Role of Multi-scale Hierarchical Structures in Regulating Wetting State and Wetting Properties of Structured Surfaces

Amplifying the intrinsic wettability of substrate material by changing the solid/liquid contact area is considered to be the main mechanism for controlling the wettability of rough or structured surfaces. Through theoretical analysis and experimental exploration, we have found that in addition to this wettability structure amplification effect, the surface structure also simultaneously controls surface wettability by regulating the wetting state via changing the threshold Young angles of the Cassie–Baxter and Wenzel wetting regions. This wetting state regulation effect provides us with an alternative strategy to overcome the inherent limitation in surface chemistry by tailoring surface structure. The wetting state regulation effect created by multi-scale hierarchical structures is quite significant and plays is a crucial role in promoting the superhydrophobicity, superhydrophilicity and the transition between these two extreme wetting properties, as well as stabilizing the Cassie–Baxter superhydrophobic state on the fabricated lotus-like hierarchically structured Cu surface and the natural lotus leaf.