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.