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Issue 22, 2013
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Particle dynamics and separation at liquid–liquid interfaces

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Experiments with magnetic microspheres crossing the interface between two immiscible liquids under the influence of a magnetic field are reported. The liquids form a bilaminated configuration in a microchannel close to which a permanent magnet is arranged. After having approached the interface, the particles “snap in”, indicating the presence of a three-phase contact line. Subsequently, the particles are drawn into the second phase, during which they deform the liquid–liquid interface and finally detach from it. The dependence of this process on the size of the microspheres is studied, showing that via transfer across a liquid–liquid interface, a size separation of particles can be achieved. Comparing the results for 1.29 μm diameter particles with those for 4.69 μm diameter particles, it is found that the small particles are able to cross the interface more easily than what is expected from a simple scaling analysis taking into account the balance between magnetic and interfacial forces on the particles. Potential reasons for this unexpected behavior are discussed. The most likely explanation involves the line tension that destabilizes smaller particles adsorbed to a liquid–liquid interface more than larger particles.

Graphical abstract: Particle dynamics and separation at liquid–liquid interfaces

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Article information

11 Jan 2013
03 Apr 2013
First published
24 Apr 2013

Soft Matter, 2013,9, 5438-5447
Article type

Particle dynamics and separation at liquid–liquid interfaces

A. Sinha, A. K. Mollah, S. Hardt and R. Ganguly, Soft Matter, 2013, 9, 5438
DOI: 10.1039/C3SM00120B

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