Physical ageing of the contact line on colloidal particles at liquid interfaces

David M. Kaz*, Ryan McGorty, Madhav Mani, Michael P. Brenner, Vinothan N. Manoharan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

185 Scopus citations

Abstract

Young's law predicts that a colloidal sphere in equilibrium with a liquid interface will straddle the two fluids, its height above the interface defined by an equilibrium contact angle. This has been used to explain why colloids often bind to liquid interfaces, and has been exploited in emulsification, water purification, mineral recovery, encapsulation and the making of nanostructured materials. However, little is known about the dynamics of binding. Here we show that the adsorption of polystyrene microspheres to a water/oil interface is characterized by a sudden breach and an unexpectedly slow relaxation. The relaxation appears logarithmic in time, indicating that complete equilibration may take months. Surprisingly, viscous dissipation appears to play little role. Instead, the observed dynamics, which bear strong resemblance to ageing in glassy systems, agree well with a model describing activated hopping of the contact line over nanoscale surface heterogeneities. These results may provide clues to longstanding questions on colloidal interactions at an interface.

Original languageEnglish (US)
Pages (from-to)138-142
Number of pages5
JournalNature materials
Volume11
Issue number2
DOIs
StatePublished - Feb 2012

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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