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Microrheology of colloidal systems

Puertas, A. M. and Voigtmann, Th. (2014) Microrheology of colloidal systems. Journal of Physics - Condensed Matter, 26, p. 243101. Institute of Physics (IOP) Publishing. doi: 10.1088/0953-8984/26/24/243101. ISSN 0953-8984.

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Microrheology was proposed almost twenty years ago as a technique to obtain rheological properties in soft matter from the microscopic motion of colloidal tracers used as probes, either freely diffusing in the host medium, or subjected to external forces. The former case is known as {\sl passive microrheology}, and is based on generalizations of the Stokes-Einstein relation between the friction experienced by the probe and the host-fluid viscosity. The latter is termed {\sl active microrheology}, and extends the measurement of the friction coefficient to the nonlinear-response regime of strongly driven probes. In this review article, we discuss theoretical models available in the literature for both passive and active microrheology, focussing on the case of single-probe motion in model colloidal host media. A brief overview of the theory of passive microrheology is given, starting from the work of Mason and Weitz. Further developments include refined models of the host suspension beyond that of a Newtonian-fluid continuum, and the investigation of probe-size effects. Active microrheology is described starting from microscopic equations of motion for the whole system including both the host-fluid particles and the tracer; the many-body Smoluchowski equation for the case of colloidal suspensions. At low fluid densities, this can be simplified to a two-particle equation that allows the calculation of the friction coefficient with the input of the density distribution around the tracer, as shown by Brady and coworkers. The results need to be upscaled to agree with simulations at moderate density, in both the case of pulling the tracer with a constant force or dragging it at a constant velocity. The full many-particle equation has been tackled by Fuchs and coworkers, using a mode-coupling approximation and the scheme of integration through transients, valid at high densities. A localization transition is predicted for a probe embedded in a glass-forming host suspension. The nonlinear probe-friction coefficient is calculated from the tracer's position correlation function. Computer simulations show qualitative agreement with the theory, but also some unexpected features, such as superdiffusive motion of the probe related to the breaking of nearest-neighbor cages. We conclude with some perspectives and future directions of theoretical models of microrheology.

Item URL in elib:https://elib.dlr.de/89373/
Document Type:Article
Title:Microrheology of colloidal systems
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Puertas, A. M.Universidad de AlmeriaUNSPECIFIEDUNSPECIFIED
Voigtmann, Th.Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIEDUNSPECIFIED
Date:21 May 2014
Journal or Publication Title:Journal of Physics - Condensed Matter
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:p. 243101
Publisher:Institute of Physics (IOP) Publishing
Keywords:microrheology, colloidal suspensions
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Research under Space Conditions
DLR - Research theme (Project):R - Vorhaben Materialwissenschaftliche Forschung (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space
Deposited By: Voigtmann, Dr.rer.nat. Thomas
Deposited On:05 Jun 2014 08:53
Last Modified:06 Sep 2019 15:28

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