Characterization of actuator behaviors of ferrogels obtained from physical and chemical cross-linking methods

Ferrogels are soft polymer materials containing a filler of magnetic particles that allow the material to be activated by magnetic fields. These materials have shown capabilities for large strains, fast response, ease of synthesis and biocompatibility and have potential applications including artificial muscles, controlled drug release systems, and hyperthermia cancer treatment. In this work, the actuator behavior for a selection of ferrogel compositions and synthesis methods are characterized including their free strain and loading behavior. Samples were synthesized using either chemical or physical methods using Sodium Tetra-borate (Na2B4O7 · 10(H2O)) or freeze-thaw cycle, respectively. Compositions consisting of PVA of 4, 8, and 12 wt% and magnetic particles of 1, 5, and 10 wt% were made. These samples were then tested for free strain and strain under loads of up to 4 times their weight by exposing them of fields from between 0.2 and 0.25T. Results show that softer samples with the largest amount of iron achieve the largest strains. Thus, chemically crosslinked sample with 4 wt% PVA and 10 wt% iron achieved the largest strain of almost 40%. However, low modulus samples exhibit low loaded capabilities with a blocked load of 1.7g identified. The physically crosslinked samples which were stiffer achieved very good loading capabilities with only a 20% strain decrease when loaded up to 400% of their weight. This translated in to an energy density of 320 J/m making these materials very promising for actuator applications.