Combining soft and hard material improves magnetic elastomers

Magnetic elastomers, smart materials that can change shape, are used in soft robotics and biomedical engineering. Because they’re often composites of polymer materials and magnetic particulate, anisotropy is essential to their efficacy. Strong magnetic anisotropy tends to keep the magnetization pointing in the same direction and makes the magnetic material more resistant to losing its useful magnetic properties. Among the methods of strengthening anisotropy are magnetic annealing and fused deposition modeling (FDM), an extrusion-based 3D printing process.

Using two metals not previously combined in elastomer materials, Ziemann et al. explored how the magnetoactive properties of hard magnetic elastomers are influenced by magnetic annealing coupled with soft magnetic particulate.

“This research focuses on creating a composite material with magnetic powder inside plastic material,” said author Sarah Ziemann. “These magnetic elastomer materials have various applications, especially in cases where applying a magnetic field can control their shape. This may be useful in engine mounts, artificial muscles, and other items that imitate biological movements. Magnetic elastomers can also be 3D printed, which increases their accessibility and provides more potential applications.”

The team created magnetically annealed filament with permanent (hard) and mixed (soft and hard) magnetic particulate for use in FDM. The powder in the composite was strontium ferrite, a permanently magnetic material that produces its own constant magnetic field; and carbonyl iron, which does not always produce a magnetic field.

Testing showed that the metals’ magnetic properties effectively transfer to the composite and that both magnetic annealing and increasing the amount of iron particulate augments the filament’s magnetoactive response.

“The more we can understand these smart materials on a microscopic level, the more we can predict and control their overall performance,” said Ziemann.

Source: “Hard magnetic elastomers incorporating magnetic annealing and soft magnetic particulate for fused deposition modeling,” by Sarah J. Ziemann, Nathan A. Fischer, Jimmy Lu, Thomas J. Lee, Michael Ennis, Thomas A. Höft, and Brittany Nelson-Cheeseman, AIP Advances (2022). The article can be accessed at https://doi.org/10.1063/5.0119669 .