We seek to harness interfacial phenomena to achieve external, reversible, and local control of wetting and adhesion properties. The large surface to volume ratios provided when devices are shrunk to the micro- and nanoscale create particularly exciting opportunities for exerting control via tunable surface interactions.
To achieve this goal, we explore two separate avenues for the control of surface and interfacial properties: control of electrostatic interactions and design of surface structure. The importance of electrostaticsis approached by studying the nanoscale limits of electrowetting on dielectric, the design of responsive films that can be employed to move drops, and the use of surface charge as a means to control the assembly of nanoparticles at the oil-water interface. Our efforts in the control of surface structure have been focused on the understanding of the mechanisms for the adhesion of tree frogs under flooded condition, and on the importance of partial contact line pinning on the morphology of capillary bridges
Out-of-Contact Elastohydrodynamic Deformation due to Lubrication Forces
Authors: Yumo Wang, Charles Dhong, Joelle Frechette
Physical Review Letters
We characterize the spatiotemporal deformation of an elastic film during the radial drainage of fluid from
a narrowing gap. Elastic deformation of the film takes the form of a dimple and prevents full contact to be
reached. With a thinner elastic film the stress becomes increasingly supported by the underlying rigid
substrate and the dimple formation is suppressed, which allows the surfaces to reach full contact. We
highlight the lag due to viscoelasticity on the surface profiles, and that for a given fluid film thickness
deformation leads to stronger hydrodynamic forces than for rigid surfaces.