Fluctuation analysis of tension-controlled undulation forces between giant vesicles and solid substrates

Analytical characterization of adhering vesicles

“…Note that the description of adhesion using a contact potential is approximate, because van der Waals forces are actually long-ranged and because membranes may fluctuate in the vicinity of the substrate: adhering vesicles actually never strictly come into contact with their substrate. Membrane-substrate separations range from 1 nm for the strongest values of W [6], to about 50 nm for the weakest adhesions [9]. The highest values of W tend to produce vesicle rupture during the adhesion process [5], owing to a strong tension induced in the membrane [8].…”

The Influence of Substrate Structure on Membrane Adhesion

“…Weakly adhering giant vesicles have been studied using reflection interference contrast microscopy [6] and have been found to lie at distances between 300Å and 400Å from a planar substrate. Here, Van der Waals attractions to the substrate are mainly counterbalanced by a repulsive entropic Helfrich force.…”

Membranes on rough self-affine surfaces

“…Nevertheless, our results will be also valid for weak lateral tension (RӶR* or slightly stretched membranes͒ as was pointed out earlier. 13 Moreover, finite-membrane-size effects can be ignored for roughness correlation lengths ͑typically Ͻ100 nm as observed in many real systems 18 ͒ sufficiently smaller than the membrane size of typical magnitude ϳ1 m. 10,13 It is found that in order for the substrate roughness to have a significant contribution on fluctuations of the membrane profile ͑effect of H), the substrate correlation length should be larger than the healing length . This is also the expected result if ones makes a comparison with conclusions regarding wetting of fluid interfaces.…”

“…Experimentally, an investigation of the membrane fluctuations induced by the roughness of the substrate on which they are bounded might be possible, because of a recent ingenious experimental development by Radler et al 10 In fact, they combined phase contrast microscopy with reflection interference microscopy, 10 which made it possible to measure both the microscopic shape and the fluctuations of the bound part at the same membrane ͑vesicle in the particular case͒. …”

“…4 Interface/surface fluctuations give rise to fundamental contributions in a variety of processes, [5][6][7] and systems with membranes. [2][3][4][8][9][10] Extensive studies have been performed already for membranes bounded by flat and uniform substrates. [1][2][3][4][8][9][10] However, real substrate surfaces are always characterized by some degree of roughness that depends on the material, the method of surface treatment, and the presence of absorbed species.…”