Sequential in-situ route to synthesize novel composite hydrogels with excellent mechanical, conductive, and magnetic responsive properties

It has great significance to develop a convenient and efficient method for hydrogels with adjustable electric and magnetic properties, which can be used in human activity monitoring and personal healthcare diagnosis field. However, it is a big challenge to balance the relationship between the conductive and magnetic categories so that electromagnetic hydrogels could be developed by an in-situ fabrication way. In this work, we firstly proposed a sequential in-situ route to form polypyrrole (PPy) and Fe3O4 nanoparticles (Fe3O4 NPs) in sequence within polyvinyl alcohol (PVA) matrix for the hybrid hydrogels with decent mechanical, conductive, and magnetic properties simultaneously, named as Fe3O4/PPy/PVA hydrogel. The as-prepared hybrid hydrogels exhibited continuous electrons transporting path and magnetic responsive properties. Specifically, a unique combination of high electrical conductivity (up to 1.95 ± 0.17 E−4 S cm−1), saturation magnetization (5.42 emu g−1) and greatly enhanced mechanical properties (tensile strength up to 575.03 ± 28.32 kPa, elasticity modulus up to 461.19 ± 24.75 kPa). More importantly, these hybrid hydrogels demonstrated potential applications in biomedical electronic devices, such as strain sensors and magnetic navigators.