Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 18: Membranes and Vesicles I

BP 18.2: Talk

Wednesday, March 13, 2013, 10:00–10:15, H44

Effect of thermal noise on vesicles and capsules in linear flow — •David Abreu and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart, Germany

Fluid vesicles and elastic capsules are micrometer-sized objects, which implies that they are subject to the influence of thermal fluctuations. In particular, their behaviour in linear flow might be affected by these fluctuations. However, most theoretical models and simulations neglect thermal noise, although it plays an important role in experiments [1].

First, we add thermal noise to reduced models of undeformable vesicles and capsules in shear flow and show that thermal effects are relevant under realistic conditions [2]. We analyze the steady states for the different dynamical regimes as well as the vicinity of dynamical transitions (i.e., tank-treading to tumbling) where intermittent behaviour due to noise always occurs.

For deformable vesicles in general flow [3], we show that thermal fluctuations have to be taken into account in order to correctly explain the trembling motion observed experimentally [1]. We recover the experimental phase diagram and analyze the statistical properties of the three steady states (tank-treading, tumbling and trembling), showing that thermal noise is strongly amplified during trembling.

[1] N. J. Zabusky et al., Phys. Fluids 23, 041905 (2011); M. Levant and V. Steinberg, submitted (2012).

[2] D. Abreu and U. Seifert, Phys. Rev. E 86, 010902(R) (2012).

[3] D. Abreu and U. Seifert, in preparation.