277597 Brownian Motion of Stiff Filaments in Confined Media

Tuesday, October 30, 2012: 10:45 AM
409 (Convention Center )
Nikta Fakhri1,2, Frederick C. MacKintosh3, Brahim Lounis4, Laurent Cognet4 and Matteo Pasquali2, (1)Third Institute of Physics-Biophysics, University of Göttingen, Göttingen, Germany, (2)Chemical and Biomolecular Engineering, Rice University, Houston, TX, (3)Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, Netherlands, (4)Laboratoire Photonique, Numérique et Nanosciences - LP2N, Université de Bordeaux, Institut d'Optique Graduate School & CNRS, Talence 33405, France

The thermal motion of stiff filaments in a crowded environment underlies the behavior of such disparate systems as polymer materials, nanocomposites, and the cell cytoskeleton. Despite decades of theoretical studies, the fundamental dynamics of such systems remains a mystery. Using near-infrared video microscopy, we study the thermal diffusion of individual single-walled carbon nanotubes (SWNTs) confined in porous agarose networks. SWNTs are the ideal system to study confined dynamics of stiff filaments. SWNTs are slender (typical diameters  0.7-1.2 nm), sufficiently long to be visualized by optical microscopy (3-15 μm), stiff (20-150 μm, scaling with d3), and share many dynamical characteristics with polymers. Surprisingly, we find that even a small bending flexibility strongly enhances their motion: the rotational diffusion constant is proportional to the filament bending compliance and is independent of the network porosity. This study establishes conclusively the dynamics of individual stiff filaments in crowded environments, elucidating the fundamental physics of how backbone flexibility affects mobility and diffusion. In addition to their relevance for the fundamental physics of stiff polymers, our results can be exploited in biological and technological contexts.

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See more of this Session: Colloidal Hydrodynamics II
See more of this Group/Topical: Engineering Sciences and Fundamentals