Enhanced Magnetic Anisotropy for Reprogrammable High-Force-Density Microactuators

The precise control of magnetic properties at the microscale has transformative potential in healthcare and human-robot interaction. This research focuses on understanding the magnetic interactions in nanostructure assemblies responsible for microactuation. By combining experimental measurements and micromagnetic simulations, the interactions in both nanocube and nanochain assemblies are elucidated. Hysteresis measurements and first-order reversal curves (FORC) reveal that the spatial arrangement of these assemblies governs their collective magnetism. A critical concentration threshold is observed where a transition from ferromagnetic-like to antiferromagnetic-like coupling occurs. Leveraging the high uniaxial anisotropy of 1D nanochains, the remanent magnetization of assembled chain structures is maximized for efficient magneto-mechanical energy transduction. By utilizing an optimized magnetic nanostructure concentration, a flexible film is fabricated, and its significantly enhanced mechanical deformation response to a small magnetic field, surpassing conventional particle-based samples by a factor of five, is demonstrated. Demonstrating excellent transduction efficiency, visible deformations such as bending and S-shaped twisting modes are achieved with an applied field of less than 400 Oe. Furthermore, the reprogrammability of the actuator, achieving a U-shaped bending mode by altering its magnetization profile, is showcased. This research provides valuable insights for designing reconfigurable and effective microactuators and devices at significantly smaller scales than previously possible.