Rheological Tunable Magnetic Fluids with Long-Term Stability

Magnetic fluids have advantages such as flow ability and solid-like property in strong magnetic fields, but have to suffer from the tradeoff between suspension stability and flow resistance. In this work, a thermal/photo/magnetorheological water-based magnetic fluid is fabricated by using oleic acid-coated Fe3O4 (Fe3O4@OA) nanoparticles as the magnetic particles and the amphiphilic penta block copolymer (PTMC-F127-PTMC)-based aqueous solution as the carrier fluid. Due to the hydrophobic self-assembly between Fe3O4@OA and PTMC-F127-PTMC, the Newtonian-like magnetic fluid has outstanding long-term stability and reversible rheological changes between the low-viscosity flow state and the 3D gel structure. In the linear viscoelastic region, the viscosity exhibits an abrupt increase from below 0.10 Pa s at 20 degrees C to approximate to 1.3 x 10(4) Pa s at 40 degrees C. Benefitting from the photothermal and magnetocaloric effects of the Fe3O4@OA nanoparticles, the rheological change process also can be controlled by near infrared light and alternating magnetic field, which endows the magnetic fluid with the applications in the fields of mobile valves, moveable switches, buffer or damping materials in sealed devices, etc.

Automated summary

This study presents a novel thermal/photo/magnetorheological water-based magnetic fluid with excellent suspension stability and controllable rheological properties. The fluid is composed of magnetic nanoparticles and a water-based carrier, and it exhibits reversible changes between low-viscosity flow state and 3D gel structure. Additionally, the rheological changes can be controlled using near infrared light and alternating magnetic field, making the fluid applicable in various fields.