Ultra‐stretchable, fast self‐healing, conductive hydrogels for writing circuits and magnetic sensors

Abstract Functional hydrogels are promising in various fields such as sensors, portable devices and flexible electronics. However, it is still a challenge to prepare a multifunctional hydrogel with conductivity and magnetism, as well as a variety of excellent properties. In the work reported, MnFe 2 O 4 nanoparticles were first loaded on polypyrrole (PPy) nanotubes using a chemical co‐precipitation method. By incorporating PPy/MnFe 2 O 4 nanocomposites with poly(vinyl alcohol) (PVA), PVA‐PPy/MnFe 2 O 4 (PPM) hydrogels were successfully prepared with the aid of borax. These hydrogels are not only ultra‐stretchable (over 1100%) and re‐moldable, but also conductive and magnetic. Moreover, the hydrogels can self‐heal within 15 s in air and 30 s in water, and adhere to various substrates repeatedly. A sensor based on the PPM hydrogel exhibits excellent performance in real‐time monitoring of magnetic field attraction and is reusable. The hydrogels can be further applied to touch‐screen pens. This work provides new opportunities for the rational design of other multifunctional hydrogels for potential applications in flexible sensors, wearable devices and health monitoring. © 2021 Society of Industrial Chemistry.