stephen j. decamp
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Active Nematics in Emulsions and Vesicles

To explore the effect of topology and confinement on active matter systems, we encapsulate active microtubule bundles in emulsion droplets or vesicles.

Nematics in Emulsions

Shown here is a water droplet in oil.  Microtubule bundles in the water phase form an active nematic on the inner surface of the oil-water interface of an emulsion droplet.
The fast streaming nematic defects on the inner surface of the emulsion droplet provide a mechanism which propels the droplet when squished between two plates of glass.

Nematics in Vesicles

In collaboration with Andreas Bausch at TUM, we confined the microtubule and kinesin based active nematic into vesicles using the cDICE method of encapsulation.
We can change the surface tension of the vesicle by inducing a hypertonic stress. The outward flow of water from the vesicle results in excess membrane containing the active nematic. The four +1/2 defects in the system then force filopodia-like protrusions which extend out of the vesicle.
The active nematic confined to the inner leaflet of the lipid bilayer of a vesicle restricts the number of defects to 4x +1/2 defects. They alternatively oscillate between a tetrahedral and planar configuration. In this video, we track the defect positions on the surface of the vesicle using confocal microscopy.
For more information on confining the active microtubules into vesicles check out this publication:
Topology and dynamics of active nematic vesicles
F. C. Keber*, E. Loiseau*, T. Sanchez*, S. J. DeCamp, L. Giomi, M. J. Bowick, M. C. Marchetti, Z. Dogic, A. R. Bausch
Science, Sept 2014; 345(6201), 1135-1139.

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Stephen J. DeCamp