Observation of the rose petal effect over single- and dual-scale roughness surfaces

Rose petals exhibit superhydrophobicity with strong adhesion to pin water drops, known as the ‘petal effect.’ It is generally believed that the petal effect is attributed to dual-scale roughness, that is, the surface possesses both a nanostructure and a microstructure (Feng et al 2008 Langmuir 24 [http://ift.tt/1zTwFrX] 4114 ). In this study, we demonstrate that the dual-scale roughness is not a necessary condition for a surface of the petal effect. A surface of single-scale roughness, either at the nanoscale or the microscale alone, within a certain roughness region may also exhibit the petal effect. The surface roughness plays the essential role on the wetting behavior and governs the contact angle in the Wenzel or Cassie state, as well as the contact angle hysteresis. A water drop on the surface of the petal effect under the condition of the advancing and receding contact angle would fall into, respectively, the Cassie and Wenzel ...

Kuan-Yu Yeh, Kuan-Hung Cho, Yu-Hao Yeh, Arwut Promraksa, Chung-Hsuan Huang, Cheng-Che Hsu and Li-Jen Chen

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