title: Shear-induced deformation of surfactant multilamellar vesicles.
abstract: Surfactant multilamellar vesicles (SMLVs) play a key role in the formulation of many industrial products, such as detergents, foodstuff, and cosmetics. In this Letter, we present the first quantitative investigation of the flow behavior of single SMLVs in a shearing parallel plate apparatus. We found that SMLVs are deformed and oriented by the action of shear flow while keeping constant volume and exhibit complex dynamic modes (i.e., tumbling, breathing, and tank treading). This behavior can be explained in terms of an excess area (as compared to a sphere of the same volume) and of microstructural defects, which were observed by 3D shape reconstruction through confocal microscopy. Furthermore, the deformation and orientation of SMLVs scale with radius R in analogy with emulsion droplets and elastic capsules (instead of R(3), such as in unilamellar vesicles). A possible application of the physical insight provided by this Letter is in the rationale design of processing methods of surfactant-based systems.
authors.affiliation: Dipartimento di Ingegneria chimica, Università di Napoli Federico II, Napoli 80125, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Pommella
authors.forename: Sergio
authors.initials: S
authors.lastname: Caserta
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Guida
authors.forename: Stefano
authors.initials: S
authors.lastname: Guido
mesh_terms: D017738:Alkanesulfonic Acids / Q000737:chemistry; D007091:Image Processing, Computer-Assisted; D008567:Membranes, Artificial; D018613:Microscopy, Confocal; D033081:Shear Strength; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D017738:Alkanesulfonic Acids; D008567:Membranes, Artificial; D013501:Surface-Active Agents; C030641:alkylbenzyl sulfonic acid