title: Electrostatic suppression of the "coffee stain effect".
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.
authors.affiliation: Department of Chemical Engineering, Imperial College London , South Kensington Campus, London SW7 2AZ, U.K.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Wray
authors.forename: Demetrios T
authors.initials: DT
authors.lastname: Papageorgiou
authors.forename: Richard V
authors.initials: RV
authors.lastname: Craster
authors.forename: Khellil
authors.initials: K
authors.lastname: Sefiane
authors.forename: Omar K
authors.initials: OK
authors.lastname: Matar