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@INPROCEEDINGS{Lang:836723,
      author       = {Lang, Peter R. and Desio, Silvia and Dhont, Jan K.G.},
      title        = {{D}ynamics of spherical particles in a crowded suspension
                      of colloidal rods{D}ynamic information from {TIRM}
                      revisited},
      reportid     = {FZJ-2017-05782},
      year         = {2017},
      abstract     = {Total internal reflection microscopy (TIRM) enables
                      measuring the interaction energy between a flat glass wall
                      and a colloidal probe sphere as a function of separation
                      distance.In an earlier contribution [1] we showed that
                      depletion potentials induced by the rod-like fd-virus follow
                      the classical low density approximation [2] at
                      concentration, at which this is expected to fail. At even
                      higher concentrations, we observed deviations from the idel
                      gas behaviour, which however show a trend opposite to
                      theoretical prediction [3]. In this presentation we are
                      discussing wheter this observation may be caused by the
                      systems dynamics, which are usually disregarded in TIRM
                      experiments The standard approach to analyse the dynamic
                      information inherent to TIRM data is extracting the probe
                      particle’s diffusion coefficient normal to the wall from
                      the mean square displacement (MSD) vs. time curves [4].
                      However, in the course of our investigation we discovered
                      that a more reliable method is to determine the particle’s
                      drift velocity from the mean displacement (MD) vs. time
                      curves.The analysis of the probe particles’ drift velocity
                      data reveals a dynamic fingerprint of the finding from
                      static data that for the large spheres and high
                      fd-concentrations the apparent depletion potential is
                      significantly deeper than expected from the classical
                      theoretical prediction.Further we observe that there is
                      potential to measure local viscosities with TIRM, by
                      measuring position dependent drift velocities and fit the
                      experimental data with the appropriate theoretical
                      expression, where the viscosity is the only free
                      parameter.Finally, we identified the reason why drift
                      velocities can be determined more reliably than diffusion
                      coefficients from the initial slope of the time dependence
                      of the mean displacement and mean square displacement,
                      respectively.[1] S. De Sio and P. R. Lang, Z. Phys. Chem.
                      229, 1161–1175 (2015).[2] S. Asakura and F. Oosawa, J.
                      Polym. Sci. 33, 183 (1958) and J. Chem. Phys. 22, 1255
                      (1954).[3] Y. Mao, M.E. Cates and H.N.W. Lekkerkerker J.
                      Chem. Phys. 106, 3721 (1997).[4] R. J. Oetama and J. Y.
                      Walz, J. Coll. Interf. Sci. 284, 323 (2005).},
      month         = {May},
      date          = {2017-05-29},
      organization  = {SoftComp Annual Meeting 2017, San
                       Servolo, Venice (Italy), 29 May 2017 -
                       31 May 2017},
      subtyp        = {After Call},
      cin          = {ICS-3},
      cid          = {I:(DE-Juel1)ICS-3-20110106},
      pnm          = {551 - Functional Macromolecules and Complexes (POF3-551) /
                      SOMATAI - Soft Matter at Aqueous Interfaces (316866)},
      pid          = {G:(DE-HGF)POF3-551 / G:(EU-Grant)316866},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/836723},
}