# Magnetic Self-Healing Composites: Synthesis and Applications
## 3 State-of-the-Art Fabrication Methods of Magnetic Self-Healing Composites
### Alternative Fabrication Methods
#### 3.4.2 Spray Deposition Method  
Spray deposition is a simple method of producing a broad range of magnetic nanocomposites. This method relies on the direct conversion of single-solution droplets generated by the automatization of a precursor in a one-step process. A precursor solution is usually sprayed into a hot wall reactor, where the solution evaporates. The solution droplets dry while airborne or in contact with the hot reactor wall and form the particles without any chemical reaction. Recently, [PERSON] et al. developed a robust self-healing magnetic nanocomposite composed of a resin matrix formed by epoxy (EP) and polycaprolactone (PCL) together with Fe\({}_{3}\)O\({}_{4}\) and SiO\({}_{2}\) microparticles in two steps [38]. First, the EP/PCL mixed-resin matrix was prepared through spray deposition. Then, magnetic microparticles were deposited on the semi-wet resin matrix by gradient distribution under gravity, followed by subsequent solvent evaporation. The results showed that cutting cracks could be rapidly thermally healed under irradiation with near-infrared light. To summarize this section, Table 2 shows an overview of the different self-healing mechanisms and magnetic fillers evaluated for magnetic self-healing composites.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fabrication Method** & **Self-Healing Mechanism** & **Magnetic Filler** & **References** \\ \hline \multirow{5}{*}{Direct Mixing} & Ionomer & Fe\({}_{3}\)O\({}_{4}\), CoFe\({}_{2}\)O\({}_{4}\) & [41; 42] \\ \cline{2-4}  & Hydrogen bonds & Fe\({}_{3}\)O\({}_{4}\) & [32; 55; 51; 52] \\ \cline{2-4}  & Diels-Alder & CrO\({}_{2}\) & [45] \\ \cline{2-4}  & & Fe\({}_{3}\)O\({}_{4}\) & [56] \\ \cline{2-4}  & Intermolecular diffusion & Fe\({}_{3}\)O\({}_{4}\) & [40] \\ \hline \multirow{5}{*}{NPs surface engineering and self-assembly} & Metal-ligand complex & Fe\({}_{3}\)O\({}_{4}\) & [36; 51] \\ \cline{2-4}  & Hydrogen bonds & Fe\({}_{3}\)O\({}_{4}\) & [32] \\ \cline{2-4}  & Boronic ester & MnFe\({}_{3}\)O\({}_{4}\) & [48] \\ \cline{2-4}  & Diels-Alder & Fe\({}_{3}\)O\({}_{4}\) & [46] \\ \cline{2-4}  & Shelf base & Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\) & [35] \\ \cline{2-4}  & Intermolecular diffusion & Fe\({}_{3}\)CoO\({}_{4}\)@Fe\({}_{3}\)MnO\({}_{4}\) & [34] \\ \cline{2-4}  & Intermolecular diffusion & Mn\({}_{x}\)Zn\({}_{1-x}\)Fe\({}_{2}\)O\({}_{4}\) & [39] \\ \hline \multirow{5}{*}{Additive manufacturing} & Hydrogen bonds/\(\pi\)-\(\pi\) stacking & Fe\({}_{3}\)O\({}_{4}\) & [49] \\ \cline{2-4}  & Schiff base & Fe\({}_{3}\)O\({}_{4}\) & [43; 44] \\ \cline{2-4}  & Intermolecular diffusion & Fe\({}_{3}\)O\({}_{4}\) & [31] \\ \hline \multirow{5}{*}{External magnetic field} & Host-guest interactions & Fe\({}_{3}\)O\({}_{4}\) & [54] \\ \cline{2-4}  & Schiff base & CIPs & [76] \\ \cline{1-1} \cline{2-4}  & Intermolecular diffusion & Fe\({}_{3}\)O\({}_{4}\) & [77] \\ \hline Spray deposition & Intermolecular diffusion & Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\) & [40] \\ \hline \hline \end{tabular}
\end{table}
Table 2: The different self-healing mechanisms and magnetic fillers reported for the reported magnetic self-healing composite fabrication methods.