Aya Yamazaki

Swimming micro-machine driven by magnetic torque

Abstract Magnetic micro-machines capable of swimming through liquid or gel were fabricated. The micro-machines were driven by an external rotating magnetic field and featured a screw-shaped structure and permanent magnet. The machines could swim under condition of a Reynolds number ( Re ) of 10 −7 , and were able to run through agar or a bovine tissue sample using the same principle. Their running behavior was dependent on the frequency and strength of the external field, and on the surrounding media. These machines have great potential for medical applications in the human body.

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.

Three-dimensional analysis of swimming properties of a spiral-type magnetic micro-machine

The swimming properties of a spiral-type magnetic micro-machine were analyzed theoretically using 3D finite volume method. The basic equations of incompressible viscous fluid flow were integrated. The flow field around the micro-machine was calculated to estimate the swimming velocity, thrust, drag, and load torque of a spiral-type magnetic micro-machine. Good agreement was obtained between the experimental and theoretical results in a low Reynolds number. Therefore, the 3D analysis method without any fitting parameters was judged to be established.

Swimming of magnetic micro-machines under a very wide-range of Reynolds number conditions

A magnetic micro-machine, a minuscule device composed of a cylindrical body with a magnet and spiral blade, swims in liquid under the force of a rotational magnetic field. To obtain a machine capable of swimming through organs and blood vessels for medical applications, it must be designed on a scale below the mm order and retain its swimming capability under highly varied conditions. The swimming properties of a spiral-type magnetic micro-machine were examined under various Reynolds number conditions by altering the kinematic viscosity of the liquid. The machine could swim in liquids with kinematic viscosities ranging from 1.37 to 5/spl times/10/sup 5/ mm/sup 2//s, which translates into a Reynolds number from 430 to 6/spl times/10/sup -7/. The Reynolds number of blood flow is within this range. In addition, the load torque for swimming was studied theoretically and experimentally. The results obtained suggested great promise for the development of a micro-machine that can be put to work inside the human body.

Fabrication of micropump with spiral-type magnetic micro-machine

In this paper, we propose a micropump using a magnetic micro-machine. Magnetic micro-machines require no power supply cables, no controlling systems on the machine body. So this micropump works without wire and is suitable for the miniaturization. We fabricated the micropump and examined its properties.

Fabrication of a spiral type magnetic micromachine for trailing a wire

A magnetic micromachine capable of trailing a wire was fabricated. The micromachine was constructed of a permanent magnet, a copper tube, and a spiral shape made of a tungsten wire. The magnet was magnetized to the diametrical direction. When a rotational magnetic field was applied, the machine rotated and moved in a silicone oil. It was experimentally found that the blade angle of the machine that produced the largest thrust force was 45/spl deg/ . The micromachine was able to trail a wire in a narrow waterway simulating a blood vessel. These results show that the magnetic micromachine has great potential for navigating medical catheters.

Wireless micro-machine with magnetic thin film

As the magnetic micro-machines are driven by a magnetic field, they require no power supply cables, no batteries, and no controlling systems on the machine body. We fabricated the spiral-type micro-machine (outer diameter; 0.14 mm, length; 1.0 mm) by a tungsten wire (/spl Phi/ 20 /spl mu/m). NdFeB film magnet was deposited on the spiral-machine by the PLD method. In the experiment, the wireless micro-machine swam at the speed of 0.2 /spl sim/ 1.6 mm/s. This result indicated that the spiral shape was suitable for miniature swimming machine.

Flow rate of micropump with spiral-type magnetic micromachine

In this paper, a micropump with spiral-type magnetic micromachine was fabricated and the flow rate of the pump was then experimentally evaluated. The pump system proposed in this work is suitable for the micro-fluid devices because they can control the very small flow rate quantitatively and the flow rate was independent of the viscosity of the fluid.

Study of a cantilevered actuator driven by magnetostriction in low magnetic field

A cantilevered actuator is fabricated in this study by sputter deposition using amorphous Fe72Si14B14 as the magnetostrictive material. The displacement of the cantilever is observed with applying the magnetic field of 10 kA/m to the width direction of the cantilever. Results show that the displacement of the cantilever increased with decreasing substrate thickness, and has a peak value at the thickness of the magnetic thin film of 0.5 mum when the substrate thickness is 7.5 mum.

Micropump with magnetic micromachine

Micropumps are studied for applications to /spl mu/TAS (micro total analysis system) systems for automatic medication, and so on. The principals of the micropumps are using piezoelectric materials, SMA (shape memory alloy), etc. In this study, we propose a micropump using a magnetic micromachine. As the magnetic micromachines work wirelessly, we can obtain a wireless micropump that is suitable for the miniaturization. In previous studies, we examined the basic properties of the pump, and we found that the produced pressure could be controlled by the frequency of the applied rotational magnetic field. In this study, we examined the properties of the pump such as the pressure and the flow rate. In addition, we proposed a disposable pump system using the magnetic micromachine.