Coating Artificial Spider Silk Fiber with Magnetic FeCo: An Effective Strategy for Creating a Flexible Magneto‐Responsive Material

ABSTRACT Combining spider silk and magnetic nanostructures is a key challenge for advancing technological fields such as soft robotics, magnetosurgery, and smart textiles. It is essential to devise approaches that also aim to expand fundamental knowledge on the feasibility of coupling the protein‐based fiber with the inorganic magnetic phase. An original strategy is presented to create magneto‐responsive artificial spider silk fibers by coating them with thin layers (nominal thickness 5nm, 10nm, and 100nm) of ferromagnetic and magnetostrictive FeCo alloy via sputtering deposition. The mechanical strength and elasticity of the produced fibers remain close to those of the uncoated material. A relationship is established between the magnetic properties of the FeCo coating and its structural characteristics, which are strongly influenced by the underlying fiber morphology. The magnetomechanical response of the FeCo coating of single fibers under strain is evaluated using magneto‐optical Kerr effect magnetometry. Experimental data, interpreted through the shear‐lag model, reveal excellent silk‐metal coupling and highlight how the coating thickness governs stress transmission and the fragmentation process. The reversibility of the magnetomechanical response is investigated, providing further insights into the silk/metal coupling. These findings contribute to clarifying how the interplay between organic and inorganic components determines the composite's overall properties.