Home List of Titles Transient responses of a wetting film to mechanical and electrical perturbations
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/190522
- Transient responses of a wetting film to mechanical and electrical perturbations
- Manica, Rogerio; Connor, Jason N.; Clasohm, Lucy Y.; Carnie, Steven L.; Horn, Roger G.; Chan, Derek Y. C.
- This article reports real-time observations and detailed modeling of the transient response of thin aqueous films bounded by a deformable surface to external mechanical and electrical perturbations. Such films, tens to hundreds of nanometers thick, are confined between a molecularly smooth mica plate and a deformable mercury/electrolyte interface on a protuberant drop at a sealed capillary tube. When the mercury is negatively charged, the water forms a wetting film on mica, stabilized by electrical double layer forces. Mechanical perturbations are produced by driving the mica plate toward or by retracting the mica plate from the mercury surface. Electrical perturbations are applied to change the electrical double layer interaction between the mica and the mercury by imposing a step change of the bias voltage between the mercury and the bulk electrolyte. A theoretical model has been developed that can account for these observations quantitatively. Comparison between experiments and theory indicates that a no-slip hydrodynamic boundary condition holds at the molecularly smooth mica/electrolyte surface and at the deformable mercury/electrolyte interface. An analysis of the transient response based on the model elucidates the complex interplay between disjoining pressure, hydrodynamic forces, and surface deformations. This study also provides insight into the mechanism and process of droplet coalescence and reveals a novel, counterintuitive mechanism that can lead to film instability and collapse when an attempt is made to thicken the film by pulling the bounding mercury and mica phases apart.
- Publication type
- Journal article
- Langmuir, Vol. 24, no. 4 (Feb 2008), pp. 1381-1390
- Publication year
- FOR Code(s)
- 0904 Chemical Engineering; 0306 Physical Chemistry (Incl. Structural)
- Capillary tubes; Deformable mercury; Electrolytes; Hydrodynamic forces; Nanometers thick; Perturbation techniques; Real time control; Thin films; Wetting
- American Chemical Society
- Publisher URL
- Copyright © 2008 American Chemical Society.
- Peer reviewed