SCIENCE CHINA Materials, Volume 61 , Issue 8 : 1112-1122(2018) https://doi.org/10.1007/s40843-017-9221-4

Rotating magnetic field-controlled fabrication of magnetic hydrogel with spatially disk-like microstructures

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  • ReceivedDec 10, 2017
  • AcceptedJan 27, 2018
  • PublishedMar 6, 2018


Composite biomaterials with controllable microstructures play an increasingly important role in tissue engineering and regenerative medicine. Here, we report a magnetic hydrogel composite with disk-like microstructure fabricated by assembly of iron oxide nanoparticles during the gelation process in the presence of rotating magnetic field. It should be mentioned that the iron oxide nanoparticles here were synthesized identically following techniques of Ferumoxytol that is the only inorganic nanodrug approved by FDA for clinical applications. The microstructure of nanoparticles inside the hydrogel was ordered three-dimensionally due to the twist of the aligned chains of magnetic nanoparticles which leads to the lowest state of systematic energy. The size of microstructure can be tuned from several micrometers to tens of micrometers by changing the assembly parameters. With the increase of microstructure size, the magnetothermal anisotropy was also augmented. This result confirmed that the assembly-induced anisotropy can occur even for the several micron aggregates of nanoparticles. The rotating magnetic field-assisted technique is cost-effective, simple and flexible for the fabrication of composite hydrogel with ordered microstructure. We believe it will be favorable for the quick, green and intelligent fabrication of some composite materials.

Funded by

the National Key Research and Development Program of China(2017YFA0104301)

the Fundamental Research Funds for the Central Universities

and the Collaborative Innovation Center of Suzhou NanoScience and Technology.


This work was supported by the National Key Research and Development Program of China (2017YFA0104301). Sun J is thankful to the Fundamental Research Funds for the Central Universities. Fan F, Sun J, Ma M and Gu N appreciate the supports from Collaborative Innovation Center of Suzhou NanoScience and Technology.

Interest statement

The authors declare that they have no conflict of interest.

Contributions statement

Fan F and Sun J designed and operated the experiments; Chen B and Li Y provided the iron oxide sample. Hu K and Wang P gave some useful advice for our experiments; Ma M contributed to the theoretical analysis. Gu N provided experimental ideas, guided the experimental process. All authors contributed to the general discussion.

Author information

Fengguo Fan is pursuing his PhD degree in biomedical engineering at Southeast University. His research interest is the assembly of nanoparticles.

Jianfei Sun received his PhD degree in biomedical engineering from Southeast University in 2008. He is now an associate professor at the School of Biological Science and Medical Engineering, Southeast University. His research interests include the fabrication of nanoelectronic devices by self-assembly of nanoparticles and their application in biomedical issues.

Ning Gu received his PhD degree in biomedical engineering from the Department of Biomedical Engineering, Southeast University, Nanjing, China, in 1996. Currently he is a Cheung Kong Scholar Chair Professor at the School of Biological Science and Medical Engineering, Southeast University.


Supplementary information

Supporting materials are available in the online version of the paper.


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  • Figure 1

    (a) SEM characterization of the Fe3O4@PSC nanoparticles (bar: 2 μm). Inset: SEM image in a larger magnification (bar: 400 nm). (b) TEM characterization of the Fe3O4@PSC nanoparticles, and the average statistics diameter is shown in the insert figure (bar: 20 nm). (c) Top and side views of a conceptual rotating magnetic field platform, and the magnet hydrogels sample. (d) Simulated magnetic field intensity of center point with distance between two magnets (inset: magnetic field simulation). (e) The simulated magnetic field intensity in central region by adjusting the distance between two poles from 1 to 10 cm.

  • Figure 2

    Characterization of a typical magnetic hydrogel sample. (a) The longitudinal section of magnetic hydrogel in optical imaging (bar: 100 μm). Right part of the figure was the corresponding binary image. (b) The transverse section of magnetic hydrogel in optical imaging (bar: 100 μm). (c) The longitudinal (bar: 4 μm) and transverse (bar: 4 μm) SEM images of a single microdisk and the local magnification (bar: 2 μm and 200 nm). (d) The longitudinal section (bar: 10 μm) and transverse section (bar: 10 μm) LSCM images of a single microdisk. (e) Fe element mapping of a single microdisk (bar: 10 μm).

  • Figure 3

    (a) Average statistical size of the microstructure with alteration of field intensity. (b) Average statistical size of the microstructure with alteration of field frequency. (c) Average statistical size of the microstructure with alteration of colloidal concentration. (d) LSCM characterization of a series of microdisks with different size (Diameter from the left to the right: 7, 12, 15, 18 and 23 μm. Thickness from the left to the right: 3, 5, 7, 8 and 8 μm. Bar: 10 μm).

  • Figure 4

    A possible mechanism for the formation of disk-like structure. (a) The iron oxide nanoparticles inside hydrogel at initial state (bar: 2 μm). (b) At the beginning of rotating magnetic field (bar: 2 μm). (c) With continuing rotating magnetic field (bar: 1 μm). (d) Intermediate state (bar: 2 μm). (e) Final state (bar: 4 μm). (f) Schematic diagram of formation process based on three forces. (g) OOMMF simulations of the demagnetization energy variation in angle range from 0° to 360° for different assembled morphology in the presence of a rotating magnetic field.

  • Figure 5

    (a) Magnetothermal measurements of an assembled magnetic hydrogel with the different incident direction of alternating magnetic field (0°, 30°, 60° and 90°). (b and c) The hysteresis loops for assembled magnetic hydrogel and disorganized magnetic hydrogel, respectively. (d) Comparison of anisotropy degree for the assembled magnetic hydrogels with different size and the disorganized magnetic hydrogel. Average statistical diameters for the three assembled magnetic hydrogel were 6, 15 and 22 μm, respectively. Average statistical thicknesses were 3, 4 and 4 μm, respectively.

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