Investigation of Swimming Behavior and Performance of the Soft Milli-Robots Embedded with Different Aspects of Magnetic Moments

Abstract

Among the development of technology, a large number of medical devices have been implemented in various forms for therapy and treatment. Remote controllability, real-time response, small size, and non-toxicity of the devices are the critically requirement to be operated in the blind, unstructured and fluidic environments of biomedical regions. Untethered soft swimming milli-robots have been developed to fulfill the remote operation in such that region under magnetic navigation. A motor-less mechanism of the soft robots utilizes a high degree of freedom provided by magnetic compliance of the deformable structure with a minimal control of the oscillating magnetic field. Theoretically, magnetic property of the soft robots is defined by magnetic moments consisting of orientation and strength. Orientation of magnetic moments can be defined by magnetizing technique, and strength of magnetic moments is obtained by their quantity in the magnetic structure. Herein, this work investigates how magnetic moments through the details of magnetic orientation and quantity affects swimming behavior and performance. The soft robots are fabricated with elastomer embedded with NdFeB microparticles to obtain three types of distinguish magnetic property in the deformable structure; the I robot has non-uniform magnetic orientation and uniform magnetic strength, the II robot has uniform magnetic orientation and non-uniform magnetic strength, and the III robot has non-uniform magnetic orientation and non-uniform magnetic strength. The results interestingly report that each type of robot's property functions mechanism and benefits swimming performance differently under the same magnetically control parameters. The I robot does not have any exceptional potential, but the II robot can be operated at the higher control frequency even reaching the step-out point. The III robot shows the greatest performance in swimming and maneuverability. These results would be useful to design a swimming soft-robot capable of applying for various purposes, especially when the demand concerns non-harm, smallscale size, soft interface and remote controllability.