Magneto-Thermal Responsive Semi-convertible Hydrogels Inspired by the Locomotion Mechanism of Earthworms

Magnetic hydrogels can be navigated in enclosed spaces under an external magnetic field to perform their intended functions. However, their ability to navigate complex obstacles, such as narrow passages and underground environments, remains limited. Inspired by locomotion of earthworms, we synthesized a magneto-thermal responsive semi-convertible hydrogel via ice-templating. By expelling a sol lubricant and contracting, the hydrogel achieves enhanced locomotion and obstacle-crossing capabilities, even in a simulated underground environment. This is achieved by introducing a magneto-thermal responsive supramolecular network (composed of gelatin and Fe₃O₄-NH₂) into a thermoresponsive polymer network of poly(N-isopropylacrylamide) (PNIPAm). The PNIPAm covalent network provides a mechanical support frame and contraction capability, while the magneto-thermal induced gelatin gel-sol transition facilitates generating a lubricating sol layer on the entire surface. The present hydrogel can adapt to complex external environments even within narrow and underground environments. It is expected to offer reasonable solutions in the field of bioinspired magneto-thermal soft actuators.