Remagnetization for Reprogramming Hard-Magnetic Soft Actuators and Effects on Reliability and Performance

Magnetic hysteresis in hard-magnetic materials, such as NdFeB, is routinely applied for programming the magnetization state and responses of hard-magnetic soft actuators. Applying magnetic fields for actuation can cause unintentional remagnetization of the structure, however. The resulting altered actuation behavior can signify degraded reliability or performance. A model of magnetization in NdFeB microparticle-based polymer composites is developed from magnetometry measurements, which makes possible quantitative prediction of remagnetization behaviors to facilitate the design of magnetic soft actuators with simultaneous high reliability and high efficiency. The onset of remagnetization occurs at magnetic fields substantially below the coercivity. A lifter serves as a simple model system for validating the model and for demonstrating reprogramming – purposeful remagnetization to predictably alter the behavior of the actuator for a new task. Figures of merit are introduced for quantifying the performance of actuators, where actuation with loads is especially susceptible to degraded performance. Future extensions of the model developed here will make possible understanding and controlling remagnetization in complex systems.