Superhydrophobic natural melanin-coated cotton with excellent UV protection and personal thermal management functionality

This study presents a new approach to imparting the combined functionalities of superhydrophobicity, UV protection and personal thermal management via the photothermal effect to cotton fabrics. Surface modification of fabrics was carried out by applying coatings containing natural melanin (NM) particles extracted from yak hair and fluorine-free polydimethylsiloxane (PDMS) polymer via a dip-pad-dry-cure process. Different concentrations of NM particles were used in the coatings and the roles of each ingredient in achieving the desired functionalities were investigated. In addition, the relationship between NM content and the resultant durability of the coatings was explored based on the variations in superhydrophobicity, UV protection, photothermal performance, and color strength of the fabrics. The results demonstrated that the non-fluorinated NM/PDMS coatings were highly effective in developing a superhydrophobic cotton fabric with a water contact angle of 164°. The NM-coated fabrics provided a rapid heating effect under near-infrared light and their temperature increased to 38.4–45.3 °C, which was up to 14.7 °C higher than that of pristine cotton. Furthermore, the application of NM particles resulted in an excellent UV protection performance and generated the UV protection factor level of 198.48 on cotton fabrics. Finally, the coated fabrics were highly breathable and showed high stability against 1000 abrasion cycles, 5 accelerated washing tests, and 70 h UV irradiation. These findings provide new pathways in the development of future functional textiles using user-friendly and biocompatible ingredients.