Five-degree-of-freedom magnetic control of micro-robots using rotating permanent magnets

Abstract

Recent work in magnetically-actuated micro-scale robots for biomedical or microfluidic applications has resulted in electromagnetic actuation systems which can command precise five-degree-of-freedom control of simple magnetic devices at the sub-millimeter scale in remote environments. This paper presents a new type of actuation system which uses an array of large, rotatable, permanent magnets to generate the same level of control over untethered micro-robotic systems with the potential for increased field and gradient strength and minimal heat generation. We show that the system can produce any field or field gradient at the workspace (including a value of zero). In contrast with previous permanent magnet actuation systems, the system proposed here accomplishes this without any hazardous translational motion of the control magnets, resulting in a simple, safe, and inexpensive system. The proof-of-concept prototype system presented, with eight permanent magnets, can create fields and gradients in any direction with strength of 30 mT and 0.83 T·m-1, respectively. The effectiveness of the system is shown through characterization and feedback control of a 250 μm micro-magnet in a path-following task with average accuracy of 39 μm.