Electrostatic Suppression of the "Coffee Stain Effect"

Alexander W. Wray*, Demetrios T. Papageorgiou, Richard V. Craster, Khellil Sefiane, Omar K. Matar

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The dynamics of a slender, evaporating, particle-laden droplet under the effect of electric fields are examined. Lubrication theory is used to reduce the governing equations to a coupled system of evolution equations for the interfacial position and the local, depth-averaged particle concentration. The model incorporates the effects of capillarity, viscous stress, Marangoni stress, elecrostatically induced Maxwell stress, van der Waals forces, concentration-dependent rheology, and evaporation. Via a parametric numerical study, the one-dimensional model is shown to recover the expected inhomogeneous ring-like structures in appropriate parameter ranges due to a combination of enhanced evaporation close to the contact line, and resultant capillarity-induced flow. It is then demonstrated that this effect can be significantly suppressed via the use of carefully chosen electric fields. Finally, the three-dimensional behavior of the film and the particle concentration field is briefly examined.

Original languageEnglish
Pages (from-to)5849-5858
Number of pages10
JournalLangmuir
Volume30
Issue number20
DOIs
Publication statusPublished - 27 May 2014

Keywords

  • CONTACT LINE DEPOSITS
  • DROPLET EVAPORATION
  • SESSILE DROPLET
  • CONVECTION
  • SUBSTRATE
  • PATTERNS
  • FLUIDS
  • FLOW

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