title: Anisotropic de Gennes Narrowing in Confined Fluids.
abstract: The collective diffusion of dense fluids in spatial confinement is studied by combining high-energy (21 keV) x-ray photon correlation spectroscopy and small-angle x-ray scattering from colloid-filled microfluidic channels. We find the structural relaxation in confinement to be slower compared to the bulk. The collective dynamics is wave vector dependent, akin to the de Gennes narrowing typically observed in bulk fluids. However, in stark contrast to the bulk, the structure factor and de Gennes narrowing in confinement are anisotropic. These experimental observations are essential in order to develop a microscopic theoretical description of collective diffusion of dense fluids in confined geometries.
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, SE-41296 Gothenburg, Sweden.
authors.forename: Kim
authors.initials: K
authors.lastname: Nygård
authors.affiliation: Forschungszentrum Jülich, ICS-3, D-52425 Jülich, Germany.
authors.forename: Johan
authors.initials: J
authors.lastname: Buitenhuis
authors.affiliation: Paul Scherrer Institut, CH-5232 Villigen, Switzerland.|Institute for Biomedical Engineering, UZH/ETH Zürich, CH-8092 Zürich, Switzerland.
authors.forename: Matias
authors.initials: M
authors.lastname: Kagias
authors.affiliation: Paul Scherrer Institut, CH-5232 Villigen, Switzerland.|Institute for Biomedical Engineering, UZH/ETH Zürich, CH-8092 Zürich, Switzerland.
authors.forename: Konstantins
authors.initials: K
authors.lastname: Jefimovs
authors.affiliation: European Synchrotron Radiation Facility, 71 Avenue des Martyrs, F-38000 Grenoble, France.
authors.forename: Federico
authors.initials: F
authors.lastname: Zontone
authors.affiliation: European Synchrotron Radiation Facility, 71 Avenue des Martyrs, F-38000 Grenoble, France.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Chushkin