Gels with magnetic properties

Materials producing strain in magnetic field are known as magnetoelastic or magneto strictive materials. A new type has been developed by preparing magnetic field sensitive gels, called ferrogels. Single domain, magnetic particles of colloidal size are incorporated into chemically cross-linked polyvinyl alcohol hydrogels. The finely distributed colloidal particles having superparamagnetic behavior couple the shape of the gel to the nonuniform external magnetic field. We have shown that ferrogels undergo quick and reversible shape transformation by changes in external magnetic field. Elongation, contraction and bending can be realized by proper arrangement of external magnetic field. Unidirectional deformation measurements have been performed and an equation for the uniaxial magnetoelastic properties has been derived and compared with experimental results.