A transient simulation to predict the kinetic behavior of magnetic-sensitive hydrogel responsive to magnetic stimulus

Abstract

Magnetic-sensitive hydrogel is widely used in fields such as biosensor, microfluidics, and drug delivery. To optimize the performance of the magnetic hydrogel, it is essential to characterize its transient behaviors. Herein, a multiphysics model was presented for the kinetics of magnetic hydrogel submerged in surrounding fluid. The magneto-chemo-mechanical coupled model allowed for large deformation, and it included the governing equations for the balances of mass and momentum. The constitutive relations were formulated with consideration of the effects of the magnetic field and chemical potential. In addition, three physicochemical response mechanisms were characterized, including hydrogel magnetization, fluid diffusion, and finite deformation of the hydrogel. Furthermore, two case studies were conducted: (i) transient swelling of magnetic hydrogels subject to static and alternating uniform magnetic fields respectively, and (ii) the transient bending of magnetic hydrogel under a nonuniform magnetic field. In a uniform magnetic field, the hydrogel elongates sharply at initial time t ≤ 4s and deforms linearly when t ≤ 14s. Subsequently, it approaches the equilibrium state. In an alternating magnetic field, the hydrogel stretches along the magnetic field direction and the displacement exhibits a pulsatile change. In a nonuniform magnetic field, the magnetic hydrogel bends towards the location of the external magnet in a relatively short time (t ≤ 2s) due to the high magnetic field gradient near the magnet. The present multiphysics model may provide guidance to optimally design the magnetic hydrogel with the magneto-chemo-mechanical coupled field.