Direction Control of a Magnetic Micromachine Capable of Moving in a Liver

Abstract

A magnetic micromachine for driving in a liver was fabricated. It consisted of a cylindrical permanent magnet, a cutting tip at the end of the magnet, and a spiral structure around the magnet. The magnet was magnetized in the direction of its diameter. When a rotating magnetic field was applied, the magnet was rotated by the magnetic torque, and the spiral structure produced a thrust force perpendicular to the rotation plane of the field. The micromachine was able to penetrate the liver of a swine and a bovine to a depth of 40-45 mm in 20-40 seconds. In addition, it was demonstrated that the driving direction of the micromachine could be controlled by changing the direction of the rotating magnetic field. The radius of a turn was 25 mm. These results show that the micromachine has great potential for medical applications such as local hyperthermia.