  Irradiation of a giant unilamellar lipid bilayer vesicle with a focused laser
spot leads to a tense pressurized state which persists indefinitely after laser
shutoff. If the vesicle contains another object it can then be gently and
continuously expelled from the tense outer vesicle. Remarkably, the inner
object can be almost as large as the parent vesicle; its volume is replaced
during the exit process. We offer a qualitative theoretical model to explain
these and related phenomena. The main hypothesis is that the laser trap pulls
in lipid and ejects it in the form of submicron objects, whose osmotic activity
then drives the expulsion.
