Institute of Solid State Research (IFF)

Fluctuations of membranes

The shapes and fluctuations of membanes are controlled by their bending rigidity, but also by their internal state, which can be either

Tethered (or crystalline) [23,24,28,37]
Fluid, or
Hexatic [67,70].

Monte Carlo simulations are an important tool to study the thermal behavior of these surfaces [47,69,71]. Triangulated surfaces are often used in such simulations. The triangulation is fixed for tethered membranes and dynamical for fluid and hexatic membranes. Hard spheres and sufficiently short tethers are used to generate self-avoidance.

Fluid Membranes

The conformations of fluid vesicles at very small bending rigidity are dominated by entropy effects. With zero pressure difference between inside and outside, the configurations are in the universality class of branched polymers [27,34,38,54].

At larger bending rigidities (of the order of the thermal energy kT), the average radius of the "arms" are given by the persistence length (which increases logarithmically with the bending rigidity) [53,54].

Driven Transport of Fluid Vesicles Through Pores

Flexible vesicles, with a bending rigidity of order kT, can squeeze through narrow (cylindrical) pores much more easily than standard lipid-bilayer vesicles (with bending rigidities of 10-20 kT) [61]. Flexible vesicles have therefore been suggested as drug-carriers through the skin (by G. Cevc, Technical University Munich).

E-Mail:Gerhard Gompper

Forschungszentrum Jülich, IFF, wwwiff@fz-juelich.de

Last modified: 19/09/2001, 09.05
URL: <http://www.fz-juelich.de /iff/personen/G_Gompper/membranes.shtml>