Characterization of Rose Petals and Fabrication and Characterization of Superhydrophobic Surfaces with High and Low Adhesion
Unlike the lotus leaf, some rose petals ( rosea Rehd ), scallions, and garlic exhibit superhydrophobicity with high contact angle hysteresis (CAH). While a water droplet can easily roll off the surface of a lotus leaf, it stays pinned to the surface. The different behavior of wetting between the lotus leaf and the rose petal can be explained by different designs in the surface hierarchical micro—and nanostructure. The rose petal’s microstructure, and possibly nanostructure, has a larger pitch value and lower height than the lotus leaf. Therefore, the liquid is allowed to impregnate between the microstructure and partially penetrates into the nanostructure, which increases the wetted surface area. As a result, contact angle hysteresis increases with increasing wetted surface area. In the case of scallion and garlic leaves, contact angle hysteresis is high due to hydrophobic defects responsible for contact line pinning. Such superhydrophobic surfaces with high adhesion have various potential applications, such as the transport of liquid microdroplets over a surface without sliding or rolling, the analysis of very small volumes of liquid samples, and for the inside of an aircraft surface to minimize the falling of condensed water droplets onto passengers. There have been few attempts to fabricate such surfaces in the laboratory.