the flap motion of wings of small flying elements driven by a magnetic torque

A theory for analyzing the flap motion of wings of small flying elements driven by an alternating magnetic field was developed. The elements have the combined wings which are composed of magnetic and polyimide sheets connected with hinges. Motion equations of wings were obtained by examining the losses of flap motion of wings in detail. They were solved numerically, and the results were studied with experimental ones. The analytical results coincide very well with the experimental ones: the difference between the theoretical and experimental results was evaluated to be less than 17/spl deg/ in terms of the elevation angle of wings. This suggests that the theory developed here is useful for determining the motion of wings and hence for designing the elements with optimal structures for flying.

Positron annihilation in electron-irradiated SixGe1−x bulk crystals

Position lifetime measurement for SixGe1−x bulk crystals has been performed. The bulk lifetime of positron in the crystals varied between those for Ge and Si. The dependence of the lifetime on the alloy composition showed an abrupt change at x=0.17–0.20 which seems to be correlated with that of the band gap energy. After 3 MeV electron-irradiation, vacancy-type defects giving rise to the lifetimes of ∼280 and ∼330 ps were detected for 0.63⩽x⩽0.82 and 0.20⩽x⩽0.40, respectively, but not for x⩽0.17. The composition-dependent vacancy production was interpreted in terms of the thermal stability of vacancies with the composition.