Single-Step Production and Self-Assembly of Magnetic Nanostructures for Magneto-Responsive Soft Films.

Magneto-responsive soft films constitute a fascinating class of smart materials and devices capable of performing various tasks, such as micromanipulation or transport, noninvasive surgery, and sensing. These components are fabricated by incorporating magnetic materials into flexible substrates. In this context, arranging magnetic particles into elongated chains exhibiting shape anisotropy has shown great potential. Here, we introduce a novel technique for fabricating magnetically responsive films using continuous single-step production and self-assembly of magnetic nanoparticles from a carrier gas at atmospheric pressure into anisotropic magnetic structures directly onto flexible polymer layers. We show that the resulting magnetic soft films exhibit significant residual magnetization and a large response to external magnetic fields. Furthermore, we investigate the magnetic properties of the nanoparticle assemblies and show that interparticle interactions play a critical role in determining the final magnetic properties of the nanostructures. Moreover, we provide experimental evidence that fusing the nanoparticles via post-annealing results in a transition from magnetostatic to exchange interactions with an ≈50% increase in the coercivity.