title: Electric-field-controlled flow in nanoscale-thin wetting films.
abstract: A novel nanofluidic system based on electroosmotic flow in nanoscale-thin aqueous wetting films is reported. The water films formed spontaneously on mica substrates in a saturation humidity environment. The film thickness was determined to be a few tens of nanometers by optical interference and fluorescence intensity measurements and was consistent with a theoretical evaluation of the thickness of a film based on the competing forces of electrostatic repulsion and capillary pressure. Lateral flow was induced by applying a dc electric field tangential to the film and characterized by tracking the position of a fluorescent probe. The mobilities of the thin fluid layer and the flow marker were lower than the predictions of the electrokinetic theory, which may be a result of adsorption of the fluorescent molecules to the mica. Confinement of the film to two-dimensional "channels" was achieved by microcontact printing of patterned hydrophobic monolayers onto the substrate. This system has the advantage of simple and inexpensive fabrication in comparison to nanofluidic devices made by traditional lithography techniques.
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, United States.
authors.forename: Jairus
authors.initials: J
authors.lastname: Kleinert
authors.forename: Sejong
authors.initials: S
authors.lastname: Kim
authors.forename: Orlin D
authors.initials: OD
authors.lastname: Velev
mesh_terms: D004574:Electromagnetic Fields; D008567:Membranes, Artificial; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D017155:Wettability
chemical_list: D008567:Membranes, Artificial