  Recent experiments by Kantsler et. al. (2007) have shown that the
relaxational dynamics of a vesicle in external elongation flow is accompanied
by the formation of wrinkles on a membrane. Motivated by these experiments we
present a theory describing the dynamics of a wrinkled membrane. Formation of
wrinkles is related to the dynamical instability induced by negative surface
tension of the membrane. For quasi-spherical vesicles we perform analytical
study of the wrinkle structure dynamics. We derive the expression for the
instability threshold and identify three stages of the dynamics. The scaling
laws for the temporal evolution of wrinkling wavelength and surface tension are
established and confirmed numerically.
