The suspended ferromagnetic particles subjected to the gradient and uniform magnetic fields experience both the translational force generated by the field gradient and the rotational torque generated by the fields strengths. Although the uniform field does not contribute to the force, it nevertheless influences the translational motion of these particles. This occurs because the translational force depends on the direction of the particle magnetization, which in turn depends on the fields strengths. To study this influence, a minimal set of equations describing the coupled translational and rotational motions of nanosized ferromagnetic particles is introduced and solved in the low Reynolds number approximation. Trajectory analysis reveals that, depending on the initial positions of nanoparticles, there exist four regimes of their directed transport. The intervals of initial positions that correspond to different dynamical regimes are determined, their dependence on the uniform magnetic field is established, and strong impact of this field on the directed transport is demonstrated. The ability and efficiency of the uniform magnetic field to control the separation of suspended ferromagnetic nanoparticles is also discussed.

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The development of efficient, energy‐saving, and automated manufacturing of free‐form variable‐thickness polymer composite components has created a step‐change and enabled technology for the composites industry seeking geometry tailoring during a mould‐less and/or additive manufacturing such as that in 3D printing. The current article presents research on magnetic field assisted 3D printing of iron particles‐embedded thermoplastic polylactic acid, during a fused deposition method based 3D printing. The magnets are symmetrically fixed on both sides of the printed nanocomposite. The setup utilised Neodymium magnets with a constant strength below one Tesla. Observations have shown that the nanocomposites being printed undergo permanent macro‐scale deformations due to the extrinsic strains induced by the iron particles' magnetisation. To provide a theoretical understanding of the induced strains, a Multiphysics constitutive equation has been developed. The evolution of magnetisation within a relatively thick nanocomposite (5 mm thickness) has been studied. A correlation has been established between the extrinsic strains from the experimental data and the theoretical solution. The theory exhibits an accurate description of the field‐induced strains provided that real‐time temperatures for the printed layers are accounted for. The results demonstrate a viable and disruptive magnetic field‐equipped fabrication with ability for permanent geometry control during a process.

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