title: Shape transitions in soft spheres regulated by elasticity.
abstract: We study elasticity-driven morphological transitions of soft spherical core-shell structures in which the core can be treated as an isotropic elastic continuum and the surface or shell as a tensionless liquid layer, whose elastic response is dominated by bending. To generate the transitions, we consider the case where the surface area of the liquid layer is increased for a fixed amount of interior elastic material. We find that generically there is a critical excess surface area at which the isotropic sphere becomes unstable to buckling. At this point it adopts a lower symmetry wrinkled structure that can be described by a spherical harmonic deformation. We study the dependence of the buckled sphere and critical excess area of the transition on the elastic parameters and size of the system. We also relate our results to recent experiments on the wrinkling of gel-filled vesicles as their interior volume is reduced. The theory may have broader applications to a variety of related structures from the macroscopic to the microscopic, including the wrinkling of dried peas, raisins, as well as the cell nucleus.
authors: Department of Physics, UCLA, Los Angeles, California 90095-1596, USA.
authors: Craig
authors: C
authors: Fogle
authors: Department of Integrative Biology and Physiology, UCLA, Los Angeles, California 90095, USA and Department of Bioengineering, UCLA, Los Angeles, California 90095, USA.
authors: Amy C
authors: AC
authors: Rowat
authors: Department of Physics, UCLA, Los Angeles, California 90095-1596, USA and Department of Chemistry & Biochemistry, UCLA, Los Angeles, California 90095-1596, USA and Department of Biomathematics, UCLA, Los Angeles, California 90095-1596, USA.
authors: Alex J
authors: AJ
authors: Levine
authors: Department of Physics, UCLA, Los Angeles, California 90095-1596, USA.
authors: Joseph
authors: J
authors: Rudnick