Magnetic Hydrogel

The combination of force and flexibility is at the core of biomechanics and enables virtually all body movements in living organisms. In sharp contrast, presently used machines are based on rigid, linear (cylinders) or circular (rotator in an electrical engine) geometries. As a potential bioinspired alternative, magnetic elastomers can be realized through dispersion of micro- or nanoparticles in polymer matrices and have attracted significant interest as soft actuators in artificial organs, implants, and devices for controlled drug delivery. At present, magnetic particle loss and limited actuator strength have restricted the use of such materials to niche applications. We describe the direct incorporation of metal nanoparticles into the backbone of a hydrogel and application as an ultra-flexible, yet strong magnetic actuator. Covalent bonding of the particles prevents metal loss or leaching. Since metals have a far higher saturation magnetization and higher density than oxides, the resulting increased force/volume ratio afforded significantly stronger magnetic actuators with high mechanical stability, elasticity, and shape memory effect.

Highly magnetic polymers

Incorporation of carbon-coated cobalt nanoparticles into polymers leads to highly magnetic plastics

The in-situ graphene coating of metal nanoparticles is a highly technical innovation of the FML laboratory. Graphene coatings inhibit the rapid oxidation of such reactive nanoparticles and enable their use in new applications. For example air-stable graphene coated cobalt nanoparticles could be incorporated into polymers like PMMA which resulted in highly magnetic properties comparable to bulk cobalt. These highly magnetic composites are still polymer melt processable by low-cost fabrication techniques such as extrusion or injection-molding. Since the graphene coatings provide an oxidation stabilization the polymer composites can be heated up to 280°C without the rapid oxidation of the metallic cobalt phase.

Features:

• Polymer processing techniques applicable
• High metal loading of 90wt% possible
• Metallic appearance
• Electrical conductivity of around 5000 S/m
• Saturation magnetization of around 150 emu/g
• Low coercivity of 100 Oersted
• High thermal stability of 280°C
• Applications: Low-cost electric engines, microcomponents
  
  
  
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Link to the scientific publication