Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Poster: Micro and Nanofluidics

CPP 30.15: Poster

Wednesday, March 24, 2010, 17:30–19:00, Poster C

Hydrodynamic effects between rotating objects and chains grafted at a wall — •Steffen Schreiber¹, Thomas Tischer², and Walter Zimmermann¹ — ¹Theoretische Physik I, Universität Bayreuth, D-95440 Bayreuth, Germany — ²Experimentalphysik V, Universität Bayreuth, D-95440 Bayreuth, Germany

We investigate two asymmetric, rotating and hydrodynamically interacting dumbbells. When the dumbbells have different asymmetries they rotate asynchronously in an external field. The angle between the dumbbell axes oscillates around a non-vanishing mean value. So the symmetry with respect to time reversal is broken. Depending on the dumbbells' shapes this causes either attraction or repulsion between them as we show in selected phase diagrams.

Secondly we investigate the motion of an ensemble of paramagnetic beads in a rotating magnetic field. After aligning the beads in a linear chain by a static magnetic field we rotate the field. Depending on its rotation frequency and on the field strength we find two regimes: For high rotation frequencies and for low field strengths the ensemble of beads forms spiral structures, whereas for low rotation frequencies and high field strengths the chain breaks up into smaller chains.

Furthermore we examine the hydrodynamic interaction between a semiflexible bead-spring chain and a plane no-slip wall, to which the chain is attached. The chain is exposed to different flow profiles. We find that the hydrodynamic interactions between the chain and the wall cause the chain to bend towards the wall. In oscillating flow fields we find an interesting asymmetric motion of the chain.