In-Process Printing and Magnetization of Ferromagnetic Elastomer with Localized Magnetic Profile for Anisotropic Actuation

An in-process printing and magnetization strategy is developed to fabricate ferromagnetic elastomers with fully customizable three-dimensional magnetization profiles. Dynamic control of an external magnetic field during printing enables localized domain alignment in arbitrary orientations, achieving anisotropic actuation at millimeter scales. Careful optimization of curing kinetics, material viscosity, and magnet positioning permits both spatially discrete and continuous magnetization while minimizing droplet deformation. This strategy also imparts sensing functionality through stray-field deflection under mechanical loading, applicable across discrete and continuous magnetized domains. Discretely magnetized structures offer robust strain sensing and information encoding capabilities. Continuous magnetization, when integrated with multi-material printing, enables the fabrication of soft robots with bioinspired, heterogeneous architectures. Demonstrations highlight this versatility, including a dragonfly with oppositely magnetized wings for tunable resonant actuation and an octopus-inspired swimmer whose magnetized legs and buoyancy chamber reproduce aquatic locomotion. Together, these advances establish a versatile platform for designing magnetically responsive systems that couple programmable actuation with biological complexity.