Synthesis, characterization, and modeling of gelatin-based magnetic hydrogel beams

Abstract

Hydrogels are soft materials that can be designed to be responsive to external stimuli such as temperature, pH change, and electric and magnetic fields. Magnetically responsive hydrogels consisting of polymer, water, and magnetic nanoparticles (MNPs) are emerging candidates in biomedical fields due to their remote application. In this work, cobalt ferrite-based MNPs prepared by the auto-combustion method are embedded in gelatin hydrogels. Cobalt ferrite-based magnetic hydrogels (HCFO) having high water content are prepared using the solvent casting method. The effective magnetic properties, such as coercivity and remnant magnetization of the hydrogels, are determined from the magnetization response (m-h curve) obtained through a vibrating sample Magnetometer (VSM). Subsequently, the HCFOs are subjected to uniaxial tensile loading to obtain mechanical properties. The size and shape of MNPs are obtained using X-ray Diffraction (XRD) and scanning electron microscopy (SEM) analysis. Furthermore, the magnetic hydrogel beams (cantilever) have been prepared and subjected to the external magnetic field. A unique phenomenological model has been proposed which can predict the finite deflection of the beam under magnetic loading exploiting the hard magnetic behavior of the HCFO. The proposed model takes into account particle concentration, finite elasticity, and magneto-mechanical coupling. The softness of the hydrogels matrix and hard magnetic properties of the MNPs results in large deflection. Further, the experimental observations and modeling predictions are in good agreement.