title: Adhesion of liquid droplets to rough surfaces.
abstract: We study the adhesion of liquid droplets to rough surfaces, focusing on how adhesion changes with surface chemistry and roughness. For hydrophobic surfaces (equilibrium contact angle θ(e)>90°), although increasing surface roughness augments apparent contact angle, it does not necessarily always reduce adhesion. In a domain defined by roughness and equilibrium contact angle, this study identifies regions where adhesion increases or decreases with increasing roughness. The two regions do not border at θ(e)=90°. It is found that making surfaces with low roughness ratio (close to 1) does not reduce adhesion unless the surface material is highly hydrophobic (θ(e)>120°). In other words, to reduce adhesion for existing hydrophobic materials (90°<θ(e)<120°), high roughness ratios are needed. Additionally, to reduce adhesion, the geometry of microstructures should be designed such that wetted fraction decreases with increasing roughness ratio. This study is of particular importance for the design of textured superhydrophobic surfaces.
authors.affiliation: GE Global Research Center, Niskayuna, New York 12309, USA. liri@ge.com
authors.forename: Ri
authors.initials: R
authors.lastname: Li
authors.forename: Azar
authors.initials: A
authors.lastname: Alizadeh
authors.forename: Wen
authors.initials: W
authors.lastname: Shang
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D057446:Hydrodynamics; D057927:Hydrophobic and Hydrophilic Interactions; D008962:Models, Theoretical; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D000269:Adhesives