Fabrication and extrusion of the PAAm-SAlg hydrogels with magnetic particles

Magnetic hydrogels have received extensive attention in various research fields due to their excellent controllability and responsiveness. In this work, we constructed a magnetic biocompatible hydrogel based on PAAm-SAlg (polyacrylamide and sodium alginate) system. The crosslinking network of this magnetic hydrogel is constructed by two kinds of chemical bonds. Magnetic particles with cores of Fe₃O₄ are embedded in hydrogel networks by physical and chemical bindings. The addition of magnetic particles has different effects on the properties of hydrogels. Firstly, compared to hydrogels without magnetic particles, the tensile strength of magnetic hydrogels increases by 40 % from 0.035 MPa to 0.049 MPa, however, the swelling property is slightly reduced. In addition, magnetic hydrogels retain the characteristics of shear thinning and excellent superparamagnetism, and the magnetic response is slightly weakened than pure magnetic particles. The printed hydrogel fiber has a diameter of 100 μm and the magnetic particles are evenly distributed in the fiber. Moreover, increasing the air pressure of printing will cause irregular bumps on the surface of the printed hydrogel.