(403b) Crosslinking Metal Manoparticles Into the Polymer Backbone of Hydrogels Enables Preparation of Soft, Magnetic Field-Driven Actuators with Muscle-Like Flexibility

The combination of force and flexibility enables virtually all body movements in living organisms. Presently used technical machines in contrast, are based on rigid, linear or circular geometries. As a possible 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. This contribution reports on the direct incorporation of metal nanoparticles into the backbone of a hydrogel and application as an ultra-flexible, yet strong magnetic actuator [1]. Carbon coated cobalt nanoparticles [2] with vinyl anchor functionality were directly incorporated into the polymerization of 2-hydroxyethyl methacrylate (HEMA). To overcome the problem of inhomogeneously dispersed nanoparticles in the polymer, the carbon shell of the particles was covalently functionalized [3] with an organic component similar to the monomer. Later favored the in-situ polymerization of the magnetic particles with the monomer and resulted in the formation of a highly magnetic, mechanical stable and homogenously dispersed polymer. 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. Depending on the final shape, different polymer blocks (60 wt% nanoparticles with respect to monomer) could be produced offering an alternative approach to flexible and magnetic actuators and artificial muscles. References: 1) R. Fuhrer, E.K. Athanassiou, N.A. Luechinger, W.J. Stark, Small, 2009, 5, 383-8 2) E.K. Athanassiou, R.N. Grass, W.J. Stark, Nanotechnolgy, 2006, 17, 1668-73 3) R.N. Grass, E.K. Athanassiou, W.J. Stark, Angew. Chem. Int. Ed., 2007, 46, 4909-12 Figure 1: Photo of as prepared soft magnetic hydrogel (a). By applying an external magnetic field the polymer can contract or elongate making it appropriate in application such as for magnetic actuator or even artificial muscles (b).