Small‐Scale Magnetic Actuators with Optimal Six Degrees‐of‐Freedom

Abstract Magnetic miniature robots (MMRs) are small‐scale, untethered actuators which can be controlled by magnetic fields. As these actuators can non‐invasively access highly confined and enclosed spaces; they have great potential to revolutionize numerous applications in robotics, materials science, and biomedicine. While the creation of MMRs with six‐degrees‐of‐freedom (six‐DOF) represents a major advancement for this class of actuators, these robots are not widely adopted due to two critical limitations: i) under precise orientation control, these MMRs have slow sixth‐DOF angular velocities (4 degree s⁻¹) and it is difficult to apply desired magnetic forces on them; ii) such MMRs cannot perform soft‐bodied functionalities. Here a fabrication method that can magnetize optimal MMRs to produce 51–297‐fold larger sixth‐DOF torque than existing small‐scale, magnetic actuators is introduced. A universal actuation method that is applicable for rigid and soft MMRs with six‐DOF is also proposed. Under precise orientation control, the optimal MMRs can execute full six‐DOF motions reliably and achieve sixth‐DOF angular velocities of 173 degree s⁻¹. The soft MMRs can display unprecedented functionalities; the six‐DOF jellyfish‐like robot can swim across barriers impassable by existing similar devices and the six‐DOF gripper is 20‐folds quicker than its five‐DOF predecessor in completing a complicated, small‐scale assembly.