We have considered in this work the Wilhelmy plate tensiometer to characterize the wetting properties of two model surface textures: (i) a series of three superhydrophobic micropillared surfaces and (ii) a series of two highly water-repellent surfaces microtextured with a femtosecond laser. The wetting forces obtained on these surfaces with the Wilhelmy plate technique were compared to the contact angles of water droplets measured with the sessile drop technique and to the bouncing behavior of water droplets recorded at a high frame rate. We showed that it is possible with this technique to directly measure triple-line anchoring forces that are not accessible with the commonly used sessile drop technique. In addition, we have demonstrated on the basis of the bouncing drop experiments wetting transitions induced by the specific test conditions associated with the Wilhelmy plate tensiometer for the two series of textured surfaces. Finally, the tensiometer technique is proposed as an alternative test for characterizing the wetting properties of highly liquid-repellent surface, especially under immersion conditions.

Hydrophobic surfaces can allow a liquid to slip over the surface and can thus reduce friction in lubricated contact working in a full film regime. Theory supports that the amount of slip can be increased if super-hydrophobic surfaces that are composed of a textured low surface energy material are used. In this work, polytetrafluoroethylene (PTFE) polymer samples were textured with a femto second laser to create super-hydrophobic surfaces by machining a hexagonal network of small circular holes with 10 and 20 m lattice sides. The frictional behavior of these surfaces was compared to the smooth PTFE samples. Surprisingly, the textured surfaces revealed higher friction coefficients than the smooth surfaces. This higher friction can be explained by a change of wetting regime due to high pressure in fluid and a possible generation of vortices in the cavities.