Dresden 2014 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 21: Pattern Formation

DY 21.8: Vortrag

Mittwoch, 2. April 2014, 17:00–17:15, HÜL 186

Cracking over patterned substrates — •Pawan Nandakishore, Anupam Sengupta, and Lucas Goehring — Max Planck Institute for Dynamics and Self-Organization (MPIDS) 37077 Göttingen, Germany

From thermal cracks on the surface of Mars to desiccation cracks in dried paint, cracking occurs at all length scales. In the above examples the substrate structure influences the resulting crack pattern. We study the effect of the substrate by generating desiccation cracks on patterned substrates over various length scales. On the macro (decimeter) scale, we dry Bentonite slurries over sinusoidal substrates and study them using time lapse photography. The wavelength, amplitude of the substrate and the layer height of the clay are the relevant parameters. We use an orientational order parameter to characterize the crack pattern. We find that the order parameter evolves non-monotonically with layer height which hints that when the layer height is comparable to the wavelength there is roughly a crack on top of every peak, such a pattern is characterized by a high order parameter. We fabricate sinusoidal substrates on the micro scale by oxidizing thin films of PDMS under strain. We deposit Bentonite, laponite and other colloidal suspensions on the patterned PDMS substrates and study their drying and cracking behavior. Combining observations at both length scales we attempt to decipher what lies beneath a crack pattern.