title: Brownian and advective dynamics in microflow studied by coherent X-ray scattering experiments.
abstract: Combining microfluidics with coherent X-ray illumination offers the possibility to not only measure the structure but also the dynamics of flowing samples in a single-scattering experiment. Here, the power of this combination is demonstrated by studying the advective and Brownian dynamics of colloidal suspensions in microflow of different geometries. Using an experimental setup with a fast two-dimensional detector and performing X-ray correlation spectroscopy by calculating two-dimensional maps of the intensity auto-correlation functions, it was possible to evaluate the sample structure and furthermore to characterize the detailed flow behavior, including flow geometry, main flow directions, advective flow velocities and diffusive dynamics. By scanning a microfocused X-ray beam over a microfluidic device, the anisotropic auto-correlation functions of driven colloidal suspensions in straight, curved and constricted microchannels were mapped with the spatial resolution of the X-ray beam. This method has not only a huge potential for studying flow patterns in complex fluids but also to generally characterize anisotropic dynamics in materials.
authors: Department of Chemistry, University of Basel, 4056 Basel, Switzerland.
authors: Raphael
authors: R
authors: Urbani
authors: Max Planck Institute for the Structure and Dynamics of Matter, CFEL, 22761 Hamburg, Germany.
authors: Fabian
authors: F
authors: Westermeier
authors: Department of Chemistry, University of Basel, 4056 Basel, Switzerland.
authors: Benjamin
authors: B
authors: Banusch
authors: Photon Science, Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany.
authors: Michael
authors: M
authors: Sprung
authors: Department of Chemistry, University of Basel, 4056 Basel, Switzerland.
authors: Thomas
authors: T
authors: Pfohl
keywords: X-ray scattering; flow geometries; flow profiles; microfluidics; particle dynamics; photon correlation spectroscopy