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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Focus: Soft Particles in Flows II (joint focus session CPP/DY)

CPP 12.1: Hauptvortrag

Montag, 20. März 2017, 15:00–15:30, ZEU 160

Particle alignment in microchannels and microjets — •Stephan Foerster¹, Mathias Schlenk¹, Susanne Seibt¹, Martin Trebbin³, Josef Breu¹, and Stephan Roth² — ¹University of Bayreuth, Bayreuth, Germany — ²DESY, Hamburg, Germany — ³University of Hamburg, Hamburg, Germany

The flow orientation of particles in microflows is of high relevance in many areas ranging from synthetic fiber production to streams of cells and proteins in blood capillaries. With current advances in device miniaturization in microfluidics, X-ray optics and high-resolution optical microscopy, it has become possible to study the flow orientation of anisometric colloids in-situ with unprecedented precision.

We investigated the flow orientation of Au-nanorods, wormlike polymer micelles and hectorite nanosheets in curved and tapered microchannels. We sursprisingly find that all anisometric particles align perpendicular to the flow orientation in the widening section of tapered microchannels. This is caused by strong extensional forces that reorient the particles. This phenomenon is even observed during the formation of microdroplets from microjets, resulting in biaxial orientations of particles in the free droplets. These findings have important consequences for the production of high performance fibers and the agglomeration of particles in blood capillary stenoses.