Field‐Dependent Rheology of <scp>4D</scp> ‐Printed Magnetorheological Elastomers Fabricated Using Fused Filament Fabrication

ABSTRACT Recent advances in additive manufacturing have enabled magnetorheological elastomers to be processed beyond conventional casting routes, allowing their field‐dependent behavior to be explored in printed architectures fabricated via fused filament fabrication (FFF). Traditional fabrication methods such as casting are limited by simple geometries, high mold costs, and post‐processing steps. Additive manufacturing, especially FFF, offers improved design flexibility and customization. This study introduces a novel MRE filament designed for 4D printing, enabling the production of complex, adaptive structures with controlled magnetic behavior. Despite growing interest in MRE, the rheological behavior of 4D‐printed MRE under off‐ and on‐state conditions remains underexplored. This work investigates the impact of an external magnetic field on the viscoelastic properties of FFF‐printed MRE. Results show that adding carbonyl iron particles (CIP) increases the storage modulus by up to 83%, enhancing stiffness and elasticity. Magnetic fields further boost these properties through dipole–dipole interactions. Surface roughness analysis characterizes the filament quality and its potential implications for mechanical and magnetic properties. The successful integration of MRE filaments into FFF‐based 4D printing demonstrates a feasible and scalable route for producing tunable smart materials relevant to emerging autonomous vehicle systems.