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.