**3.4 Layer-by-layer (LbL)**

Layer-by-layer (LbL) assembly is a prevalent method for coating substrates with functional thin films [35]. It can be applied for coating substrates with polymers, colloids, biomolecules, and even cells, which offers superior control and versatility when compared with other thin film deposition techniques [36]. The versatility is due to the possibility of integrating different materials, creating defined layer sequences, orienting anisotropic materials within layers [37].

The process is based on a sequence of steps that leads to the exposure of the substrate to the material that will be deposited on the thin film. In general, more than one coating layer is formed, that is, multilayer thin films are obtained. Some technologies for films deposition by LbL include immersive; spin; spray; electromagnetic; and fluidic assembly [35, 36]. Immersive LbL assembly is the most widely used method, and it is typically performed by manually immersing a planar substrate into a solution of the desired material followed by three washing steps to remove unbound material [35]. **Figure 6** shows a schematic representation of the immersive LbL assembly method.

**Figure 6.**

*Schematic representation of immersive LbL assembly. Adapted from Richardson et al. [35].*


*Summary of some thin film deposition techniques used for NTF growth showing the main advantages, disadvantages, and applications.*

*Nanocomposites Thin Films: Manufacturing and Applications DOI: http://dx.doi.org/10.5772/intechopen.103961*

The advantages of this technique include simple and versatile process; applied straightforwardly on almost any surface; nanoscale functional films; applied to planar surfaces, spherical particles, inside pores, and onto other more complex geometries; among others. The LbL process requires time for atomistic relaxation at the interfaces. may suffer from high internal stresses, which can cause film delamination. This technique can be used for light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs) device manufacturing; water purification; solar cells; optics; batteries; drug delivery; tissue engineering; functional fabrics; antibacterial coatings; biosensors; photonics applications; liquid or gas separation; among others [35–39].

Schematic representation of an application of coating deposited by the LbL technique with the function of membrane for liquid or gas separation is shown in **Figure 7**.

#### **3.5 Summary table**

The thin film deposition techniques presented in this chapter present advantages, disadvantages, and several applications that are commented in **Table 1**.

### **4. Conclusion**

Nanocomposite coatings can be applied in several areas to improve properties such as hardness, wear, and corrosion resistance, tribological properties, among others. The synergistic effect exhibited in nanocomposite thin films shows the importance of mixing materials where specific properties are obtained but which would be difficult or even impossible for individual materials to exhibit. To obtain the synergism of the properties, it is necessary to establish the appropriate treatment parameters and select the most appropriate film deposition technique for a given application. Thin film growth techniques can be performed by several routes, which leads to the development of many variations in thin film deposition methods. Some of these methods/ techniques were seen in this chapter and have application field in several areas. We hope that this chapter stimulates research on nanocomposites thin films in terms of studying their properties, developing, or improving thin films and the techniques for growing these films.

### **Acknowledgements**

The authors thank the research funding agencies CNPq, CAPES, and FAPEAL for the financial support.

### **Conflict of interest**

The authors declare no conflict of interest.
