Magnetic double-network hydrogels for tissue hyperthermia and drug release.

Magnetic-field driven soft materials have found extensive applications in fields such as soft robotics, shape morphing and biomedicine. Compared to magnetoactive elastomers (MAEs), magnetic hydrogels have shown significant advantages for in vivo applications, because of their better biocompatibility, as well as their soft and wet nature. However, the poor mechanical properties and ion sensitivity of conventional magnetic hydrogels will severely limit their applications especially under physiological conditions. Double network hydrogels are tough and stable, but do not respond to environmental stimuli. Here magnetic double network (M-DN) hydrogels have been developed with outstanding mechanical performances and ion-resistant stability. M-DN hydrogels show a high modulus of ∼0.4 MPa and a high toughness of ∼1500 J m-2. The volume, magnetic and mechanical properties of M-DN hydrogels show negligible deterioration in ionic solutions. M-DN hydrogels exhibit magnetic responsiveness and have been used for tissue hyperthermia and drug release by magnetic induction heating. The induction heating behavior of M-DN hydrogels can be tuned to meet the clinical requirements, by changing the magnetic field strength or the composition of magnetic hydrogels. M-DN hydrogels may be inspiring to the development of responsive DN hydrogels and expand their more potential applications in load-bearing biomedical engineering.

Super tough magnetic hydrogels for remotely triggered shape morphing.

Despite their potential in various fields such as soft robots, drug delivery and biomedical engineering, magnetic hydrogels have always been limited by their poor mechanical properties. Here a universal soaking strategy has been presented to synthesize tough magnetic nanocomposite (NC) hydrogels. We can simultaneously solve two common issues for magnetic hydrogels: the poor mechanical properties and poor distribution of magnetic particles. The toughness of the magnetic NC hydrogel achieves approximately 11 000 J m-2. The outstanding properties of tough magnetic hydrogels will enable myriad applications. Here we demonstrate a new application for remotely triggered shape morphing. Heterogeneous structures based on magnetic hydrogels are shown to evolve into bio-inspired three-dimensional (3D) shapes (lotus flowers) from 2D-structured sheets. The self-folding of the structure is controlled by the magnetothermal effect in an alternating magnetic field. The capability to control the shape morphing of a multi-material system by a magnetic field may emerge as a new general strategy for programming complex soft structures.