Eur. Phys. J. Special Topics 223, 1859-1867 (2014)
https://doi.org/10.1140/epjst/e2014-02231-x

Regular Article

Electrohydrodynamic controlled assembly and fracturing of thin colloidal particle films confined at drop interfaces^*

¹ Department of Physics, Norwegian University of Science and Technology, Hoegskoleringen 5, 7491 Trondheim, Norway
² Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
³ Matière et Systèmes Complexes, Université Paris 7 Diderot, 10, rue Alice Domon et Léonie Duquet, 75205 Paris, France

^a e-mail: zrozynek@ichf.edu.pl
^b e-mail: jon.fossum@ntnu.no

Received: 30 June 2014
Revised: 21 July 2014
Published online: 22 September 2014

Abstract

Particles can adsorb strongly at liquid interfaces due to capillary forces, which in practice can confine the particles to the interface. Here we investigate the electrohydrodynamic flow driven packing and deformation of colloidal particle layers confined at the surface of liquid drops. The electrohydrodynamic flow has a stagnation point at the drop equator, leading to assembly of particles in a ribbon shaped film. The flow is entirely controlled by the electric field, and we demonstrate that AC fields can be used to induce hydrodynamic “shaking” of the colloidal particle film. We find that the mechanical properties of the film is highly dependent on the particles: monodisperse polystyrene beads form packed granular monolayers which “liquefies” upon shaking, whereas clay mineral particles form cohesive films that fracture upon shaking. The results are expected to be relevant for understanding the mechanics and rheology of particle stabilized emulsions.