(A–C) TEM images of magnetite nanoparticles: small (SMIONSs,
A) and large (LMIONSs, B) spheres and nanorods (MIONRs, C). The scale
bars represent 200 nm. (D) Storage modulus G′
of hybrid gels (PIC and PAAM) of the three magnetic nanomaterials
as a function of magnetic flux density B (conditions:
aqueous solutions with nanoparticle concentration of 25 mg mL–1, PIC concentration of 0.5 mg mL–1, T = 37 °C, PAAM concentration of 30 mg mL–1). The stiffening compared to pure PIC at B = 1 T is indicated. (E) Magnetic stiffening is fast and
reversible, indicated by 19 cycles of 20 min each (10 min field on,
10 min off). Conditions: the concentrations of PIC and MIONRs are
0.5 and 25 mg mL–1, respectively. Data points are
recorded every 6 s.