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Flow profile near a wall measured by double-focus fluorescence cross-correlation

MPS-Authors
http://pubman.mpdl.mpg.de/cone/persons/resource/persons48359

Lumma,  D.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons47641

Best,  A.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons47914

Gansen,  A.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons47866

Feuillebois,  F.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons48627

Rädler,  Joachim O.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons48921

Vinogradova,  Olga I.
MPI for Polymer Research, Max Planck Society;

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Citation

Lumma, D., Best, A., Gansen, A., Feuillebois, F., Rädler, J. O., & Vinogradova, O. I. (2003). Flow profile near a wall measured by double-focus fluorescence cross-correlation. Physical Review E, 67(5): 056313.


Cite as: http://hdl.handle.net/11858/00-001M-0000-000F-621C-9
Abstract
We present an experimental approach to flow profiling within femtoliter sample volumes, which allows the high-precision measurements at the solid interface. The method is based on the spatial cross-correlation of the fluorescence response from labeled tracer particles (latex nanospheres or single dye molecules). Two excitation volumes, separated by a few micrometers, are created by two laser foci under a confocal microscope. The velocity of tracer particles is measured in a channel about 100 μm wide within a typical accuracy of 0.1%, and the positions of the walls are estimated independently of any hydrodynamic data. The underlying theory for the optical method is given for an arbitrary velocity profile, explicitly presenting the numerical convolutions necessary for a quantitative analysis. It is illustrated by using the Poiseuille flow of a Newtonian liquid with slip as an example. Our analysis yields a large apparent fluid velocity at the wall, which is mostly due to the impact of the colloidal (electrostatic) forces. This colloidal lift is crucially important in accelerating the transport processes of molecules and nanoparticles in microfluidic devices.