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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: Poster: Wetting, Micro and Nano Fluidics

CPP 34.10: Poster

Mittwoch, 13. März 2013, 16:30–18:30, Poster C

Imaging of drops on superhydrophobic surfaces in the Cassie and Wenzel states — •Periklis Papadopoulos, Lena Mammen, Xu Deng, Doris Vollmer, and Hans-Jürgen Butt — Max Planck Institute for Polymer Research, Mainz, Germany

A droplet deposited or impacting on a superhydrophobic surface rolls off easily, leaving the surface dry and clean. This remarkable property is due to a surface structure which favors the entrainment of air cushions beneath the drop, leading to the so called Cassie state. The Cassie state competes with the Wenzel (impaled) state, where the liquid fully wets the substrate. To utilize superhydrophobicity, impalement of the drop into the surface structure needs to be prevented. Recently, we demonstrated the capability of laser scanning confocal microscopy (LSCM) to image water drops on an array of micropillars [1]. While the drop evaporates from a pillar array, its rim recedes via step-wise depinning from the edge of the pillars. Once the pressure becomes too high, or the drop too small, the drop slowly impales the texture. The thickness of the air cushion decreases gradually. As soon as the water-air interface touches the substrate, complete wetting proceeds within milliseconds. LSCM opens a novel approach to study wetting dynamics, which is of high scientific and technological interest.

[1] P. Papadopoulos et al., Langmuir 2012, 28, 8392-8398