title: Maxwell-Wagner polarization and frequency-dependent injection at aqueous electrical interfaces.
abstract: We demonstrate a new type of alternating current (ac) interfacial polarization and frequency-dependent fluid displacement phenomenon at a liquid-liquid electrical interface. Two fluid streams--one with a greater electrical conductivity and the other a greater dielectric constant--are made to flow side by side in a microfluidic channel. An ac electric field is applied perpendicular to the interface formed between the liquid lamellae, and fluid is observed to displace across the liquid-liquid interface. The direction and magnitude of this displacement is frequency dependent. At low ac frequency, below the interfacial inverse charge relaxation time, the high-conductivity fluid displaces into the high-dielectric stream. At high frequency the direction of liquid displacement reverses, and the high-dielectric stream injects into the high-conductivity stream. The interfacial crossover frequency where the liquid displacement direction reverses is dependent on differences in electrical properties between the two fluid streams, and is well explained by Maxwell-Wagner polarization mechanics.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Johns Hopkins University, 221 Maryland Hall, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Desmond
authors.forename: Nicholas
authors.initials: N
authors.lastname: Mavrogiannis
authors.forename: Zachary
authors.initials: Z
authors.lastname: Gagnon
mesh_terms: D004553:Electric Conductivity; D008962:Models, Theoretical; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water