Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 46: Micro- and Nanofluidics II
CPP 46.2: Vortrag
Freitag, 18. März 2011, 11:00–11:15, ZEU 222
Structural Transitions in a Two-Dimensional Microfluidic Crystal — •Jean-Baptiste Fleury1, Ohle Caussen2, Stephan Herminghaus2, Martin Brinkmann2, and Ralf Seemann1,2 — 1Saarland University, Saarbrücken, Germany — 2Max Planck Institute for dynamic and Self-Organization, Goettingen, Germany
To understand the fundamental principles of droplet packing and manipulation in microfluidic channels we explore the static arrangement of a train of monodisperse water-in-oil emulsion droplets trapped in a straight, quasi two dimensional microfluidic channel with flat rectangular cross section. The length of the droplet train at constant droplet number can be varied by liquid plugs which act as two movable pistons. In this experimental setting we control the static compressive force applied by these plugs and allow the emulsion to mechanically equilibrate by an exchange of the continuous phase with a reservoir. As a result of the changing longitudinal confinement the droplets self-organize in different packing geometries, depending on their size, which can be distinguished by the topology of their contact network. These experimental results are in good quantitative agreement with our analytical calculations of the droplet arrangement, based on minimization of the interfacial energy. The theoretical predictions of droplet organization in different packing geometries also holds true when the structure is flowing in microfluidic channels. Indeed, these flowing structures self organize in periodic lattices that correspond to local minima of the relevant energy functional already discuss in the static case.