Multi-physics coupling simulation and design of magnetic field-driven soft microrobots in liquid environments.

• Developed a numerical analysis method that couples multiple physics (Magnetic-Fluid-Solid). • Investigated the locomotion modes of two exemplary magnetically propelled miniature soft bionic robots: bionic midge larvae and bionic jellyfish. • Uncovered two major driving mechanisms of flexible microrobots induced by a magnetic field: deformation and rotation. • Proposed a theoretical model of a bionic fish tail fin robot that depends solely on a rotating magnetic field for propulsion. • Presented a comparative analysis of swimming efficiency, flexibility, stability, and relative advantages of these three robots operating in liquid environments. Magnetic field-driven soft microrobots have widespread applications in biomedical science, microfluidic chips, nanoengineering, and various other domains. However, the existing methods for designing such magnetic-driven flexible robots largely rely on experimental trial and error or steady-state numerical simulated results, which fall short of meeting the intricate requirements for magnetic field editing and magnetic domain distribution. Addressing this issue, a multi-physics coupling numerical analysis method encompassing Magnetic-Fluid-Solid mechanics was developed. A complete process for transient numerical simulation resolution has been achieved. Utilizing this analysis method, the motion patterns of two typical prototypes of magnetic-driven miniature soft bionic robots, a bionic midge larvae robot, and a bionic jellyfish robot, have been analyzed. The central role of the magnetic field in driving these robotic designs—causing deformation in microrobots by designing magnetic domains and spinning the microrobots by controlling the magnetic field—has been revealed. We developed a theoretical model of a bionic fish tail fin robot driven solely by a rotating magnetic field and conducted comparative studies on the swimming efficiency, flexibility, stability, and relative advantages of the three types of robots. The impact of different magnetic domain distribution rules and different magnetic field driving methods on a robot's performance is analyzed, validating that higher swimming efficiency can be achieved by designing a robot's magnetic domains so that they undergo magnetic displacement under magnetic torque resulting in deformation. This innovative analysis method holds potential to provide valuable references for designing motion patterns of magnetically driven microrobots within liquid environments, thereby deepening our understanding toward various complex gait mechanisms involved in biological swimming. [Display omitted] [ABSTRACT FROM AUTHOR]