title: Measurement of a structured backflow in an open small channel induced by surface-tension gradients.
abstract: We present experiments in which the laterally confined flow of a surfactant film driven by controlled surface tension gradients causes the subtended liquid layer to self-organize into an inner upstream microduct surrounded by the downstream flow. The anomalous interfacial flow profiles and the concomitant backflow are a result of the feedback between two-dimensional and three-dimensional microfluidics realized during flow in open microchannels. Bulk and surface particle image velocimetry data combined with an interfacial hydrodynamics model explain the dependence of the observed phenomena on channel geometry.
authors.affiliation: Departament de Química Física, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Catalonia, Spain.
authors.forename: Alba
authors.initials: A
authors.lastname: Pulido-Companys
authors.forename: Josep
authors.initials: J
authors.lastname: Claret
authors.forename: Jordi
authors.initials: J
authors.lastname: Ignés-Mullol
authors.forename: Francesc
authors.initials: F
authors.lastname: Sagués
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D044085:Microfluidics / Q000379:methods*; D008956:Models, Chemical; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D013501:Surface-Active Agents; D004134:Dimyristoylphosphatidylcholine