A review on recent progress and techniques used for fabricating superhydrophobic coatings derived from biobased materials

Abstract

Superhydrophobic coatings with remarkable water repellence have emerged as an increasingly prominent field of research with the growth of the material engineering and coating industries. Superhydrophobic coatings address the requirements of several application areas with characteristics including corrosion resistance, drag reduction, anti-icing, anti-fogging, and self-cleaning properties. Furthermore, the range of applications for superhydrophobic coatings has been substantially broadened by the inclusion of key performance features such as flame retardancy, thermal insulation, resistance to water penetration, UV resistance, transparency, anti-reflection, and many more. Numerous research endeavours have been focused on biomimetic superhydrophobic materials because of their distinct surface wettability. To develop superhydrophobic coatings with a long lifespan, scientists have refined the processes of material preparation and selection. To accomplish water repellency, superhydrophobic coatings are usually fabricated using harmful fluorinated chemicals or synthetic polymers. Utilising materials derived from biomass offers a sustainable alternative that uses renewable resources in order to eliminate the consumption of these hazardous substances. This paper provides an insight of several researches reported on the construction of superhydrophobic coatings using biomass materials such as lignin, cellulose, chitosan and starch along with the techniques used for the constructing superhydrophobic coatings. This study is a useful resource that offers guidance on the selection of various biobased polymers for superhydrophobic coatings tailored to specific applications. The further part of the paper put a light on different application of superhydrophobic coatings employed in various disciplines and the future perspectives of the superhydrophobic coatings.

Fig. 1. Superhydrophobic property found in nature: rose petals, eyes of mosquitoes, lotus leaves, cuticles of insects.

Fig. 2. Representation of water droplet on hydrophilic surface, hydrophobic surface, superhydrophobic surface, water droplet in Wenzel state and water droplet in Cassie–Baxter state respectively. Reproduced from ref. with permission from Progress in Organic Coatings (2019), copyright 2019.

Fig. 3. (A) Global yield, (B) market value of superhydrophobic surfaces. (C) Companies offering SH products that are appropriate for smooth substrates and are available commercially. Statistical evaluations of 32 marketed SH materials suitable for building SH surfaces on smooth substrates: (D) wettability, (E) stability, and (F) preparation method. Reproduced from ref. with permission from Science Advances, copyright 2023.

Fig. 4. Electrochemical deposition technique. Reproduced from ref. with permission from International Journal of Implant Dentistry, copyright 2017.

Fig. 5. Electrospinning technique. Reproduced from ref. with permission from IntechOpen, copyright 2023.

Fig. 6. Sol–gel technique. Reproduced from ref. with permission from InTech, copyright 2017.

Fig. 7. Hydrothermal synthesis technique.

Fig. 8. Dip coating technique.

Fig. 9. Spray coating. Reproduced from ref. with permission from IntechOpen, copyright 2022.

Fig. 10. Self-assembly technique and layer by layer deposition technique. Reproduced from ref. with permission from Molecules, copyright 2022.

Fig. 11. Lithography technique. Reproduced from ref. with permission from Elsevier, copyright 2016.

Fig. 12. Illustration displaying the procedure for developing the composite superhydrophobic coating. Reproduced from ref. with permission from Materials, copyright 2017.

Fig. 13. Schematic representation of the steps required for developing a superhydrophobic surface based on LNPs and the possible chemical reactions that may occur (FOTS). Reproduced from ref. with permission from RSC Advances, copyright 2022.

Fig. 14. Diagram illustrating the superhydrophobic coating's fabrication procedure using HLNPs and Fe₃O₄. Reproduced from ref. with permission from Journal of Environmental Chemical Engineering, copyright 2023.

Fig. 15. Diagrammatic representation of the modification of lignin and the process of fabricating a durable superhydrophobic coating. Reproduced from ref. with permission from Molecules, copyright 2022.

Fig. 16. A schematic illustration of the multipurpose, durable, superhydrophobic coating's preparation procedure for swift and intelligent water removal. Reproduced from ref. with permission from Carbohydrate Polymers, copyright 2020.

Fig. 17. (a) Chemical reaction occurring the of preparing superhydrophobic coating. (b) Schematic representation of preparing superhydrophobic coating using CNCs (PTA@CNCs) and ODA and its applications. Reproduced from ref. with permission from ACS Sustainable Chemistry & Engineering, copyright 2022.

Fig. 18. Scheme for preparation of superhydrophobic coatings using cellulose nanocrystals (CNC)–SiO₂–phosphorylated lignin (PL) rods. Reproduced from ref. with permission from Polymers, copyright 2023.

Fig. 19. Schematic representation of fabricating SiO₂@CNF-M water dispersion and the coating. (a) The AFM morphology of CNF. (b) The SiO₂@CNF and (c) SiO₂@CNF water dispersion's TEM morphology. (d) SiO₂@CNF-M coated on paper SEM morphology. Reproduced from ref. with permission from Carbohydrate Polymers, copyright 2022.

Fig. 20. A schematic representation of preparation procedure of multi-coloured superhydrophobic coatings. Reproduced from ref. with permission from Carbohydrate Polymers, copyright 2021.

Fig. 21. (a) Demonstration of one pot method used for preparation of SH coatings using chitosan stearoyl ester (CSSE). (b) Demonstration of superhydrophobic characteristics on silicon wafer. Reproduced from ref. with permission from Carbohydrate Polymers, copyright 2018.

Fig. 22. Preparation demonstration of SH coating on cotton fabric using chitosan, tannic acid and polydimethylsiloxane. Reproduced from ref. with permission from Chemical Engineering Journal, copyright 2023.

Fig. 23. Schematic preparation of superhydrophobic cotton using chitosan–PAni–ZnO–STA composite coating. Reproduced from ref. with permission from International Journal of Biological Macromolecules, copyright 2023.

Fig. 24. Schematic preparation process using chitosan by layer-by-layer assembly. Reproduced from ref. with permission from International Journal of Biological Macromolecules, copyright 2023.

Fig. 25. Schematic representation of process used for preparing eco-friendly self-cleaning starch-based films. Reproduced from ref. with permission from ACS Sustainable Chemistry & Engineering, copyright 2020.

Fig. 26. (a) Schematic representation of fabricating process of EHR-SNP, EHR-SNP-A, and nano-starch-based superhydrophobic coatings. (b) Evaluation of superhydrophobicity of the coating on different consumable liquids and for acid and basic liquids enabling pH sensing property. Reproduced from ref. with permission from ACS Sustainable Chemistry & Engineering, copyright 2021.

Fig. 27. Illustration of fabrication procedure of superhydrophobic coatings using starch–polyhydroxyurethane–cellulose nanocrystals (SPC). Reproduced from ref. with permission from ACS Applied Materials & Interfaces, copyright 2021.

Fig. 28. Applications of superhydrophobic coatings in solar, marine, automobile, textile, construction and medical industries.