Fabrication of Smart Water-Repellent and Antifouling Coatings from Natural Materials: Recent Advances and Sustainable Applications

Proshat Azizi¹ Arad Amiri² zahra zaghari³

1) Scientific Research Institute of Iran Research Club
2) Scientific Research Institute of Iran Research Club
3) Department of Biology, Faculty of Basic Sciences, Tehran Science and Research Unit, Islamic Azad University, Tehran, Iran

IOI Code : ABEB-ACABCF
Publication : 4th International Conference on Recent Advances in Engineering, Innovation and Technology - Belgium(eitconf.com)
Abstract :
    Background and Aim: Superhydrophobic and antifouling coatings inspired by natural structures such as the lotus leaf have attracted increasing attention due to their wide applications in self-cleaning, anti-icing, corrosion resistance, oil-water separation, and UV protection. However, the reliance of conventional methods on fluorinated compounds and synthetic polymers has created serious environmental and economic challenges. This paper aims to systematically review recent advances in the design and fabrication of hydrophobic, antifouling, and multifunctional coatings based on natural materials, with emphasis on studies from the last decade (2014–2026). Methodology: This study is a systematic review covering reputable databases including ScienceDirect, RSC Advances, Wiley, Springer, and patent databases (Google Patents, Patsnap, USPTO). Inclusion criteria encompass articles and patents published between 2014 and 2026 focusing on natural materials (lignin, cellulose, starch, tannic acid, plant waxes, and proteins) for hydrophobic and antifouling coatings. The paper is structured around four main axes: (1) theoretical foundations of hydrophobicity and Cassie-Baxter, Wenzel, and Young mechanisms; (2) natural materials and key functional groups; (3) fabrication methods including layer-by-layer, particle coating, spray, dip-coating, and surface chemical modification; and (4) functional properties and smart applications. Key Findings: Analysis of studies shows that combining modified lignin nanoparticles with natural fatty acids provides coatings with contact angles above 150° and antibacterial, self-cleaning, and UV protection properties (Forsman et al., 2024). Using tannic acid as a binding agent and cationic starch as a substrate has produced coatings with a contact angle of 170° and a sliding angle below 1° (Zhang et al., 2024). Nanocellulose-based coatings (CNC/CNT/PU) with a contact angle of 160° have simultaneously delivered smart functions including rapid water removal, conductivity, and antibacterial activity (Zhu et al., 2020). Furthermore, the TA-g-PDMS coating with 99% transparency, 5B adhesion grade, and >99% antibacterial efficiency has significantly improved the photostability of organic solar cells (Tan et al., 2025). Comparative analysis shows that the CS/TA/ODS/SiO₂ coating with a 170° contact angle exhibits the highest performance among the reviewed coatings, while carnauba wax with 145° shows the weakest performance. Innovation and Contribution: This paper is the first comprehensive review that places different natural materials into a unified comparative framework and quantitatively analyzes the relationship between chemical structure, fabrication method, and final functional properties. Additionally, for the first time, the hierarchical structure of a leaf is introduced as a design template for multilayer coatings: cuticle (SiO₂/ODS), epidermis (tannic acid), mesophyll (cationic starch), and vein (substrate). This structural analogy provides a novel framework for designing multifunctional coatings. Challenges and Perspectives: Despite significant environmental advantages, natural material-based coatings face challenges such as moderate mechanical durability, limited scalability, and the use of organic solvents in fabrication. Proposed solutions include controlled crosslinking, using kraft lignin (a paper industry byproduct) as a low-cost raw material, and developing water-based and solvent-free methods. Analysis of publication trends shows exponential growth since 2020, aligned with environmental concerns and stricter regulations against PFAS compounds. Conclusion: Hydrophobic and antifouling coatings based on natural materials offer a sustainable and efficient alternative to conventional fluorinated coatings. Lignin, cellulose, tannic acid, and natural waxes, each with their unique properties, enable the fabrication of coatings with superhydrophobicity, antibacterial activity, self-cleaning, and UV protection. With continued interdisciplinary research and overcoming durability and scalability challenges, these coatings are expected to be widely applied in textiles, packaging, construction, medical, and marine industries.

Keywords : superhydrophobic natural materials lignin tannic acid self cleaning coating leaf structure sustainability antimicrobial