Generalized models for advancing and receding contact angles of fakir droplets on pillared and pored surfaces.

Understanding how surface properties determine the mobility of a fakir droplet on patterned surfaces, which is typically characterized by advancing and receding contact angles, is important in the design of superhydrophobic surfaces for tailored applications. However, most analytical models of the contact angles are limited to a specific motion direction and surface type, e.g.

Depinning force of a receding droplet on pillared superhydrophobic surfaces: Analytical models.

It was experimentally shown that a depinning force of a receding droplet on a micropillared superhydrophobic surface has an apparently linear correlation with the maximal three-phase contact line attainable along an actual droplet boundary. However, the experimental observation has not yet been supported by any theoretical basis or analysis. This study establishes an analytical model that theoretically supports the experimental observation on the basis of the dynamics of a contact line.

Anti-Icing or Deicing: Icephobicities of Superhydrophobic Surfaces with Hierarchical Structures.

Superhydrophobic surfaces have gained tremendous attention for icephobic properties, including anti-icing and deicing. The former is about how much a surface can delay the ice formation, whereas the latter is about how easy the surface can let the ice go off after freezing. In this study, superhydrophobic surfaces with different surface roughnesses and wettabilities were tested for both anti-icing and deicing purposes to investigate their correlation in association with the different surface properties.

Bubble Movement on Inclined Hydrophobic Surfaces.

The movement of a single air bubble on an inclined hydrophobic surface submerged in water, including both the upward- and downward-facing sides of the surface, was investigated. A planar Teflon sheet with an apparent contact angle of a sessile water droplet of 106° was used as a hydrophobic surface. The volume of a bubble and the inclination angle of a Teflon sheet varied in the ranges 5-40 μL and 0-45°, respectively.

Large-amplitude, reversible, pH-triggered wetting transitions enabled by layer-by-layer films.

We report on the use of layer-by-layer (LbL) hydrogels, composed of amphiphilic polymers that undergo reversible collapse-dissolution transition in solutions as a function of pH, to induce sharp, large-amplitude wetting transition at microstructured surfaces. Surface hydrogels were composed of poly(2-alkylacrylic acids) (PaAAs) of varied hydrophobicity, i.e.