Magnetothermal dehydration induced deformation of hydrogel structures: Modelling and experiment

Magnetic hydrogels have found broad applications in soft robotics and bioengineering, due to their facile actuation response and good biocompatibility. However, the actuation of magnetic hydrogels embedded with superparamagnetic nanoparticles remains challenging because of the low magnetization. In this work, we investigate the magnetothermal dehydration induced deformation of magnetic hydrogel-elastomer structures through modelling and experiments. The magneto-thermosensitive hydrogel undergoes significant volume change and dehydration under the application of alternating magnetic field. The magnetothermal dehydration of hydrogel is modelled by considering the heat generation of nanoparticles, heat transfer, and volume collapse of thermosensitive hydrogels. These sequential physical processes have not been considered by previous models. The magnetothermal dehydration model can predict the nonlinear temperature change and abrupt volume collapse of magneto-thermosensitive hydrogels during phase transition. Integrating the magnetothermal dehydration with the phase-evolution approach, we obtain the bending solution of magnetic hydrogel-elastomer bilayers. The magnetothermal dehydration induced bending deformation has been realized and predicted in various conditions, including various magnetic particle content, hydrogel thickness and magnetic field intensity. The deformation of complex structures has been further achieved and numerically reproduced by implementing the dehydration strain and modulus change into finite element analysis. This work may provide guidance for the shape morphing and applications of magnetic hydrogels.