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.