Expansion and rupture of charged microcapsules?

Materials Horizons Pub Date: 2013-10-11 DOI: 10.1039/C3MH00099K

Abstract

We study the deformations of pH-responsive spherical microcapsules – micrometer-scale liquid drops surrounded by thin, solid shells – under the influence of electrostatic forces. When exposed to a large concentration of NaOH, the microcapsules become highly charged, and expand isotropically. We find that the extent of this expansion can be understood by coupling electrostatics with shell theory; moreover, the expansion dynamics is well described by Darcy's law for fluid flow through the microcapsule shell. Unexpectedly, however, below a threshold NaOH concentration, the microcapsules begin to disintegrate, and eventually rupture; they then expand non-uniformly, ultimately forming large, jellyfish-like structures. Our results highlight the fascinating range of behaviors exhibited by pH-responsive microcapsules, driven by the interplay between electrostatic and mechanical forces.

Graphical abstract: Expansion and rupture of charged microcapsules
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