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We report the deformation and unbinding of weakly adhering giant vesicles under hydrodynamic shear forces. Linear shear fields are generated in a flat cell and vesicle adhesion onto a supported membrane is generated by electrostatic forces between oppositely charged lipids. The hydrodynamic flow in the aqueous medium near the outer side of the vesicle, within the vesicle and the tanktreading motion in the membrane are observed by tracing small markers attached to the vesicles or suspended in the medium by confocal laser scanning microscopy. The lift force generated by the rotational flow in the vesicle was estimated to be at least two orders of magnitude larger than predicted by the simple theory.

The electrostatically controlled adhesion of giant vesicles on supported membranes is studied by microinterferometry allowing quantitative evaluation of contact formation and surface profile near the contact area. Under suitable conditions the adhesion induced segregation of charged lipids in one of the membranes of contact zone. This leads to patches of tight contact and decoupled blisters, which are demonstrated for the first time. The stabilization of the pressurized blisters is rationalized in terms of counterion accumulation in the contact area ensuring charge neutrality.

Due to a technical problem in printing, the quality of the images of fig. 2 and 4 resulted very bad. In the following page, we publish again the two figures, sincerely apologizing to the author for the unpleasant inconvenience.