Enhancing Liquid Repellence through Surface Roughness

2 Enhancing Liquid Repellence through Surface Roughness 

If the liquid, on the other hand, sits on top of the surface features without penetrating the valleys , air will be enclosed between the droplet and the substrate and the liquid/air interface increases (cf [4,5]). In this Cassie-Baxter state , the solid/liquid interface approaches a minimum. The further increase of surface area (i.e. spreading of the droplet) is hindered for energetic reasons [5]. The apparent contact angle observed xmder these conditions is usually described by the simplified equation 

Among the first to show super-hydrophobicity on rough artificial surfaces were Onda and co-workers [20,21] and later Miwa etal. [22]. Agood overview presenting various related concepts is given in [23]. 

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