Mechanical properties of ferrogels based on polyacrylamide filled with strontium hexaferrite microparticles studied using stress-strain and ultrasonography tests

This study is aimed to define the dependence of the mechanical properties of ferrogel (FG), chosen as a prospective scaffold for cellular technologies, on the concentration of magnetic particles (MPs) embedded into composite. FGs based on polyacrylamide hydrogel filled with the strontium hexaferrite (SrFe12O19) MPs with weight fraction in the range of 0 – 11 % were investigated with the use of two independent approaches: stress-strain testing of mechanical deformations in step-wise and dynamic modes and by medical ultrasound imaging. Stress-strain test showed that the increase of MPs concentration in FG resulted in significant increase of elastic storage modulus (G’), loss modulus (G’’) and dynamic viscosity coefficient (η’) of the magnetic composite. According to the ultrasonography test, the increase of MPs concentration in FG provided the enhancement of FG visualization. The larger was the MPs concentration in FG, the higher was brightness of the ultrasound image at the surface of FG and inside its bulk. Close correlation was found between the elastic storage modulus (G’) and the brightness at water/FG interface for full range of MPs concentrations.