Berlin 2015 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 62: Poster - Dynamics

DY 62.16: Poster

Thursday, March 19, 2015, 16:00–18:00, Poster A

Contact angle hysteresis of a capillary bridge - control with inkjet printing — •Simeon Völkel, Ingo Rehberg, and Kai Huang — Experimentalphysik V, Universität Bayreuth, 95440 Bayreuth, Germany

When walking on the beach, one can notice a stripe of particularly firm ground splitting the dry sand and the sea. The stiffness of partially wet granular matter, particularly in the so called pendular regime, arises from the cohesion conveyed by the capillary bridges between adjacent granular particles. Existing models describing such a cohesive force typically include a constant contact angle between the wetting liquid and the particle as a parameter. In practicical situations, e.g. wet sand at the beach, an equilibrium contact angle should not be taken as granted due to environmental changes such as raining or draining.

In order to address experimentally such an influence, we control the volume of a single capillary bridge between two spherical particles with nanoliter resolution using an ink jet printer and employ evaporation for volume withdrawal. Using this technique we can drive our system into a limit cycle, which in turn allows precise measurement of the contact angle hysteresis via image analysis.