Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Poster: Focus: Wetting on smooth and rough surfaces: From spreading to superhydrophobicity

CPP 30.4: Poster

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

Light induced switching of surface wetting of azobenzene decorated silicon nanograss surfaces — •Jonas Groten and Jürgen Rühe — Universität Freiburg, IMTEK

The wetting behavior of high aspect ratio nanorough surfaces depends on the surface energy of the involved materials. Depending on the value of the surface energy superwetting, Wenzel type wetting or superhydrophobicity can be observed. These wetting regimes are separated by sharp transitions at well defined surface energies. We have coated a silicon surface consisting of high aspect ratio nanoscale needles (``black silicon'') with a polymer monolayer containing a fluorinated azobenzene moiety. The azobenzene moiety can be switched between the cis and the trans state through illumination with light of appropriate wavelengths. In the described system the surface energy of the polymer coating is adjusted to the energy value which separates the distinct wetting regimes of the nanorough surface. This coupling allows for large changes in the surface wetting behavior even when the surface energy upon illumination is only rather small. As a consequence the surface can be reversibly switched from a superhydrophobic state with roll off tilt angle < 2° to a completely sticky surface with no roll off at all or from a strong Wenzel-type wetting state to a superwetting surface.