Mechanically and Magnetically Property-Tunable Magnetorheological Silicone Elastomers Prepared by UV Curing for Smart Transport Packaging Sensors

Silicone elastomers containing magnetic materials are both magnetically responsive and flexible, providing sensors with high sensitivity, excellent elasticity, and good durability and wearability. Nonetheless, challenges persist in controlling the density of the cross-linked network and optimizing their mechanical properties, which limits their sustainable application in emerging fields. In this work, magnetorheological elastomers (MREs) with tunable mechanical and magnetic properties are developed by filling modified magnetic nanoparticles into silicone elastomers using UV light to initiate the thiol-ene click reaction. The gel content and cross-link density of the silicone elastomer could be accurately controlled by UV curing to optimize its mechanical properties. The monomer conversion of the material reached up to 91%, and polymerization took only 15 s. The gel content and cross-link density of the material reached up to 92.23% and 4.145 × 10^-4 mol/cm³, respectively. Additionally, magnetic nanoparticles with improved dispersion by capped silica and grafted sulfhydryl groups were prepared, and the mechanical and magnetic properties of the magnetorheological elastomers were tuned by adjusting the parameters of the preparation process, the ratio of the MRE raw materials, and the alignment direction. The developed 60° anisotropic MREs are integrated into a PVDF piezoelectric substrate to prepare a piezoelectric sensor with excellent magnetically responsive piezoelectric sensing characteristics, which has stable reliability and cyclic durability, with its voltage increasing with the increase of the magnetic field strength. Its signal remains stable in 400 magnetic field sensing cycling tests and can be used in smart packaging, which not only provides physical protection but also responds to changes in the external magnetic field. Our findings significantly advance the theoretical and experimental understanding of silicone elastomer materials and offer new technological avenues for the manufacturing of flexible, magnetically responsive sensors.