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

3.2.3 Graphene
The application of graphene in the development of superhydrophobic cotton fabrics has gained significant interest due to the material's unique properties. Graphene, a two-dimensional, single-layer lattice of carbon atoms, imparts a unique combination of physical and chemical characteristics that make it a valuable nanomaterial in surface modification applications.
One approach involves the use of polydopamine/reduced graphene oxide (PDA/rGO) to coat the cotton fabric, followed by the in situ growth of copper nanoparticles on the prepared surface. Further modification with stearic acid (STA) changes the wettability of the cotton surface from superhydrophilic to superhydrophobic, with a water contact angle (WCA) of 153°. The resulting PDA/rGO/Cu/STA cotton demonstrates excellent electrical conductivity (as high as 6769 S·m^-1) and stability, thanks to the stearic acid's protective effect against copper nanoparticle oxidation.
This graphene-enhanced superhydrophobic cotton has shown potential in a variety of applications, such as oil-water separation, electrically driven smart surfaces, electromagnetic shielding, and body motion detection. Remarkably, the superhydrophobic cotton can be used to detect human motions in both ambient and underwater conditions, recognizing human motion from air into water and various underwater activities, such as bending, stretching, and ultrasound. This multifunctional cotton device could serve as an ideal sensor for underwater intelligent devices, highlighting the breadth of possible applications for superhydrophobic graphene-enhanced cotton fabrics​ [18]​.
3.3 Other Techniques
In the realm of superhydrophobic cotton fabric creation, a number of techniques are being explored beyond the commonly known methods like sol-gel processing, layer-by-layer assembly, and chemical vapor deposition. Here are some other techniques:
Durable Water Repellent (DWR): This technique involves treating the fabric with a DWR finish that makes it water-repellent. While this method is commonly used for fabrics, its application to cotton for creating superhydrophobic surfaces is an area of exploration​ [19​].
Nanocomposite Coatings: Superhydrophobic coatings can be created from various nanocomposite materials like Manganese oxide polystyrene (MnO₂/PS), Zinc oxide polystyrene (ZnO/PS), precipitated calcium carbonate, and carbon nano-tube structures. The application of these materials to cotton fabrics is a promising area of research​ [19]​.
Silica Nano-Coatings: This technique utilizes silica-based gels that can be easily applied either by dipping the object into the gel or via aerosol spray. It is currently one of the most cost-effective methods for creating superhydrophobic surfaces​ [19]​.
Fluorinated Silanes and Fluoropolymer Coatings: These materials are known for their low surface energy, which contributes to the superhydrophobicity. Their application to cotton fabrics is a potential area for investigation​ [19]​.
While these techniques present promising avenues for creating superhydrophobic cotton fabrics, they also pose some challenges. One significant challenge is the delicate nature of superhydrophobic coatings, which can be easily damaged by abrasion or cleaning, thus potentially limiting their durability in real-world applications​ [19]​. Furthermore, environmental and safety considerations must also be taken into account in the development and application of these coatings​ [19]​.