Biomimetic superhydrophobic surfaces: multiscale approach.
Micro- and macrodroplet evaporation and condensation upon micropatterned superhydrophobic surfaces built of flattop pillars are investigated with the use of an environmental scanning electron microscope. It is shown that the contact angle hysteresis depends upon both kinetic effects at the triple line and adhesion hysteresis (inherently present even at a smooth surface) and that the magnitude of the two contributions is comparable. The transition between the composite (Cassie) and wetted (Wenzel) states is a linear effect with the microdroplet radius proportional to the pitch over pillar diameter. It is shown that wetting of a superhydrophobic surface is a multiscale phenomenon that involves three scale lengths. Although the contact angle is the macroscale parameter, the contact angle hysteresis and the Cassie--Wenzel transition cannot be determined from the macroscale equations and are governed by micro- and nanoscale effects.
Nosonovsky
Michael
M
National Institute of Standards and Technology, 100 Bureau Drive, Stop 8520, Gaithersburg, Maryland 20899-8520, USA.
Bhushan
Bharat
B
D040761:Biomimetic Materials / Q000737:chemistry*; D003198:Computer Simulation; D057927:Hydrophobic and Hydrophilic Interactions; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D013499:Surface Properties
D046911:Macromolecular Substances