Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 13: Interfaces and Thin Films I (joint session with CPP)

DS 13.5: Talk

Tuesday, March 17, 2015, 11:15–11:30, C 243

Crack-Free Hierarchical Wrinkle Patterns — •Bernhard Glatz and Andreas Fery — Physical Chemistry II, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany

Wrinkling is a mechanical instability phenomenon of thin films: Wrinkles form, if a system consisting of a hard, thin layer in strong adhesive contact with a soft, thick elastomer is subject to in plane compression. Under these conditions, a buckling instability results in a periodic surface corrugation with well-defined wavelength. In that regard PDMS is a well-established elastomer since it allows the in-situ generation of a glassy layer by oxidization processes as plasma or UVO. It comprises however side features as cracks and line defects, which form in most wrinkling process and are not predictable yet. We demonstrate a crack-free method where line defects are arranged by modifying the substrate: A stiffness gradient between two covalently linked PDMS phases induces a change in the wrinkle periodicity along the border of both. We tuned the ratio of the phases and so received several hierarchical line defect patterns. Furthermore computer simulations helped us to understand the observed structures. Such crack-free wrinkles with predictable defect positions allow applications as channel junctions in microfluidics or templates for particle alignment.

[1] B. A. Glatz and co-workers (in preparation)