title: Mechanism of Spontaneous Blebbing Motion of an Oil-Water Interface: Elastic Stress Generated by a Lamellar-Lamellar Transition.
abstract: A quaternary system composed of surfactant, cosurfactant, oil, and water showing spontaneous motion of the oil-water interface under far-from-equilibrium condition is studied in order to understand nanometer-scale structures and their roles in spontaneous motion. The interfacial motion is characterized by the repetitive extension and retraction of spherical protrusions at the interface, i.e, blebbing motion. During the blebbing motion, elastic aggregates are accumulated, which were characterized as surfactant lamellar structures with mean repeat distances d of 25 to 40 nm. Still unclear is the relationship between the structure formation and the dynamics of the interfacial motion. In the present study, we find that a new lamellar structure with d larger than 80 nm is formed at the blebbing oil-water interface, while the resultant elastic aggregates, which are the one reported before, have a lamellar structure with smaller d (25 to 40 nm). Such transition of lamellar structures from the larger d to smaller d is induced by a penetration of surfactants from an aqueous phase into the aggregates. We propose a model in which elastic stress generated by the transition drives the blebbing motion at the interface. The present results explain the link between nanometer-scale transition of lamellar structure and millimeter-scale dynamics at an oil-water interface.
authors.affiliation: Department of Applied Physics, Faculty of Science, Tokyo University of Science , Katsushika, Tokyo 125-8585, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sumino
authors.affiliation: KENS&CMRC, Institute of Materials Structure Science, High Energy Accelerator Research Organization , Tokai, Ibaraki 319-1106, Japan.
authors.forename: Norifumi L
authors.initials: NL
authors.lastname: Yamada
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899-6102, United States.|Center for Exploration of Energy and Matter, Indiana University , Bloomington, Indiana 47408 United States .
authors.forename: Michihiro
authors.initials: M
authors.lastname: Nagao
authors.affiliation: Department of Education, Aichi University of Education , Kariya, Aichi 448-8542, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Honda
authors.affiliation: Department of Physics, Graduate School of Science, Chiba University , Chiba, Chiba 263-8522, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kitahata
authors.affiliation: Biology and Soft Matter Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831-6393, United States.
authors.forename: Yuri B
authors.initials: YB
authors.lastname: Melnichenko
authors.affiliation: KENS&CMRC, Institute of Materials Structure Science, High Energy Accelerator Research Organization , Tokai, Ibaraki 319-1106, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Seto