A self-healing magneto-responsive nanocellulose ferrogel and flexible soft strain sensor.

Crosslinks are the building blocks of hydrogels and play an important role in their overall properties. They may either be reversible and dynamic allowing for autonomous self-healing properties, or permanent and static resulting in robustness and mechanical strength. Hence, a combination of crosslinks is often required to engineer the 3D network of hydrogels with both autonomous self-healing and required robustness for strain sensing application; however, this complicates the fabrication of such hydrogels. The facile, yet versatile, approach used in this study is to forgo the use of extra crosslinks and instead rely solely on the properties of magnetic nanocellulose to fabricate a tough, stretchy, yet magneto-responsive, ionic conductive ferrogel for strain sensing. The ferrogel also gives stimuli-free and autonomous self-healing capacity, as well as the ability to monitor real-time strain under external magnetic actuation. The ferrogel also functions as a touch-screen pen. Based on our findings, this study has the potential to advance the rational design of multifunctional hydrogels, with applications in soft and flexible strain sensors, health monitoring and soft robotics.