Simultaneous Six-Degree-of-Freedom Control of a Single-Body Magnetic Microrobot

Abstract

As precise motion-controlled applications of mobile untethered devices emerge into real-world scenarios, full manipulator dexterity will be required. In rigid bodies without joints, one such requirement will be the ability to control all six-degrees-of-freedom (DOF). Magnetic fields and their spatial gradients are ideal for micromanipulation due to their long-range strong forces and torques, but the 6-DOF closed-loop control of such devices is a current challenge. Here we present a single-body microrobot that simultaneously demonstrates all 6-DOF. We accomplish this through the magnetic shape anisotropy of the microrobot design, yielding magnetization components, which are used to generate a torque about the 6 $^\text {th}$ DOF. We show that, under our design conditions, we can independently control the magnetic field as well as the magnetic force and torque. This allows for the open-loop control of the other rotational DOFs, assuming the microrobot net magnetization vector will align with the magnetic field. We also describe a method that enables posing the 6 $^\text {th}$ DOF without feedback. These methods will enable the development of mobile submillimeter magnetic structures capable of full 6-DOF control for bioengineering, lab-on-a-chip, and desktop micromanufacturing applications.