Micromechanics of Interactions Between Hard Magnetic Particles and Soft Matrix on Magneto-Mechanical Actuation

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This award studies the micromechanics of the magneto-mechanical actuation of hard-magnetic soft active materials. These materials utilize the interactions between embedded hard-magnetic particles and applied magnetic fields to achieve actuation of the soft matrix materials. Hard-magnetic soft active materials are a new group of soft active materials that can be activated rapidly, reversibly, and remotely. These materials are composites with hard-magnetic particles embedded in soft matrices. The actuation is achieved through transferring the magnetic micro-torques in the magnetic particles to the soft matrix. They have demonstrated many advantages, such as untethered complex deformation, rapid response speed, and reversible actuation, showing promising potential for applications in soft robots and biomedical devices. However, due to the relatively new development of these materials, the understanding of how the microscopic behavior drives the macroscopic material actuation remains unknown. The work will provide the fundamental knowledge of the magneto-mechanical actuation mechanism of hard-magnetic soft active materials at the micromechanics level, the theory that can connect macroscopic effective properties with microscopic structures, and the understanding of how the stretch-induced softening effect can affect the macroscopic actuation. This project will provide new knowledge on how particle-particle and particle-matrix interactions can contribute individually and collectively to the actuation by using a micromechanics approach. The new knowledge will be used in a theoretical model to obtain the effective residual magnetic flux density. The work will also investigate how the Mullins effect affects actuation. The synergetic development on theoretical models, simulations and experimental testing will provide an effective platform to correlate the micromechanics and macroscale mechanical response of stimuli-responsive soft composites with micro-fillers. The project will use the exciting demonstrations of hard-magnetic soft active materials in soft robots as vehicles to promote STEM education with a focus on students from underrepresented groups as well as K-12 education.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.