Towards Gradient-Based Actuation of Magnetic Soft Robots Using a Six-Coil Electromagnetic System

Soft materials with embedded magnetic properties can be actuated in a contactless manner for dexterous motion in restricted and unstructured environments. Magnetic soft robots have been demonstrated to be capable of versatile and programmable untethered motion. However, magnetic soft robots reported in literature are typically actuated by utilizing magnetic fields to generate torques that produce deformation. By contrast, this work investigates the utilization of field gradients to produce tethering forces for anchoring soft robots to the working surface, in conjunction with the use of magnetic fields to generate torques for deformation. The methodology applied here uses a six-coil electromagnetic system for field generation. The approach to achieve the magnetic field and gradients desired for soft robot motion is described, along with the restrictions imposed by Maxwell's equations. The design and fabrication of the soft robots is explained together with calculations to assess the capabilities of the actuation system. Proof-of-concept demonstrations of soft robot motion show Hexapede robots with the ability to `walk' untethered on the ceiling of the workspace, working against gravity; and lightweight Worm robots made of thin strips of material are demonstrated to locomote while staying in contact with the ground.