Experiments with Active Emulsions

author: Stephan Herminghaus, Dynamics of Complex Fluids Department, Max Planck Institute for Dynamics and Self-Organization (MPIDS), Max Planck Institute
published: June 13, 2012,   recorded: June 2012,   views: 220
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Slides

Slides
0:00 Experiments with Active Emulsions
0:29 Dynamics of Complex Fluids
1:54 Droplet-based microfluidics
5:27 Gel emulsions in microchannels - 1
7:10 Gel emulsions in microchannels - 2
9:37 Inducing chemical reactions - 2
10:43 Controlling/changing droplet positions - 1
14:27 Controlling/changing droplet positions - 2
15:28 Controlling droplet contents
18:34 Formation of bilayer membranes - 1
20:11 Formation of bilayer membranes - 2
21:15 Properties of membranes
23:51 Applications: towards nanoscience - 1
24:04 Applications: towards nanoscience - 2
24:16 Dense emulsions in micro-fluidics - 1
26:56 Dense emulsions in micro-fluidics - 2
28:01 The Belousov-Zhabotinsky (BZ) Reaction - 1
29:01 The Belousov-Zhabotinsky (BZ) Reaction - 2
29:09 The Belousov-Zhabotinsky (BZ) Reaction - 3
29:30 The Belousov-Zhabotinsky (BZ) Reaction - 4
30:07 The Belousov-Zhabotinsky (BZ) Reaction - 5
30:52 The Belousov-Zhabotinsky (BZ) Reaction - 6
31:42 Droplet arrays and coupling - 1
33:00 Droplet arrays and coupling - 2
34:15 Droplet arrays and coupling - 3
35:44 'Active' emulsions: Belouzov-Zhabotinski reaction - 1
38:26 'Active' emulsions: Belouzov-Zhabotinski reaction - 2
39:49 'Active' emulsions: Belouzov-Zhabotinski reaction - 3
40:38 Locomotion of BZ droplets
40:55 Free running droplets - 1
42:27 Locomotion of BZ droplets
42:31 Free running droplets - 1
43:13 Free running droplets - 2
43:18 A little bit of theory
45:21 Locomotion flow field
45:47 Velocity control - 1
47:03 Velocity control - 2
47:25 Fingerprints of non-equilibrium - 1
48:03 Fingerprints of non-equilibrium - 2
48:26 Collective phenomena far from equilibrium
48:32 Collective effects: hydrodynamic interations
49:56 Particle Tracking Velocimetry (PTV)
51:01 Pair correlation
51:42 Another system: liquid crystals in surfactant solution
52:41 Director is aligned with direction of motion
53:23 Pair interaction
53:41 The energy source: formation of a micro-emulsion
54:33 The smectic version: 'myelin' formation
55:37 ...'myelin' formation: 'telephone cords' ... - 1
56:56 ...'myelin' formation: 'telephone cords' ... - 2
57:32 ... and a hierarchy of structures!
59:30 Thank you for your attention!
60:27 Droplet arrays and coupling - 3

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Description

Experiments are presented with emulsions showing various types of 'active' collective behavior. Ensembles of aqueous droplets containing Belouzov-Zhabotinski (BZ) oscillators are shown to exhibit coupling patterns depending on the formation of lipid bilayers between them. We observe target waves, quorum sensing, and spiral waves in two-dimensional rafts of mono-disperse emulsions. As the volume fraction of the dispersed phase (i.e., the droplets) is reduced, we observe self-propelled motion of the droplets, which can be controlled by the BZ reaction if desired. We propose a simple mechanism based on Marangoni stresses which accounts for this motion. Swarming is shown to exhibit pronounced correlation features which depend strongly on the raft density. While the bromine release provides the energy source for this type of self-propulsion, we present an alternative system based on liquid crystals which shows similar collective behaviour, but whose motion has a longer lifetime and is fuelled by the spontaneous formation of a microemulsion. Based on the meso-structure of the liquid crystal, it enables, aside from simple droplet motion, much more complex patterns to evolve, the details of which are yet far from understood.

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