Spiral-type micro-machine for medical applications

Abstract

Spiral-type magnetic micro-machines, which are driven by a rotating magnetic eld, are characterized by their wireless operation for swimming. The machines have to swim in a lower Reynolds number (Re) environment, when the machines are downsized, and work inside the human body. In this study, using various silicone oils whose kinematic viscosity ranged from 500 to 5 £ 10 5 mm 2 /s, the swimming performance of the machine in an environment characterized by a low Reynolds number was examined. The machine, with a cylindrical NdFeB magnet as main component, could swim in the oils with Re D 10 ¡7 . This Reynolds number is same as that of a micro-machine with micron size swimming in the water. In addition, the machine could turn by controlling the external rotational magnetic eld, therefore the swimming direction of the machine could be controlled. Using these principles, a magnetic micro-machine, which can run in a gel, was also fabricated.

Magnetic Actuation Based Motion Control for Microrobots: An Overview

“…The microrobot is steered in the horizontal plane by a uniform magnetic field. As for helical swimmers actuated by a rotating magnetic field, researchers estimate the rotation direction of the field; for example, a rotating magnetic field with a fixed rotation axis to actuate the helical swimmer to follow a straight line [36,40,73]. Then, Ghosh et al [37] achieved following a curved trajectory (e.g., "R@H") with their helical microrobots, which were navigated by a pre-programmed controller to actuate the magnetic field.…”

“…Researchers have used different magnetic actuation systems allowing differently-sized workspace and degrees of freedom (DoF). Various motion control methods have been applied, developing from open-loop control [36,37,40,41] to closed-loop point-to-point positioning control [35,42] or closed-loop path following [43]. The aim of this paper is to review the magnetic actuation systems and the motion control methods for microrobots.…”

Mini and Micro Propulsion for Medical Swimmers

“…For instance, a spiral-type micro robot was designed by Ishiyama et al [53], which mimicked the cilium propulsion of natural bacteria. The robot could even swim in high viscosity oil (500 mm 2 /s) at a Reynolds number of about 10 −7 and had a maximum velocity of 0.022 mm/s.…”

Scaled-up helical nanobelt modeling and simulation at low reynolds numbers

“…Step-out frequencies of helical robot in their rotating propulsions have been revealed in [5], [8]. Researchers found that the forward velocity grows linearly with the applied field until a step-out frequency.…”

“…This group tested the swimming performances of spiral type micro-machines at low Reynolds number. They predicted that this spiral type micro-machine with a length of 11.5 mm could still be scaled down to micrometer-sized machine [5].…”