Superhydrophobicity in Cotton Fabrics: Mechanisms, Techniques, and Future Directions Abstract

3.1.3 Chemical Vapor Deposition (CVD)
Chemical Vapor Deposition (CVD) is a highly effective technique for creating superhydrophobic cotton fabrics. This process involves the deposition of a gaseous reactant onto a substrate, in this case, cotton fabric, to form a solid coating. The coating's properties, including its roughness and hydrophobicity, can be precisely controlled by adjusting the deposition parameters. Specifically, for superhydrophobic cotton fabrics, coatings of different materials, such as fluorinated compounds and polymers, are often used. These materials inherently repel water and, when combined with the surface roughness achieved through CVD, result in a superhydrophobic surface.
For instance, a study demonstrated the use of a fluorine-containing epoxy polymer, P(GMA-r-MMA)-g-PFPA, which was obtained through traditional radical polymerization. This polymer was blended with amino-modified nano SiO2 and used to dip-coat a cotton fabric. By carefully controlling the solution concentration, immersion time, and drying conditions, a superhydrophobic surface was achieved, with a maximum water contact angle of 150 degrees. This coated fabric showed excellent oil-water separation performance, with efficiencies of up to 99% for batch operations and 98% for continuous operations​ [12]​.
It should be noted, however, that while CVD is a promising method for creating superhydrophobic cotton fabrics, it also presents challenges. These include the need for specialized equipment, potential environmental concerns associated with the deposition materials, and the requirement for precise control over the deposition process to ensure the desired superhydrophobic properties. Despite these challenges, CVD remains a valuable tool in the development of superhydrophobic cotton fabrics, and ongoing research is likely to further refine and enhance this technique.
3.2 Use of Nanomaterials
Nanomaterials offer promising avenues for imparting superhydrophobic properties to cotton fabrics due to their ability to enhance surface roughness and hydrophobicity. A variety of nanomaterials have been employed in this context, each bringing unique properties and benefits to the table.
Silica (SiO₂) nanoparticles and zinc oxide (ZnO) nanoparticles are among the most commonly used materials for creating superhydrophobic cotton fabrics. The ZnO nanoparticles, for instance, can be prepared through sol-gel techniques and coated onto cotton fabrics using methods such as spin coating, which results in a superhydrophobic surface with a water contact angle of 154 degrees [​13]​.
Similarly, the use of silica nanoparticles, often in conjunction with tetraethyl orthosilicate (TEOS), has been reported for the preparation of superhydrophobic cotton surfaces. This approach involves alkali and plasma-etching treatments, followed by the addition of the nanoparticles, creating a robust, superhydrophobic surface that maintains mechanical and chemical durability [14]​.
The use of nanomaterials in superhydrophobic coatings has also been shown to enhance durability, a crucial factor considering the wear and tear fabrics typically undergo. Moreover, nanomaterials open the door for specialized applications such as in the biomedical field, where liquid repellency is of particular importance​ [15]​.
Inorganic-organic hybrid nanomaterials have also found application in this field. These hybrid materials offer the advantage of combining the unique properties of both inorganic and organic components, thereby improving the performance of the resulting superhydrophobic surfaces [​13]​.
While the use of nanomaterials has shown promising results, it also poses challenges, especially in terms of cost, scalability, and environmental impact. However, the ongoing research in this field aims to address these issues and explore more efficient and sustainable practices for the production of superhydrophobic cotton fabrics.