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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 22: POSTERS Micro- and Nanofluidics

CPP 22.14: Poster

Wednesday, February 27, 2008, 16:00–18:30, Poster A

Optical diffraction reveals microscopic properties of the superhydrophobic state. — •Helmut Rathgen and Frieder Mugele — Physics of Complex Fluids, University of Twente, The Netherlands

We study the microscopic liquid--gas menisci formed at the texture of a superhydrophobic surface, making use of the inherent optical diffraction of the material. By measuring the angle dependence of the diffracted intensity, and comparing the experimental data to theoretical optics calculations with varying curvature of the menisci, we effectively solve the inverse diffraction problem and are able to measure the shape of the menisci with nanometer resolution. We study the shape of the menisci as a function of hydrostatic pressure. Next, driving the menisci in an ultrasound field, and measuring time--resolved diffraction intensities, we observe their nanometer scale oscillations. By comparing to unsteady Stokes flow theory, we find that the frequency response of the collectively oscillating menisci is governed by strong hydrodynamic interaction.