Spiral-type micro-machine for medical applications

The spiral-type magnetic micro-machine, which is driven by a rotating magnetic field, is characterized by wireless operation for swimming. The machine has to swim under a lower Reynolds number environment, when the machine is downsized and working inside the human body. In this study, using various silicone oils whose kinematic viscosity ranged from 1 to 5×10⁵ mm²/s, the swimming performance of the machine at low Reynolds number was examined. The machine composed of a cylindrical NdFeB magnet could swim in oils under condition of Re=10^-7. This Reynolds number is the same as that of a micro-machine with micron size swimming in water. In addition, the machine could turn by controlling the external rotational magnetic field, and therefore the swimming direction of the machine could be controlled. Using these principles, a magnetic micromachine, which can run in a gel, was also fabricated