Fabrication of High‐strength Magnetically Responsive Hydrogels by Synergistic Salting‐out and Freezing–thawing and Application of Their Shape Deformation and Swimming

Smart hydrogels have been known for their remarkable applications in various fields of research. Among these smart hydrogels, magnetically responsive hydrogels are more famous because of the ease of their manipulation and a much quicker magnetic response. However, many magnetic hydrogels exhibit fragile and brittle properties. In this study, a smart combination of salting-out and cyclic freezing-thawing was utilized for the first time to deal with sodium alginate/polyvinyl alcohol based magnetic hydrogel. The optimized magnetic hydrogel has outstanding mechanical properties with 6.66 MPa at the elongation at break of 282%, Young's modulus of 2.51 MPa, and worked with extension at fracture Wext of 9.31 MJ m(-3). The magnetic hydrogel could be easily controlled by magnet, such as swim freely in water when controlled by three-dimensional electromagnetic field. All the results show that these newly fabricated magnetic hydrogel can also carry out many difficult tasks in terms of magnetic response mechanics. This type of tough and magnetically responsive hydrogels can be used for numerous applications such as in swimming robots, flexible gripper, bionic of natural cartilage.