Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Poster: Wetting, Micro and nanofluidics

CPP 21.16: Poster

Wednesday, March 28, 2012, 11:00–13:00, Poster A

Three-dimensional imaging of water drops on hydrophobic surfaces by confocal microscopy — •Periklis Papadopoulos, Hans-Jürgen Butt, and Doris Vollmer — Max Planck Institut for Polymer Research, Mainz, Germany

The microscopic description of wetting of a rough or structured solid surface by a liquid is still a challenge. Nano- and micrometer-sized inhomogeneities cause pinning of the three-phase contact line, preventing drops to reach their global equilibrium. To investigate the relation between the local, microscopic and the macroscopic contact angle, we image water drops on microstructured surfaces by laser scanning confocal microscopy (LSCM). The microstructures consist of cylindrical pillars arranged in a square lattice. Both the substrate and water are fluorescently labeled, allowing for accurate imaging of all interfaces and the three-phase contact line. Contact angles can be measure with accuracy of 1^∘ and spatial resolution of a few µm. The “microscopic” contact angle close to the substrate varies by up to 30^∘ along the wetting line, depending on the precise position. This variation, along with the contact line profile, causes deviations of the drop shape that persist at heights more than one magnitude larger than the size of the microstructures. This detailed information will allow us to tune the wetting properties of rough and patterned surfaces.