Regensburg 2013 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 44: Wetting, Micro- and Nanofluidics
CPP 44.1: Invited Talk
Thursday, March 14, 2013, 15:00–15:30, H39
Dynamic reorganization of droplets: from Foams to Phonons — •Ralf Seemann1,2, Jean-Baptiste Fleury1, Ulf D. Schiller3, Shashi Thutupalli2, Ohle Claussen2, Stephan Herminghaus2, Gerhard Gompper3, and Martin Brinkmann1,2 — 1Experimental Physics, Saarland University, Germany — 2MPI for Dynamics and Self-Organization, Göttingen, Germany — 3Theoretical and Soft Matter Biophysics, FZ Jülich, Germany
The stability and the mechanical response of monodisperse droplet packing in quasi 2d micro-channels are discussed for different packing density under static and dynamic conditions: Very dense droplet arrangements are analogous to foam and can be described by geometrical means provided the friction with the side walls is low. At reduced droplet fraction where the droplets are still in mechanical contact, the resulting droplet arrangements are stabilized by virtue of the Laplace pressure. Depending on the exact choice of parameter a droplet packing can have a negative compressibility separating into stable domains of higher and lower packing fraction. When flowing along a microfluidic channel these unstable droplet arrangements develop complex non-equilibrium re-arrangements similar to avalanches. Reducing the droplet fraction even further so that the droplets do not touch each other, the flowing droplets experience each other by dipole-like hydrodynamic interactions and can be excited to show collective oscillations which can be described by a phonon-type behavior.