A Master Curve for Magnetically Tuned Mechanical Hysteresis in Strain-Stiffening, Self-Healing Polysaccharide Hydrogels

Precise control over the mechanical properties of biomimetic hydrogels is critical for applications in biomedicine, tissue engineering, and soft robotics. In this study, we present a strategy to finely tune the mechanical hysteresis of strain-stiffening, self-healing magnetic hydrogels by applying external uniaxial magnetic fields during gelation. The hydrogel network is formed via dynamic covalent imine bonds between chitosan and oxidized hyaluronic acid, while embedded iron microparticles generate anisotropic microstructures under steady magnetic fields, providing directional reinforcement. The mechanical response of the hydrogels is governed by two key parameters: the strain amplitude under oscillatory shear and the strength of the applied magnetic field. By combining magnetostatic finite element simulations with rheological experiments, we define a scaling variable that combines field and strain effects, enabling a master-curve representation. The magnetic hysteresis parameter, ranging from –78.8 to +147.6, quantitatively captures this tunable behavior across strain amplitudes up to 3000% and magnetic field strengths up to 354 kA·m–1. Such predictability allows for the rational design of hydrogels with tailored mechanical responses. Furthermore, short-term in vitro assays with human fibroblasts showed no detectable cytotoxic effects under the conditions tested, providing an initial indication of cytocompatibility and motivating further investigation of these materials for potential biomedical applications.