Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 9: Membranes and Interfaces

BP 9.8: Talk

Tuesday, February 26, 2008, 12:30–12:45, PC 203

Adhesion of Fluid Vesicles at Chemically Structured Substrates — Gunnar Linke, Reinhard Lipowsky, and •Thomas Gruhn — Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany

Spatial immobilization of vesicles is important for many vesicle applications like the usage as chemical reactor in nano laboratories or as modules in membrane sensors. A controlled fixation of a vesicle can be achieved by adhering it to a finite adhesive domain on an otherwise repulsive substrate surface. We have studied this scenario with the help of mesoscopic Monte Carlo simulations. If the vesicle is larger than the attractive domain, the spreading of the vesicle onto the substrate is restricted by the size of this surface domain. Once the contact line of the adhering vesicle has reached the boundaries of the domain, further deflation of the vesicle leads to a regime of low membrane tension with pronounced shape fluctuations, which are now governed by the bending rigidity. For a circular domain and a small bending rigidity, the membrane oscillates strongly around an average spherical cap shape. If such a vesicle is deflated, the contact area increases or decreases with increasing osmotic pressure, depending on the relative size of the vesicle and the circular domain. The lateral localization of the vesicle's center-of-mass by such a domain is optimal for a certain domain radius, which is found to be rather independent of adhesion strength and bending rigidity. For vesicles adhering to stripe-shaped surface domains, the width of the contact area perpendicular to the stripe varies non-monotonically with the adhesion strength.