writer：Wang, M.; Hu, T.; Bisoyi, H. K.; Yu, Z.; Liu, L.; Song, Y.; Yang, J.; Yang, H.*; Li, Q.*
keywords：Magnetic Fluid
source：期刊
specific source：Small, 2023, 19, 2204609
Issue time：2023年

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, we fabricate a

thermal/photo/magneto rheological water-based magnetic fluid 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 three-dimensional gel structure.

In the linear

viscoelastic region, the viscosity exhibits an abrupt increase from less than

0.10 Pa·s at 20 °C to about

1.3×104 Pa·s at 40 °C. Similarly, the storage modulus is about 0.022 Pa at 20 °C and increases to about 1.0×104 Pa at 40

°C, which

is 10 times the loss modulus. Benefitting from the photo-thermal and

magnetocaloric effects of the Fe3O4@OA nanoparticles,

the rheological change process also can be controlled by near infrared (NIR)

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.