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Microstructure and viscoelasticity of confined semiflexible polymer networks

Nature Physics volume 2, pages 186–189 (2006)Cite this article

Abstract

The rapidly decreasing dimensions of many technological devices have spurred interest in confinement effects1. Long before, living organisms invented ingenious ways to cope with the requirement of space-saving designs down to the cellular level. Typical length scales in cells range from nanometres to micrometres so that the polymeric constituents of the cytoskeleton are often geometrically confined. Hence, the mechanical response of polymers to external confinement has potential implications both for technology and for our understanding of biological systems alike. Here we report a study of in vitro polymerized filamentous actin confined to emulsion droplets. We correlate observations of the microstructure, local rheological properties and single-filament fluctuations. Enforcing progressively narrower confinement is found to induce a reduction of polymer fluctuations, network stiffening, structural heterogeneities and eventually cortex formation. We argue that the structural and mechanical effects can be consistently explained by a gradual suppression of single-polymer eigenmodes.

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Figure 1: Actin solutions encapsulated in sufficiently small emulsion droplets are locally more heterogeneous and more elastic than bulk solutions.
Figure 2: Confinement of actin networks into bio mimetic microcavities of diameters less than the average length of the actin filaments decreases the thermal contour undulations and increases the local network elasticity measured by microscopy and active microrheometry, respectively.

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Acknowledgements

We thank M. Rusp for the actin preparation. We are grateful for the discussions with E. Frey, C. Heussinger and M. Bathe. The work was supported by SFB563 and SFB 413 and partly by the ‘Fonds der Chemischen Industrie’.

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Authors and Affiliations

  1. E22-Biophysics, Technische Universität München, James Franck Straße, 85748, Garching, Germany

    M. M. A. E. Claessens, R. Tharmann & A. R. Bausch

  2. Institut für Theoretische Physik, Universität Leipzig, Postfach 100920, 04009, Leipzig, Germany

    K. Kroy

  3. Hahn-Meitner Institut, Glienicker Straße 100, 14109, Berlin, Germany

    K. Kroy

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  1. M. M. A. E. Claessens
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  2. R. Tharmann
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  4. A. R. Bausch
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Correspondence to A. R. Bausch.

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Claessens, M., Tharmann, R., Kroy, K. et al. Microstructure and viscoelasticity of confined semiflexible polymer networks. Nature Phys 2, 186–189 (2006). https://doi.org/10.1038/nphys241

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