Biomimetic Superhydrophobic Surfaces by Nanoarchitectonics with Natural Sunflower Pollen

Superhydrophobic surfaces, known for their water-repellent, and self-cleaning properties, are widely used in various applications. These advanced functional surfaces exhibit high contact angles (>150°), achieved through low surface energy chemistries and hierarchical roughness. Natural sunflower pollen is micron-sized spherical particles with nano-sized spikes on the surface. This study engineered superhydrophobic coatings using the unique hierarchical structure of sunflower pollen and low surface energy additives like polydimethylsiloxane (PDMS) and silane additives such as 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FTS), octadecyltrichlorosilane (OTS) and dichlorodimethylsilane (DCDMS). The pollen content significantly modulates surface structure, roughness, and water contact angle. Higher pollen content enhances roughness and water repellency by creating micro-nano hierarchical structures. Pollen-PDMS-FTS and Pollen-PDMS coatings demonstrated the highest water contact angles (165 ± 2° and 163 ± 3°, respectively) and lowest sliding angles (4.5 ± 1° and 7.6 ± 2.6°, respectively), achieving a "lotus effect." Conversely, Pollen-PDMS-OTS or Pollen-PDMS-DCDMS coatings resulted in high sliding angles and water adhesion, producing a "rose petal effect." These "lotus effect" coatings are effectively applied in self-cleaning and water displacement in oil pipelines on hilly terrain. This study provides insights into the interplay between hierarchical structure and surface-free energy for designing superhydrophobic surfaces tailored for specific applications.