Patent ID: 8028722

Claim:
A fluid handling device having an anisotropic wetting surface portion, the anisotropic wetting surface portion comprising: a substrate with a multiplicity of asymmetric substantially uniformly shaped microscale or nanoscale asperities thereon, each asperity defining a first asperity rise angle and a second opposing asperity rise angle relative to the substrate, the asperities being structured to present a retentive force ratio (f 3 /f 2 ) greater or less than unity when the retentive force ratio (f 3 /f 2 ) is determined according to the formula: f 3 /f 2 =sin(ω 3 +½Δθ 0 )/sin(ω 2 +½Δθ 0 ) where ω 2 is the first asperity rise angle in degrees, ω 3 is the second asperity rise angle in degrees, and Δθ 0 =(θ a,0 −θ r,0 ) where θ a,0 is a true advancing contact angle of a fluid in contact with the surface in degrees, and θ r,0 is a true receding contact angle of the fluid on the surface in degrees.